WELCOME to the cryogenic filling station. You drive in, insert your credit
card in a slot, touch the screen and enter your personal identification number.
Then you wait. A robot arm emerges out of the ground, finds the cap of the fuel
tank and removes it. A nozzle starts disgorging liquid hydrogen at 鈭�253
掳C. After three minutes, the robot refits the cap, withdraws and you drive off
with Born to Run blaring out from the CD player.
Fanciful? Not according to German car manufacturers, BMW and Mercedes-Benz.
In collaboration with one of Germany鈥檚 largest oil companies, Aral, they have
funded the development of a robot filling station that can successfully refuel
cars with petrol or diesel. The only task left is to adapt the robot to deliver
ultra-cold liquid hydrogen鈥攁 challenge that engineers are confident they
will soon overcome (see Box).
If they are right, one of the biggest barriers to the commercial introduction
of the hydrogen-fuelled car will have been swept aside. 鈥淚 think there is no
doubt our children will be driving cars fuelled by hydrogen,鈥� says Theodor
Eckel, a hydrogen researcher part-funded by BMW in Bavaria. BMW already has six
hydrogen-fuelled cars on the road.
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Hydrogen, the simplest and one of the most common elements on Earth, has long
been trumpeted as the world鈥檚 environmental saviour. When burnt in a car engine,
it produces no carbon dioxide鈥攖he principal global warming gas. And even
without emission controls, the engine pumps out only 30 per cent of the nitrogen
oxides and 10 per cent of the hydrocarbons that come from petrol engines fitted
with catalytic converters. The hydrocarbons come from carbon oxides in air and
tiny amounts of oil in the combustion chamber. According to Nejat Veziroglu,
president of the International Association for Hydrogen Energy, hydrogen is 鈥渢he
permanent solution鈥� to the world鈥檚 environmental problems.
So far, however, it has failed to deliver. The best way to produce hydrogen
is to electrolyse water. The gas is then liquefied ready for transport. But watt
for watt, these processes make hydrogen more expensive than fossil fuels. Its
extreme low temperature also makes liquid hydrogen difficult to handle and
distribute. And these are not the only problems. As everyone knows from the
dramatic film clip of the conflagration that destroyed the Hindenburg airship in
1937, hydrogen is highly inflammable. It is also at the core of the H-bomb.
Hydrogen has, in other words, a serious public relations problem.
German industry, however, is taking hydrogen seriously and is trying to solve
these problems. BMW, a world leader in the field, says it could start marketing
the first commercial hydrogen-fuelled cars in 2010. A study for the German
government by an independent group of scientists, technologists and economists
estimates that 2 per cent of all cars will be fuelled by hydrogen by 2025. 鈥淗alf
the age of mineral oil is already behind us,鈥� proclaims BMW. 鈥淲hat we need are
alternatives that save energy and protect the climate鈥攁nd the sooner we
start to use them, the better.鈥�
When BMW put four of its hydrogen-fuelled cars on display at the 11th World
Hydrogen Energy Conference in Stuttgart in June, American visitors were
astonished. They鈥檇 never seen anything like it. 鈥淵ou can kick the tyres and feel
it,鈥� says Jay Keller, hydrogen programme manager at the Sandia National
Laboratories in Livermore, California. 鈥淭he car had leather seats, and when you
sat in it, it looked like a BMW, it smelt like a BMW and it ran like a BMW.鈥� He
admits that the German car industry is moving much faster than he expected.
Keller, whose team is developing a hybrid car engine that burns hydrogen and
powers an electric motor, accepts that the US lacks industrial leadership.
American car manufacturers have little motivation for pursuing hydrogen-fuelled
cars. 鈥淓urope doesn鈥檛 have huge energy supplies, and people are sensitive about
environmental quality,鈥� he says. 鈥淚n the United States, we have cheap energy and
any serious air quality problems are limited to regions such as Los
础苍驳别濒别蝉.鈥�
Franz-Josef Wetzel of BMW regularly drives one of the company鈥檚 hydrogen
demonstration cars, which also run on petrol. The engine is designed with two
parallel fuel-injection systems, one for hydrogen and one for petrol: all you
have to do to change from one to the other is to flick a switch next to the gear
lever. Wetzel says that on hydrogen the car generates 150 horse power and has a
top speed of 210 kilometres per hour, compared to 210 horse power and 240 kph on
petrol.
The big problem with the car is that at present hydrogen costs three times as
much as petrol, and a hydrogen-fuelled car will cost up to twice as much as a
conventional car. 鈥淧eople will only buy hydrogen cars if they are forced to by
pollution controls,鈥� he says, 鈥渙r if they are consumer pioneers.鈥� BMW expects
that with technological innovation and mass production, these costs will fall,
but it accepts that hydrogen is never likely to be as convenient and cheap as
petrol is today. Instead, it justifies its enthusiasm for hydrogen on the
grounds that emission standards for car exhausts are growing ever stricter. By
the year 2000, the company says, legal limits around the world for most exhaust
emissions will be less than 5 per cent of what they were in 1970. Hydrogen is
the best way to produce 鈥渮ero-emission鈥� cars that will meet the new
standards.
The main difference between a conventional and a hydrogen-fuelled car is the
design of the fuel tank. Liquid hydrogen is stored in a large, cylindrical
bottle behind the rear seat. It holds 120 litres of liquid hydrogen at up to
five times atmospheric pressure and weighs 60 kilograms when full. The hydrogen
is kept cool by 70 thin layers of aluminium and glass fibre, vacuum-packed into
a 3-centimetre gap between two metal skins鈥攍ike a giant, super-efficient
thermos flask. A medium-sized passenger car can travel about 400 kilometres on a
full tank, says Wetzel, which is about half as far as a petrol-driven car can
go.
BMW has subjected the tank to a series of demanding safety tests. It has been
completely engulfed in flames at over 900 掳C for up to 70 minutes, perforated by
solid objects and squeezed until it breaks with its safety valves completely
blocked. Sometimes the gas leaked out, sometimes it burnt, but it never
exploded. The hazards of hydrogen, says Wetzel, are 鈥渘o greater than
辫别迟谤辞濒鈥�.
At the moment, Wetzel鈥檚 car is filled at a hydrogen research centre partly
funded by BMW at Neunburg vorm Wald in Bavaria. Pipes from a 3000-litre
container of liquid hydrogen, coated with dripping ice, are connected to the car
manually before the fuel is fed into the tank. The pump nozzle is pushed into
the tank and a pneumatic system closes an air-tight rubber seal. It is vital to
avoid human contact with liquid hydrogen because the extreme cold would cause
severe burns.
Wetzel says that five years ago it took more than an hour to fill the tank,
and a quarter of the hydrogen was lost in the process. Now it takes under three
minutes with zero loss, compared with a 2 per cent loss from a petrol pump.
Within a few years, maintains Wetzel, hydrogen refilling will be carried out by
robot. The real stumbling block, BMW accepts, is building up a country-wide
liquid hydrogen supply network 鈥攁 process that could take another
generation.
In the meantime, BMW has started marketing cars fuelled by compressed natural
gas, and is planning to introduce liquefied natural gas cars within a few years.
The company sees these gas cars as transitions towards the hydrogen-fuelled
car. Filling stations can take their natural gas from the existing supply
system, and natural gas engines emit lower volumes of greenhouse gases than
petrol engines. BMW researchers believe that much of the equipment for storing
and transporting natural gas could also be used for hydrogen.
One of BMW鈥檚 main competitors, Mercedes-Benz, is also pursuing hydrogen, but
has abandoned the internal combustion engine altogether. Earlier this year, the
company unveiled a prototype electric vehicle called Necar II which is powered
by fuel cells. The cells work by reversing the electrolysis of water. Hydrogen
is fed through an anode, and oxygen鈥攁s air鈥攖hrough a cathode. In the
centre is a polymer electrolyte coated with a platinum catalyst, which
encourages hydrogen to break apart into a proton and an electron. The protons
pass through the electrolyte and react with oxygen to form water. The electrons
generate a current (see
Diagram).
Virtually the only exhaust emission from Necar II is water vapour.
Mercedes-Benz says it is the world鈥檚 first car powered by a fuel cell suitable
for everyday use, and predicts that it will be in commercial production by 2010.
This contrasts with a plan by the US Department of Energy to produce America鈥檚
first prototype fuel cell car in 2004. Fuel cells are also being investigated by
General Motors, Ford, Chrysler, Toyota, Honda and Renault. 鈥淲e can earn money
from fuel cell technology,鈥� says Helmut Werner, the head of Mercedes-Benz.
Necar II uses 300 fuel cells, developed by a Canadian company, Ballard, to
generate 50 kilowatts of electricity. It carries two cylinders of hydrogen gas
in its roof and looks more like a minibus than a car. The prototype is rated at
about 45 horsepower, with a maximum speed of 110 kilometres per hour and a range
of 250 kilometres. Its range may be increased by Mercedes-Benz鈥檚 next plan to
use methanol as a fuel and produce hydrogen onboard to feed the fuel cell.
Cracking water
Because of the limitations on range and speed, the first users of fuel-cell
vehicles will probably be city bus companies and other concerns using large
vehicles that do not have to travel quickly over long distances. Ballard has
developed an electric bus with a 275-horsepower 鈥渮ero-emission鈥� engine using
hydrogen fuel cells. Three of them are due to begin trials in Chicago early next
year.
But whether hydrogen鈥檚 energy is liberated by internal combustion or fuel
cells, if it鈥檚 going to become the fuel of the future we鈥檙e going to need lots
of it. Cracking water with electricity generated from fossil fuels makes no
sense because any environmental gains from using hydrogen would be wiped out by
pollution from the power plants. So German power companies are trying to produce
hydrogen with electricity from solar cells. Two of Germany鈥檚 leading power
companies, Bayernwerk and Siemens, are investing DM60 million (拢25
million) in Solar Hydrogen Bavaria (SWB), the company that runs the research
centre at Neunburg vorm Wald.
There, amid quiet wooded hills, 4200 square metres of solar cells generate up
to 350 kilowatts of electricity to produce hydrogen from distilled water. At
present, the process is far from economic: the plant鈥檚 hydrogen costs 30 times
as much as hydrogen made commercially from methane. 鈥淧hotovoltaics are the most
elegant but the most expensive solution,鈥� says Theodor Eckel of SWB.
Production costs are likely to come down as the technology improves, or if
particularly sunny sites are developed. BMW is studying a plan to build a 100
megawatt solar plant in north Africa. The idea is to replicate plants in
California that use the heat concentrated by parabolic mirrors to generate
electricity. Hydrogen would be produced nearby and then shipped to Germany.
鈥淭his could signal the start of a new form of international trade in energy,鈥�
says BMW. As a first step, the company has commissioned the Wuppertal Institute
for Climate, Environment and Energy in Germany to investigate the environmental
impact of large solar power plants.
Eckel says that wind turbines, wave machines and hydroelectric schemes could
all make 鈥渃lean鈥� hydrogen. The most ambitious scheme is the Euro-Quebec
Hydro-Hydrogen Pilot Project in Canada. Researchers there want to use cheap
hydropower from the St Lawrence River to produce hydrogen. One option envisaged
for the project, which is sponsored by the European Union, Quebec and Canada,
involves building a fleet of 192-metre-long tankers, each capable of carrying 15
000 cubic metres of liquid hydrogen across the Atlantic.
Other plans, for a hydrogen-fuelled plane and a fleet of hydrogen-fuelled
buses and cars at Munich airport, are equally grand. No one doubts that
switching to hydrogen fuel, produced from renewable energy sources, will
dramatically cut air pollution. The big question is still whether hydrogen will
ever be economical.
In any case, there is another factor to be taken into account. Phil Goodwin,
professor of transport policy at University College London, points out that the
main constraint on car growth is not pollution or economics, but congestion. If
people in developing countries owned as many cars as in the developed countries,
the total number of vehicles in the world would increase by between five and ten
times. 鈥淓ven if every car in the world ran on hydrogen from the oceans, there
would still be no room for them on the streets,鈥� he says.
Fuel cell anatomy: the catalyst encourages hydrogen to break apart, releasing
energy
* * *
Pumping gas the automatic way
THE Fraunhofer Institute for Manufacturing Engineering and Automation in
Stuttgart is home to a filling station with a difference. It is fully automated,
so unless car drivers want to top up on chocolate or check the tyre pressures,
they need never leave their seats.
The robot reads information about the make of the car, the fuel it accepts
and the location of its fuel tank by interrogating a chip on the car鈥檚
undercarriage. It scans the car with lasers to work out its precise position. A
robot arm can then position itself to within 2 centimetres of the outer fuel
flap.
With two infrared 鈥渆yes鈥�, the robot searches for reflections from a circular
foil sticker on the fuel flap. It opens the flap with two suction cups, and
searches for an identical circle of foil in the middle of the filler cap. It
slots into the cap, opens it by turning it through 25掳, removes it and inserts a
nozzle to start pumping fuel. The whole process takes no more than three
minutes.
Stefan Schmid of the Fraunhofer Institute points out that the specially
designed tank cap and the identification chip can be easily retrofitted to most
modern cars, and can be opened by hand for manual filling. The petrol company,
Aral, is expected to open the first robot filling station for the public at its
headquarters in Bochum, near D眉sseldorf, before the end of 1998. The main
technical problem in adapting the robot to deliver liquid hydrogen is the need
to improve the seal on the fuel tank. This is not particularly difficult, says
Schmid. 鈥淲e can handle it in a few years.鈥�