Fuel
cells are very much the power source for the new millennium. All
of the leading names in the automotive industry have active fuel
cell development programmes and many major utility and energy companies
have also recognised their potential. Johnson Matthey is playing
a vital role in bringing this exciting new technology to market.
What are fuel cells?
A fuel cell is an electrochemical engine that converts the energy
of a chemical reaction directly to electricity. Hydrogen and oxygen
are combined over a catalyst to produce electricity and water.
Johnson Matthey has been actively involved in fuel cell technology
for many years, supplying the catalysts used in the phosphoric
acid fuel cells used to provide electrical power and drinking
water for both the Apollo and Shuttle space programmes. However
the type of fuel cell best suited to mass market applications
such as cars and for use in the home is the Polymer Electrolyte
Membrane (PEM) fuel cell which operates at 80ºc and is robust
enough for these demanding applications.
How
does a PEM fuel cell work?
PEM fuel cells are essentially very simple. They have no moving
parts. At their heart are two catalysed electrodes separated by
a sheet of polymer. The catalyst is coated onto a sheet of special
carbon fibre paper that acts as a gas diffusion layer. The catalyst
layer is in contact with the polymer membrane. Hydrogen is supplied
to one side of the cell (the anode) and oxygen to the other (the
cathode).The membrane prevents the two gases from mixing but it
also has the unique ability to conduct protons.The catalyst on
the anode ionises the hydrogen gas and protons can then pass through
the membrane and react with the oxygen in the presence of the
catalyst on the cathode to form water. The reaction is completed
by the hydrogen electron rejoining the proton via a wire, thus
creating an electrical current.
The membrane and the two gas diffusion
and catalyst layers are laminated together to create a Membrane
Electrode Assembly (MEA).This is placed between two gas flow plates
that distribute hydrogen and air to either side of the MEA.Together
these five components form a single cell. Each cell generates
about 0.7 volts so they are stacked together to add up to a usable
200 to 300 volts.This is called a Fuel Cell Stack.
Do we need new forms of power generation?
Over 70% of the power that we use is consumed by our cars and
in homes and offices. Producing power at the point of use is potentially
very attractive but the technology used must be clean, quiet and
efficient.
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| Evaluating the performance of the latest fuel cells at Johnson Matthey’s Technology Centre in the UK |
Fuel cells are clean enough for power to be generated at the
point of use utilising a variety of fuels. When run on hydrogen,
the fuel cell is a true ‘zero emissions’ source of power, emitting
only pure water. They produce no particulates, are extremely quiet
and can operate in the same room as people with almost no detrimental
impact on the local environment. Fuel cells are thus ideally suited
for use in micro Combined Heat and Power (CHP) applications in
the home. In these applications 3 to 10 kilowatts of electricity
can be generated by a fuel cell and the heat produced can be used
to heat, or even air condition the building. The ability to utilise
the heat greatly increases the efficiency of the fuel cell system
and provides many benefits over electricity generated by central
power stations and transmitted over long power lines.
Johnson Matthey and fuel cells
Johnson
Matthey is the world’s leading producer of the specialised anode
and cathode catalysts at the heart of the fuel cell.The company
has committed many years of R&D to the development and optimisation
of these catalysts and supplies a wide range to fuel cell manufacturers.
It also has a great deal of expertise in the development and optimisation
of the Membrane Electrode Assembly and aims to supply completed
MEAs to customers. Each MEA design has different performance characteristics
and JM has leading edge catalyst and materials technology to ensure
the best possible performance from this key component. Much of
the progress made in recent years towards commercialisation of
fuel cell systems has resulted from this unrivaled expertise.
But the story does not end there...
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| A Plug Power residential fuel cell system (Photograph courtesy of Plug Power Inc.) |
There is currently no infrastructure to distribute hydrogen
to our homes and cars. Even if there were a means to fill up your
car with hydrogen, current methods of storing it on board the
vehicle would make the tank too big or too heavy to give it sufficient
range or acceptable performance and still leave room for any passengers.
So fuel cell cars will initially use a catalytic reformer to generate
hydrogen from a liquid hydrocarbon fuel such as methanol. Similar
systems will be used to generate hydrogen from natural gas for
use in fuel cell powered micro CHP systems in homes and small
offices.
Johnson
Matthey has developed patented fuel reformer technology known
as HotSpot™ to generate hydrogen rich reformate that can be fed
into a fuel cell, from methanol or natural gas. Development work
on HotSpot™ reformers for gasoline, Liquid Petroleum Gas and other
hydrocarbon fuels is ongoing.The reformate gas stream contains
small amounts of carbon monoxide (CO) which can poison the fuel
cell catalyst. A further, highly selective catalyst is used to
clean up the CO without losing any of the hard won hydrogen.
Not all of the hydrogen that is fed into the fuel cell is converted
into electricity and water. A small amount is contained in the
exhaust gas from the anode and can be used to heat the fuel reformer
via an anode exhaust burner. This is another specialised catalytic
component for which Johnson Matthey has leading edge technology.
A fifth catalyst is used to remove any unreacted hydrocarbons
from the clean exhaust gas.
These five key catalytic stages will provide Johnson Matthey
with net revenue opportunities that are an order of magnitude
greater than those of its current autocatalyst business where
JM provides the emission control catalyst only.
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| Ford’s P2000 fuel cell prototype vehicle. A family sized car powered by a fuel cell (Photograph courtesy of Ford Motor Company) |
When will we see fuel cells on our
roads and in our homes?
The automobile industry is targeting to have the first "production"
fuel cell vehicles on the road by 2005. XCELLSIS, a joint venture
to manufacture fuel cell engines between DaimlerChrysler, Ford
and Ballard Power Systems, believe they will have several thousand
fuel cell vehicles on the road by 2005. The other car companies
will also launch fuel cell vehicles at around this time. Industry
estimates are that between 600,000 and 1 million fuel cell cars
will be produced per year by 2010. Even at these levels, fuel
cell cars will only represent 1 to 1.5 % of total world car production.
Mass production of fuel cell cars will depend on the success of
these first cars. Importantly, fuel cell cars will be more desirable
than conventional cars as they will be more fun to drive and have
more electronic features such as remotely controlled air conditioning
and heating systems.
Fuel cell powered residential CHP units may well be commercially
available sooner than cars. Leading developers of these residential
systems such as Plug Power in the United States have announced
that they plan to start marketing units in 2002 and will have
100,000 units in the market by 2003.
