Alec Brooks with tzero electric sports car
Alec Brooks with AC Propulsion's tzero electric sports car. Brook's delivered a withering analysis of fuel cell technology at this week's public workshop in Sacramento.

Fuel Cell Disruptor

Part One of presentation at December 5, 2002 ARB public workshop.

By Alec Brooks

I have been closely following the ZEV mandate since it was adopted in 1990. In the early years of the mandate, EVs were the 'new thing' and were the darlings of the media. Over the years the mandate has been changed, delayed, and weakened under tremendous pressure from automakers.

When I started to read the background information describing the latest round of proposed changes, I was initially encouraged to see on the first page that the pure ZEV was still going to be a requirement. However, after reading the document through, I had the sinking feeling that the proposed new regulations spelled the death knell for zero emission vehicles.

I say this because it appears that CARB has effectively given up on battery electric vehicles, and is placing a high risk bet that fuel cell vehicles will in fact become practical in the future.

While this may in fact happen, it is not at all certain. There was a lot of publicity earlier this week about fuel cell vehicles from Toyota and Honda entering service. Toyota's press release headline from Monday this week proudly proclaimed their fuel cell vehicle to be "Market Ready". This is of course a tiny exaggeration. As John O'Dell reported in Tuesday's LA Times: "Representatives from both companies call the deliveries historic, but they cautioned that it will be decades before motorists can walk into a dealer's showroom an drive away in one of the vehicles."

But are fuel cell vehicles really the holy grail – the end game for providing clean personal mobility? The popular and accepted view is that they are.

The thinking goes along the lines of: fuel cells far more efficient than an IC engines because they are based on an electrochemical process rather than combustion; they are quiet, there are no moving parts, no greenhouse gas emissions, only pure water for emissions, and will have far more range than battery electric vehicles. It sounds great.

But today I want to share with you some perspectives on fuel cell and battery electric vehicles that differ from the conventional wisdom.

First – what about driving range and efficiency of fuel cell vehicles – where is the data? There have been a lot of pronouncements but not much in the way of data. Actual range and hydrogen consumption data are very closely held, but there are some indications that might indicate that there are problems with range and efficiency.

In the Michelin Bibendum challenge last year, the fuel cell vehicles that participated drove relay-style in legs of only 30 miles between Fontana and Las Vegas. The vehicles were tested for efficiency as part of the event – but the companies that brought the fuel cell vehicles made it a condition of their participation that the actual hydrogen consumption data not be released.

Another example is the ride and drive event at the Future Car Congress in Washington DC this past summer. A number of fuel cell vehicles along with hybrids, a battery electric, and a diesel were made available for test drives over a very short course – about a half mile. During the course of the day, only the fuel cell vehicles had to leave the ride and drive to go refuel. Not even the battery electric RAV4 had to do this.

There was recently a rally for fuel cell vehicles driving down Highway 1 between Monterey and Santa Barbara, a distance of 250 miles. There were four refueling stops set up along the way.

Finally, the California Fuel Cell Partnership 2001 highlights showed 754 hydrogen refueling events for the 34,000 miles covered by the fuel cell vehicle fleet, or about 45 miles on average between refuelings.

When automakers quote range in their press information, we don't know what the test cycle is. But it seems to be of the 'up to so many miles' kind of figure. I've asked engineers that work on fuel cell vehicles what the range is, and at first I get a stock answer – something like "100 miles". Then I ask is this the urban cycle range? "well, no". "What is the urban cycle range?". "Lower". "A lot lower?" "yes".

The range problem might be overcome by a future hydrogen storage breakthrough that would allow enough hydrogen to be stored on board to match the range of what drivers are used to.

But what about fuel economy? How much hydrogen do fuel cell vehicles consume per mile traveled? This is a more important metric than how efficient a fuel cell stack is at a particular operating point. The amount of Hydrogen stored or consumed is conveniently measured in kilograms. It turns out that a kilogram of hydrogen contains very close to the same amount of energy as a gallon of gasoline -- about 33 kWh. This is at best converted into about 16 kWh of electricity in a fuel cell system. Mr. Norihiko Nakamura, Toyota Executive Advisory Engineer for fuel cell development, said at the 2002 Future Car Congress that the best fuel economy that fuel cell vehicles can achieve is about 62 miles per kg of hydrogen (or about 62 miles per gallon equivalent). In fact, Toyota claims 64 miles per kg as the uncorrected combined fuel economy from in-house testing – quite impressive.

The EPA recently completed testing of the Honda FCX. For 2003, the EPA now lists two ZEVs: one battery electric vehicle – the RAV4EV, and one fuel cell vehicle – The FCX. The test results shown here for the FCX are corrected to window sticker values. The uncorrected number to compare with the Toyota FCHV is about 58 miles per kg. The window sticker for the FCX shows the expected average consumption at 50 miles per kilogram. But today's hybrid vehicles, the Honda Civic and Toyota Prius, essentially match these numbers with 57 and 58 mpg uncorrected combined EPA ratings.

Thirty to sixty miles per gallon equivalent doesn't sound too bad at first, but when you consider what goes into getting the hydrogen in the first place, the picture is not so rosey.

The Toyota FCHV is based on the Highlander sport utility vehicle. With it's fuel economy rating of 64 miles per kg, the FCHV appears to be the most efficient fuel cell vehicle, more than twice as efficient than the base Highlander with rating of 28.2 mpg.

With four 5000 psi hydrogen tanks holding a total of 3 kilograms of hydrogen, you could theoretically drive 192 miles if you can match the uncorrected EPA test results. (Toyota claims a "maximum" range of 180 miles and a realistic range of 150 miles).

It is interesting to estimate the performance that might be expected from hypothetical natural gas hybrid version of the Highlander. Based on the fuel economy of the Prius relative to conventional cars, it could be expected that a natural gas hybrid highlander would have an uncorrected combined fuel economy rating of about 42 mpg. Not nearly as good as the FCHV's 64 – or is it?

If the hydrogen is produced with natural gas, then expressing the FCHVs fuel economy based on natural gas consumed in making the hydrogen brings it back to the same 42 mpg. In round numbers, you need to start with 1.5 units of natural gas energy for every one unit of hydrogen energy stored in the high pressure tank on the vehicle. So there is no energy or CO2 benefit of the fuel cell version.

There is a very small emissions benefit – but CNG SULEVS are already considered clean enough to qualify for solo carpool access. A benefit of the CNG hybrid version is that the driving range would be a whole lot better; even though it uses on-board fuel energy at a 42 mpg equivalent rate vs. 64 for the fuel cell version, the same tanks would hold about 3.2 times more energy in natural gas as compared to hydrogen, yielding a driving range that would be 2.1 times greater, or about 400 miles.

The popular long term future vision for fuel cell vehicles is that the hydrogen would be made by electrolysis with renewable electricity. The flaw in this argument is that it is not fair to claim the cleanest form of electricity generation to a particular type of load, leaving the dirtier electricity generation to everyone else.

Calculations of the upstream emissions associated with recharging battery electric vehicles are usually based on the average power mix; not by singling out the cleanest electricity just for EVs. All forms of generation involve some form of impact; there is always something about any form of generation that someone won't like. So it certainly matters how much electricity is needed per mile traveled.

According to Stuart Energy Systems, it takes about 60kWh of AC electricity to make and compress one kg of hydrogen. Let's compare the electricity used to make hydrogen with the electricity to charge batteries for the two EPA certified ZEVs – the Honda FCX and the Toyota RAV4EV.With the FCX the EPA says a kilogram of hydrogen is good for 50 miles. So the AC electricity usage is 1.2 kWh/mile.

By contrast, the RAV4EV has a combined city/highway energy consumption rating of only 0.3 kWh/mile –a factor of four lower. This is about the same relative difference as between a Cadillac Escalade and a Honda Insight. That electricity for the fuel cell vehicle won't be cheap as it is with EVs. With off peak rates, it would cost just under $5.00 for that 50 miles worth of hydrogen; with regular rates it could be $14 or more. Refueling time could be a problem too if done at home.

With the same 32-Amp 240-Volt power used for EV charging, an electrolyzer could make only about 1 1/4 kg of hydrogen (good for 62 miles) running flat out for 10 hours – typical of off-peak charging from 9:00 p.m. to 7:00 the next morning. That's only six miles of range recovery per hour.

The figure below sums up the relative fuel consumption for 100 miles of travel for the two 2003 certified ZEVs. On the left is the case where natural gas is the base energy source. It is assumed to be converted to hydrogen with a reformer for the FCX, and is burned in a modern combined cycle powerplant to make electricity to charge the RAV4. It takes 64 percent more natural gas to go the fuel cell route. On the right is the case of using electricity as the base energy source, such as would be the case with wind energy. The difference here huge – a factor of four.

Natural Gas Use per 100 Miles
  • H2 from NG Reformer
  • Electricity from combined cycle power plant (7000 BTU/kWh)
  • Electricity Use per 100 Miles
  • H2 from Electrolyzer
  • If new wind or solar generating capacity is built specifically to support zero emission vehicles – it really does matter what kind of vehicle it is used for. For a given amount of vehicle-miles per year -- fuel cell vehicles will need to have 3 to 4 times as much land or other resources dedicated for generation as compared to battery electric vehicles.

    And finally there is the cost issue. If there are concerns that battery electric vehicles are too expensive to manufacture, there should be even greater concerns about fuel cell vehicles. At the Future Car Congress this past June, Toyota's Norihiko Nakamura said the following in his remarks about fuel cell vehicles:

    "If a certain level of mass production can be achieved the cost should be dropped drastically. But a great amount of effort is needed to bring the cost to even two to three times that of a standard vehicle"

    Think about it – this is the view from Toyota, the company that knows how to manufacture and sell the Prius profitably for 20,000 dollars.


    Times Article Viewed: 10498
    Published: 07-Dec-2002


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