Basking in the Sun

This is a guest post by Tom Murphy. Tom is an associate professor of physics at the University of California, San Diego. This post originally appeared on Tom's blog Do the Math.

Who hasn’t enjoyed heat from the sun? Doing so represents a direct energetic transfer—via radiation—from the sun’s hot surface to your skin. One square meter can catch about 1000 W, which is comparable to the output of a portable space heater. A dark surface can capture the energy at nearly 100% efficiency, beating (heating?) the pants off of solar photovoltaic (PV) capture efficiency, for instance. We have already seen that solar PV qualifies as a super-abundant resource, requiring panels covering only about 0.5% of land to meet our entire energy demand (still huge, granted). So direct thermal energy from the sun, gathered more efficiently than what PV can do, is automatically in the abundant club. Let’s evaluate some of the practical issues surrounding solar thermal: either for home heating or for the production of electricity.

Heat as Something Useful

In physics classes, I often catch myself repeating the mantra that heat is a disordered, useless state of energy that is generically the endpoint of an energy flow process. For example, the energy allocated to the fast-spinning wheel of an upside-down bicycle will slowly drain away as the wheel stirs the air, makes sound, and suffers friction at the bearing. Every one of these energy paths results in heat, until 100% of the invested energy is dissipated and the room is a tad warmer as a result. We will never reassemble the lost energy into useful form, once entropy has claimed it. All of this is true enough, but I feel very awkward uttering the words that heat is the graveyard of energy flow, and must place an asterisk on the statement.

The asterisk is that the overwhelming majority of our societal energy consumption makes use of heat—over 90% in the U.S.! So heat does not deserve the bad rap as a worthless waste product. Rather, heat runs our world! Sometimes we just want the heat directly, via: natural gas for furnaces, hot water, and cooking; heating oil for the home; and gas and coal for industrial process heat. This accounts for 20% of our total energy demand, leaving about two-thirds of our total energy consumption in the form of heat that powers heat engines for electricity production, transportation, and machinery. In short, all the energy we get from fossil fuels, nuclear, and biomass derives from heat. That’s hardly useless!

Radiant Heat

The Sun transmits its energy to Earth across the emptiness of space via radiation. Each square meter of surface at a temperature, T, emits radiation at a rate of σT4, where T is expressed in Kelvin (important!) and σ = 5.67×10−8 W/m²/K4. This constant is easy to remember via the sequence 5-6-7-8. Ignoring for now the subtleties of greenhouse gases, the surface of Earth—typically at 288 K—emits 390 W/m². The Sun, on the other hand, at 5800 K, emits 64 MW per square meter!

Summing over the area of the spherical Sun, at 109 times the radius of Earth, we find the total radiant power of the Sun to be a whopping 3.9×1026 W. Now that’s a light bulb! The Sun’s radiant energy spreads into all directions, creating a sphere of light. At the distance of the Earth, that sphere has an area of 4πr² ≈ 2.8×1023 m², where r is the mean Earth-Sun distance. Dividing these huge figures, we find that the radiant intensity at Earth is 1370 W/m²—which I hope will be a familiar number by now for Do the Math readers.

We can also turn the σT4 relation on its head and say that a patch of full sun (at the ground) receiving 1000 W/m² corresponds to a radiant temperature of 364 K, or a blistering 91°C. This means that a black panel in full sun could get this hot if no paths other than radiation were available for cooling the panel. We would then say that the panel is in radiative equilibrium with the Sun. But air can carry away heat by convection. The self-convection of a hot, flat plate will be about 10 W/m² per degree of difference between the panel and the surrounding air. Requiring the sum of radiative and convective losses to add up to the input power of 1000 W/m² yields a solution of about 55°C (328 K; 131°F) if the surrounding air is at 20°C. This assumes that the plate has no heat paths available through the (insulated) back side. If, on the other hand, it is a thin panel allowing convection on both sides, it will be cooler—although the “heat rises” phenomenon will suppress heat flow on the back side relative to the front, if the plate is indeed level. Just for fun, if we get an additional 5 W/m²/K of convective loss off the back, the equilibrium temperature drops to 47°C (117°F). It all seems reasonable.

Passive Solar: Putting Heat to Use

The simplest way to replace fossil fuel energy with solar energy is called a window. A single uncoated piece of glass will transmit 92% of visible light (the rest reflected) when light comes straight in (down to 75% at a 20° grazing incidence, 60% at 10° grazing). The glass is opaque to ultraviolet light and mid- to far-infrared (IR) light, but lets over 95% of the unreflected incident solar spectrum pass.

Considering that windows in houses/buildings tend to be vertical, we can evaluate the energy input through windows, taking transmission loss, reflection loss, and angular foreshortening into effect. Because the Sun is higher in the sky in the summer, the window appears foreshortened to the direct sunlight, and also reflects more. So a south-facing window automatically admits more heat in the winter than in the summer, with no adjustment. Putting an overhang over the window—ideally with some vertical space between the window and overhang—can eliminate the summer noon-time contribution entirely. The figure below illustrates the fraction of incident direct-sun energy (think 1000 W/m²) admitted by the window. Vertical reference lines indicate the noon-time elevation of the sun at a latitude of 40° for the winter and summer solstices. The noon-day sun will be somewhere between these values all year. Adjustment to other latitudes involves a simple shift of the dashed lines by the latitude difference.

Fraction of incident direct energy (perpendicular to rays) making it through a vertical window. The overhang extends an amount that is half the window height, and optionally is spaced 0.2 window-height-units above the top of the window.

So it is not a stretch to admit energy in excess of 500 W/m² into your home in winter sun. You can stack up the equivalent of a dozen or so space heaters pretty quickly.

Drab Winter?

Sounds great, but winters are not always the sunniest of times. However, it’s not as bad as you might fear. Every photon of visible light that makes it through your window—even if coming from a drab gray cloud—deposits the same amount of heat no mater how convoluted its path from the Sun. Indeed, a measurement campaign in my home has revealed that the attic gets surprisingly warmer (10°C, or 18°F) than the ambient air even on a day of heavy clouds when my solar PV system only caught one-quarter of the usual amount of light. So we can use the NREL database for a flat plate collector (in this case, a window) oriented south at a 90° tilt to represent the amount of energy a window would grab. The following table indicates the equivalent number of full-sun hours per day during the heating months for Seattle, WA (on the poor end), St. Louis MO (a representative U.S. average solar city), and San Diego (my home).

The table also includes the number of equivalent full-sun hours per day a 2-axis concentrating system would recover, which is a good proxy for the average daily number of hours of direct sun. The window can often get more energy than is present in full sun due to the diffuse gain, which is the case for six out of the seven months for Seattle in the table above.

If a house had four large windows facing south, each 2 m wide and 3 m tall, a typical Seattle day in December would deposit 900 W/m² (from earlier graph, low elevation sun) times 24 m², or about 22 kW of power for about 1.3 hours. This amounts to 28 kWh of energy (corresponding to about 1 Therm of natural gas energy).

To make this amount of heat work, the house must be extraordinarily well insulated, use fancy windows, and be draft-free—using a heat recovery ventilator. But such feats can be accomplished in passive home design, even in climates that would appear to be completely hostile to the notion of passive solar heating.

It is also often advantageous to have several days’ worth of thermal storage in the home to average out the sunny and cloudy days. A dark, massive rock or brick wall can do the job—preferentially opposite the huge south-facing windows to directly soak up the solar input. At a specific heat capacity of 1000 J/kg/K and a density of 3000 kg/m³, a rock wall 0.5 m thick and matching our 24 m² window footprint will see a temperature rise of about 2°C for every hour of sunlight poring onto it. A good sunny day pumping five hours of solar energy into the mass would raise its temperature 10°C, so that lazy air pulling off heat at 2 W/m²/K would initially pump out 2400 W of power after the sun is down (assuming the back of the wall is insulated), and provide about 2 days of heat with no additional input.

Of course a number of engineering challenges surround clever passive solar thermal design, and I should pull away before the post gets bogged down (too late, you say?). Perhaps I will return to the topic later. For now, it is worth understanding that the amount of solar radiation incident on a house can be sufficient to provide heating even in unfavorable climates. I should add one caveat: that passive heating may be sufficient 90% of the time, requiring either backup heat or—preferably—flexibility in dealing with a colder house the other 10% of the time.

Hot Water

Using the sun to heat water is a very similar concept. We saw that a flat black plate in the sun can get pretty toasty. In practice, flat panel collectors can hang onto about 60% of the incident solar energy, transferring this to the water. Heat paths via radiation through the glass on the front, convection of air within the panel, and conduction through the back and mounting frame all contribute to loss. For radiative loss, radiation from the black panel is intercepted by the glass (thermal IR is not transmitted by glass), warming it up. This can then radiate both skyward and back to the absorber. A second piece of glass (double-pane) can cut down radiation losses, by returning approximately half of what would otherwise have been lost off the front panel. Some fancy units evacuate air to minimize convective loss, and the backs can be insulated to reduce loss. Given all these thermal leaks, holding on to 60% of the incident energy is pretty impressive.

Example construction of simple flat-panel collector.

Let’s assume your household requires 300 liters of hot water each day—the equivalent of four “long” 10 minute showers at a healthy flow of 8 liters per minute. This, by the way, is far more than I believe is really necessary for a household—even if it is typical. If the water comes in at 10°C, and is heated to 60°C, then we need to supply 15,000 kcal of energy—following the definition of the kilocalorie. Considering 60% efficiency and allowing for some daily loss in storage, we need to provide 30,000 kcal of solar input each day, amounting to 35 kWh of energy. As it turns out, tilting a panel to 54° in St. Louis gives at least 3.5 hours of full-sun-equivalent (1000 W/m²) even in December, so that we need 10 m² of panels (a bedroom’s size).

Two panels on roof provide hot water.

Solar Thermal Electricity

The relatively low temperatures achieved by flat panels in the sun do not encourage exploitation in the form of heat engines for making electricity. But we can fix this through the simple act of concentration. No—not simply thinking really hard about it. Much like a magnifying glass can be used to burn paper, any piling-up of solar flux can elevate the temperature. I have personally melted pennies, boiled water, and turned sand into glass with a large hand-held Fresnel lens. Even a bunch of flat mirrors directing sunlight onto a common spot can create formidably high temperatures.

Concentration is expressed as a ratio, so if I take a circular magnifying glass 100 mm in diameter that makes an image of the sun 1 mm across, the concentration factor is 10,000 (the ratio of areas). Using our radiative relation, the resulting 10 MW/m² corresponds to a temperature of 3600 K! That kind of temperature will melt any metal, if you put the concentrated light onto a fleck of metal smaller than the bright spot. Typical boilers in power plants produce a hot temperature of about 1000 K. Achieving a comparable temperature via solar input requires a concentration in excess of 60.

One downside is that concentration implies tracking, which adds to complexity. Two-dimensional concentration—like a magnifying glass—requires two-axis control to keep the hotspot on the small target. One-dimensional concentration—such as a parabolic trough—only requires tracking along one axis. The concentration ratio of a 1-D concentrator is roughly the square-root of the 2-D variety, but that’s okay if we only need concentration ratios around 100 or so. One-dimensional concentration is also far more forgiving of imperfections in the reflector shape (can be made more cheaply).

Another downside of concentration is that it requires real direct sunlight to work. Can you see a sharp shadow on the ground? If not, concentration is effectively dead. In essence, the concentrator is forming an image of the sun—sometimes a stretched-out linear image in the case of trough collectors. Forming images of clouds onto the collector will not get it very excited. It needs the real thing. Comparing the effective yield for tracking configurations at different sites gives some sense for how some places are differently advantaged to exploit solar thermal. In general, desert areas do very well.

The table above gives average daily yields (kWh/m²/day, or equivalent hours at 1000 W/m²) for three types of solar collection in four locations, each entry giving worst-month/yearly-average/best-month values. The first is for a flat plate tilted to the site latitude (appropriate for PV or hot water), followed by 1-axis concentration tilting along a N-S axis, and finally a 2-axis concentration configuration. Solar thermal makes the most sense in areas where more energy will be collected than with PV panels—but this is not a rigorous criterion, since solar thermal offers some advantages over PV, as we’ll discuss in a bit. In the table above, only Dagget, California—in the Mojave desert— has concentration beating flat-panel PV for total energy. Other desert cities in the Southwestern U.S. likewise are favorable toward solar thermal electricity. But it’s definitely a location-dependent technology.

Solar Thermal Schemes

Schemes abound: 1) power towers where an array of individually-steered flat mirrors are angled to put sunlight at the top of a tower in the middle of the array; 2) satellite-dish-looking segmented bowls with a heat engine at the focus; 3) parabolic trough arrays with a hot-oil-carrying pipe running down the focus; 4) and others topologies, I am sure.

Solar "power tower" outside Barstow, CA.

Taking the simple parabolic trough as an example, about 70% of the incident energy makes it into the 400°C fluid running within the central pipe. Heat carried by the oil makes steam to turn turbines, in the traditional power plant sense. The efficiency of the power plant portion is in the usual ballpark of 30%. These two factors alone produce 20% efficiency, but other losses tend to push it down to 15% or so. The troughs are typically oriented north-south, with daily tracking (e.g., pivot about the hot pipe). Self-shadowing becomes an issue, mitigated by providing ample room between collectors. If you want to track the sun as low as 15 degrees elevation with no shadowing, for instance, only one-fourth of the land area is utilized. East-west orientations are also possible, performing less well year-round, but more uniformly throughout the year.

Parabolic trough collectors.

Parabolic troughs are pretty neat, I think, for a variety of reasons. First, the parabolic shape accomplishes focus independent of the slant angle of the light in the direction along the axis: mathematical perfection no matter the angle. This leads to the second serious advantage—already discussed—of single-axis tracking along a north-south axis. The ability to transport the heat along the axis using a fluid/pipe is unique to this design, making it convenient to schlep the heat around where you want it. Finally, because the shiny material only needs to be bent in one direction (far easier than a bowl-shape), the reflectors are relatively inexpensive to make.

Evaluating a realized example, the Nevada Solar One plant has a 64 MW nominal capacity, generating 134 million kilowatt-hours of energy per year. Dividing these two implies about 2100 hours of full-power operation per year, for a duty cycle of 24%, or 5.7 hours per day. The NREL database for Las Vegas expects a north-south single-axis tracker to get an average of 6.2 hours per day horizon-to-horizon. So not too far off. The plant cost $266 million to build, amounting to $4.15 per Watt. Pretty similar to installed solar PV. The plant occupies about 1.6 km² of land, computing to 40 W/m² at nominal full power. This is 4% of the incident 1000 W/m² (at the height of summer), which is pretty close to what we would guess for a 15% efficient collector occupying 25% of the land area. I love it when the numbers make sense!

A Storage Boon

One serious perk to solar thermal—not yet exploited as fully as it might be—is thermal storage. Make hay when the sun shines, and squirrel it away for overnight use. All solar thermal plants have short-term immunity from intermittency due simply to the thermal mass in the system. Solar thermal plants are designed with varying degrees of storage, many just aiming for several hours to better follow the peak demand curve into the evening. But as renewables gain dominance over fossil fuels (as I’m hoping they do), storage will become increasingly important. To my mind, the ratio of storage to collection is pretty straightforward to change (i.e., bigger vat of hot fluid), so that in principle solar thermal plants could achieve days of storage with little added complexity. We can’t say this about PV or wind. And storage efficiency for a large container grows linearly with the tank’s dimension, since it the energy contained scales like volume, while thermal loss paths tend to scale with area.

One of the Winners

We looked at three categories of using heat from the Sun: passive home heating, hot water, and solar thermal electricity. Virtually anything involving direct use of solar energy—as opposed to hydroelectric, wind, waves, etc. as secondary and tertiary derivatives of solar input—is bound to end up on the abundant side of the story. And so it is with these three, although perhaps given that the first two are confined to the meager area represented by rooftops and/or windows—rather than the entire land area—they should more fairly be stashed in the “potent” box.

Solar thermal electricity definitely joins the camp as an abundant resource. Some of the other abundant resources described to date (nuclear breeders, geothermal depletion, and more to come) present technical hurdles or other practical barriers that diminish my excitement for them. I won’t claim that solar thermal electricity has no difficulties (reflectors get dusty/abraded by desert sands, for instance). But it’s pretty low-tech, utilizes over a century of experience in running heat engines, allows storage to be an integral part of the design, and is super-abundant on the scale of things. All the same, we have found yet another viable way to make electricity, doing little to directly address a liquid fuels shortage.

The low-tech nature of solar thermal makes it especially robust in tough times. I can imagine personally designing and building a passive solar home, flat-plate thermal collectors for hot water, and even a parabolic trough to create steam. I can’t say the same about a PV panel, a nuclear reactor, or geothermal wells kilometers deep. It gets my vote.

We’ll see nuclear fusion next week. Sound familiar?

I've found it strange that there is a lot more discussion of PV systems for the home than solar space heating and hot water heating.

If anyone is interested in some do-it-yourself possibilities see:

Thanks, Great link!

I built two of the "$1K Solar Water Heating Systems" featured at Buildit (slightly modified) for about $300 for both. It took me a few years to scrounge the materials, but they work great. I did the copper/aluminum version and used glass instead of the polycarbonate, installed as a simple drainback system. Just follow their directions.

Decided to build a solar water heater. Looked around for an effective way to do it around here. Still trying to get the pipe 4 months later :(


Instant shower:

200' of 1/2" black drip-tube $60
Fittings to join and to hoses: $5
flexible hose to spray nozzle
Garden spray nozzle
Mixing valves (Way too hot in summer)

Run a rope through the coils of tubing, attach the rope up high against a sunny wall, and spread the coils out along it. Secure the rope to the wall at a few points along the way to correct for droop.

...A very nice thing to have if you have nothing else.

Yep, have done similar. This time I want to build a good quality, repeatable panel that can be linked into my hot water tank. Additionally it has to be easily moved when I need to and yet resist a good storm. I have a design that may work well but 3/8" copper pipe seems to have gone extinct.


I'm going to build a version of That type retains nearly full wall insulation when the sun isn't shining. I got a couple hundred ft2 of twinwall poly for $30 at our used construction materials place. Much went to covering the windows in the house (mobile home), which made an obvious difference. The collector will go on my little shed, where I spend most of the day. I bought black felt and screws new. The wood, polyiso board, and glazing are all used. This is tar paper shack technology, or close to it.

I've build a couple of similar collector systems. Your use for the hot air collectors in a shed should work OK, but the collectors would probably produce more thermal energy if the air flow were moved faster with some sort of fan setup. That's because the thermosiphon effect is very weak over the height of a single story wall. As a result, much of the thermal energy collected results in heating air too hot and thus more of the energy goes thru the cover to the outside than would be desired. A small fan system powered with an appropriately sized PV panel is the approach often taken.

Another problem is moisture, as the collectors are the coldest spot in the inside air loop and condensation results. For a shed, that's not much of a problem, but for a house, where there's likely to be much more water vapor in the air, the condensation can damage the collectors. Even with your shed heater, pay close attention to drainage from the inside of the twinwall, as well as sealing the bottom of the twinwall to limit water entry when it rains.

One more issue to consider is that the twinwall material has a special UV resistant layer covering on the outer surface, which prolongs the lifetime time before the polycarbonate degrades. Since you are working with used material, you must be careful to place the twinwall facing in the proper direction when installing it. Be especially careful not to scratch the outer side, as that will destroy the protective layer. New twinwall is delivered with a plastic "wrap" over the outer side, which is a thin translucent plastic which is removed at the end of the installation procedure. Lastly, do not use any mechanical method to later clean the surface which could cause erosion or scratches...

E. Swanson

Also being able to close the vents between panel and room at night so it doesn't become a big chiller.


To keep the post short, I didn't mention my free fan. I already have the parts to make a controller which runs the fan when the collector is warmer than the shed. The system I linked to uses thin plastic flapper doors to seal at night. With the fan, I can use foam board. I'll watch for condensation, but my shed has very little moisture in addition to the outside air, which is plenty dry in Boulder.

A really good seal when the collector is cool should eliminate the moisture problem if this is used for a house. An electrically controlled flapper would do. I've seen radiator valves that could be adapted, and I may have one rescued from the trash.

I can still read the printing marking the UV resistant side.

I have about a ton of machinery in there, but Cp of iron is about a tenth that of water. I may add a few 20 gallon barrels of water for thermal mass. The barrels are free from an auto repair shop within barrel rolling distance.

In the summer, I'll probably remove the glazing, reversing the fan and flappers. Nights are always cool, so venting till dawn will probably keep me cool all day.

I'm hoping to buy a different trailer which will have a long wall on the south. In this climate, I think the system will work very well, but experience with the shed will tell.

Sounds interesting, let us know how it goes. BTW, your saying about the radiator valves set me thinking. There are actuators for greenhouse windows that are use to open the vents as the greenhouse warms up. They have a fair bit of push to them. Maybe these could help control flaps, use one to drive pull cords, or switch fans. Just a thought.


Dr. Murphy, your description is similar to one I've seen for decades. Trouble is, there's lots of information left out of that description. You make passive solar appear to be a good choice, which it may be for milder winter climate zones. However, for colder climates, the energy loss thru the windows becomes quite large, which reduces the energy available to heat the interior. This can be especially painful on colder nights, as the large expanse of glass tends to lose heat rapidly. There's no mention in your article of the need to insulate the glass at night and on cold, cloudy days. Also, you didn't mention the use of water panels for space heating, which may provide a better option in colder climates than strict passive gain. That's because the hot water panels can't lose any energy at night.

The important point is that the output of any solar thermal collector is a function of the difference in temperature between the collector and the environment. There have been several methods employed to describe this situation, the best being the rather standard graph of collector efficiency versus temperature difference and incident solar energy. I don't have a copy of such a graph, but they are often presented in any good text on the subject, going back to Duffie and Beckman's text Solar Energy Thermal Processes, from 1974. Perhaps you have such a graph available and can post it for our edification...

EDIT: HERE's a generalized graph, which shows how efficiency changes with insolation for the 3 basic types of solar thermal low temperature collectors. Notice that the efficiency drops off rather fast as the insolation declines, even if one uses evacuated tube collectors. The most efficient are the unglazed collectors, typically used for heating swimming pools during the warmer months of the year.

E. Swanson

Passive Solar is a highly utilized feature of much of Maine 'Green' Construction, and is not only a good choice, but an essential one.. no less than having hefty insulation around the rest of the envelope..

It was hardly expected for this post to be comprehensive around each application, but anyone who puts in lots of windows still has the opportunity every day to add in one of a number of window insulating approaches, if they had been somehow unaware of this key weakness of windows.

This is a book I was able to borrow recently, and need to pick up a copy of, when I get some more birthday cash.. some of the ideas are klunky, but the whole collection of thoughts opens up the possibilities pretty thoroughly.


Indoor insulation behind large modern windows is not a particularly good way to go, but shutter systems, like those pictured in the linked book add, are quite promising. I think I will order a copy today, thanks. Our CCHRC is working on shutter designs as well. Of course I'm a bit slow to get at even my backlog (yes my pellet boiler is still waiting on me to finish up, apparently 750 gallons of fuel oil a year has not been a big enough motivator at $4/gal +- just yet) but January certainly has been inspiring.

The first number this season, second number average season
through January 31, 2012

MONTH TO DATE 2839, 2261
SINCE DEC 1 4725, 4401
SINCE JUL 1 8840, 8532

Thorsten Chlupp has built completley solar thermal heated homes up here. The first one pictured is on the grid, but the second, a quite attratctive one, is off grid. Lots of thermal storage under the building--but it does work. Lots of windows too. A bit on the expensive side though.

oh, in case you wondered average annual heating degree days a tad under 14,000

Thanks for the info.

Yes, I'm eager to try out exterior insul. shutters, too.

Our winters seem to be around 5000-6000 heating degree days.. those houses are inspiring!


We have already seen that solar PV qualifies as a super-abundant resource

Except for the painfully obvious fact that solar PV and other so-called "renewables" are utterly and completely dependent for their very existence, literally from cradle to grave, on a vast prior investment in industrial infrastructure that is 90% powered by..., wait for it..., FOSSIL FUELS! In short, not even remotely "super abundant", and getting less so by the day.

Funny how otherwise smart people can be so blind and dumb when it comes to their favorite techno-fantasy.


"Except for the painfully obvious fact that solar PV and other so-called "renewables" are utterly and completely dependent for their very existence, literally from cradle to grave, on a vast prior investment in industrial infrastructure that is 90% powered by..., wait for it..., FOSSIL FUELS! "

Gosh, Jerry, that applies to virtually everything these days. As my PV panels have been producing for years with no fossil fuel inputs since their installation (unless you include the rubber squeegee I use to clean them on occasion), I would say that they are far superior to most other energy sources in this respect. PV also pumps all of our water and circulates the active solar water heating system. Zero emissions, no repairs, no noise, no complaints; they just bask in the sun and do their job. I wish all of my investments were that good. I believe we have a different range of expectations.

Ghung (& Dohboi),

I realise I'm low on the IQ scale around here, however isn't there still the "replacement/longevity" argument? (What's a panel's efficiency after 25 years? Do panels generally survive that long? How are panels installed in the late eighties holding up? Links anyone?). For ones installed today, are they to be replaced by "more of the same", or are 2037 panels expected to be of far superior quality? Will there even be panels then?

Why not wait until we get it right and in the meantime do what needs to be done anyway (3 or 4 people in a car during peak-hour, one trip per week to the shop not five, etc... Oh yeah, silly me - that'd take away "choice").

I really don't see the point of current so-called "green" solutions. They just don't seem good enough to be a long-term/scalable solution for our grandchildren.

Cheers, Matt

There is an article about some guy in Vermont who bought some Arco panels in 1980 and decided to test them recently; still producing at or near full power, IIRC. My first Siemens panels (October 1994 production date) have been in continuous use since early 1995 and are still producing over their rated output. This one pumps water for the garden; about 250 gallons on a good day. It began its career powering a highway sign that was run over by a truck, then spent 6 years on the roof of my RV.


Two other identical panels pump all of the water for the house to a tank about 120 feet above the spring. I have 36 other panels, differing ages, not a single failure yet. [touch wood].

What was it you asked? Oh: "Why not wait until we get it right..." Gosh... not sure what to say. That seems to be what most folks are doing. I suppose we could have waited, pay the monthly power bill and go to Disney World every year. I still have to breath the nasty air and all that.

[edited to correct date]

Ghung, what is the setup you have in the background there for the organic/edible solar collectors?

Does the plastic cover everything , with mulch over the plastic, and the tomato in just a small hole, presumably with the dripper to the same point?

No weeds, but does the soil breathe with this arrangement?

Hi, Paul.

The white stuff is white landscaper's fabric found really cheap at salvage (I suppose because nobody wants white landscape fabric). Helps keep the super pigweed at bay. The drip irrigation saves a lot of water; we poke a piece of fence wire into the root area of each plant and just slide the tubing down it (no emitters to clog). That photo was 3 years ago just prior to moving the panel to its new mount.

Last year we used some black biodegradable "plastic mulch" (like commercial growers use) as an experiment and had amazing results. It holds moisture in the mounded rows, prevents weeds, and the worms love it. It also warms the soil (solar collector), allowing for earlier planting. We built the rows about three weeks before we planted; kills any weeds and draws in worms, etc.. Cut x-shaped slots in the plastic and poke the plants in. Add a drip tube to each plant and watch'em grow. We laid ours by hand (do not attempt on a windy day!) and piled regular mulch around the edges to hold it down.

Mulch between rows becomes next year's organic matter. It's not very 'organic or sustainable', I know, but it works great for tomatoes, peppers and cucurbits. I may be hooked. We got two 4400' rolls for $80, enough for 30+ years. It certainly frees up labor for other things. Plenty of air seems to get to the roots, as the worms will attest to. It also prevents over-watering from heavy summer downpours (bad for near-ripe tomatos) and prevents erosion and soil leaching. This is one high tech growing method that seems to really work, but it has it's trade-offs, like most things. This method could provide some major advantages in a subsistence/survival growing situation.

'organic or sustainable'
it's not supposed to be a religion <>?- )
Pragmatism rules in my book--in Darwin's too if I recall (okay not the sexual selection part but certainly in the eating part) . Some seem to forget that the Peak Oil we are talking about here is still running through 75mbpd of crude plus the other liquids. That is a whole lot of oil. Stretching that stuff out is a big part of what this is all about--I'd imagine the oil you save using those fabrics and avoiding food transportation costs (from places that may use the same fabrics) stretchs out the barrels some.

I think you've put the numbers here before but a refresher would be nice, what sort of payback time has there been for you PV system? Do you have extensive solar thermal as well? If I recall you are off the grid, but seem to have some crazy modern ammenities like dog dryers (I can see where they would make life more pleasant to canine lovers with sensitive olfactory systems). Yours is hardly a bare bones operation.

"Yours is hardly a bare bones operation."

Taking away all of the add-ons and "bonus features", I designed the house to be 'bare bones' in a sense. Passive heating and cooling, well insulated, plenty of ambient light, wood heat, integrated root cellar, gravity water; all may seem a bit primitive to most folks, but translate into a structure that would be quite livable without electricity and and fossil fuels, especially compared to most modern homes. Even the simple water heater in the wood stove will thermosyphon on its own, though not as efficiently as using a pump. I also allowed for a wood cook stove if it comes to that. Still shopping around for a good buy.

The garden could be gravity irrigated and has a small pond next to it if a bucket brigade becomes necessary. Plenty of natural mulch around.

As for payback in the financial sense, who knows? The PV system may never pay itself back in a one-to-one comparison of actual KwHs produced, but taking into account the avoided ~$16k cost of bringing in grid power when we began building, and factoring in the system as a whole (passive solar, spring water (didn't have to drill/maintain an expensive well), passive cooling (no AC bill), so on, I expect we're at or beyond the break-even point. Not being utterly reliant upon complex external systems has incalculable value, IMO. Of course, current financial considerations will become moot when the financial system crashes. Those who've paid these things forward will have an advantage (something we've realized over the last three years). What good is a house that you can't afford to live in?

Note: We didn't gain these advantages by throwing money into the system. We built our home, including the PV system and batteries, for significantly less per square foot than my brother built his similarly sized, well-built conventional home (nearby). These advantages are the result of design strategies, location and orientation, avoiding vanity add-ons, and a willingness to modify our lifestyle somewhat. We also used quite a bit of salvaged and repurposed materials.

Case in point: Our living area floor is the original polished slab, great for passive solar. My brother has carpet and hardwood which, in addition to the original cost, need to be replaced or refinished every few years. We've considered a surface treatment (tile, stain or terrazzo), but when my brother's girlfriend saw the house, she said she wouldn't do a thing to the floors ("They've developed a beautiful patina!") Area rugs suffice for now, and can be carried outside and beaten clean, as in the old days ;-)

The resale strategy is to stay put and turn the place over to whichever of our kids seems most worthy, which also takes depreciation/appreciation out of the picture. Other folks may have differing strategies... depends on one's world view I guess.

As for dog dryers, etc. ... I still earn some money grooming dogs, though I am moving away from that. I'll still groom our standard poodles, who currently have no practical purpose other than that they are remarkable, intelligent, superior companions, and are perhaps the most versatile breed there is. We also have a great little squirrel/rat dog that we rescued from the gutter....and a cat..

Have you tried newsprint, Ghung? I use black and white newsprint (free) covered with plenty of leaves to hold it down. It all decays nicely by the next year. Colored newsprint sometimes contains lead, so we avoid that. Water soaks through slowly.

I have read that red plastic actually improves your tomato production, according to the researchers, but never tried it.

Newspaper is great, but we don't have a good source (getting the tiny local paper online now). Some of the universities have found that different plants respond to different colored plastic mulch. I think a Study at UNC found that tomatoes grown on red plastic had a 12%+ production increase over black or white. I'm sure that commercial growers would see this as an advantage. Black was reported to be a good general purpose choice. We got ours from a guy whose machine didn't like the biodegradable stuff. It seems to have a different texture/stretchability. We laid ours by hand and it works great. I built a roller stand and we just pull it out, anchor one end and start stretching/anchoring along the row.

The machines are amazing; creates the mounded row, stretches the material and folds dirt over the edges. Another machine (depending on the crop) punches the holes and pushes the plants in. They also have drip tape incorporated into the plastic for irrigation, or a system that pulls/places the drip tape along with the plastic.

While some folks may disagree with using oil-derived plastics in this manner, it is a low till, low erosion and water saving method of increasing production of many crops. It also allows for reduced fertilizer/herbicide/pesticide use, reduces runoff of these chemicals, and increases growing seasons somewhat. It occurs to me that such a system could be pulled with draft animals on a smaller scale.

Thanks Ghung, I am continually impressed by your operation and how well it seems to run - to us remote observers anyway. I will (hopefully) have a project to create an urban farm later this year, so am interested in these sorts of things. A small commercial organic grower I know has used the black biodegradable plastic (comes from Norway!) and his comments are similar to yours, though without the innovative drippers!

I have long concluded that any mulch system is way better than none at all, and then you start splitting hairs about exactly which is best - though I don't like the non breathable plastic types.

I did see a very interesting one in Australia that used scrap pieces of drywall as mulch sheets around trees. They placed pieces around the seedling for a radius of about 2', and had them slope in towards the seedling to funnel rain. Kept weed competition away for about 2 yrs, the worms loved it as the birds couldn;t get them, and added gypsum to the soil (which it needed). Finally, they had the local landfill pay them to take away the drywall waste -$150/ton - as that was cheaper than the $250 to have a commercial recycler take it from this rural town.

Apparently this system doubled the growth rates and survivability of the eucalyptus seedlings.

I'll be using alder woodchips for my mulch this year - have tens of cubic metres of the stuff available. Alders are nitrogen fixers and their wood composts faster and grows more mushrooms than anything else around here (BC coast). When the forestry operations do their "regrowth", they try to cull out alder shoots, though they leave them, along the road edges. Where there are alders, you can see the pine/fir/cedar trees are visibly healthier and taller.

Best hopes for smart solutions for growing stuff!

I still use lots of organic mulch, but the "super pigweed" (amaranth) has gotten bad here and defies regular mulch; grows right through it.

Super weeds: Giant Pig weed in the American South

May I introduce the Giant Pigweed, our super weed. The video piece (Pigweed Story by ABC NEWS) shows this prolific crazy weed that is so strong that it can break heavy farm equipment. Monsanto, the company who created roundup throws the blame on the farmers saying they used too much roundup, which created the situation where the weed developed. Further comments from a company spokes person said that a fix would not be ready for seven years. Their argument makes little sense. The plant took on the resistant traits period, and then spread it to their friends.

Entire fields are being abandoned where the weed is out of control, and heavy equipment is useless.

I hope you don't get this stuff; prolific and nasty. It has deep roots and sharp spines that make hand weeding painful. The good news is that plastic mulch, especially if laid down several weeks early, seems to mostly prevent it from coming up. I suppose we could just let it grow and harvest the amaranth seeds :-0

Yes, you could just harvest the seeds. I have paid $10/lb for amaranth seeds that I mix into my oatmeal. Apparently they can also be ground to make a good flour.

Or you can eat the laves the same as you would for spinach;

more discussion here;

My organic gardener friend actually grows amaranth - a truly spectacular plant;

I mean really, a plant that grows without you trying, is immune to roundup, seems unbothered by insects, and produces high protein (15%) edible, storable grain - what's not to like?

Would be even better of someone brought a lawsuit against Monsanto for it....

If the roots and stems are as tough as you say, has anyone tried processing them for the fiber, say for rope, etc.? That way it is like pigs, where they use everything but the oink.


To be clear, the giant pigweed is a much tougher plant than the red amaranth pictured. The amaranth stalks are actually edible (and high in fibre!), I am not so sure about the pigweed. Can;t find any information about using it for fibre either.

It would probably make a good feedstock as a biofuel - harvest the grain, and turn the stalks into pellets.

In any case, it seems like a classic example of a weed being a plant that someone simply hasn't found a use for...

Sure is a lot easier to grow than cotton!

Thanks for the link, Ghung. It's VERY good to know PV has a longer life than a single human generation. Clears up a doubt.

Re my comment, "Why not wait until we get it right...", I did go on to write (in the same sentence), "...and in the meantime do what needs to be done anyway (3 or 4 people in a car during peak-hour, one trip per week to the shop not five, etc..." - it's a bit like my Auntie Liz, diehard, self-professed greenie taking offense when I asked whether the 4 tonnes of steel I-beams in her new "green" house had been manufactured here in Australia or overseas in China. Or when I suggested the old house they'd knocked down was sound enough, why hadn't she simply "greened" it up instead of starting from scratch?

Seemed kinda wasteful.

I try not to be too wasteful myself, that's my input (and point). For much of the time (greater than 90%), I work from home, travel by plane perhaps once every 5 years, ride a motorbike, holiday locally with family (within 200km), buy good gear (my work computer is 15 years old, for example), etc. Why installing PV panels and other devices (that fundamentally are offered up as BAU solutions) take precedence over ridding the world of "the awful waste" of my fellow Joes and Janes continues to baffle me.

For sure I'm pro-green, but Jeebers, let's address the other elephants (waste and wanting more and more) first!

Cheers, Matt

To add a wrinkle onto the PV longevity, I am reassured that we have SEEN PV that lasts as long as it does, and there has been subsequent research in order to eliminate the yellowing and other aging of the encapsulant, which is the clear coating that keeps the cells and the electrical connections away from air and moisture.. but we are also seeing the PV industry dutifully scrape every cost in the process down to the minimum, in order to satisfy this constant call to reduce cost, and I wonder how much planned and unplanned obsolescence is becoming part of the panels that are being built now, as they get thinner and cheaper.

So, we do KNOW how to make panels like the ones that have lasted for ages, and I can only hope that that institutional memory has been written down in places we can get back to (nudge, nudge, open-source libraries) if we find we have turned down dead-end paths, and need to back up.

Not that I relish giving fuel to those who will despise the technology overall, but I think these are valid concerns.. which is the same reason why I need to go down to the ancient housing salvage store to get a decent Doorbell any more!

You still get what you pay for!.. somehow or other..

My dad's hot water panels have worked for going on 30 years now. Last year, he had to disassemble them and reattach (via tie wire) the copper pipes to the aluminum plate, and give it a new coat of black paint. It's back in use now. Also, he has gone through a lift-pump, although the new cartridge models last a lot longer I expect. Myself, I've had a system for 6 or 8 years, and I just had to replace the glycol, but that's it. My dad's system is a drainback, so he has to flush it and replace distilled water every couple years.

They say the payoff is 10 years in economic terms, but heck, that sure competes favorably with the trajectory of most people's portfolios. I call it a real investment. One of those things you spend money on now, and it keeps paying you back for a long time after that. A very long time in the case of solar. Pretty much as long as the place is still standing for passive solar.

Best hopes for hot showers,

Here, Here!

It's amazing how the picture of PV gets painted by some folks as if it was simply dredged out of a barrel of crude, as well. As you say, the manufacturing system of the whole industrial world is currently tied to oil, but how many of the thousands of products that come from it even start to return their invested energy, let alone surpass it? And can we start to look at the specific processes to identify where PV can be independent of Petroleum?

It seems to me there's no better place to remember that 'correlation doesn't equal causation' ..

Ok, I'm off to cook some dinner and restore my blood-pressure a little.

Everyone be nice now! Each of these kids has a mother!

I was wondering when someone would bring up this tired old argument, which basically boils down to saying that we are currently in an energy regime that is dependent on ff.

Well, duh.

That doesn't mean that renewables could never be produced with any other power source.

Funny how otherwise smart people can be so blind and dumb when it comes to their favorite lame argument.

There are real arguments against the viability of renewables for running BAU, but this is not one of them.

Not pointing the finger at any one person - this is an argumentative season - so posting this in contentious threads -

Please review the Readers Guidelines at, particularly these points:

2. Make it clear when you are expressing an opinion. Do not assert opinions as facts.

3. When presenting an argument, cite supporting evidence and use logical reasoning.

4. Treat members of the community with civility and respect. If you see disrespectful behavior, report it to the staff rather than further inflaming the situation.

5. Ad hominem attacks are not acceptable. If you disagree with someone, refute their statements rather than insulting them.

Or, as my mother would say, "Pleasant voices!"

Thanks for trying to keep us civil, Kate.

. . . or, "inside voices!" :]

Fortunately, our abundance of fossil fuels is beyond substantial. And then we'll develop the hydrates!

That's why it's called "transition".

The only reason why PV and other renewables are not manufactured using renewable energy is because the industrial infrastructure was built to use fossil fuels.

Anything requiring electricity or process heat to operate doesn't really discriminate on how that heat was generated, or those electrons moved, and you can even actually smelt metals using solar energy, if you have the right gear. We don't.

As for transportation, trains can be run on electricity, and thus renewable energy, and ships were for centuries before the advent of steam engines. Don't poo-poo that concept as archaic: many cargo shippers use big kites to help reduce fuel consumption and have otherwise slowed their pace to near what a wind-powered ship could get as a further cost-saving measure.

So, yes, you go out and buy a PV panel and it was most definitely made and shipped with fossil energy.

But it doesn't NEED to be done that way, that's just the momentum of the extant industrial infrastructure.

Cheers yourself,


This guy has been working on a low-tech solution to the tracking problem

I was surprised to see a piece posted by GTA that was not completely dismissive of renewables.

It is indeed good that there is very great promise for solar beyond standard PV.

The only way all of these plus wind...could come anywhere close to supplying a large portion of our energy needs any time soon is through their large and rapid build up corresponding with a large and rapid build DOWN of our energy requirements.

We waste so much energy in so many ways in the US, that a reduction by half should be achievable with little immediate real pain. Another halving should be achievable with a bit more creativity and a bit of pain. One or two more halvings will be difficult but probably necessary. We should keep in mind that domestic use of petrol in the UK during WWII dropped by 95%--those are the kinds of reductions we need to be aiming for. In GW, we are facing a crisis that threatens our existence, after all, every bit as much, and even more so, than in WWII.

Once we get our energy requirements down to 5-10% of current needs, all sorts of things become possible. Short of such cuts, almost nothing is realistically possible. As Nate says, we do not have an energy shortage so much as an expectations longage.

Making such cuts politically palatable to the public is another issue. But then, we are experts at creating advertisements to make ourselves do all sorts of much crazier and more dangerous things.

We should keep in mind that domestic use of petrol in the UK during WWII dropped by 95% -- those are the kinds of reductions we need to be aiming for.

Go on, try to get elected under that banner.

"Making such cuts politically palatable to the public is another issue."

Who wants to get elected?

No need. That would be 'outrunning the lion..'

.. just figure out how to survive on that remaining 5% (or whatever it actually is), and you've outrun all the slower gazelles!

In GW, we are facing a crisis that threatens our existence, after all, every bit as much, and even more so, than in WWII.

Grotesque statement.

Sometimes the truth can be grotesque. That doesn't make it any less true.

The global CO2 heat-forcing experiment now underway will likely make WWII look tame. Probably tens of millions versus billions, and that's IF our descendants manage to survive it at all.

Some 2.5% of the worlds population was killed in WWII, double that again in injury, a nearly successful attempt was made to annihilate entire ethnic groups, and Europe's and Japan's infrastructure was raised to the ground. I hope to see a decline in the burning of a cubic mile of oil per year in the atmosphere. But the idea that a global temperature increase over 100 years of 1-6degC would do worse than WWII is either a grotesque ignorance of that war, or a grotesque egoism and infatuation with the issues of the modern day. It is also dangerous if allowed to eclipse attention to other issues such as infectious disease (HIV, malaria, tuberculosis, influenza), education, basic nutrition.

I don't think you understand the implications of an increase in temperature of 5 or 6C. Here's just one problem. The human body cools itself by sweating, the sweat evaporating to remove the heat. However, if the dew point temperature is close to the body temperature, say 95F (35C), the sweat can not evaporate from one's body. As it is now, in summer some ocean locations, such as the Gulf of Mexico, experience water surface temperatures approaching 30C. If that temperature were to rise to 35C, the air above being saturated would result in a dew point approaching the deadly level. Without some sort of cooling shelter, people could die, even while sitting in the shade. And, that's just one of a host of other impacts, which combined could result in vary many deaths...

E. Swanson

..not to mention spreading the opportunities for those infectious diseases, and any number of molds and fungi to propagate in the new temp and humidity balances.

It could become an Axis of Weevils!

...and, I have to add, the loss of species, the extensive drought and flooding, the acidification of the oceans that will accompany such a CO2 driven temperature rise, the rampant wrecking of existing ecosystems (on which we happen to rely for - well, life) will lead to starvation and death far in excess of that caused by WWII.

It ain't gonna just be a 'warmer and cozier' planet.

It also isn't going to end after a few years. With a lot of the effects being cumulative.

I am curious, what sort surface temperatures in bodies of water like the Bay of Bengal and the Gulf of Thailand today? And not to be flippant but if temps do rise to the point people are dying sitting in the shade near the Gulf of Mexico likely people will abandon such places. That of course will put population pressures on the more livable places remaining and of course if the pressures are too great there will be conflict. Speed of climate change (up to a certain temp that is) is everything too big a delta and it will get messy.

The wet-bulb temperature (Tw) at which a human body can't shed waste heat to cool off by sweating anymore is about 35 degrees C. At this temperature and above humans can't stay for prolonged periods (hours) nor do any work because of overheating. In other words: stay too long in an area with such temperatures (and humidity) and you will die.

Luckily such situations are not occuring (yet) as in deserts and tropical regions Tw never exceeded 31 degrees C during the last decade. But 7 degrees warming could render large areas of the earth off-limits to humans and even lower temperatures prohibit people doing any work because of the much-reduced ability to sweat off waste heat.

(A) Histograms of temperature (Black), Maximum Temperature (Blue), and Wet-bulb Temperature Tw (Red) during the last decade (1999–2008). (B) Map of Wet-bulb Temperature Tw.

Source: An adaptability limit to climate change due to heat stress (Sherwood 2010, PNAS)

Quite a risk if we're not actively going to reduce our GHG emissions.

It is the 'prolonged period' part that seems fuzzy to me. I've had heat stroke in the tropics as I was first coming down with dysentery, so I know the pain first hand, but I've worked in some darned hot spots for extended periods when I was healthy as well--though probably never more than 6-8 hours without some break away from them.

from the linked abstract
While this never happens now, it would begin to occur with global-mean warming of about 7 °C, calling the habitability of some regions into question. With 11–12 °C warming, such regions would spread to encompass the majority of the human population as currently distributed. Eventual warmings of 12 °C are possible from fossil fuel burning

I'm guessing that is talking burning all the coal in the 12°C scenario. I'm all for leaving all the coal in the ground we can somehow manage to for others to use in less less harmful ways (if at all) a few millennia from now myself. I hold out little hope we won't burn the oil and gas we can just as quick as we can, regardless what sort of economic and political upheavals churn about the globe.

We get over 33C and high 90s humidity here during the summer. Just breathing is enough to break out in a sweat. You learn to drink a LOT of water and electrolytes - WHO style powder sachets, homemade and Gatorade. About the only way to get relief is under a cool shower on standing in the rain. You really want to stay absolutely still without tensing a muscle, twitch=sweat.


HERE's a graphic showing current ocean temperatures for the Western Hemisphere. While not what you requested, it shows the temperatures in some locations to the west and south of Mexico and Central America approaching 30C. Wait a few months and there will be patches of red on that graph. Of course, SSTs aren't air temperatures, but over the ocean, they are close...

E. Swanson


I bookmarked the parent link, it will compliment the NSIDC site I monitor very nicely.

Where there's hail storms, solar panels on your roof will be smashed to smithereens when some large hailstones hit them. A large chunk of hail will punch a 4 inch hole in the galvanized roof panels on a round steel grain bin. When larger than normal size hail hits, it will rip right through a solar panel. Losses, not any gain. Roof mounted pv panels where there's hail is probably not a good plan.

You would think sheet metal would be tougher than that, but it's not. I saw a radiator cap fly right through the hood of a pickup truck one time leaving a tear in the metal about 3 inches in length by about 3/4th inch wide. It took off from the radiator like a speeding bullet.

You'll need shelter to protect the pv panels from potential damage when severe weather happens and it will. Increases costs considerably if you have a cement block shelter for your pv panels. Build so they won't get ruined.

A passive solar panel I installed ca. 1981 had a low voltage fan which circulated the heat absorbed from the black surface on the vertically installed panel on the side of a house. Worked fairly well, even during cold days.

Hail damage to PV panels is fairly rare. Mine have withstood golf ball+ size hail with no damage (yes, I was freaking out). Also, my panels are insured for their original purchase price. In fact, a big hail storm would allow me to almost double my capacity at today's prices ;-)

I think it is a bit naive to assume insurance that is affordable to the average homeowner is going to survive the coming decades.

Granted. In my case I can run to the utility room (my wife calls it the inner sanctum) and switch the trackers to manual, tilting all arrays to their full east position, almost vertical, offering some protection. Then again, nothing's perfect, as some folks seem to insist renewables be.

I've been fielding statements about why PV or passive solar, etc. doesn't or won't work for 16 years now. 'Naive', they called me. One guy I know went around telling folks that I have a secret grid connection somewhere. Jeez!

I'm glad that your passive system works to your satisfaction. Adding manually controlled movable insulation, such as insulating curtains, works, but someone must be on the site to actuate them. Or, one could install a mechanical system to close and open shutters or curtains, which adds both to the complexity and expense. My negative experience with passive led me to build a house with both passive and active system elements and I expect to add insulated shutters later, perhaps using 2 inches of Styrofoam sandwiched between some 1/4 inch plywood.

Weather has something to do with it as well. One interactive web site google found says that my local heating degree day total for 2010 was 6762 and for 2011 it was 6369, using a balance point of 70F. For Murphy, NC, 2010 was 5264 and 2011 was 4881. One should not forget that if one can live with a lower inside temperature, the heating degree days demand would be less as well...

E. Swanson

Depends on what you use for your clear lid. Ribbed polycarbonate is pretty tough stuff, supposed to be hailproof. My dad (in Florida, abundance of high-angle sun) uses some translucent fiberglass panel.

I'm curious about the heat estimate. When I was a kid, when my dad built his first solar panel using old glass from a recycled sliding door, when we set that thing down in the (summer, mid-day) sun, the temperature inside shot up to 220 inside of 5 minutes. I think that the use of actual glass gives you a miniature greenhouse that lets you exceed 91C. Another system that he built for some friends managed to heat a couple of hundred gallons of water to I think 190F (88C) when they left on a long vacation -- the reason I recall the temperature, which seems improbably high in light of the physics above, was that we had to go over before their return and drain a good portion of that deadly-hot water out of it. Would the IR-reflecting window glass used on the panel allow such a high temperature, or have I misremembered something that is impossible? (And yes, he insulated the backs and the connecting pipes and the tanks.)

That is the principle behind hybrid solar power systems.
You run a cooling fluid behind the solar cells to keep them from overheating and collect the heat to use elsewhere.

They are more complicated, but you get more benefit at the same time (hot shower and radio from the same unit!)

The temperatures quoted of 88 deg C is perfectly normal if there is no heat dump to control excess heat. 130~150 is possible on hot Days at the panel if the system is allowed to go into stagnation. I normaly set Max cylinder tem at 85 Deg c along with mixervalve on draw off set to about 50deg.
When tank temp exceeds 85 deg I wire extra relay on out put from controler to bring on centeral heating pump (with out boiler)to dump excess heat .
Efficiencies quoted at 60% are way to low decent flat panel will gige around 75~78% Vacuum tube about73% but with a much lower drop off in losses as the temperature difference rises between tube and exterior (Tm-Ta)
Irish Made Thermomax efficiency 77.9~73.9% one of the better ones

By the way Got text from customer today to say his 120 tube 10.5 Sqm vacuum tube system had raised 400l tank to 55 deg today before underfloor heating had turned on in the evening. Outside temp 4 deg clear and sunny all day Dublin Ireland

The water can get hot enough to melt foam insulation.

I'm not sure what temperature that is. This happened middle of last summer when the sensor came loose from the panel and was setting on the roof. Here in Florida it continued to work well enough I didn't realize there was a problem until I saw the loose sensor.

One issue in the design I am doing is keeping the collector plate off the polystyrene slab, that will insulate the back, for just that reason. The foam rubber insulation has a higher temperature rating 110 C IIRC.


Where there's hail storms, solar panels on your roof will be smashed to smithereens when some large hailstones hit them.

This is simply not true. It is amazing how much this myth gets parroted around.

Question: Are skylights non-existent in hail country? (How much of the country is 'hail country'?)

.14 lbs is not much weight. If you are ever caught in a thunderstorm that produces hail, it hurts a lot and you take shelter fast. A baseball sized hailstone falling from 30 thousand feet will hit hard.

They may be hail proof and may not sustain any damage, but I wouldn't mount them on the roof where I've seen it hail more than just a few.

.14 lbs is not much weight.

It is the approximate weight of a 2" ball of ice. And the speed at the test is approximately that off such a hailstone falling from thousands of feet. How often does 2" hail occur where you are from? (Around here it has never happened in recorded history, AFIAK.)

Once it reaches terminal velocity drop height loses relevance.


Compare Solar One to a Nuclear Power Plant: generates 19,700 million kilowatt-hours annually. So to replace one nuke plant you would need 150 Solar Ones at a cost of $40B and 240 square kilometers of land.

The Chicago metro area (pop 9.8M) consumed 292,000 million kilowatt-hours of electricity in 2005 (most recent data I could find). So to power Chicago with solar thermal would require 2,179 plants and 3,500 km2 of land at a cost of ~$600B. To put that in perspective the entire city of Chicago is only 606.1 km2.

This is the heart of the problem for solar - land use and cost. Do that math.

"This is the heart of the problem for solar..."

The problem is us you... comparing apples and oranges, not to mention your expectations.

Of course you could eat your lunch off of them, and raise your kids below them.. but who's counting? (You can also privately finance and insure them.. cool huh?)

The Chicago metro area (pop 9.8M) consumed 292,000 million kilowatt-hours of electricity in 2005 (most recent data I could find). So to power Chicago with solar thermal would require 2,179 plants and 3,500 km2 of land at a cost of ~$600B. To put that in perspective the entire city of Chicago is only 606.1 km2.

To put your argument in perspective, the land area that matches the population figure you quote is actually 28,116km2.

And we can take this further, because you actually didn't 'do the math' right at all.

First, I think your number for electricity consumption is wrong. Here's the reference I'm using for Chicago CMA, which is slightly smaller than CSA.

85,498,236,248 kwh
page 11

That's 85.5 TWh.

Divide by 8760 hours in a year to get 9,760,072 kW average power or 9.7 GW

Now I'm going to use PV instead of solar thermal because I know more about it. Convert to thermal as you wish.

At a capacity factor of .15% , to supply 9.7 GW you need 65 GW or 65,000 MW

Now to convert to land area, we need a reference. I'm going to use the system on the "Sunset Reservoir San Franisco California" (type that into Google Earth). It's 5MW, and measures 300m by 175m, or .052km2. That's 95MW/km2.

65,000 MW at 95 MW/km2 = 684 km2

Also at $4/watt that would cost ~$260 billion.

Let's assume for arguments sake your figures are correct. Since fossil fuel prices are still relatively affordable, I would think investing now in the construction of Solar power would be the wisest investment since the on-going operating costs of Solar plants is relatively affordable. It certainly beats giving $700 billion to Wall Street.

240 km2 for a solar thermal plant is much smaller than the evacuation radius of 80 km (20,100 km2) needed in the event of a core meltdown and breach of the containment structure. There is no failure of a solar thermal plant that would require such a widespread, lifelong evacuation. After the Byron Nuclear Generating Station is decommissioned, there is no guarantee the nuclear fuel and other radioactive equipment will be transported to another site for disposal. The entire 7.2 km2 site may become a nuclear waste dump unable to produce power again for millions of years.

So to replace one nuke plant you would need 150 Solar Ones at a cost of $40B

Sounds cheap. How much does that one nuclear plant costs?

Just from memory, I will throw out a WAG of ~ 5 Billion U.S. Dollars, for a plant in the U.S.

The author of this blog claims that, with 'certify once', serial-produce thereafter streamlined engineering, production, and licensing/regulatory processes, nuke plants could be built for ~ $500M U.S., in the U.S.

I have difficulty buying the lowball estimate...

The low sounds too low but a standard design being production lined would have a big effect on cost over ones made individually by hand.


I used the $5B number because that is what I could find with a /very/cursory Google search...from my memory of actual costs of the most recent reactors, and applying a bit of judgement to that on increased costs for licensing/safety features post-Fukishima, and assuming a continuance of the 'custom' every-time new build/license approach...I honestly would WAG $10-12B right now...

...perhaps a more streamlined licensing regime and a more 'assembly-line' modular part production approach might actually result in an improved $5B per each complex price...vice $10-12B.

One thing I think about is that even though one can streamline the qualification of the reactor parts/modules, each site will have different site-specific risk factors...seismic risks, tsunami, floods from rivers, hurricanes, tornado, terrorism events, different soil/rock substrates for the excavations, etc.

...not quite as easy as parking an assembly-line-made RV at various RV parks across the country...

Thanks, Tom, as always! (and Gail too)

As I've posted before, building a passive/active solar home has been perhaps the best investment of my life. A view of the south side of our home, shortly before completion:


Passive solar gain provides the bulk of our heating during our 4300+ heating degree days, this despite a climate with an average 65 inches of rainfall. Carefully calculated roof overhangs and deciduous plants provide shade in warmer months. Thermal curtains prevent much of the heat loss at night and on cloudy days, though, unless it's really cold, we don't bother to close them. It just hasn't been necessary most of the time. Wood heat is used as a booster/supplement rather than a primary heat source except during the coldest cloudy periods. Cold, clear winter days see amazing heat gain. No grid or fossil fuel energy has been used to heat the house in years, even though we have a propane backup for the radiant slab system (code required). The small windows at the top of the house open to provide excellent passive cooling in summer. Ceiling fans do the rest (excepting a tiny window AC unit in our bedroom for my wife's hot flashes on the warmest nights; rarely used).

Thermal storage: Besides the thermal mass of the slab and house, thermal storage is provided by a 450 gallon insulated plastic water tank; inputs include two (soon to be three) homebuilt solar water heaters, the wood stove and a resistive dump load for excess PV production. I plan to utilize heat from our diesel backup generator as well at some point. This provides radiant heat to bathrooms, etc., which get no direct solar gain, and supplements radiant heat in other spaces as needed. It also supplies all of our domestic hot water via a copper coil heat exchanger. Very little high tech involved in any of this excepting the PV system. Simplicity begets reliability, and most of this is modern application of very old technology. I've learned to question most complex high tech solutions for marginal efficiency gains.

Here's a Mother Earth DIY article some may find useful: Solar Heating Plan for Any Home

Tom, I didn't see a mention of Space Solar Power in your solar article.
The sun delivers about 9.6 times more energy to a PV array at GSO compared to one on your roof. Even better, SSP is baseload - 24/7, clean, safe and reliable. IF you convert the intermittent output of ground PV or wind to baseload through storage, the advantage of space based solar power increases.
Using the lowest cost bulk energy storage now known, CAES (Compressed Air Energy Storage), Space Solar Power would deliver at least 71 times more energy to an electric grid, and that assumes you can predict the weather perfectly. SSP's advantage is likely over a one hundred times better than wind or ground PV in real world conditions. I can show you the arithmetic if you like.
The world SSP leader is probably Japan's SSP consortium with a $2 Trillion yen project to build a prototype SSP satellite by 2025.

Space Solar power was a national debate topic
this year. ("Loyola Sacred Heart High School's speech and debate team racked up its 29th consecutive state championship title, and once again made national records... "Student body president Tawnie Kerr did policy debate. It's a tough assignment. She and her partner explored the question of developing space based solar power.")

Space Solar Power Institute
Space Solar Power Workshop

"Space Solar Power would deliver at least 71 times more energy ..."

Why must the solution always be more? Just askin'...

It'd be interesting to see Dr. Murphy do a "Do the Math" column on aggregate probability as it relates to thresholds and boundary conditions for something to actually happen in the human world. That world is a complex and chaotic place, but getting a first-pass perspective on the practicality of something need not be complex.

That is, for a given project, how many things need to happen in timely sequence while being robust against probable real-world perturbations and hiatus, and what is a reasonable individual probability of each? Multiply those probabilities. Voila.

For instance, mining the moon for He3 to run human civilization on fusion power, starting from the world and politics and scientific expertise we actually have, has a number of rather unlikely thresholds to surmount in the time available. Similarly, while something like "space solar power" looks good from the point of view that "if we had it and it worked, the numbers would be good", it fails some basic tests in terms of likelihood of implementation by humans as they actually exist in the Now, or likely Future.

Seems like for that class of project, there's a tacit "step one: secure a benevolent and wise world dictatorship". Otherwise one gets into problems involving the likelihood of actually lofting a space armada in an age of financial hardship and shrinking economies, and people taking umbrage at various aspects of it.

This is the sort of thing OldFarmerMac would have pointed out, but since he's not here, I'll note it.

Cheers, and another good keypost.

Mining the Moon for He3 is a silly goal while He3 fusion has not been commercially demonstrated. He3 is readily available at your local chemical supply house.
It's much easier to collect the energy from the BIG fusion furnace already up there. They say it has enough fuel for several billion years. That's a good next step.

a silly goal

Policy (both Government and Private) doesn't have to make sense.

Besides, once we've got a moon mining operation up and running, then obviously HE3 fusion will suddenly become practical through the magic of Cornucopianism. :lol: We have to find an accessible reserve of Pixie Dust, though.


Some time ago I witnessed a discussion on Marginal Revolution (a blog about economics) where people were claiming that, if a futures market was created betting on the Higg's boson existence, we'd be able to know how probable it was. (That was before December, 2011) I was a bit disturbed about the rationale, thus I asked them to confirm it, and some people did confirm.

So, I guess there won't be a lack of people beliving that if we set a He3 mining operation, that we'll be one step closer to a working fusion reactor.

I'm still not quite confortable with that knowledge, but, well, it is this way.

Folks don't usually have much interest in poorer performing energy sources, consumer goods, drugs, farm land, etc.,

I'm not much of a theologian, but Isaiah 9:6-7 answers your question more directly, Ghung.

So, hows that early launch date for the Solaren concept coming along?
There's nothing on their web site these days...

E. Swanson

It cost $1,000 to put just one pound of equipment into low earth orbit, it would also have to be a polar orbit which would cost even more, kerosene is used mainly in the lower stages and the price of that will rise. you would have to put thousands of tons into orbit, that's forgetting all the auxiliary equipment both in space and on the ground,the price is too high it is just a wet dream.

...besides, we'll be too busy paying for Newt's moon base ;-/

The cost of launch depends on the flight rate. High flight rates, such as SSP requires would drive the cost below $100 per pound to orbit, which enables SSP.

Financially, SSP is like building Hoover Dam in orbit, the cost is all up front. Nearly no fuel cost and very low maintenance and operational costs.

Polar orbits are not what you want. Geosynchronous is the correct orbit to get 24/7 sunshine. We have much experience there. Polar doesn't provide 24/7 sunshine to the Sunsat and doesn't provide a constant delivery angle (geometry) to the grid.

Please start being realistic, it has cost us up too present 100 billion just to put up that international space station in low earth orbit, what is it 250 miles, Geosynchronous orbit is a hundred times further out and you would have too you would have to put up there perhaps a hundred equivalents in weight up too that orbit. The cost is just mind boggling. That's apart from the waste of dumping thousands of rockets into the ocean, and what for a solar panel that gives 71 times more power during the day than one on earth. This is too ridiculous for words, perhaps the best and politest description of this boondoogle is pie in the sky.

I don't if space solar will prove unworkable, but it is not because of those reasons.

'We' did not put up the international space station, the government and NASA did with an expensive vehicle designed to haul people around re-enter the atmosphere with wings. Private enterprise can do things a bit more efficiently. Lift costs are now $6 million / ton to LEO* and $13 million / ton to Geo sync and falling, with costs posted on the web by the launch company for all to see. For comparison that's $3 billion to launch the 450 tons of ISS. No, thousands of boosters need not be thrown away. The USAF came up with a concentrator design with power density 1kW/kg, so a 4GW/4000mt array costs $52B to lift to GEO, and likely $18B by next year with heavier lift vehicles*. That's $4.5/W, better than US nuclear on terra firma.

The energy to lift to GEO appears to be about 360MJ/kg (35.7k km, 3.1km/s). The payback time (ERoEI) for a 1kW/kg solar array, lift energy only, is then 4-5 days, times the loss factor for transmission back to the surface.

* $2 million / ton to LEO in 2013.


Please explain too me, what don't you understand, That is still $1,000 a pound too low earth orbit and using your figures over twice that to geo-sync-orbit . That is $2,000 to get one pound of panel up to Geo-sync-orbit, a 250 watt panel weights approx 40 pounds that means if my maths are right that it is going to cost you $80,000 dollars to get one panel up to the right orbit. I think first solar has got its prices down to $1/watt which puts the panel price at $250 dollars a panel which means that for the price of getting one panel up too geo-sync-orbit I can have 320 panels at zero-sync-orbit. Now ask Ghung or any of the other PV aficionados what they would prefer. 320 panels producing electricity now at zero-sync-orbit, or one panel at geo-sync-orbit maybe in 20 years time. Where he only has to call his local dealer if one goes wrong who, sends out a technician from the local town, who doesn't have to travel the equivalent of twice round the world to do his job.

The solar arrays used in space are much lower mass than those on Earth, since there's no gravity, winds, rain or snow. The arrays are typically constructed of thin sheets of plastic, which may be stored in rolls similar to a window shade. However, the vary large scale of the proposed solar power satellites would require very low mass structures, both for the arrays and the supporting structures. The lift calculations must also include the mass of the support structure, the electronics and the antenna used to beam down the microwave energy, as well as any rockets and fuel required for station keeping and attitude control. Some proposed designs use reflectors to concentrate the sunlight onto a smaller area, thus reducing the area of the PV cells needed to produce the desired power. Repair would most likely be performed by robots, which would add to the complexity of the overall system, thus further increasing the cost...

E. Swanson

...he only has to call his local dealer if one goes wrong who, sends out a technician from the local town,..."

I'll take it one step farther; I'm my own technician. For the most part, if I can't fix it, I don't want it. I prefer to be the master of my machines rather than a slave to the machine's servants. In fact, I view all of my gizmos as transitionary devices needed to ease the withdrawl of me and mine from our addiction to unsupportable and unnatural infrastructure. We're heading back to what is the normal state of being human. As Greer points out so eloquently this week, we are all slaves to the machine; have, in fact, become one with it.

Peak oil is thus a predicament rather than a problem, since nothing we or anyone else can do will make it go away. Instead, we and our descendants down through the millennia to come will have to live with the reality of a world much less lavishly stocked with concentrated energy sources than the one our ancestors inherited a few short centuries ago. The task awaiting us and our descendants is that of finding creative and humane responses to that implacable reality. To that challenging and rewarding task, in turn, the current obsession with fantasies of salvation via machine offers no help at all. Quite the contrary, by distracting attention from the adjustments that will have to be made, the obsession makes the work ahead of us more difficult than it has to be.

The second sense in which the obsession with machines gets in the way of a useful response to the predicament of peak oil is that it pushes responsibility for doing something onto someone else. I sincerely doubt that any of my readers have any influence worth noting over the decisions involved in building giant wind turbines, say, or developing thorium reactors, or turning some substantial fraction of Nevada into one giant algal biodiesel farm. This makes it easy to insist that steps like these are the appropriate response to the coming of peak oil, since the people doing the insisting don’t have to follow through on the insistence; it’s all somebody else’s job.

It's easy to spot the folks who've become part of the machine. Despite my perhaps misguided tech solutions to providing most of our energy needs, most all of these solutions require my active participation, my oversight. While some here may posit that automation "frees" them up to do other things, I submit that the other things they are doing are virtually all in service to automation, and the faux security they think it provides. Where's the fun, the humanity in that?

Spaced based energy?! We already have space based energy; always have. More concentrated sources of energy are the devil that will destroy us; likely already have. Blasphemy, I know...

a 250 watt panel weights approx 40 pounds

Please read again. The USAF design uses reflective concentration for most of the collection area which focuses on a small area of highly efficient PV (up to 35%), which totals to 1kg/1kW (450W/lb), or so is claimed the USAF. I don't have a handle on the engineering details, but I don't see any physics standing in the way of 1kW/kg. Remember the solar insolation at Geo is 1366W/m^2, round the clock. Much of what get's sent to orbit would effectively be polished aluminum foil with some mechanical support. So in your calculations, look at the mass of Al foil per meter squared, the cost of Al foil per meter squared.

BTW: $6000/lb to GEO w/ light lift, maybe half that with heavy next year.

Well, let them convince the investors, I have listened to these Space proposals and think it's simply babble.

Then again, we have Jerry and company who are telling me that PV itself is babble.

It's funny enough to make a musical out of.. but meanwhile, I just had my lunch and am now in my office, basking comfortably in both places under yesterday's sunlight, with a very modest little system under a 40 watt shell panel and a mere 12ah storage cell. I don't need to convince anyone but my wife, and that bright source over the Sink area has brought this issue well forward in that regard.

Finding from the NSS report:

Achieving launch costs of $200/lb or $440/kg could make the Commercial Baseload feasible, if the energy were sold at @ 8‐10 cents per kWh.
So still a factor of 15X or so to go on lift.

I just skimmed this paper at your link.

I found this paper to be long on (fuzzy) words and short on numbers (let alone any substantive math).

There was a lot of 'We recommend that government agency 'X' be tasked to do 'Y', and 'some agency' be tasked to do 'Z', etc.

As other here have said, if this is practical/feasible, then the investors will fund it, including governments.

I am not holding my breath for the day we will see those nifty-looking SBSPS systems gleaming in orbit (per the nice artist renditions in the paper).

The spacelift and the on-orbit engineering, both for assembly and O&M, will be a lot more complex and expensive than some folks are imagining.

I'm only interested in the long term feasibility, as I don't see SBSP economic feasibility absent a dwindling of coal and gas which appear to be decades away.

Curiously, it seems common place on TOD to follow a complaint about a lack of detail or mathematical basis with predictions lacking any detail or mathematical basis.

The concept certainly doesn't require breakthrough 'warp drive' or 'Unobtanium' required...but I do not judge any large-scale Space-Based Solar Power implementation to be economically feasible in the near future.

As far as "...mathematical basis...and ...detail..."...I apologize, I do not offer my own detailed engineering and business case analysis...I simply skimmed the paper (and I have read about this concept for decades) and I stated that I did not see the ;'numbers being run'.

If any nations want to push this noodle, perhaps Japan then Germany would top the list...China may be interested as well, given its population and ambitions to raise its 'standard of living'.

However, any large-scale Space-Based Solar Power implementation (and by 'large-scale I mean providing most of the trons for just any one of the4 three countries I mentioned) would require a global consortium, a World-wide my opinion.

...I do not judge any large-scale Space-Based Solar Power implementation to be economically feasible in the near future.

Agreed. Though again I assess the major reason being ample terrestrial sources that can produce electric power for 10-11 cents / kWh for decades to come (fossil/nuclear now, nuclear/solar/wind soon), and SBSP staying just out of reach as more expensive, but not a lot more, for when it is eventually needed in the future.

I agree that large-scale SBSP is not impossible in the future...many, many things will have to 'go right' for this to happen, though, IMO.

As a geek I like the idea of space-anything, but I think the costs are not likely to come down 15X. I suppose anything can happen, but
kind of makes it seem unlikely. If we assert real inflation at 10%, then in 7 years, the lift cost would have to be down 30x, I would think. Plus rockets run on fuel, and the BRICs sure seem to be able to buy up GNE, especially w/ western economies tanking. Of course, a realist can't be too developed-world-centric these days; I can see the Chinese or Indians actually launching some arrays, and maybe Brazil down the road if their pre-sal operations pull in some real tech. As a nation, it never hurts to be able to give free (or even nominally) power handouts at will, it's a huge green national-pride emblem, and oh, yeah, everyone down below sees the power density in that beam, even if the subject never comes up...


Once we've got thousands of kW in orbit supplying us power, we've also got weapons to attack hostile alien fleets with. Just turn the CSPs around and melt their ships. :)

You are going to need a couple of very long pipes for space solar heating.


The Sun, on the other hand, at 5800 K, emits 64 MW per square meter!

It is amazing the amount of energy the sun is emiting per square meter.

and the absolutely horrible efficiency of the delivery system. 64 MW per square meter and we get what, 1000 per? For a couple hours a day? Pathetic!!

If you want to enjoy the full 64 MW, all you have to do is move to the surface of the sun. I'm glad the delivery is as "inefficient" as it is. A misuse of the term, really.

Oh, you don't have to move to the sun to take advantage of its output. You can just build one of these.

Once we get the laser launch systems in place in Mercury's orbit, you'll get some efficiency gains. :D

I recall reading that there were many solar water heaters in the Los Angeles area around the time of the first world war, but that they largely disappeared after natural gas became available

There are records of solar collectors in the United States dating back to before 1900,[3] comprising a black-painted tank mounted on a roof. In 1896 Clarence Kemp of Baltimore, USA enclosed a tank in a wooden box, thus creating the first 'batch water heater' as they are known today. Although flat-plate collectors for solar water heating were used in Florida and Southern California in the 1920s there was a surge of interest in solar heating in North America after 1960, but especially after the 1973 oil crisis.

See Appendix 1 at the bottom of this article for a number of country-specific statistics on the "Use of solar water heating worldwide".

Top countries worldwide


Except for the painfully obvious fact that solar PV and other so-called "renewables" are utterly and completely dependent for their very existence, literally from cradle to grave, on a vast prior investment in industrial infrastructure that is 90% powered by..., wait for it..., FOSSIL FUELS!


There are records of solar collectors in the United States dating back to before 1900,[3] comprising a black-painted tank mounted on a roof...

But... but Ghung... where are Jerry McManus's fossil fuels in all this!!! It must be wrong!! Wrong I tell you...

One serious perk to solar thermal—not yet exploited as fully as it might be—is thermal storage.

This is the part that I find useful. The ability to increase the capacity factor by storing heat energy for later use.

It will be interesting to see how the SolarReserve and BrightSource and other projects progress over the next few years. There are some questions to be answered regarding efficiency, economics, reliability and longevity, but worth keeping an eye on to see how they perform.

Neither the Solar "power tower" outside Barstow, CA nor a parabolic trough array are very efficient at converting sunlight into intensely focused heat. But there are alternatives ... which do involve a better topology ... I'll describe one which was first implemented by Archimedes of Syracuse:

In the Bible, not only does a parable sound like a parabowl ... but it also sounds like a pair of bowls. So how to place a pair of bowls to amplify light energy?

Simple, really.

Create one large paraboloid of revolution with the shiny surface on the inside of the parabowl. Create another smaller paraboloid of revolution with the shiny reflective surface on the outside of the parabowl. Place the smaller bowl inside the outer bowl so both inner and outer parabowls share the same focus. When the inner parabowl is aligned to be 'symetrically pointed in the same direction' as the outer parabowl ... almost all the sunlight coming into the outer parabowl is reflected by the inner parabowl towards the directrix. If the inner parabowl has a 'circle area' of only 10% of the 'circle area' of the outer parabowl ... 90% of the sunlight entering the outer parabowl will be focused into 1/10 the previous area hitting the earth's surface.

The output from this pair of two bowls could then be input into another pair of two bowls, each of smaller dimension than the first pair. (Yes, it's easier to post a picture but I don't have the tools to do as such.) In theory, one could infinitely repeat this pattern in a recursive manner to focues all the Sun's heat at a single point in space ... which any mathematical topologist can prove. But ignoring math theory and concentrating on easy to implement physics ... if the first bowl is ballpark 3 meters in diameter, and sunlight bounces off three more smaller bowls ... the sunlight should be concentrated enough to easily and quickly boil water.

Such a 'portable device' is better for home and on site use ... as a great deal of energy is lost via long distance electrical lines ... which are required to distribute the energy created by the solar power tower in Barstow.

Readers should note the above description may be of patent material ... and funny how the US Congress has recently changed patent law from 'first to invent' to 'first to file' ... don't forget filing a patent costs money and patent lawyers are not cheap. I'm in poor health and I'm too tired to argue with either the patent office or patent lawyers. Please keep in mind both Archimedes and Christ more than likely built such a device before any attempt at such a construction is undertaken in the 21st century. And trying to 'sell a patent' is next to near impossible as well ... better to own the factory and ignore intellectual property rights, build and sell the thing, make money, and let the poor soul who filed the patent try to get some money thirty years after the fact.

Yes, I'm a cynical as Diogenes of Sinope ... and as sick as Diogenes the Cynic.

In the Bible, not only does a parable sound like a parabowl ... but it also sounds like a pair of bowls. So how to place a pair of bowls to amplify light energy?

You cannot 'amplify' light energy. The power delivered from the sun is roughly 1000 watts per m^2, there is no way around it. Any bowls past the first add nothing to the power of the collector. The focus of the collector is determined by the curve of the bowl.

An example:

I should be more specific ... you are correct in saying that energy is not amplified ... but I am correct in saying ENERGY DENSITY is intensified.

Using the previous comment as an example and assuming 1370 watts of Sunlight hits a square meter of the Earth's surface:

With a parabowl of 3 meters in diameter, 1370*3.14159*1.5*1.5 ( the last three numbers are pi times the radius squared ) = 9683 watts of solar energy enters the first bowl. So 9683 watts is spread out over 7.0685 square meters, which is the 'circle area' of the largest bowl.

Assuming 90% of 9683 watts of energy is 'squeezed' into an area 1/10 the size the previous bowl ... leads to .90*9683 watts spread out over .10*7.0685 square meters. Thus the energy density or 'solar flux' has been amplified from 1370 watts per square meter to 12,328 watts per square meter, ( 12,328 = .9*9683 / (.1*7.0685) ) and actually there's a way to even better this flux increase ... but to continue the recursion,

Assuming 90% of the energy output from the second bowl is 'spewed out' from the fourth bowl but is squeezed into an area 1/10 the previous 'circle size' of the second bowl ... leads to the energy density being increased to 110,960 watts per square meter ( .9*.9*9683 / (.1*.1*7.0685) ).

So some watts have been lost because I only have 7843 watts (.9*.9*9683) output by the fourth bowl, but all this energy has been compressed into an area of about .07 square meters ... which is a circle area of about a foot in diameter. It's the energy density of 110,960 watts per square meter that can easily boil water upon contact.

Obviously, the above numbers are under 'ideal circumstances' ... but even if I loose alot of energy from such things as an imperfect shaped bowl or bad bowl alignment (and other problems) ... it's still good enough to boil water quickly.

Light is indeed not amplified, but it can be concentrated. Light arriving at the earths surface is originating from the surface of the sun and is diluted over a large area because of our distance to the sun. Using a lense this diluted solar energy can be concentrated but the theoretical limit to the temperature at it's focus point is the suns surface temperature.

So you can concentrate the suns energy back to the original temperature (theoretically) but not beyond the suns temperature (which would be the case if you somehow could amplify it). Therefore the maximum theoretical temperature in a solar furnace is about 6000 K.

Note that the iconic power tower east of Barstow, CA was constructed as a pilot project (first operational in 1981), used as a testbed for further research, and demolished in 2009. You can find video of the controlled demolition online. The site is now vacant graded land. Prior to the decision to demolish the plant, private individuals were squatting onsite and stripping the facility of scrap materials for sale.

There are dramatically larger power towers being constructed a few hours north on I-15, just inside the CA border with NV. The mirrors will cover nearly 6 square miles, focused on 3 towers.

For those who are interested, there is a hybrid technology which combines PV and Solar Thermal (flat plate collector variety, rather than Concentrating Solar Power) - we call it PV-T (photovoltaic thermal).

Rather than putting a long description here, it's probably easier simply posting a link to our website, which describes how it works in layman's terms (apologies to all the engineers for whom it's probably too simplistic...) -

There are, of course, downsides; the main one being the technology's propensity either to deliver too much hot water (thereby impairing electrical production) or too little (due to a combination of location, weather and the way the panels are out together).

Both can be overcome: too much hot water can be disposed of overnight by circulating the heat from the tank back through the panels, thereby creating "space" for the next day's production. Too little hot water can be backed up by more traditional heating sources, or by running the low temp thermal output through a water/water heat pump to upgrade it - we call this the Hybrid Solar Solution (

Apologies for the commercial "spam", but I believe this stuff has relevance to the topic...

r4ndom also mentioned this idea upstream. As you said, PV panels produce best when cool and any useful hot water production needs to be perhaps 50+ degrees higher than a PV panel's 'thermal sweet spot'; the panels will be too warm or the water will be too cool. Also, pumping water would likely offset any production gains from the PV. It's one of those things that looks good until you do the math. Methods to move air passively over the panels may get better results. It's one reason I prefer ground mounts vs. roof mounting; it increases production, especially in summer.

At today's prices, if you have the space, it's likely more cost effective to just add more PV. This is my plan since my balance-of-system is about 40% under its rated capacity. I oversized the wiring and controllers for this reason (in part).

Well, we've sold lots of these panels so I'm not sure I agree with you entirely - though, for you, it would not make sense because you've already got your hot water demands covered, so just adding more PV would make sense.

A lot depends on location..... for example, we have a big (for us) project in Saudi Arabia going ahead at the end of the year - using exhaust air from a building's air-con system to cool the panels - 3rd party calcs suggest that PV-T will outperform the most efficient PV panel by >20% in output per kW installed....

Generally speaking, any cooling of the PV component is beneficial, the more so in strong sunlight/high temperatures, and any heating of water above incoming mains temperature is beneficial (as long as you have the demand for it).

Most PV manufacturers consider normal operating temperature to be 45C (panel surface), but panel "capacity" is measured at panel surface temperature of 25C (the sweet spot) - PV-T helps close that gap somewhat, and, speaking purely for myself, I'm quite comfortable showering with water in the tank at "only" 45C....

Interesting conversation.

Thanks for bringing in your experience with PV + Thermal, I've been curious how real-world experiences have gone.

I'm not dismissing Ghung's point about that mismatch, but I think the addition of Heat Pumps at your site is one good response to having water that's 'not quite there' for DHW uses, and I would also expect that using this output in other 'preheating' combinations would also be useful, even if it means that much more equipment to fulfill the later stages..

It would also seem that the heat-pump could even work the 'used' hot water, in order to grab much of the remaining heat, and send it back up to the PV as cooled as possible for best heat transfer, similar to Heat Recovery Ventilators do with home air movement.

Lots of ways to juggle these parts!


Hey Bob, you may recall this article which appeared in the Portland Press Herald last fall:

Solar rising with tax credits, lower costs
Rebates can cut a project's expense while photovoltaic panels cost half what they did three years ago.

The falling price of photovoltaic panels, along with the advent of special heat pumps and super insulation, is creating an opportunity in Maine that energy experts could hardly imagine a few years ago. Now some of the state's leading solar installers, including Solar Market, have begun installing so-called PV panels on homes and businesses to harvest sunshine for baseboard heaters.

The new economics of PV panels also has some companies moving away from promoting solar-thermal collectors designed to heat water, a mainstay of the business in Maine for 30 years.

"We stopped selling solar hot water three years ago," said Naoto Inoue, who owns Solar Market and has hot-water panels on his house. "I would never do it again. I would put up all PV."


Last month, our two person household consumed an average of 3.85 kWh of electricity per day for domestic hot water purposes and we wash all of our laundry in either warm or hot water so there's some opportunity to pull that back if need be.

For a breakdown of our January consumption, see:

In theory, we could cut that to less than 2.0 kWh a day by installing a heat pump water heater. A HPWH runs between $1,700.00 and $2,000.00 whereas a solar thermal DHW system would likely set us back $6,000.00 or more. Given our relatively sunless Januaries (an average of just 2.9 hours of direct sun per day) a thermal system may not be capable of supplying all of our needs at any one point in time, in which case a backup source of heat would be required, most likely electric resistance. In addition, we'd have to subtract the overhead related to the operation of the circulation pump(s) and control system. Much better, so it would seem, to take those same dollars and invest them in PV which would have the added benefit of being presumably less trouble prone and less costly to maintain over the long haul. However, the big benefit of PV over thermal is that you can effectively "bank" anything surplus to your needs during the summer months when production rates are high and withdraw those same "savings" from your electrical utility during the winter months when production is low*. There's really no cost-effective way to do this with solar thermal, at least on this scale.


* This is pretty much standard practice for most if not all utilities as I understand it. You can view NSP's "enhanced" net metering policy at:

Hi Paul, thanks for the insights

I've been leaning toward installing a PV array just because I can now (later maybe not) and because wires are a lot less hassle than pipes--a real concern for those who might not be able to baby sit their homes during long spells of 75-100 heating degree days, generally occurring in the couple months that have no direct sunlight anyway... Of course heat pumps here require solar thermal summer earth recharging or a heck of deep hole, but electricity is dear so that kind of balances things out even without the pumps.

Is partial snow coverage of the bottom of PV panels a concern with all designs? My prime location is across my 36' east-west upper ridge line (I like my birches and that gets above their shadows when leafed out), where I would essentially stand the panels up off about about a 14° roof. I can raise them if need be, as I'll likely be having my neighbor fab the brackets regardless, but that is just more work which I would rather avoid. My guess is the panels would melt a small space off their face in any significant direct sunlight and I wondered if that would be sufficient?

You're most welcome, Luke. Right off the top, I should note that our home is a poor candidate for solar. For one, it's oriented east-west, our roof is punctuated by multiple dormers, and we're heavily shaded on our southern exposure year-round by a mature stand of trees. Secondly, we receive a relatively modest 1,770 hours of sunshine each year, a large percentage of which, as you might guess, falls during the summer months (December is our worst month at an average of 2.1 hours per day). But beyond this, the economics just don't pencil out for us -- 119.5 kWh for the month of January at 13.336-cents per kWh works out to be just under $16.00. And January is probably our worst month because inlet temperatures are at their lowest this time of year and we wash larger, heavier items of clothing which translates into more loads and, in turn, greater hot water use (we also tend to take somewhat longer, hotter showers).

I'm guessing that a HPWH and a thermal solar system could theoretically cut our DHW costs by equal amounts, but in either case the savings won't likely be much more than $100.00 per annum. At least the installed cost of a HPWH would be about one-third that of a thermal solar system and, most importantly for us, it would help offset the operation of our power guzzling dehumidifier; in effect, a HPWH would provide "free" DHW six to eight months of the year as a by-product of keeping our basement mould and mildew-free.

Like you, I'm somewhat leery of anything related to plumbing due to the potential for leaks, so all things being equal I would favour PV over thermal for this reason alone. However, for grid-tied applications, the ability to enter into a net metering arrangement with your local utility is what seals the deal for me because then you're not being handicapped by the season variation in output. Plus, you can use this banked electricity in any way you see fit, and not just the production of DHW; of course, a single purpose/dedicated system does just that.

Anyway, those are my thoughts for what they're worth.


thanks Paul,

I'll have to see what the water heater coil inside my wood pellet boiler system does to to my power usage, when all is up and running. I have seasonal issues with sun as well. NO direct sunlight hits my house--there is a ridge about a half mile to the south that blocks the few hours of very low direct sun for five weeks each side of solstice (precious little actually generated at the CCHRC test site then anyhow). Of course the flip side is long hours of sunlight later on but maximizing that would require tracking which in my case would require flattening about an acre of birches and putting up a ground mounted system--always trade-offs.

CCHRC has run arrays of 16@165W panels both fixed and tracking and come up with comparable pack back periods- about 9 years give or take with the Solar World panels and local power rates (couple year old data)

actual output below

good to have a go to local resource like the CCHRC

The CCHRc is a very impressive place - was there in Aug 2010.

At that time they also had a "poor man's concentrating PV", which used pv cells surrounded by reflective prisms - looked like a giant silver waffle. That one had to be tracked to work, and they said that in fall/winter/spring that it has less production than the standard panels because it lost the reflection from the snow!

Interesting that, two years ago, the payback periods were the same. With today's panel prices being substantially lower, I expect that fixed panels are now the better bet.

Interesting that, two years ago, the payback periods were the same. With today's panel prices being substantially lower, I expect that fixed panels are now the better bet.

Those are my thoughts too--I haven't dug too hard yet as I've other irons in the fire that need a bit more heating up. CCHRC probably has more current stuff than that chart on the web, and I certainly will get over and talk to someone involved in their ongoing solar projects before I buy anything. They do some neat stuff there.

And yes insolation, especially in March/April does benefit from our brilliant white snow cover--I'm hoping in my case the galvanized roof-which offers its own mounting design challenges-does a bit reflecting for me as well.

Running my numbers through this solar estimator put the return at iffy, but I will be doing the design/installation with minimal hired help (pretty much just hiring my welder neighbor who happens to have a boom truck or two in his yard, and an a licensed electrician for the work which absolutely requires one-I know a few). I never figure my own labor into anything on my house. I will have to dig deeper on the actual out of pocket I will incur--no interest expense planned/as the return should be better than what my poor pension assets have been dragging in the last few years. The page linked above does give this general cost breakdown
About 60% of the cost to install a solar-electric (PV) system goes to the solar photovoltaic (PV) panels, 10% to an inverter, 15% to direct labor, and 15% to the "balance of system" (BOS) costs. That is probably close enough for me to figure from.

I think I might make some noise at a borough meeting as well. It wouldn't be that much skin off anyone's butt if PV or solar thermal systems were not added to assesed property tax values. Over time they should help on everone's electric rates. Just a thought. Are there such property tax exemptions for PV and the like out there anywhere that you know of?

That urban agriculture project you are embarking upon sounds interesting, will it be in BC or elsewhere? Do you think you might get up this way again? Feel free to drop me an email if you get a chance, I check the box listed in my TOD profile every month or so, and of course immediately if I notice a heads up on these boards.


Arizona’s property tax exemption was established in June 2006 (HB 2429) and originally applied only to “solar energy devices and any other device or system designed for the production of solar energy for on-site consumption.” For property tax assessment purposes, these devices are considered to add no value to the property.

HB 2332, signed in July of 2009, expanded the exemption to include other renewable energy technologies, as well as combined heat and power systems, and energy efficient building components. The bill defines renewable energy equipment as "equipment that is used to produce energy primarily for on-site consumption from renewable resources, including wind, forest thinnings, agricultural waste, biogas, biomass, geothermal, and low-impact hydropower."

thanks--I couldn't gather from the summary if a net metered grid tied PV system qualifies as equipment that is used to produce energy primarily for on-site consumption from renewable resources. I'm guessing it does as long as it is sized to roughly equal the homes historical electrical usage. That may explain the caveat below.

To qualify for the property tax exemption, the property owner must provide their county assessor with documentation affirming the actual purchase and installation, including costs, of the eligible equipment. This documentation must be submitted no less than six months before the notice of full cash value is issued for the initial valuation year.

Still that seems like make work for something like a PV or solar thermal panel system--it would be easier for the assessor to simply 'not see them'. The assessor could have simple guidelines for array sizes relative to home square footage that fit the bill...but then we are talking a govt. tax entity, they thrive on red tape.

That is a pretty minor quibble though, I do laud Arizona's move. Are all property taxes state taxes in Arizona or rather does the state have the power to direct what locales can and can't tax as property? This may seem a odd question, but here in Alaska some communities have not been incorporated into a borough and there are no property taxes in those areas (I obviously do live in a property taxing borough, thus my interest in the subject). I really don't know how property taxing authority works elsewhere.

Hi Luke, I am not sure about that calculator - I suggest the NREL's PVWatts Calculator

That said, the CCHRC will have *exact* data that you can use...

I wouldn't use their cost estimates either. For panels, you should be able to get down to about $1.50/W, and inverters run about $0.5 to $0.75/W. Racking and other, I don't know.

You should have at least some choice of suppliers up there?

The urban farm project, if it happens, will be in BC at - of all places -Whistler ski resort!

I am also trying to do some micro-hydro projects there and here on the coast - lots of small creeks on the sides of mountains!

I'd love to get back up there again, though I can't see it happening for at least a year or two - no one will pay me this time! Thanks for the offer though, and I'll take you up on it if I do.

I don;t think i'll stay at the Klondike Inn again though...

yeah I forgot you stayed in that doozy, our first nights in town weren't in much better. We are dug into our hill comfortable enough these days.

Thanks for the link and the numbers. One row across the ridge of some Sharp 216W a guy just up the road is peddling would be a 2160W array max. That's about 82% of the CCHRC array charted above, I lopped off another 12% due to my morning sun loss but that might be heavy most of the year when comparing fixed arrays. That gives me a whopping 1700kwh a year if the above chart ends up representative 1800kwh if I captured 75% of what CCHRC catches the months I have sun--I do have room for second array that would not shade the top run if I mount it at the bottom edge of the roof but that one might get more tree shadow. Those panels are going for $2.75/W. Best deal in town. We do feel shipping up here, but I've been known to ship from Anchorage suppliers when I felt I was getting hit too hard locally. Roof racking will be a bit of a pain, but it's easy to have metal stuff fabbed in this supply hub.

The numbers don't look like a slam dunk on the first rough calc. My roughly generated numbers don't match up all that bad with the ones my linked solar calculator generated either. It had a 4KW peak power system generation about 3770kwh a year. I would have 4.32Kw peak power system generating 3985Kwh hours a year if I didn't subtract another 7-12% for later morning sunrise. That reduction still might be a little heavy. I'll need to do a actual sunrise logging--sunset will actually be behind the array most of the months they get sun. A more SE/NW orientation would be better, but tough on my roof. More thought required.

Farming Whistler, interesting? Pretty good sunlight there sometimes? Thought about heading there for the Olympics, but for some hard to fathom reason we usually end up heading toward warm ocean beaches if we get out on winter trips.

The 2nd night was somewhere else, and much better. I really enjoyed Fairbanks, would love to visit again. The Klondike does make for a good travel story, though not one I feel the need to experience again!

With your latitude, there certainly is a real production gain from tracking - in the summer at least.

There are some interesting DIY trackers on build it solar.

I had read - somewhere else, years ago, about someone who made their tracker using an old landscape trailer. They took the stub axles off, and put them-sideways-on the end of the trailer, so that it would rotate around the hitch. They used 5W motor from a bbq rotisserie to move the thing - had it geared down so to make the trailer do a full arc in 24 hrs. Then just adjusted the tilt every month or so. Great if you have the flat land...

Seems to me you place might be a good candidate for a small win turbine - I''ll bet you get a bit of that in winter. If you are already set up for panels, wouldn;t be that hard to add...

I like the look of these;

or this neat little unit

You local supplier-ABS Alaskan has access to bunch too, and will know what works out there.

Too bad you don;t have a creek you can tap for hydro!



You might not have read my reply to HinH above, but a single tracking array would have to be a low ground mounted tower and would require levelling around an acre of rather stately if slender birches. Really not acceptable.

I took this shot just past solar noon today. The sharpest shadows, aside from the porch roof columns are from trees 30 feet away.

This site makes up handy little calendars--great location choices all over the states, haven't played with it much for places beyond our borders. My sunrise was two hours behind the official time today and it will set somewhat early for the next couple few/weeks as well. Then the ridge to the south fades out of the afternoon solar track. But the top of the hill I am built on rises another 500 ft or so to my east. My biggest windows face west, where I get long hours of sun come between the spring and fall equinox.

Today, with as low a sun angle as we have, spruce trees 300 feet away cast significant shadow. My location is not prime. Of course come March things look much better. This conversation has started me keeping a simple log with some supporting pictures.

I could have individual or couple panel segments mounted to the roof that tracked, it would reduce the size array that will not shadow itself--that was the germ of an idea when I typed 'more thought required' so you and I certainly were tracking in line there.

My roof roof truss structure is very stout. I removed the ridgeboard and hinged the rafters to each other then lifted the entire top section you see, about 16'x36' including eaves. I raised that roof section from a 13½ inch in 12 pitch to a 2¾ inch in 12 pitch to make room for bedrooms. Once raised I fabbed a scissor truss arrangement onto the raised rafters which is firmly anchored to the north side rafters which still sit at the original 13½ pitch. It is stout but I would not raise too big a towers off it. Rack design will be challenging, and tracking racks more so.

Wind is a no go in this part of the interior. I might be working on GVEA's Eva Creek wind project this summer but it is on the very windy downsweep of the north side of the Alaska Range some 90 miles SSW of here. Fluffy snow can sit on birch trees unmolested for weeks on end in these parts. If you ever read Jack London's 'To Build a Fire' you might recall it was the lack of wind in the Yukon interior that led to the guy's downfall--at least in the more popular later written version of the tale. Jack had the guy survive in the version he originally wrote.

Interesting aside on that London story. I was doing my student teaching in an Athabascan village south of Tok back during Bush I's Gulf War. I had my high school students (all five of them grades 9-12) read the later written version and carry it forward. A senior, and the lone guy in the class, did a riveting job. He wrote it in first person. It ends powerfully. As he (the student) is walking down the trail in the bitter windless cold, he stumbles over something half buried in the snow. He looks down and sees it is a frozen man. My students final line
"I walked a little faster"

Hi Luke,

I've been trying to get caught up with the backlog of audits that accumulated during my time off-work (I knocked-off twenty-five today, three of which will generate over 40,000 kWh in savings per annum, so we're making headway).

A photo log is an excellent idea and should help you weigh your various options (you have a beautiful home, btw). Any sense how well a tracking system might perform in your local climate? Heavy snow, freezing rain and high winds could certainly wreck much havoc.

I'll be keen to learn more about your plans as they develop. Thanks, too, for the reference to Jack London's 'To Build a Fire'... I'll reserve a copy at our local library.


Hi Paul,

Don't look too hard at my unfinished T111 covering. Five ongoing additions that I'd best get away from this blog and get going on again. Kind of don't seem to get the same ERoEI (Enjoyment returned on Energy invested) out of working on the place, anymore.
?- ) Let's hope I am keen enough to develop my plans.

Haven't read London in a long, long time, but that student's ending stuck with me better than anything of Jack's. Probably my single best teaching memory--I never did do it full time for an entire year. No need to go to the library though, just a 12 page short story.
To Build a Fire
Lets hope I keep up with the log, I don't know that I have ever had the record keeping discipline you seem to display. Thanks for the encouragement.

Still trying to wrap my head around it. Sadly I can't wrap my wallet around it, as appealing as it sounds.

I have to think that this stands on the vagaries of finance, and that energetically, I would still tend to opt to have both direct Heat and Electrical Solar incomes..

Inoue has also been saying lately that he doesn't want to do little rooftops any more, but that we need to put our eggs into bigger baskets, and make a bunch of Util. Scale installations.

He's a smart guy, but I don't always have the same intentions or perspective.. I'm too much of a generalist, perhaps, and have to apply a 'both/and' rule instead of an 'either/or' ..

"When you choose not to decide, you still have made a choice.." sort of..

Hey Bob,

There's a lot to be said about being fully independent of the electrical grid and I'm rather envious of folks like Ghung who have achieved this. If our personal circumstances were different with respect to local climate and our home's site-specific deficiencies, or if there were four shower happy teenage daughters under our roof, rest assured, I'd be whistling a different tune. I guess my point is that we should carefully weigh all options and decide which one works best for us. And although I tend to focus more on the economic factors, there can be other good reasons as you know as to why we might favour one solution over another, e.g., greater energy independence and resilience, a reduced environmental footprint, and so on.

I've decided for better or worse that we'll be married to the grid for the foreseeable future, so I've concentrated most of our efforts on reducing our energy demand. I've also implemented multiple backup strategies to address grid outages, albeit adding more complexity along the way and substituting one dependency for another, when my natural inclination is to go the other way. Lastly, because the environmental costs associated with grid-supplied electricity can be extraordinarily high, and that's certainly true for us given our province's heavy dependence upon fossil-fuelled sources, I've opted for 100 per cent renewable energy from Bullfrog Power; not a perfect solution by any means, but about the best I can do in this regard.


One of my first posts at the Pickens Plan site about four years ago started with a reference to passive solar

"Tell us about your experience with alternative energy:
There should be more emphasis on passive solar. I have been reading and playing ball by the light of the sun since my childhood in Amarillo.
I am a little younger than Boone but first met him playing basketball in Amarillo around 1945. Amarillo was windy. The AHS students were nicknamed Sandies, presumedly because of the sandstorms.
What excites you about this campaign?
Conservation offers a chance to delay a possible Malthusian dieoff. Windpower might help but subsidies make it difficult to evaluate EROI. I appreciate this opportunity to continue a hobby dating from the late 50's. I discussed Hubbert with Boone when he spoke at Cal Tech in 1985. I had the late Buz Ivanhoe put him on the free print mailing list for the Hubbert Center Newsletter when it started in 1996.
What do you want to do to help?
Discuss pickensplan on oily sites such as the oil drum, yuku downstream ventures, the Jay Hanson inspired sites at Yahoo groups and at the junk science site
The Hubbert Center Newsletter, funded by the late L. F. Buz Ivanhoe, was originally sent by mail. It was first copied for the internet by Jay Hanson and eventually evolved to "

Cats have a pretty good sense for solar thermal. They know just where the floor and walls has soaked up the right amount of heat for the evening. One fur head has figured the best spot to get the pre-warmed concrete in the morning along with the direct sun PLUS the sun reflected from the windows all in the same spot. It amazes me just how far we are behind cats for this energy resource.