All you need to know about fuel cells
Extracted from:The Economic
Times
Hyderabad Edition
04-06-2001
- What are fuel cells?
- Where does the hydrogen used in fuel cells come from?
- What is the advantage of using fuel cells?
- How would a fuel cell-powered car compare to one powered by a battery?
- What are the difficulties in fuel cells becoming more widely used?
- How much do fuel cells cost?
What
are fuel cells?
These are devices that convert fuel into electricity where the fuel is not burned in a
flame (as in conventional engines) but oxidised electrochemically.
This means that fuel cells are not constrained by the fundamental law that governs heat
engines, the Carnot limit, which specifies the maximum theoretical efficiency that a heat
engine can reach.
Fuel cells have much in common with batteries, which also convert energy that is stored in
chemical form into electricity. In contrast to batteries, however, they oxidise externally
supplied fuel and therefore do not have to be recharged.
A fuel cell consists of two electrodes sandwiched around an electrolyte. Oxygen passes
over one electrode and hydrogen, which is the fuel, over the other, generating
electricity, water and heat. Thus fuel cells need a supply of hydrogen to work.
Where
does the hydrogen used in fuel cells come from?
There are three main methods that scientists are researching for inexpensive hydrogen
generation. All three separate the hydrogen from a ‘feedstock’, such as fossil
fuel or water - but by very different means
Reformers: Any hydrogen rich material can serve as a possible fuel source. This
includes fossil fuels - methanol, ethanol, natural gas, petroleum distillates, liquid
propane and gassified coal. The hydrogen is produced from these materials by a process
known as reforming
Enzymes: Hydrogen can also be generated from bacteria and algae. The cyanobacteria,
an abundant single-celled organism, produces hydrogen through its normal metabolic
function.
Cyanobacteria can grow in the air or water, and contain enzymes that absorb sunlight for
energy and split the molecules of water, thus producing hydrogen.
Solar and wind-powered generation: By harnessing the renewable energy of the sun
and wind, researchers are able to generate hydrogen by using power from photovoltics,
solar cells, or wind turbines to electrolyze water into hydrogen and oxygen.
Hydrogen becomes an energy carrier - able to transport the power from the generation site
to another location for use in a fuel cell.
What
is the advantage of using fuel cells?
When hydrogen is used as an energy source in a fuel cell, the only emission that is
created is water, which can then be electrolysed to make more hydrogen - i.e the waste
product supplies more fuel.
This continuous cycle of energy production has the potential to replace traditional energy
sources in every capacity - no more dead batteries piling up in landfills or
pollution-causing, gas-guzzling combustion engines.
Fuel cells could thus dramatically reduce urban air pollution and decrease oil imports in
countries like India that are dependent on imported crude oil.
According to US Department of Energy projections, even if a mere 10% of automobiles in the
US alone were powered by fuel cells, regulated air pollutants would be cut by one million
tons per year and 60 million tons of the greenhouse gas carbon dioxide would be
eliminated. Oil imports could reduce by 800,000 barrels a day.
How
would a fuel cell-powered car compare to one powered by a battery?
Fuel cell automobiles are an attractive advance from battery-powered cars. They offer the
advantages of battery-powered vehicles but can also be refueled quickly and could go
longer between refuellings.
At present, both Daimler-Benz and Toyota have methanol PEM fuel cell cars. The Mercedes
car runs on a 50 kW fuel cell. The Toyota car has a 25 kW fuel cell engine, and a battery
that stores extra energy created when the brakes are applied. A commercial model is
planned to be released in the near future.
Much of the technology that automobile companies are now using in fuel cell cars involve
getting the hydrogen from another source, namely methanol or gasoline, but research is
being done so that elemental hydrogen may be stored by itself.
What
are the difficulties in fuel cells becoming more widely used?
The major drawback is that hydrogen is more expensive than other energy sources such as
coal, oil and natural gas. Researchers are helping to develop technologies to tap into
this natural resource and generate hydrogen in mass quantities and cheaper prices in order
to compete with the traditional energy sources.
How
much do fuel cells cost?
One company commercially offers fuel cell power plants for about $3,000 (Rs.1,38,000) per
kilowatt. At that price, the units are competitive in high value, "niche"
markets, and in areas where electricity prices are high and natural gas prices low.
A study by Arthur D. Little, predicted that when fuel cell costs drop below $1,500 per
kilowatt, they will achieve market penetration nationwide. Several Companies are selling
small units for research purposes. Prices vary.
Fuel cells will have to be much cheaper to become commercial in vehicles. Conventional car
engines cost about $3,000 to manufacture. More research is needed to bring the cost of
fuel cells down to that level.
DaimlerChrysler have pledged to have a viable, commercial fuel cell vehicle available in
2004
