Electric Commercial Vehicles
Posted by Gail the Actuary on April 9, 2009 - 11:12am
This is a guest post by Alan Searchwell from Kingston, Jamaica. His Oil Drum name is islandboy.
Electric trucks do more than what most people think they are capable of doing. In this post, I will talk about both electric trucks and other commercial electric vehicles.
Back in July 2008, someone challenged me in Drumbeat to point out some really heavy duty electric vehicles that can move say, a fully loaded 40 foot container. I fired off a reply featuring lots of links to electric or hybrid trucks and delivery vans. Both in that comment and in this post, I rely heavily on autobloggreen.com for the research, since it is a blog almost exlusively dedicated to "green" transportation issues.
One of the trucks in the July 19, 2008 comment was a really heavy duty electric truck in use at the port of Los Angeles.
Battery Operated Trucks
The port of Los Angeles is an interesting case. It seems to me that the electric truck and the port are a match made in heaven. The trucks used by the port basically shuttle containers around the port and to warehouses and rail yards nearby. This means that there is very little risk of a truck with a sixty mile range being unable to make the trip out of the port and back. In addition, with the port being the base of operations, charging and/or battery exchange stations can be set up right where the trucks work.
When my original Drumbeat comment was written, the port of Los Angeles electric truck were still in a trial stage. Recent news suggests that the trial referred to in my original post was a success, so much so that the port has placed an order and started taking delivery of 20-25 more units being produced at the manufacturers new production facility located in the Los Angeles metropolitan area. The manufacturer also hopes to sell additional units to other customers.
In the UK, Smith Electric Vehicles and Modec have been in manufacturing and selling plug in, battery electric vehicles for at least two years. Modec has a list of customers using their trucks at their web site with pictures of the trucks in company livery, as does Smith Electric Vehickes.
Small North American manufacturers like Canadian Electric Vehicle (CEV) have also produced viable battery electric vehicles for use in and around airports. Fifty of CEV's electric trucks are on duty at airports from New York's JFK and Chicago's Dulles to Los Angeles's LAX airports. Other clients include Southwest Airlines, Shell Oil, and British Petroleum, which buys CEV vehicles for its Australian division.
Series Hybrids
Series Hybrids are similar in concept to the Chevy Volt in that the internal combustion engine (ICE) is never connected to the wheels by a transmission of any kind but instead drives an electric generator providing power for the electric motors. Coupled with batteries, this allows the ICE to be run at close to its maximum efficiency at all times. Significant cost savings can be achieved by this approach. This has been the experience of London Transport, New York MTA and public transportation systems of other North American cities.
Heavy duty series hybrids are not new. They were one solution to transferring the massive amounts of power needed to move the giant earth movers used in mining operations. The technology has also been used widely in railway locomotives.
There are significant numbers of series hybrids in operation in the New York City area bus fleet. This photo is from the bus manufacturers news page
• MTA New York City Transit and the MTA Bus Company will take delivery of 850 Orion VII Next Generation diesel-electric hybrid transit buses by early 2010. This order will bring the MTA's diesel-electric hybrid bus fleet to almost 1,700 units, making it the largest diesel-electric hybrid fleet in the world. With this order, Orion brand transit buses will account for almost 50-percent of MTA New York City Transit's entire fleet.
• OC Transpo has ordered up to 202 Orion VII Next Generation hybrid diesel-electric hybrid transit buses to be delivered by 2010. This delivery will make OC Transpo the third largest hybrid bus fleet in Canada.
Similar technology exists in London where the fleet is being expanded to include double decker series hybrid buses.
Another series hybrid that has been evaluated by the New York MTA is an intresting unit manufactured by DesignLine. This unit uses electricity generated by an onboard micro turbine manufactured by Capstone Turbine Corporation, a supplier of micro turbines for use in Combtned Heat and Power applications. This turbine boasts one moving part with air bearings. It will be interesting to see how these fare in the long term. What makes this vehicle unique is that its traction motor and auxilary power unit (turbine-generator) contain a total of three moving parts!
Parallel Hybrids
Parallel hybrids are vehicles that can have the wheels be driven by the ICE or the electric motor or both. They are easily the most mechanically complex hybrids and fall into two main camps. The two mode hybrid being implemented by GM/Allison, Daimler, BMW and Chrysler(?) typically consist of a motor/transmission unit containing:
• two AC motors;
• three planetary gear sets;
• four multiplate clutches;
• two hydraulic oil pumps.
Toyota uses a slightly less complex but similar system in their Hybrid Synergy Drive. The other main parallel hybrid type uses an electric motor sandwhiched between the ICE and the transmission with a clutch to disengage the ICE when not required leaving the electric motor to move the vehicle. Otherwise these systems are very similar to traditional ICE driven drive trains. These systems usually dispense with a starter motor and the alternator with the traction motor filling all three roles, as is the case with Volvo's ISAM amd Mitsubihi-Fuso's system.
Misubishi Fuso has been selling a parallel hybrid light truck in Japan for a couple of years now and has ten evaluation units in London. GM-Allison has sold a significant number of their two mode hybrid buses in North America and Eaton Corporation has supplied Coca-Cola Enterprises with the largest single order to date for trucks using the company's hybrid system, over 100.
Electric Advantages
Electric drive systems should be able to gain some serious traction in the commercial vehicle market since electric drive in commercial vehicles is a more viable option NOW. One reason is that a large percentage of delivery vehicles operate on fixed routes and schedules so their use and charging cycles can be planned with more certainty than an individual's personal transportation. Smaller delivery vehicles also tend to do shorter range trips, so electric drive systems are a particularly good fit. Routes can be planned so that vehicles return to base long before they run out of juice. In addition, fleet operation bases can be equiped with high power fast charging stations or battery swap stations, if fast turnaround times are more important than the cost of spare battery packs. School buses, airport shuttles and other pasenger moving operations that frequently move people on routes that are less than 50 miles round trip also present opportunities.
For example, during a recent trip to the US, I spent some time at a car rental location and observed that there were a couple of shuttles making trips to Miami International Airport and back, a trip that I estimate takes less than half an hour to complete. Also at the location were several shuttles sitting idle. If these shuttles were electric, the idle ones could be plugged in while the shuttles were working. When the working ones need charging, they could be plugged in and one of the idle ones used to replace them.
Electric drive vehicles also tend to have lower maintenance costs. The only parts that can really wear out in an electric moter are the two motor shaft bearings. One only need look at electic motors used in industry and commerce for an indication of how much maintenace will be required. The only oil changes that are required relate to transmissions and final drives. These oil changes are less frequent than the oil changes required by an ICE.
If regenerative braking is used, the vehicles are able to go more than twice as far between brake lining replacements. In series hybrids, clutches and complex tranmissions are not required so drive train maintenance can be greatly reduced while the ICE used to generate power can be set up to operate under optimum condions extending service intervals and the useful life of the engine.
What's on the horizon?
In late 2007, Daimler introduced 16 new buses and trucks with different driving systems and "greener" fuels. These have formed the basis for many of the hybrid vehicles in use today. Research continues as they are currently testing a lithium iron powered series hybrid articulated bus. British bus builder Optare recently held a demonstration drive of its new Solo EV electric bus at the Millbrook proving ground in central England.
Volvo is supposed to be introducing a parallel hybrid to the European market this year that operates in electric mode at low speed and has regenerative braking. An article with a video of the truck in operation is here. Smith Electric Vehicles, after many false starts, finaly appears poised to begin production at a Kansas City production facility in the third quarter of 2009. They have an arrangement with Ford to electrify the Ford Transit Connect as a BEV (battery electric vehicle) light-duty van scheduled for production in 2010. Azure Dynamics, one the suppliers for the US based tests of light to medium duty delivery vans for companies like FedEx and UPS, continues to develop it's offerings and has signed new Sales & Service agreements with some Ford dealerships to work on the company's Balance Hybrid Electric commercial trucks. Electric Vehicles International and aspiring electric truck manufacturer Electrorides both offer medium duty battery electric trucks that appear to be based on the ubiquitous Isuzu NPR cab and chassis.
The main drive systems suppliers that I could identify are BAE Systems, Eaton, Enova and Azure Dynamics. The companies all appear to be in reasonable financial health and look to have sufficient orders going forward. One supplier, Odyne, was apparently insolvent and was acquired by DUECO. If the stimulus package provides an opportunity to this nascent industry, it might survive and provide a basis for a new generation of trucks and buses that will provide both a reliable and cost effective option for the transportation needs of industry and commerce as we enter a post peak world.
According to Zerotruck's math, it would appear that electric commercial vehicles are not hard to justify in terms of the savings compared to the additional cost of going electric.
Edit
I didn't realize that this post wasn't quite finished when I posted it. (This was the second draft, not final.) These are some important paragraphs that were added to the final.
Electric Pros and Cons
Battery powered electric vehicles have restricted range. Overcoming the range restriction carries significant penalties in terms of battery pack size weight and/or cost. For commercial vehicles, the range limits are not an insurmountable problem as a large percentage of delivery vehicles operate on fixed routes and schedules so their use and charging cycles can be planned with more certainty than an individual's personal transportation. In addition, larger commercial vehicles tend to have more space that can accommodate larger battery packs without impacting the cargo or passenger areas. Smaller delivery vehicles tend to do shorter range trips so smaller battery pack sizes offering limited range are not a big issue. In any case, routes can be planned so that vehicles return to base long before they run out of juice and the fleet operation bases can be equipped with high power, fast charging stations or battery swap stations if fast turnaround times are more important than the cost of spare battery packs. In some cases the loading bays at destinations could be equipped with fast charging stations so that batteries could be topped up for the onward or return trip while the vehicle is being loaded or unloaded. School buses, airport shuttles and other passenger moving operations that frequently move people on routes that are less than 50 miles round trip also present opportunities.
Although Electric drive systems attract a higher initial capital cost of at least 30% more than a similar conventional vehicle, they should be able to gain some serious traction in the commercial vehicle market since electric drive in commercial vehicles results in significantly lower operating costs in the form of reduced fueling costs and lower maintenance costs. The only parts that can really wear out in an electric motor are the two motor shaft bearings and one only need look at electric motors used in industry and commerce for an indication of how much maintenance will be required there. For battery electric vehicles, the only oil changes required, are for transmissions and final drives which are less frequent than the oil changes required by an ICE. If regenerative braking is used, the vehicles are able to go more than twice as far between brake lining replacements. In series hybrids, clutches and complex transmissions are not required so drive train maintenance can be greatly reduced while the ICE used to generate power is usually set up to operate under optimum conditions, extending service intervals and the useful life of the engine.
What Should We Be Doing Next?
The fact is that while electric drive systems are being produced by the hundreds, internal combustion engines and their related transmissions are being produced by the hundreds of thousands. Component costs will not come down as long as these relatively minuscule number of electrically driven vehicles are being manufactured and sold. It is the classic cache 22, for prices to come down volumes must go up but, for volumes to go up, prices must come down. In this situation, something must happen tip the scales and make the new technology irresistible, like the fuel price shocks of 2008. However in this post shock recessionary climate, fuel prices have plummeted and the new, more efficient but, initially more expensive technology has lost it's luster resulting in buyers returning to the safe haven of buying what they've always bought. It is still quite remarkable that many of the electrically driven commercial vehicles have sold in the numbers that they have and it lends credence to the thinking that the long term savings from their use are quite significant. According to Electrorides' numbers, it would appear that electric commercial vehicles are not hard to justify in terms of the savings compared to the additional cost of going electric.
If we wait for the next fuel price spike to stimulate demand for electric vehicles, several of the key players may fail and disappear in the meantime. Tax incentives, purchase rebates, increased fuel taxes are all tools governments can use to stimulate demand during hard times. If, as many readers of theoildrum believe we are perilously close to if not past the peak of world oil production, we are going to need alternatives to the almost exclusively fossil fuel powered transportation infrastructure that exists today. Hopefully the stimulus packages being devised around the world will help to provide an opportunity to this nascent industry, so that it will survive and provide a basis for a new generation of trucks and buses that will provide both a reliable and cost effective option for the transportation needs of industry and commerce as we enter a post peak world.
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If the entire commercial transport system was to go electric ( I realize we dont have to go 100% electric but its hypothetical) then what sort of strains would that put on the grid?
Would this mean, for example, a doubling of existing coal and nuclear plants?
Gautr,
I believe that most North American electricity grids have some spare capacity (about 7TW total in the US) during the day but as much as 30% spare capacity at night. Most battery charging can and should take place during the night when other demands are low. Many power stations are much better suited to continuous (or near continuous) power outputs with long lag times between changes in the load requirements and the ability of the power station to supply it. This is particularly true for Nuclear power plants. The "peaking power plants", which are so popular these days often use natural gas power turbines (e.g. GE) which can adjust their output within minutes instead of hours or days but with high CAPEX expense.
I believe that if you take the current 7TW output of the US grid, multiply by 30% that you more than provide enough power for a 100% conversion of the car (and truck) fleet to electric IF the charging is down at off-peak times (the majority). The problem is not the availability of electricity. It is the availability of capital (and energy) to build all of the cars and trucks to replace the existing infrastructure. Do a calculation of how much money and energy it would to replace the entire car fleet and you will see that it is a huge investment. Even with a 100% replacement of the existing car fleet at their normal end-of-life point and it takes a huge commitment and about 17 years to convert the fleet. That is a long time when Peak Oil is probably already upon us. Changing behaviors and attitudes is even tougher. We have a tough time ahead. I hope that most of your readers have a good back-yard garden planned for this summer!
Ian
By my calculations that's 0.7TW surplus to peak capacity(700GW), but not all of that is really available at off-peak times, 440GW is from natural gas, that is kept mainly for peak demand, and 70GW is hydro. If they were used as well in off=peak periods would not have enough NG or water. Until wind power becomes a larger part of energy, only coal could expand to supply off=peak( about 90GW surplus); that's still a lot of vehicles(90Million) that could be charged.
I read an artical recently about an electric battery that charges almost instantaneously. This was proposed as a big leap for the production of electric vehicles but if spare capacity is greater during the night then should the slow charging batteries stay?
Off-peak rates are lower than peak rates, most people don't drive around at night, but do in the day, so night charging makes sense, but if you are on a long trip it would be nice to be able to re-charge every hour or so, while having a coffee or burger. One to 2 minutes is fast enough, but 15 mins would be OK for a trip if your range was 2-3 hours driving.
I think for long-distance travel battery size should be calibrated to match bladder size. :)
For a family truckster vacation, 15min downtime every 2-3 hours would be fine. I can't imagine having to stop every hour for that long though. For a frequent business traveler, a stop every 4 hours is probably the minimum. I know on a "good" trip I make one stop for gas and food on a 9.5 hour drive, quite routinely.
This isn't to say that memes can't change, but for easy step-in the new solution shouldn't be too painful. Better rail would probably be a better long-term solution -- until then, I think I'd rather rent a gas vehicle and pay the price for longer trips, and leave the EV at home.
Electric trucks and buses aren't suited to long haul routes. Do you mean electrified rail for long haul and electric trucks for local deliveries?
Inter-city freight, taken entirely by electric rail (about 4x to 5x as efficient as electric trucks, not counting battery weight on trucks), would take less than 3% of current US electricity.
Alan
Some years ago, I calculated that a total replacement of petroleum transport fuel would require a 40% increase in US electric generation at worst. Given that the typical efficiency of light-duty vehicles is considerably less than 20% and electrification of freight via railroads and e.g. Bladerunner trucks would have substantial cuts in energy demand, we might be talking 30% or even less.
Add to that the potential reduction in transportation from relocalization, and the percentage would drop even further.
You will never ever get an electric motor to deliver the power a tubo-charged 500 hp Cat delivers. Long haul rigs run 24/7 from the east coast to the west coast.
You're right. You don't know.
"Today's diesel-electrics are impressive machines indeed. From the early days where a diesel road locomotive would be 1500-1700 h.p., we now see single diesels which have 6000 h.p."
http://www.essortment.com/all/locomotiveengin_rwoc.htm
Long Haul rigs will become a fond memory, and there will be fine toys and models built to commemorate them. The above will be the coast to coast option (the genset must be replaced by electric lines, of course..).. unless you go through Panama or the NW Passage. The 'diesel' is a gen-set, but the power to the wheels is from an Electric Motor.
"MOVIN' ON"
Tagline:
A gypsy trucker is a man with a dream.
Plot:
A pair of big-rig truckers, one a crusty old veteran, the other a college-educated youngster, team up to haul cargo across the country.
Is Momma's boy, Obama, a gypsy trucker in disguise? Maybe? Who knows?
An electric motor doesn't need to deliver the same power as an ICE engine. They can deliver peak torque from zero rpm.
An even more intersting serial hybrid in the Netherlands: e-traction
Their web site mention certification of results:
So what are the overall figures here for production? For 2006 the US sported 8,819,007 trucks: BTS | Table 1-11: Number of U.S. Aircraft, Vehicles, Vessels, and Other Conveyances. As in the passenger vehicle market EVs or hybrids have a long way to go before they begin to have much impact on total fuel demand.
Just like oil has a long way to go before it begins to have much impact on total fuel consumption. ;)
Coca-Cola Enterprises has been researching and investing in hybrids for about 8 years. We began by looking into a fully-electric truck, but as you know there was no way we could use them for our large delivery routes - they couldn't handle the load. We've now deployed about 180 33,000 GVW medium-duty hybrid trucks for high-traffic urban deliveries (gas stations, convenience stores) and are in the process of deplying 150 additional 55,000 GCW hybrid tractors for long haul, big-store deliveries (groceries, Wal-Marts). These are remarkably capable vehicles for large loads and our drivers really love them because they're so quiet. We also launched a pilot of hybrids in Belgium earlier this month.
That said, we're still looking into how we can leverage fully-electric vehicles. They probably won't work for deliveries, but could work for our electric vans (like the ones from Smith Electic Vehicles) could be viable options for sales teams or for equipment repair/delivery. Trying to find carbon-responsible delivery vehicles for large delivery routes has been a challenge, but there are options out there... and as more companies follow the pioneers' lead and invest in hybrids/full electric vehicles, the upcharge will decrease and companies will be able to place more on the road.
From March 5: Kenworth Receives Major Hybrid Tractor and Truck Order From Coca-Cola Enterprises: Business Wire Business News: PCAR - MSN Money
I see how there are incentives for replacing diesels with hybrid or LNG trucks in the American Recovery and Reinvestment Act: Kenworth Medium Duty Hybrids, T800 LNG Trucks Eligible for U.S. Federal Stimulus Package Aid
Was that a major factor for Coke's purchase, or was that in the works before the passing of the ARRA in Feb.? And are your fizzy competitors making waves about buying Kenworths themselves?
The order referenced above was actually our second order with Kenworth... we originally purchased 120 side-load hybrids in 2008; the 185 additional this year were prior to the announcement of the ARRA.
We haven't seen a lot of other companies coming to the forefront about purchasing hybrids, perhaps in part because it's only one tool in an overall fleet emission reduction strategy. We feel it's important to help pioneer this technology, though - hopefully more companies will jump on board.
Can someone with some engineering knowledge explain why for domestic transportation (rather than haulage / public transport) the manufacturers are making parallel hybrids rather than serial hybrids? The serial hybrid is intrinsically more efficient, and much lighter, I would have thought. A one litre diesel unit running at a constant 3000 rpm to generate electricity to power a small hatchback would give you 100mpg and all the acceleration you would want, I expect. But instead we have the Prius and the Insight. What am I missing?
I'm just guessing because I don't have insider knowledge, but I suspect it is the parallel design allows an undersized electrical system to be mated to a full sized ICE. The existing Toyota hybrids use the electrical component for an occasional efficiency assist (during times when the both the battery change is sufficient, and the total demand for power is low). A series design implies that the electrical delivery system (generator and motors), must be capable of sustaining maximum acceleration.
IMO thats the way to go. Maximum benefits from the electric drive (high torque at low rpm, no tranmission, regenetive braking etc) then as soon as the batteries are ready (cheaper) just add 5, 10 or 15 kWh's worth to extend the all electric range.
Not really.
Those extra batteries add weight. More weight for structure to support those extra batteries.
Severely diminishing returns.
Alan
Not really.
1) The Chevy Volt battery only weighs 400 lbs, and displaces some other weight, and
2) Weight adds relatively little energy consumption on a electric vehicle with regenerative braking. Aerodynamics are much more important.
That 400 lb requires a hundred+ lbs of structural weight to support. Likely 10 mm wider tires, heavier springs, bigger wheel bearings & shock absorbers, thicker sheet metal (remember that 400 lb must be controlled in an accident from any direction). Add the weight of battery cables as well.
That is an appreciable % of the total weight of the car.
Adding a second 500+ lb for a second battery reduces the range of the first 400 lb battery.
My SWAG is that 400 lb of "dead weight, sprung" adds 150 to 250 lb of extra weight.
Alan
Alan,
You are right about needing that additional >150 lb, weight, but Nick has a good point about air resistance being more important that weight especially if the larger batteries allow a higher % of regenerative braking to be captured, and if vehicles have harder tires.
Most city driving is going to be electric only, while most long distance driving will be at constant high speed dominated by air resistance. Owners that always need to travel >40 miles each way or are unable to re-charge at work, could benefit from larger range, I would suggest batteries that can use more than 50% of the charge, at expense of having to replace sooner.
It may be that GM will up the useful capacity with further testing. If I was the CEO I wouldn't be concerned about 10 years warranty, just sell the cars without batteries and have yearly lease payments on the batteries about the same cost as servicing. People are going to see that's cheaper than buying petrol every week. They already take responsibility for the drive train of a ICE for 5 years, PHEV's are going to cost less for drive train warranty, so can spend it on battery replacements. Taxis could pay a lease based on miles.
"That is an appreciable % of the total weight of the car."
Sure, but it doesn't matter.
"Adding a second 500+ lb for a second battery "
Yeah, but no one's really talking about doing that.
1) adding additional battery capacity to, say, a Prius, would allow other things to get smaller, like the fuel tank, and the ICE.
1b) as I said before, weight's not that important in an EV or Extended range EV.
2) we're not talking about adding additional battery capacity to, say, a Prius, we're talking about a whole new system, which is more efficient: .2 KWH/mile, which is the same or less than a Prius.
It's 15% of an ICE vehicle. It's 2/3 as much as an electric train. With 4 people, it's less than an electric bike per pax-mile (at the same speeds).
It's low enough. The perfect is the enemy of the good.
You think electric bikes use more than 50 Wh/mi? The claims I've seen put them around 20.
Well, you see, I qualified that as "at the same speeds".
An electric bike might use only 10wh/mile, but that's at 5-15 miles per hour. Bikes have terrible aerodynamics (though not a big cross-section), so an input of 50Wh/mile will be needed to allow you to move close to the normal cruising speed for a Prius (if you're that kind of risk taker).
OTOH, a Prius at 10MPH might well use only 800W, or 80Wh/mile (and 20Wh/pax-mile, with 4 passengers).
"2) Weight adds relatively little energy consumption on a electric vehicle with regenerative braking. Aerodynamics are much more important."
Not really true.
In an electric vehicle the energy from regenerative braking returned to the wheels to get the vehicle moving from stopped or to go faster is in the 60 to 65% range. The generator/motor can only convert 90% (general efficiency for large, 50hp+ motor) of the kinetic energy (1/2m[v squared])into electricity. This power (amps x volts) is then converted by the battery into stored chemical energy, which has an efficiency of maybe 80 or 90%. The faster you put the energy in the battery (greater amps) the greater the heating of the battery as the internal resistance (R) of the battery is constant and the heat energy (waste energy) goes up by the square of the amps (Ohms law w = I squared * R)).
When the battery's energy is quickly convert from chemical energy into electrical energy the reverse process loses energy as heat since current flows through the battery and the motor. Thus, kinetic energy of car into chemical energy of battery (braking action) is 90% x 85% for 77%, then battery chemical energy into kinetic (acceleration of car) is 85% x 90% for 77%. So 77% x 77% is then 60% for overall regenerative efficiency.
Trains are much more efficient at regenerative braking!
Trains have very large motors, 200hp for transit car, 1000hp for locomotive, so their efficiency is higher, between 95 to 98% and the energy is put into the electric power grid for another train to use (transit trains are a couple miles apart on copper transmission cable using DC power) so losses here are maybe 2 or 3%. Thus trains have a 85 to 90% regenertive braking efficiency. New transit power systems are using stationary flywheels driven by large motors to store this extra braking energy that is not immediatly needed by nearby trains. Overall conversion efficiency of flywheels are 92 to 98% according to Pentadyne.
mbnewtrain,
According to MacKay"sustainable energy without hot air", cars require about 0.1kWh/km to overcome rolling resistance( this is approx proportional to weight) but at 40km/h(city traffic) air resistance is 0.2kWh/km(x2) and at 100km/h(expressway driving) air resistance is 0.6kWh/km(x6 rolling resistance).
A larger battery will allow more recovery of braking compensating for extra weight in city driving, but on long distance ICE travel the extra battery weight will be a very small part of energy use, since >80% is due to air resistance.
your analysis makes a good case for larger batteries,= better regenerative braking efficiency, so a Prius will not recover as much braking energy as a Chevy Volt because it has a smaller battery.
Were that true, the car would require 60 kW (roughly 80 horsepower) to cruise at 100 km/hr. This is utterly bogus; a vehicle with 2 m² frontal area and a Cd of 0.29 running at 100 kph through air at 1.25 kg/m³ would have ½A Cdρv³ = 7.8 kW of air drag.
Sanity checks are your friend.
Engineer,
The example was for a car with CdA=1.0, for a Prius, (CdA=0.6) he gives half of that 40kWh/100km(total) at 100km/hr, possibly he was thinking of a large SUV? Whatever, air resistance increases v^3, rolling resistance almost constant.
Your velocity term has one too many exponents.
Result should be about 300W of air drag.
Does it really? Let's take a look.
In the expression ½A Cdρv³, the terms ½ and Cd are dimensionless. Let's drop them.
We're left with Aρv³, which have the units (m²)(kg/m³)(m³/sec³). The result has the units of kg-m²/sec³, which happens to be equal to joules (kg-m²/sec²) per second, or watts.
Hmmm. Good thing you didn't have any money riding on that. ;-)
Actually, it's trivially obvious. The highest-order term of air drag rises as speed squared, but power is drag times speed so its highest-order term is speed cubed.
Ideally it would be weight neutral as would replace most of the steel in the car with aluminium and carbon fibre, but as you said in doing that you have increased your costs. Since the main use of the electric drive is for regen braking and launch assist, the batteries could be supplemented with supercapacitors for a much lower total weight.
Enemy of State's post is correct.
Also, development on these started more than 15 years ago, when li-ion wasn't feasible; NIMH wasn't fully tested; and batteries were much more expensive.
The Prius design leverages a relatively small battery (effective capacity = .35 KWH) and electrical system, and is relatively conservative. The Prius parallel design is optimal for a small expensive battery. A serial hybrid, like the Chevy Volt, is no more efficient if the battery is the same size as the Prius.
The planned Chevy Volt 8 KHW effective battery capacity is an optimal design for a world where batteries are a lot less expensive than they were then, and a bit less expensive than they are today. Fortunately, that's highly likely by the time the Volt is mature, in 2-4 years.
A series hybrid tends to be less efficient and heavier AFAIK. With a parallel hybrid a manufacturer can put more power from the engine to the wheels more efficiently, since the mechanical energy doesn't have to be converted to electricity and then back to mechanical energy, and this also allows for a smaller motor all things being equal because more of the power the engine makes can get to the wheels. In terms of power, a serial hybrid also has to carry more batteries with a smaller engine in order to see the same power output. For instance a one litre diesel at 3k rpm would make ~30hp at the flywheel, and ~18hp at the motor. Top speed would probably be limited to ~70+mph on flat ground, and less on an incline.
All things considered, a diesel has superior off-load efficiency compared to a gasser, but also costs more, so hybridization of a diesel results in diminishing returns, especially since production diesel sub-compacts can get ~100mpg@55mph and so on. Spending an extra $5k for an extra 10-20mpg just isn't worthwhile, even in Europe where fuel prices are higher.
"A series hybrid tends to be less efficient and heavier AFAIK"
In practice, probably not: the Chevy Volt is spec'd for 50 MPG, for the roughly 20% of travel that will take place using the ICE. Sure, at highway speeds a mechanical connection between the ICE and the wheels is efficient, but the conversion losses for ICE->electric motor->wheel are small. OTOH, if the ICE is completely disconnected from the wheels, you can optimize the ICE's performance more, especially RPM.
Finally, the serial hybrid design allows all-electric performance. In a parallel hybrid, it's difficult to avoid using the ICE, even for relatively short trips.
In practice, the Volt hasn't been spec'ed for anything over any EPA test cycle, and I wouldn't place much in pre-production claims, especially since Chevy wanted to have the test run without recharging the batteries so they could get a 100+mpg figure. In terms of efficiency, an electric drivetrain is around 85% efficient at road load, and at best generator efficiency is around 90%, so we're looking at ~76% efficiency at best. The change in speed in a parallel hybrid results in a ~96% drop in efficiency, so we're looking at a 20% drop in efficiency at least when going with a serial hybrid instead of a parallel hybrid. Course, going with a serial hybrid bypasses many licensing issues, and for a PHEV running on all electric power, the larger motor is required, but in terms of engine efficiency parallel hybrids tend to be better than series hybrids, since there is less in the way of energy conversion, although they are both much better than conventional drivetrains given normal driver habits.
In terms of using the pack, both a parallel and series can use the same amount of energy and go the same distance all things being equal, since in both cases we're just looking at battery to motor efficiency. A parallel plug-in hybrid offers better efficiency when using gasoline and more power to the wheels in a slightly smaller package all things being equal, but a series plug-in hybrid avoids licensing issues with parallel hybrid tech, and allows more in the way of packaging options, such as having the motor in back and engine up front, as opposed to the combined package seen in parallel hybrids today.
"the Volt hasn't been spec'ed for anything over any EPA test cycle"
I'm not sure what you're referring to. I think this article may give better info: http://gm-volt.com/2008/09/26/calculating-the-volts-eps-rating-more-than...
" The change in speed in a parallel hybrid results in a ~96% drop in efficiency,"
I assume you mean 4% drop. I'm not clear how you're getting from that chart to a 4% drop. I would note that in a Prius that real-world MPG varies enormously, depending on driver habits (i.e., lead-foots get a less efficiency) where a serial-hybrid engine speed is automatically controlled.
Your article is interesting, but the abstract doesn't give any test-cycle or overall numbers.
Let's remember that that a 40 mile electric range covers 80% of miles driven, on average, so the efficiency in that 40 mile range is much more important. A serial hybrid with 40 mile range will eliminate liquid fuel consumption for those 80% of miles, whereas plug-in parallel hybrids still use a fair amount of fuel in that range.
The article talks about how GM wants to include the charge from the battery in testing, something other manufacturers aren't allowed to do these days, and mentions 50mpg. They also mentioned that the Volt would cost $25-30k initially, and then ran that up to $40k, so I wouldn't put much stock in what they say. If you want to see an accurate comparison, wait until the EPA publishes the Volt's EPA combined cycle test results and compared them to other cars of similar type/size.
Yup. The drop comes from running the engine through a much wider rpm range, with the 4% drop in fuel efficiency, as opposed to running it at a fixed speed and getting hit with the 25% drop in fuel efficiency from converting mechanical energy to electricity and back again.
Test cycles actually, but unless you have any convincing info or can rewrite the laws of physics, a serial drivetrain will be less efficient in terms of drivetrain efficiency when using gasoline than a parallel one because the energy has to change forms more often. Basic physics. Unless running at a fixed speed allows for a proportionally greater increase in engine efficiency, which it doesn't AFAIK, then a serial layout is less efficient.
All things being equal, a serial PHEV with 40 miles of range will use exactly as much stored energy as a parallel PHEV with 40 miles of range does. Just because a hybrid has a parallel layout doesn't mean it has to operate in blended mode during the first 40 miles, at least if we're looking at a fair comparison. After that, the parallel hybrid will use the gasoline more efficiently AFAIK. It isn't a huge difference, but it's certainly present.
Rolfwaffle,
"The article talks about how GM wants to include the charge from the battery in testing, something other manufacturers aren't allowed to do"
No other manufacturers to date are wanting to test a vehicle that can go first 40 miles without the ICE engine, THAT'S THE BIG advantage of the Chevy Volt. The all electric EV's don't need a mpg rating because they don't have an ICE engine.
"All things being equal, a serial PHEV with 40 miles of range will use exactly as much stored energy as a parallel PHEV with 40 miles of range"
We are not talking about energy use, it's petrol use! Are there any parallel PHEV that don't use any petrol in first 40 miles of average driving?
If we have a real fuel shortage,(ie none) serial PHEV drivers and EV drivers will be able to still use a vehicle for short trips, ALL other vehicles may have to be parked.
We aren't talking about what share of the market each manufacturer wants, we're talking about whether or not serial PHEVs are as efficient as parallel PHEVs.
Um, petrol is chemical energy. The drivetrain that uses it most efficiently, all things being equal, is the most efficient drivetrain. Are there any serial PHEVs that don't use any petrol in the first 40 miles of average driving? No. There are no production PHEVs available to the public. There are pre-production parallel and serial PHEVs, but no one has even released comprehensive specs, and if oil prices stay low they may get canned.
If we have that sort of a fuel shortage any PHEV owner, serial or parallel, will still be able to use their vehicle provided they can charge it, just like EV owners, and cyclists believe it or not. ;)
You seriously underestimate the improvement in engine efficiency. See the efficiency map below (from this article):
Engine efficiency in that operating regime is roughly doubled.
Your own figures in this comment are inaccurate, because you're including battery losses when the power would be flowing directly from alternator to motor.
If it becomes important enough to minimize the losses when running with the sustainer on, the electronics could include a cycloconverter to bypass both the battery and inverters. There goes the rest of your argument.
Parallel hybrids already operate at peak efficiency, see the BSFC map I posted earlier. In the case of the Prius, operating over a ~4k rpm band as opposed to a fixed speed results in BSFC dropping from ~230g/kWh to ~240g/kWh, so we're looking at ~37% peak BTE to a little less than 37% peak BTE. If you were comparing conventional vehicles to a serial hybrid, then your statement would be accurate, but parallel hybrids already operate near peak BTE for SI engines, given emissions/drivetrain losses as well. The only loss is from operating at lower/higher engine speeds with the associated pumping/friction losses, so a going from ~37% BTE to ~35.5% BTE, compared to only operating at peak BTE.
If you reread the comment you may notice that I was using the other poster's assumptions, so it isn't that I think it's accurate for the Volt to be running power through the batteries all the time, but that I was using their own figures to illustrate that mine were more or less the same.
In terms of power output, the engine/alt will provide all the power once the batteries reach 30% soc, but that also means the engine will see the same change in BSFC wrt speed that parallel hybrids like the Prius see.
Anyway, ~75-80% would probably be the efficiency spread depending on the power requirements, since the engine will be operated in a manner almost identical to the engine in a parallel hybrid, w/ the exception that it's converting mechanical energy to electrical energy, and then back to mechanical energy, as opposed to putting mechanical energy directly to the road.
Cycloconverter or not, the Volt's engine will have to operate proportionally more efficiently than the engine's of other parallel hybrids like the Prius. Clearly the engines in parallel hybrids already operate at or near peak BTE, so as you rudely stated, "there goes" that portion of your argument, and in order for the Volt to be as or more efficient than a parallel hybrid, it's engine must operate ~25+% more efficiently (outside of using a cycloconverter, which I've seen nothing about it using) than similar engines in parallel hybrids. If you have proof of this, via a BSFC map preferably, I'm all for it.
I think we're wandering away from the important thing here: a vehicle like the Chevy Volt isn't really a "plug-in serial hybrid", it's an EV with a range extender. In the real world it will only use the ICE for 20% of miles driven, and use only 10% as much fuel as the average ICE vehicle. The electricity it uses will be mostly at night, and be synergistic with wind and nuclear power, which need night time demand and demand-side buffering.
OK, down to niggling details:
"The article talks about how GM wants to include the charge from the battery in testing,"
Not really. It talks about how testing would need to be broken down into two parts: EV-mode (charge-depleting) and hybrid mode (charge sustaining. "I spoke with Mike Duoba who is a national expert on plug-in hybrids at the Argonne National Lab and who chairs the SAE committee charged with developing efficiency labeling standards for plug-in cars.
He describes a methodology typically used called the full charge test. In this test, the E-REV runs through standard federal driving cycles until the car switches from charge-depleting to charge-sustaining mode. It then runs for an additional cycle. One then calculates the gallons of gas used over the number of miles driven."
You're not suggesting that EPA testing ignore the EV-mode, are you?
"They also mentioned that the Volt would cost $25-30k initially, and then ran that up to $40k"
Well, they initially said below $30k, and now they're saying high 30's. Why? because they realized they have a hit on their hands, plus they got a $7.5K credit, and they know they can charge more. Not a perfect reason, but when you're on the edge of bankruptcy, I think we can agree it's what they should do.
"The drop comes from running the engine through a much wider rpm range,"
People can get anywhere from 35MPG to 75MPG (or more) depending on how they drive. There are more variables than just RPM. A big one is the fact that the Volt can turn the engine off entirely, eliminating the waste that comes from just running when you don't need to.
"a serial drivetrain will be less efficient in terms of drivetrain efficiency "
But, does it matter? If the Prius can get 60MPG on the highway, properly driven, and the Volt only gets 50MPG, does it matter? A Prius, driven the standard 12k miles, uses 240 gallons/yr. A volt would use 48-60, depending on the MPG: a 12 gallon difference.
The perfect is the enemy of the good.
more later....
Those are the same thing AFAIK. In terms of naming conventions, there is no such thing as an EV with an integrated (factory) range extender. If something has both an electric motor/battery pack and an engine moving it, it's a HEV. If it can be plugged in to recharge the on-board battery pack, it's a PHEV. If there's no factory engine, just a motor, then it's an EV. If there's a removable genset, maybe even a pusher, then it's an EV with a range extender.
E-Rev instead of PHEV is just some bizarre marketing scheme GM is pushing, maybe because of all the bad publicity they got because of the EV1?
Real world electricity consumption versus gasoline consumption depends on real world drivers, and since we don't know what the demographics of PHEV purchasers looks like, we can't say much about how much it would use compared to a conventional vehicle or a conventional hybrid. In terms of charging, the excess probably won't come from nuclear power since it's already at 95% capacity factor. Wind otoh could be a suitable resource, and it seems to be scaling pretty well so far. there's certainly enough transmission capacity at night for a fleet of PHEV sedans, and as long as renewable installations continue to outpace PHEV sales, we shouldn't have to use coal for off-peak charging, although some areas may still use it due to good ol' boy politics.
And during the first part it's using energy from the battery pack, which is exactly what I was saying.
Course, this is somewhat unfair since other hybrids need to have the batteries near a full charge after the test, so why shouldn't the Volt comply with that requirement? I could also see separately rating the Volt, eg it'll travel 30+ miles over the combined EPA City/Highway tests on just electricity, and when it's depleted it gets 45+mpg on gasoline over the EPA combined, but mashing everything into one test doesn't give the consumer a transparent view of what kind of energy consumption they're looking at.
No, I'm suggesting the EPA publish the electric and gasoline data separately. For instance, saying it can go 30+ miles on the batteries over the EPA combined cycle (40+ miles city and 20+ miles highway, or whatever the specifics are) and it has an combined EPA mileage rating of 45+mpg (with whatever mileage highway and city).
I think I answered most of this in another reply (to your last comment).
I added a few things to my previous comment, which I think you missed because you were answering the previous version. I'll copy it there:
"They also mentioned that the Volt would cost $25-30k initially, and then ran that up to $40k"
Well, they initially said below $30k, and now they're saying high 30's. Why? because they realized they have a hit on their hands, plus they got a $7.5K credit, and they know they can charge more. Not a perfect reason, but when you're on the edge of bankruptcy, I think we can agree it's what you should do.
"The drop comes from running the engine through a much wider rpm range,"
People can get anywhere from 35MPG to 75MPG (or more) depending on how they drive. There are more variables than just RPM. A big one is the fact that the Volt can turn the engine off entirely, eliminating the waste that comes from just running when you don't need to.
"a serial drivetrain will be less efficient in terms of drivetrain efficiency "
But, if it were true, would it matter? If the Prius can get 60MPG on the highway, properly driven, and the Volt only gets 50MPG, does it matter? A Prius, driven the standard 12k miles, uses 240 gallons/yr. A volt would use 48-60, depending on the MPG: a 12 gallon difference.
The perfect is the enemy of the good.
All right, let's cover the last few niggling details:
"All things being equal, a serial PHEV with 40 miles of range will use exactly as much stored energy as a parallel PHEV with 40 miles of range does."
Not really.
1)Electric energy uses far fewer BTU's than chemical energy: .2 KWH/mile, vs .7 KWH/mile equivalent for gasoline (35 KWH/gallon / 50 MPG). To the extent that the parallel PHEV is using the gas engine, it's being less efficient, and
2) Peak Oil is a liquid fuel shortage, so savings gasoline is a bit more important, and
3) electric energy is going to be, in general, much lower CO2 per BTU.
"Just because a hybrid has a parallel layout doesn't mean it has to operate in blended mode during the first 40 miles, at least if we're looking at a fair comparison."
No, but in the real world it will: you have to drive very carefully not to engage the ICE below the cutover speed, and of course, you can't drive above the cutover speed.
"After that, the parallel hybrid will use the gasoline more efficiently AFAIK. It isn't a huge difference, but it's certainly present."
Again, not overall - the most efficient engine is the one that's not running.
I think you should reread my post, or maybe I should be clearer, probably both. All things being equal, the parallel PHEV isn't using the gas engine until the serial PHEV is using the gas engine. In other words, for the first 40 miles, a 40 mile serial and parallel PHEV use the same amount of stored energy from the batteries, and only the energy from the batteries. After that the parallel PHEV uses gasoline more efficiently than the serial PHEV.
First off, there's no "real world" example of either, because there are no production PHEVs, and second, you're assuming different operating behavior because it suits your argument. All things being equal, a serial and parallel PHEV will have the same operating parameters, glider, and so on. In other words, they'll both have a 80kW, or whatever, electric motor, and they'll both operate on just the battery until whatever SOC, and which point they'll switch over to the ICE, and at which point the parallel hybrid will be more efficient at using gas than the serial is. We have to compare them on equal footing, otherwise other one of us could assume a serial or parallel hybrid was more efficient than a parallel or serial hybrid because in our example, the parallel or serial hybrid was in a dump truck and the serial or parallel hybrid was in a velomobile. ;)
Then you aren't comparing serial versus parallel, but blended versus un-blended, or whatever, which is fine, but not what I talked about. I'll say it one more time, all things being equal, a parallel hybrid is more efficient than a serial hybrid at using gas. We can't assume one will operate in blended mode while the other won't unless all we want do nothing but present a disingenuous argument, in which case we don't even need to go that far, just plunk whichever one we don't like in a garbage truck and the other one in a velomobile. ;)
I think I understand, now, why we're talking past each other - you're talking about the theoretical, and I'm talking about the models that will be for sale in the next 5 years.
"All things being equal, the parallel PHEV isn't using the gas engine until the serial PHEV is using the gas engine. "
Theoretically true, but not true for the big contender here, the plug-in Prius. See this article: 14 specially customized plug-in hybrid Toyota Priuses didn't do much better than standard Priuses in fuel efficiency. Google's own fleet of hybrids and plug-in hybrids (Ford Escapes) are only averaging 28.6 mpg while their pluggable versions of the Escape hybrd get 37.7 mpg for a 32% improvement. That's not quite what we'd want.
The main problem is that they're starting with a Prius or Escape. Both of these are parallel hybrids which use both the gasoline engine and the electric motor, even if you stay within the 30 mile range of the batteries. If you drive with a leadfoot or at highway speeds, the battery doesn't get used that much.
A series hybrid plug-in like the Chevy Volt has only an electric motor. It uses only the battery for the first 40 miles. 78% of commuters wouldn't use any gas at all. Combine that with 50 MPG (twice as large as the average US light vehicle) for the 20% of driving after the battery runs low, and overall fuel consumption would be reduced by about 87%* (for a 567% improvement in MPG!).
* A Volt would use about 20% as much fuel as a very efficient (35MPG) conventional car - that's 12.6% as much fuel as the average 22MPG car.
Are you aware of any PHEVs from major manufacturers that behave like a ErEV (IOW, that can run solely on the electric motor at highway speeds, turning off the ICE)?
Thanks Nick. You've made it clear why series hybrids are superior solution. Parallel hybrids are probably a bridge to nowhere. Series hybrids on the other hand could end up as BEV with improved, cheaper batteries or Fuel Cell vehicles with affordable fuel cells.
One point about the ICE being used in the different variants is that aggressive driving will cause the ICE to be used a lot more in a parallel hybrid. Whether the ICE is used or not depends on the output power required so uphill driving, hard acceleration or anything that requires more power will cause the ICE to come on line. In an ER-EV the ICE will not come on before the batteries reach a certain stage of depletion regardless of how you drive. So if you drive both cars aggressively over a 10 mile route, the gas used by a Prius or equivalent is any body's guess while the gas used by the Volt = 0.
On the commercial vehicle front the numbers speak volumes. This news from Jan 2008 is about GM-Allison securing orders fo 1,732 of their two-mode hybrid buse and expecting to deliver their 1000th in the same month. The month before Daimler announced that they had received orders for 1052 more of their series hybrids. What is significant though is that the New York MTA alone already had a fleet of 850 with the order to double that by 2010. The OC Transpo order of 202 buses to be delivered by 2010 would make it the THIRD largest hybrib bus fleet in Canada. If you look at the Daimler Orion News page, they seem to be chalking up higher numbers than GM-Allison. Added to that porsena's comment about BC Transits experience with their parallel hybrids and contrast that with the NREL assesment of the NYC (series) hybrid bus program and you'll see where I'm coming from.
Alan from the islands
I think you are being too conservative with electric drivetrain efficiency. I can see alternator efficiencies in the 92 - 93% range especially if optimized to run at the specific single speed output of the engine. Motor + power control electronics efficiency can be closer to 90% though will vary with load and often at times will be less. Battery storage efficiency will detract somewhat being anywhere from 70 - 95% depending on technology. Let's not forget that the transmission in the parallel approach is not lossless as well. It is better than the electricity only approach but not better enough to forego the flexibility and optimization advantages of the series approach.
A series hybrid has to be the longer term goal. The parallel is a stop gap measure. Many alternative drive trains like fuel cells produce electricity directly without undergoing conversion from mechanical. In combination with Alan's electric rail proposal, it gets us closer to petroleum free transport.
I don't think I am, at least for a powerful motor capable of moving a 3000lb car. AC Propulsion specs puts their AC150 drive train (motor/power electronics) at 86% road load, and a 92% efficient alternator charging a 95% efficient battery, which seem to be in line with your high estimates, is at ~75% eff overall. Both parallel and serial setups require gear reduction, unless you want a direct drive 12k rpm AC motor capable of running 800+mph with 195/50R15 tires. ;)
Series or parallel these days seem to be depend on whether or not the manufacturer has access to the appropriate licenses, and what the desired vehicle specs are. All things being equal, a parallel offers better efficiency in terms of gasoline use, but this is in exchange for less acceleration to an extent, although this can be offset to a certain extent with a power split device and the additional ~50lb weight penalty.
"....Both parallel and serial setups require gear reduction, unless you want a direct drive 12k rpm AC motor capable of running 800+mph..."
Many AC motors can run at variable speed using "variable frequency drive" controller that allows motor to run at low RPM with greater power output. No transmission is needed . Many manufacturer's process equipment uses these controllers to vary the speed of motors and deliver large torque across a range of rpm's. Been done for 30 years.
What kind of power output are we talking about? Keep in mind the problem isn't speed, but power output at a given speed, since the motor would only be at ~750-1500rpm from ~50-100mph if it drove a wheel directly (w/o gear reduction). Can what you referred to somehow make the 200hp available at 12000rpm/800+mph in a direct drive setup now available at 100mph?
Edit- Btw, the Volt is almost certainly going to use gearing suitable for the 115mph top speed, not direct drive. ;)
When people say "transmission" in this context, they usually mean something beyond a fixed-ratio final drive. That's all most of these vehicles would need; the EV1 had one gear reduction, as does the Tesla roadster.
Which in turn are determined by the price of batteries, which determines whether it is worthwhile to make a vehicle which can operate as a pure electric. If the power or energy capacity of an affordable battery is too low, the engine will be operating much of the time anyway and the best implementation is parallel. If the engine is needed only as a sustainer, series works as well and relieves many packaging requirements in addition to allowing the sustainer to be optimized for efficiency, as matters like throttle response become irrelevant.
The price of the batteries aren't what solely determines vehicle specs, since each manufacturer seems to want to carve out a specific niche. It influences design, but so do many other things. In terms of series versus parallel, parallel will always be more efficient in terms of liquid fuel consumption all things being equal, unless the manufacturer can increase engine efficiency more than 25%, and in that case it isn't an all things being equal situation. Fewer energy conversions means fewer losses, especially since the engine on the Volt is supposedly going to be operated similarly to the engine in the Prius, so they can't even optimize for friction/pumping losses at a certain speed, not that it would increase BTE from 37% to ~45% in a small engine. That's heavy duty diesel territory IIRC.
Yes, but it prices many desirable vehicle configurations out of the market. E.g. it took high-performance NiMH to get parallel hybrids to market; conventional lead-acid just couldn't do the job. The high power density Li-ion technologies are re-writing the book yet again.
Says who? It makes no sense to do that, and the configuration certainly doesn't require it even in charge-sustaining mode.
You forget that the Volt configuration greatly relaxes demands on the engine for things like throttle response; a 3-second ramp to full power is entirely acceptable. You can optimize other things at the expense of transient response.
The last parameters I saw for the Volt stated 50 MPG in charge-sustaining mode, which is not particularly good. The sustainer engine is much bigger than necessary for the job (probably reflecting internal company politics); that can be fixed. There is no real reason that the engine cannot be optimized for one set-point and operated there unless absolutely required. There is also no real reason that a small diesel sustainer cannot use an insulated combustion chamber, pressure-wave supercharging, Diesel-Atkinson cycle, and other tricks to squeeze the maximum out of its fuel with minimal mechanical changes.
There's a lot of wasted energy in a typical ICE powerplant. Some parts of it, like exhaust overpressure, can be partially captured by turbocharging (or pressure-wave supercharging) and mostly tapped with turbocompounding or overexpansion. Modern control systems capable of tricks like HCCI can manage the touchier aspects of these also. If you start putting these tricks together I would not be surprised to see 45% in a small powerplant.
I don't see that. The HSD transmission can produce engine speeds much closer to optimum than you appear to believe possible.
that's a typo, it should be a 4% drop in efficiency. In other words, going from peak BTE at 230g/kWh in the Prius, to ~240g/kWh at the low/high rpm operating extremes.
With a parallel hybrid you can scale down the motors. The electric can provide some nominal power for cruising at highway speed and the ICE can pitch in when power levels above that are needed. With a serial hybrid the electric motor has to be scaled up to meet peak power demand by itself, the charging system in turn has to be scaled up if you need peak power for lengthy periods. There's trade offs that vary depending on the application and its a juggling of peak power requirements, space requirements, motor capacities, battery sizes, weight and cost. I think the Prius sometimes behaves like a parallel and sometimes like a serial depending on what its doing.
Take a look at www.megavan.org small, cute, cheap, highly flexible and can lug 400kg up to 30 miles. Designed to the EU quadricycle classification.
US total electric power capacity is roughly 1.1 TW http://www.eia.doe.gov/cneaf/electricity/epa/epat2p2.html
Electric Trucks without batteries
http://en.wikipedia.org/wiki/Trolleytruck
Best Hopes,
Alan
100mpg Hummer/SUV anyone?
http://www.rasertech.com/media/movies/html/fev_jan09.html
Nick.
I'm not sure if this is the best freight solution, but it might be valuable to use electric trucks for local delivery and to drive the trucks onto electric rail cars for long-haul to be charged in transit. Once at the destination, the truck can disembark and deliver the materials where needed.
Why carry the drivetrain, wheels, chassis etc. ? Just lift the payload, in a container, onto a double stack container train on one end and off at the other end.
Or place origination and/or delivery point on rail spurs.
Best Hopes for Rail Only Transport,
Alan
They're gonna have to do a hell of a lot better job making that electric truck look 'Macho', to generate mass sales. Maybe some phoney rough sounding exhaust too, so it sounds powerful. Remember, always sell the sizzle, not the steak.
The news is not all good. BC Transit has been running parallel diesel hybrid buses for almost four years and just last month started trial of a hybrid double-decker. The company says the original hybrid buses cost more to buy and run (pdf) than current conventional diesels unless there's a special subsidy, and that carbon emissions are under 15% lower than new diesel-only buses.
porsena,
That makes sense, diesel engines are reasonably efficient in city traffic, so the 15% saving is mainly capturing re-generative braking. Now if those buses had been series hybrids, and with fast re-charge at some bus stops, they could have reduced diesel use by >90%, 15% from regenerative braking, 75% from running 3/4 time as electric only.
I say make the electric rail vehicles small.
Do they really need to be big? Is bigger really better ?
They already make one. It's called a trolley. Used in several cities including Portland and New Orleans. They have about twice the floor space as a bus but require only 1/2 the energy to move at 30mph.
http://www.cs.uiuc.edu/homes/friedman/car29/tn_NOPSI__29_jpg.jpg
In service since 1896 in New Orleans.
Best Hopes for proven solutions,
Alan
It's a feature of carrying groups of people.
250 people weigh on average around 20 tonnes.
You need a vehicle structure which can carry that safely. That will be around 40 tonnes.
You need an engine which can accelerate 60 tonnes
You need brakes which can stop 60 tonnes.
Then you need a rail infrastructure which can carry the 60 tonnes. And that's per carriage.
Rail is big because it carries groups.
If you carry individuals the whole equation changes. Then you can have a very small light system.
Interesting article and a breath of fresh air, thanks. It makes a change from the usual nonsense we get on TOD about electric cars which we don't need, rather than electric commercial vehicles which we do need.
If a sufficient degree of localisation is achieved, then there is good reason to adopt commercial electric vehicles for use in the local economy. Personal transport can be via feet, bike or bus/trolley car/train combination.
But I won't be holding my breath till it happens.
Light Rail Vehicles
http://www.trolleystop.com/lightrail.htm
http://tinyurl.com/dkafn8
http://www.ultralightrail.com/HTML_Files/INTRODUC.HTM
http://www.ibabuzz.com/transportation/2007/11/01/ultralight-rail-just-li...
And a technology which could potentially do away with personal and commercial vehicles generally:
http://en.wikipedia.org/wiki/Personal_rapid_transit
Impractical, unproven with ridiculous, fairy tale claims by promoters; without any real world proof.
Decades of trying and no real niche (small & specialized) found yet, although airports MIGHT work.
To claim that PRT can replace "generally" all people & freight movement is absurd. PRT cannot pass ADA requirements in USA (wheelchair self evacuates if stranded) so they cannot be built here.
Costs of prototype PRTs are out of controi (see Morgantown, Miami, etc.).
Best Hopes for Proven Technology,
Alan
I still feel this could be of some value ...
http://www.andygraham.net/railbike/railbike.htm
Highly practical. Unproven yes, but being proven right now, at Heathrow and Masdar City in Abu Dhabi.
Proven technologies aka rail simply can't do the job people need. Despite massive subsidies less than 10% of passenger miles are by rail in developed countries. In fact, people will almost certainly resort to the horse and cart before having to rely on rail because it is physically unable to make the journeys people require.
Already in use for freight movement at the largest port in the EU. Frog have had what is essentially a PRT system in place at Rotterdam for moving freight around for several years.
e.g.
http://www.youtube.com/watch?v=RdNb5vi_23Y
Good luck sitting in traffic then.
Morgantown isn't PRT for a start. The ATS system at Heathrow is within budget and on time. Perhaps it's simply better management. Perhaps the technology is no longer based on prototypes.
In Sweden 2008 were 20% of all travels longer then 100 km via rail, the 2007 market share were 16% and the trains are more or less full. We are now doing a large scale experiment by opening passanger rail for free competition as freight rail has been turned into a reasonably working market. The benefits will however be limited due to lack in capacity in the rail system that will take a decade or two to fix but some new operators have busines ideas that can fill empty slots.
The government passanger rail company is making a small profit but the profit is limited due to deliveries of new trains and renovations of old trains.
Usage of short haul rail depend on the buiding structure and travel patterns built up during decades. The most rail intensive region is the Stockholm region where the total travel market share 2007 were 24% collective traffic, 3% biking, 29% walking and 44% car travel. The per mile market share were 28% collective traffic, 1% biking 3% walking and 68% driving. The distribution between collective travels during a regular workday were 975 000 by bus, 1094 000 subway, 242 000 "s-train", 123 000 tram.
There are about a dozen possible and reasonable heavy investments in rail travel in Stockholm but it is indeed very expensive to build them. They need a healthy economy that amortizes them for several decades but that is ok since they are usable for +100 years. There are also a few reasonable sports for PRT:s but that is another kind of niche solution that is very expensive to establish. The obvious low cost short term addition to the travel infrastructure is establishing biking infrastructure since that market share is tiny while such infrastructure takes little room and has low cost.
But the bulk of the travels will continue to be with cars, the long term question is probably if will be with tiny wehicles that sacrifices comfort, capacity and safety or with larger electrical or plug in wehicles. And I expect that towns and cities with good collective traffic, espcially with rail, will continue to thrive.
Transportation is a complex web of overlapping systems where what can be accomplished depends on manny generations of previos investments.
less than 10% of passenger miles are by rail in developed countries.
Simply bad "facts" (a specialty of PRT promoters in my experience). And since PRT will not be doing cross country trips, irrelevant. Urban trips are what counts.
Trams + bicycles + walking can handle the vast majority of urban trips.
Velibs (rental bikes, first half hour free) are working on a large and growing scale. *MUCH* larger "installed base" than PRT.
And it is true that PRT cannot meet the ADA requirement for self evacuation of wheelchair passengers in the USA, a fact ignored by PRT promoters.
And since PRT cannot perform as the promoters claim, (no evidence to the contrary), PRT will make no differnce in traffic congestion.
Latest 'commuting to work" stats for New Orleans
Bicycling - 3%
Walking - 4.4%
Streetcars & Buses - 20.x%
Motor Vehicles (including scooters & motorcycles, a decent % by observation) - 72%
Suitable investment in proven technologies and less parking could get car use below 1/3rd. No PRT required.
Alan
It seems like we went over this before, but the PRT system can be debunked by anyone who has been to a crowded ski area. There is no way you would fill up private rail cars to the capacity of trains or highways without having six lane rail tracks. You would substitute traffic jams with big crowds jams waiting to get on just like the lift at crowded ski areas.
This article shows good potential for local delivery trucks using hybrid systems to decrease use of diesel fuel.
The main drawback to any grand scale US plan for electric vehicle that take power from the grid is the need for source energy. Although the power generating system of the US may have 30% spare capacity at night, what energy source would provide the extra gigawatts to charge all the batteries?
Solar and wind supply less than 2% of US electric power, while coal supplies 52%, nuclear around 17%, and natural gas around 20 to 22%, and balance mostly hydro. Given the split between these sources, I would say most new power would have to come first from natural gas and second from coal, with wind as a smaller distant third source. Sounds like we need to examine where the extra natural gas would come from and how the over taxed railroads can haul the coal before advocating a large percentage (25% or more) of our road vehicles take power from the grid.
mbnewtrain,
If all new trucks and cars were electric,it would take 30 years to replace existing fleet of vehicles, say 3% a year.
This would require eventually 3000GWh/day or 125GW average(30% increase) to power these 250 million vehicles. This would mean an increase in new energy production of 3.75GWa each year.
Now lets look and see if wind power could supply all of this; last year US added 8.3GWcapacity =2.7GWa, so if wind capacity increased by 30% next year could start immediately supplying all new electric vehicles. Considering that wind power has been increasing by 30%for last 10 years it's not a big stretch to think that wind power will at least increase by 30% next year or in 2 or 5 years time.
That's all we need as far as supplying power!, building all new vehicles as EV or PHEV is a much larger challenge
A big part of it, maybe all, could come from Negawatts.
There is simply so much wasted energy built into our system. Of course those existing watts are still coming from the dirty sources you mentioned, but it does offset the need for a lot of increased generation.
The small municipal government where I work has just purchased its first GEM NEV. It is a two-seater with a flat-bed in back, for use by our public works dept - water meter reading and various other light duties. Working great, already getting a lot of use. Before, they were always hopping into a pickup truck, so this will definitely save energy.
I added some paragraphs to the end of the post that I missed. I think these are very helpful.
Electric Pros and Cons
Battery powered electric vehicles have restricted range. Overcoming the range restriction carries significant penalties in terms of battery pack size weight and/or cost. For commercial vehicles, the range limits are not an insurmountable problem as a large percentage of delivery vehicles operate on fixed routes and schedules so their use and charging cycles can be planned with more certainty than an individual's personal transportation. In addition, larger commercial vehicles tend to have more space that can accommodate larger battery packs without impacting the cargo or passenger areas. Smaller delivery vehicles tend to do shorter range trips so smaller battery pack sizes offering limited range are not a big issue. In any case, routes can be planned so that vehicles return to base long before they run out of juice and the fleet operation bases can be equipped with high power, fast charging stations or battery swap stations if fast turnaround times are more important than the cost of spare battery packs. In some cases the loading bays at destinations could be equipped with fast charging stations so that batteries could be topped up for the onward or return trip while the vehicle is being loaded or unloaded. School buses, airport shuttles and other passenger moving operations that frequently move people on routes that are less than 50 miles round trip also present opportunities.
Although Electric drive systems attract a higher initial capital cost of at least 30% more than a similar conventional vehicle, they should be able to gain some serious traction in the commercial vehicle market since electric drive in commercial vehicles results in significantly lower operating costs in the form of reduced fueling costs and lower maintenance costs. The only parts that can really wear out in an electric motor are the two motor shaft bearings and one only need look at electric motors used in industry and commerce for an indication of how much maintenance will be required there. For battery electric vehicles, the only oil changes required, are for transmissions and final drives which are less frequent than the oil changes required by an ICE. If regenerative braking is used, the vehicles are able to go more than twice as far between brake lining replacements. In series hybrids, clutches and complex transmissions are not required so drive train maintenance can be greatly reduced while the ICE used to generate power is usually set up to operate under optimum conditions, extending service intervals and the useful life of the engine.
What Should We Be Doing Next?
The fact is that while electric drive systems are being produced by the hundreds, internal combustion engines and their related transmissions are being produced by the hundreds of thousands. Component costs will not come down as long as these relatively minuscule number of electrically driven vehicles are being manufactured and sold. It is the classic cache 22, for prices to come down volumes must go up but, for volumes to go up, prices must come down. In this situation, something must happen tip the scales and make the new technology irresistible, like the fuel price shocks of 2008. However in this post shock recessionary climate, fuel prices have plummeted and the new, more efficient but, initially more expensive technology has lost it's luster resulting in buyers returning to the safe haven of buying what they've always bought. It is still quite remarkable that many of the electrically driven commercial vehicles have sold in the numbers that they have and it lends credence to the thinking that the long term savings from their use are quite significant. According to Electrorides' numbers, it would appear that electric commercial vehicles are not hard to justify in terms of the savings compared to the additional cost of going electric.
If we wait for the next fuel price spike to stimulate demand for electric vehicles, several of the key players may fail and disappear in the meantime. Tax incentives, purchase rebates, increased fuel taxes are all tools governments can use to stimulate demand during hard times. If, as many readers of theoildrum believe we are perilously close to if not past the peak of world oil production, we are going to need alternatives to the almost exclusively fossil fuel powered transportation infrastructure that exists today. Hopefully the stimulus packages being devised around the world will help to provide an opportunity to this nascent industry, so that it will survive and provide a basis for a new generation of trucks and buses that will provide both a reliable and cost effective option for the transportation needs of industry and commerce as we enter a post peak world.
Tax incentives, purchase rebates, increased fuel taxes are all tools governments can use to stimulate demand ...
Until we are building out Urban Rail at close to an adequate rate (minimum $60 billion/year) I am generally opposed to wasting any gov't incentives on energy inefficient (directly and indirectly via supporting energy wasting urban & suburban forms) EVs.
Let the marketplace drive their development.
Finance experiments using Urban Rail "off peak" for trolley freight before EV trucks (although EV trucks are be the one exception to the above).
The best is the enemy of the good, and we are SEVERELY under investing in the best solution.
Best hopes for Urban Rail, bicycles & walking, NOT EVs,
Alan
Excellent article. This is the first time I have ever seen names given to the types of hybrids (Series & Parallel) but the distinctions will make it much easier to communicate to people. I have not purchased a hybrid to date because I have been waiting for a series model to hit the market. If we could get some numbers to show others about the efficiency improvements that would be great! I have heard a great deal of discussion on TV about how inefficient ICE cars are due to the amount of energy lost to heat and friction. It seems like a no-brainer to me that series hybrids should be significantly cheaper to manufacture and sell because they have about 1/3 the mechanical parts and two trunks!
In my final draft, I also took a shot at some of the established electric motor and auto-electrics component suppliers. Very few of them if any seem to have a significant interest in pure electric traction systems for cars and trucks. They're way too heavily invested in making starter motors, alternators and fuel metering systems for ICEs.
As for parallel hybrids, they add a good deal of complexity to already complex systems with the only advantage being lower fuel consumption and reduced brake lining wear. I do not see GM's two mode hybrid as a good long term solution and I suspect that Daimler's series hybrid buses will continue to outsell GM's two mode hybrids.
If/when oil becomes scarce and/or expensive, series hybrids will be much more attractive. It will probably not be difficult to retrofit series hybrids with improved battery packs, plug in capability and different types of power plants (fuel cells, turbines, CNG, biofuels or whatever). The fact is that plug in, series hybrids can take advantage of any source of electricity and if someone came up with the "holy grail" of batteries, they could remove the on board generators and be used as pure battery electric vehicles. Parallel hybrids have their ICE as an integral part of their traction systems and thus do not have electric motors that are capable of moving the vehicle on their own under various conditions of load or terrain. I view it as an attempt to maintain the ICE status quo while getting a little electric help on the side.
What we need are more disruptive technological changes that can break the strangle hold that the ICE has on us and I tried to bias the article towards stuff that I saw as fitting that bill.
Alan from the islands
The best commercial electric vehicle BY FAR is the railroad.
All "automobile-like" electric vehicles suffer from some basic engineering difficulties, notably the problem of carrying energy, which means a big, heavy expensive battery. "Technology" is supposedly solving this problem, though the production of batteries that are less big, less heavy, and more expensive. Not much of a solution.
This is why, when I survey the options for electric vehicles, I conclude that the natural engineering solution is a very small vehicle, which minimizes the need for power, in turn minimizing the need for a self-defeating big, heavy, expensive battery. Thus, the $500 electric scooter.
A reorganized urban space, in which auto-like vehicles are not necessary, is a far better solution in almost all situations.
I suppose there will be the usual whiners and complainers, who say that this is so difficult because of the capex costs, but I would also suggest that making a billion electric vehicles -- and their big, heavy, expensive batteries -- also involves some capex. The fact of the matter is, we are rebuilding our urban spaces all the time anyway, so why not just rebuild it in a sensible way rather than in a stupid way? If 5% of urban spaces are rebuilt each year -- due to natural depreciation of structures -- then in 20 years we could rebuild 100%, and it wouldn't cost any more than it would just to keep what we have.
We are abandoning and rebuilding our urban environments all the time. Whole cities have been depopulated and abandoned -- look at Detroit, Buffalo, Akron, Pittsburgh, etc. -- and whole cities have been built from almost nothing -- Phoenix, Atlanta, San Diego etc. It is ridiculous that people have their silly panic attacks about building and living in a new urban environment, when this has been the continuous rule for the past hundred years.
Econ;
I agree that the smartest direction for EV's is a very small vehicle, from Electric Scooters and bikes up to the 'MiniCooper' sized 4-wheelers.. but I am still baffled when I hear discussions about 'trying to get the 40 mile range EV, when people are still getting 80 to 100 in their RAV4 EV's.. ( www.sealbeach.org )
Is it about Chevron holding those NiMh patents? We've got better EV's from older tech already, and that's in a blocky, high resistance formed car..
I also think light rail and intercity electric rail are higher priorities than EV.. but I don't think 'cars' are going away either.. just coming down to a more fitting scale and number.
Bob
I generally agree, with one small suggestion.
Electric scooters, good.
Electric assist bicycles, better.
The optional use of human muscles (and slightly better rolling and aerodynamic resistance) give the nod to eBikes IMHO.
Best Hopes for efficient EVs,
Alan
PS: Good quality regular bicycles (and tricycles), best :-)
.
basic rail transportation ...
http://www.railriders.net/index1.html
Have changeable wheels
http://www.youtube.com/watch?v=bN8lp-tN_-A