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19th Dec. 2002
Is fuel cell the right
solution to zero emission cars?
By Anton Bech.
Fuel cell today
It looks like the fuel cell is what we all are waiting for. At least it is the impression most car manufactures and car magazines try to present the public. Power from hydrogen is high tech and clean energy so it is trendy. The car makers tell us we just have to wait another 10 to 20 years before it is available to the public.
Energy efficiency
The fuel cell technology is well known today and the performance for the system has been recognized. The focus has for a long time been addressing the possibilities rather than the efficiency of the system.
It has now been transparent, that the fuel cell vehicle is using significantly more power than the battery powered vehicle.
According to the article on EVWORLD Fuel cell disruptor by Alec Brooks in story id=464,
where the Toyota RAV4 EV is compared with the HONDA FCX the energy consumption factor is like:
Battery car RAV4 El = 30 kWh/100 miles.
Honda FCX= 1 kg hydrogen / 50 miles, equal to 2 kg hydrogen / 100 miles.
To make and distribute 2 kg hydrogen takes 2 x 60 kWh = 120 kWh.
The fuel cell powered car (Honda FCX) is using: 120 kWh /100 miles
The battery powered car RAV4 El) is using: 30 kWh /100 miles
In this case the fuel cell car is consuming 4 times more energy as the battery powered car.
I did a theoretical calculation on the power efficiencies for the fuel cell vehicle and the battery vehicle. The result was 3 times more power used pr kilometer (or miles) by the fuel cell car compared with the battery car (see www.evguide.nu/ZEVanton.htm >
).
Whether it is a factor 3 or 4 is anyway too high to be ignored. The fuel cell energy system is and will apparently always be an inefficient power system compared with the battery system.
Making sense of it
I can't figure out why the car industries are so hooked on promoting a propulsion system, which has so low an energy efficiency and is expensive. Besides there is no infrastructure as filling stations for hydrogen powered cars. Electric cars can be charged at home as well as in many public areas for a very little investment. The only reasons for the car makers to favorite fuel cell cars are as far as I can see: They want to gain the publicity value from working with up front technology and they want to stall the changes from petrol to something else as long time as possible.
The downside of the battery car
As an owner of a Peugeot 106 electric I know what limitations the car has but never the less it is our most used car. We drive it for 18.000 km pr annum, which is twice as much as our petrol car does. The car has a range of 80-110 km / charge and can be recharged between 40 minutes and 5 hours depending on the power source.
The limited range and the charging time is not a problem in daily use as driving to work and shopping, but it becomes an obstacle on long country rides and long distance travel. There is a solution to this, which is different from sitting and waits on lithium batteries to become cheaper, safer and more durable.
How to overcome the range and charging time problem
There is one major fault in the way these battery cars are designed. The problem is not the capacity of the battery but the fact the batteries are an integrated part of the car. If the car batteries were changeable units like the batteries on a cable free bore machine, the car would have two options to regain power: To charge power from the grid or to swap the batteries. If the car is fitted with changeable battery boxes, the car could do long distances with a "pit stop" for each 80-100 km, where the boxes are swapped to fully charged ones. To swap the batteries could be an automated action, where the car enters a confined space, which looks as the toll station at a bridge or highway. Here the car driver rolls down the window and insert an id-card. Then the car will be fixated and a sub terrain robot will dismantle the discharged batteries and replace them with fully charged one. Thereafter the gate will open and the car can drive on again. The whole procedures do not have to take more than two to three minutes and the car is ready for another 100 km.
Battery box
Technical the battery units must be according to a defined standard, so they fit to all cars. I.e. one unit is a box with 120 V 60 Ah from NiMH batteries. The number of boxes can vary from car to car depending on the size of vehicle. In the box there is a computer. The computer tells the board instruments in the car the energy level, counts the charge and discharge of the batteries and control the charger in the car. When the batteries are swapped, the car owner is charged for the use governed by the data from the battery box computer. It is similar to the cell phone, where the owners pay a monthly fee and a fee for the calls.
Another benefit with this system is that the car owner does not have a personal economical risk in case the battery package breaks down.
Where are we
To make cars with changeable battery boxes is technical possible with today's technology. The NiMH battery performance is fine for electric vehicles.
For the time being it seems to be hen and egg. It would make much more sense to make this system works than to spend a huge amount of money on the energy inefficient hydrogen fuel cell cars and infrastructures.
See also and feel free to use my power point presentation on:
www.evguide.nu/ZEVanton.htm >
Eng. Anton Bech
Denmark.
antonbech@mail.tdcadsl.dk
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