Researchers have come up with a solution to a problem which has been haunting green energy research for a long time — a new type of fuel cell that is cheap to produce.
Conventional means of electricity production, such as coal plants, depend on the heat generated by burning coal for generating electricity. The emissions generated from burning coal and other fossil fuels are the primary cause behind global warming. Fuel cells provide a greener alternative for electricity generation. This is because a fuel cell operates in a manner such that the chemical energy stored inside the fuel of a fuel cell is directly converted into electricity, without any burning.
Hydrogen fuel cells are the most common kind of fuel cells. When hydrogen and oxygen react, they fuse together to create water. This reaction also leads to generation of energy. In a hydrogen fuel cell, the energy generated by this reaction is used as electricity.
While this process of energy generation is much better than burning fossil fuels, making fuel cells operational at a commercial scale poses its fair bit of challenges. Most fuel cells require temperatures that are too high or too cool to be feasible for cheap, mass production. Polymer electrolyte membrane (PEM) cells operate at around 100°C. The low temperature means the chemical reactions happen slowly, often requiring expensive metals such as platinum to catalyse and speed up the process. Solid oxide fuel cells (SOFC) operate at 1000°C, and thus require expensive metal alloys that can sustain such high temperatures.
Since long, scientists have been on the lookout for a fuel cell that can operate at midrange temperatures, at around 500°C.
Such cells can also give a boost to renewable energy. In the production of solar and wind energy, one of the major problems is storing energy for times when sunlight or wind is not available. Fuel cells which operate at midrange temperatures can help in energy storage. They can convert the electricity generated by a solar panel or wind turbine into a fuel, such as hydrogen. This fuel can then again be converted into electricity.
Such fuel cells have been designed, but until now, they could not generate enough power to be commercially viable.
A group of researchers led by Sossina Haile, a chemical engineer at Northwestern University in US, may have cracked the problem. They have produced a fuel cell which can generate 550 megawatts of power per centimetre square of area at a temperature of 500°C. This is 50 megawatts more than the minimum requirement for commercial viability. They reported the results of their study in Nature Energy on Monday.
The team was able to achieve this by increasing the rate at which a chemical reaction occurs inside a fuel cell. They added a dense layer of catalyst which eased the passage of protons into the electrolyte of the cell. Since a greater number of protons could now pass through, more of them would take part in the reaction and more energy would be produced by the cell.
However, certain challenges still exist before this fuel cell can be rolled out for the market. At present, the cells are only a few centimetres in size. Making larger versions of this cell is difficult as the technique used to increase power generation of these fuel cells is complex to perform on an assembly line.
Sossina Haile says that other researchers should now work on solving these problems.