What are fuel cells
Fuel cell is a device that directly converts the cehmical energy of a fuel into electricty and heat in a very efficient and environment friendly way.
Fuel cells process schema.
A Fuel cells operates like a car battery but, as it uses an external fuel, it can continuously generate electricity as long as fuel (typically hydrogen) and oxidant (air) are fed to its electrodes.
A fuel cell is able to operate on different fuels, has a very high conversion capability and represents a significant contribution to energy saving and to meet Kyoto protocol targets thanks to its ultra low emissions.
Different Fuel Cell Technologies
There are basically 6 different fuel cell technologies, that can be classified according to the electrolyte used and the operating temperature:
- Polymer Electrolyte Fuel Cells, operating at low temperature (60-80°C) are the preferred technology for automotive applications, although they are not perfectly suited for stationary power generation.
- Phosforic Acid Fuel Cells, developed since the late 60s, are the only mature technology, but they suffer an intrinsically high cost, due to the use of precious metals as catalyst.
- Solid Oxide Fuel Cells operate at very high temperature (900-1000°C) and are a very promising technology for stationary power generation, although there are still technological problems related to the use of a metal-ceramic combination at very high temperature.
- Molten Carbonate Fuel Cells have an operating range from some kWs up some MW. Operating at high temperature (650°C) they don’t need precious catalysts and are very tolerant against fuel composition without the drawbacks of SOFC temperature related problems. They generate high grade heat and they are very well suited for cogeneration. Presently MCFC technology is developed in the US, in Japan, in Korea and, in Europe, by Ansaldo Fuel Cells, active since over 20 years.
There are two more fuel cell technology, less relevant to power generation.
Direct methanol fuel cells, targeting the very low power range (few Watts), are a potential substitute to batteries for portable electronics (cellular phones, radio equipment etc.) while Alkaline Fuel Cells, developed for space applications, need extremely pure gases and have practically no use in civil applications.