Driving Quietly: Testing the Cars of the Future
- Luke Tonachel
- Vehicles Analyst, New York City
- Blog | About
- Posted October 1, 2008 in Moving Beyond Oil
Last Friday, I was invited to the Consumer Reports test track to drive some of the cars of the future. It wasn't a typical test scene - no revving engines or the odor of petroleum. With the exception of the patter of rain drops, it was quiet. Sure, the cars were running but primarily on electricity.
Take, for example, the Ford Escape Flex-fuel Plug-in Hybrid (a bit of a mouthful, I know). As I started driving it around the track, I noticed a dashboard display with 'Engine Off'; I was quietly cruising on just the electric motor powered by a 10 kWh battery. I goosed the 'gas' pedal and got to about 30 mph before the engine started and seamlessly blended-in power to the wheels. Ford is already testing a fleet of these cars and expects to have them available to customers in the next few years.
I also drove around in the Nissan's entry into the hydrogen fuel cell vehicle world, the X-Trail FCV (Honda's FCX Clarity was also there). The X-Trail is not close to hitting the showrooms, but it definitely drove like a real car.
As my colleague Roland Hwang points out in the NY Times, there are three horses in the race to replace gasoline: electricity, hydrogen and biofuels. Cars driven by electricity and hydrogen have the same efficient and quiet drivetrain: the wheels of the vehicle are driven by an electric motor. The two cars differ in their source of electricity with plug-ins using a battery charged from an electrical outlet and fuel cells using a tank of hydrogen and fuel cell stack to create electricity. The flex-fuel plug-in Escape brings in the third element to a basically petroleum-free car. When driving demands call for extra power or a range that goes beyond the storage capacity of the battery, the engine can be fueled by sustainably-produced biofuels.
Also on display were some very near-term fuel-saving technologies that will show up in model year 2009 vehicles. Ford showed off their EcoBoost, which combines gasoline direct injection engine with turbocharging to allow smaller, more-efficient engines to operate with the same power performance as larger, thirstier predecessors. EcoBoost is an example of a host of technologies available today, such as high-speed transmissions and electric auxiliaries, that can dramatically improve conventional vehicle fuel economy. Using off-the-shelf technology, we could have a new fleet of cars and trucks that averages 35 mpg by 2015 instead of the 25 mpg of today.
My day at the track was completed with a Michael J. Fox reenactment of Back to the Future. No need to trigger the flux capacitor, though. This DeLorean drives on electricity-just like our future.
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Comments
Earl Killian — Oct 1 2008 01:37 PM
You correctly observe that
but you don't explain the significance of "the source of electricity." Unfortunately that omission is important.
Because BEVs and FCVs are identical in most respects, and a FCV is essentially a BEV where some (but not all) of the batteries/capacitors have been replaced by a hydrogen tank and a fuel cell, and the plug is optional (but probably desirable), it is straightforward to compare the vehicles. Use an identical 200 Whe/mi for motor to wheels. The DOE's FreedomCar's goal for fuel cells at their peak efficiency is 20kWhe of electrical output per kilogram of hydrogen fed into it. Thus to power the wheels one mile we need 10g of hydrogen (or 100 mi/kg). FreedomCar's goal is still a ways off (the best current FCV is at 68 mi/kg). Next, according to NREL, "An efficiency goal for electrolyzers in the future has been reported to be in the 50 kWh/kg range, or a system efficiency of 78%.". Thus 10g/mi of hydrogen to operate a FCV of the future requires 500 Whe/mi at the electrolysis station. This is a factor of two higher than the BEV requirement, which would be 229 Wh/mi at the plug and 247 Wh/mi at the power station. If hydrogen production occurs at the renewable electricity plant, then we should factor in H2 pipeline efficiency (e.g. 4% loss), and if not we should factor in grid efficiency (7% loss), for delivering the electricity to distributed hydrogen fuel stations (making FCVs 539 Wh/mi). At best, if the research goals are someday achieved, FCVs require 2.2× as much renewable electricity production. Powering the US 2050 vehicle fleet with hydrogen and FCVs would require 2107 TWhe/year of renewable electricity production, compared to 964 TWhe/year for BEVs. Using Concentrated Solar Power (Stirling dishes) as a renewable energy example, FCVs would need 8226 square miles, compared to 3765 square miles for BEVs. What is the justification for consuming this additional land and habitat? Wouldn't this additional land be better used toward solving our electricity greenhouse gas emissions, instead of wasting it on inefficient FCVs?
FCVs will also cost us much more to drive. Twice the renewable electricity requires twice the land area, and so the cost must be at least twice per mile. However, this does not include the cost of the capital plant to produce hydrogen from renewable electricity. NREL estimates this adds $1.74 per kg of hydrogen. Using $0.07/kWhe as the power plant cost for renewable electricity, and adding in the $1.74/kg, gives 5.5 cents per mile, 3.2× times the BEV cost of 1.7 cents a mile. These calculations are based upon the cost of production; retail markup for hydrogen is likely to be higher than the retail markup for utility electricity, which would widen the gap further. Why should we burden our citizens and our economy with three times the cost?
Will improvements in technology make renewable FCVs more competitive? Basic physics suggests this is unlikely. FreedomCar's goals are already aggressive, at 78% efficiency (of HHV) for electricity to compressed hydrogen, and 60% (of LHV) for hydrogen back to electricity. The laws of thermodynamics do not allow such conversions of the form of energy to be perfectly efficient and in the case of hydrogen FCVs we are starting with liquid water and the exhaust of the vehicle is water vapor, and so the energy of vaporization (the difference between the LHV and HHV, 18% for H2) must come from somewhere. Electric vehicles are fundamentally more efficient.
Jim Bullis — Oct 2 2008 03:56 PM
More simply stated, hydrogen requires a great amount of energy to produce and there can be a great deal of CO2 produced in the process, and it really is acting as a carrier of energy.
Actually, electricity should be recognized as largely a carrier of energy, since it also is produced by burning fuel.
The looming disaster is that the fuel to make electricity that will handle the added load from vehicles will mostly be coal. That seems to be a near certainty based on an appraisal of economic reality.
An effective way to fix the personal transportation problem is to make cars that are fundamentally more efficient. To accomplish this, a very different kind of car must be accepted. An example of a way efficient cars could be built can be seen at www.miastrada.com. With cars like this very little energy would be needed, and the particular source would be relatively unimportant. (I am involved in the Miastrada project.)