Applications of SOFC technology
SOFCs are already finding wide ranging applications: delivering environmental and economic benefits within transport, industrial equipment, cooling, power, disaster relief and similar applications where grid power is not available.
Residential/Combined Heat and Power
SOFCs are well suited to stationary power generation for homes and businesses. Their high temperatures make them particularly efficient for Combined Heat and Power (CHP) systems, as waste heat can be put to good use for heating and cooling.
An in-home micro-CHP system would replace a boiler, becoming a single power source and removing the need to buy electricity from the grid. Its fuel cell would produce electric power from gas pumped into the home, while using waste heat for heating or cooling. Excess energy can be sold back to the grid – reducing energy bills.
In the UK gas costs around 4p per kilowatt hour at the time of writing. If we can convert it to electricity at 60 per cent efficiency, it would cost 6p per kWh to generate electricity in the home. This compares to around 14p per kWh if bought directly from the grid. A medium sized house will use around 3200kWh of electricity a year, so this would represent a saving of £256 per year. Further savings can also be made on gas bills as CHP will also provide heating.
Larger scale systems can also be used at a whole building level or for industrial applications from powering entire factories to keeping machinery cool. Considerable power is saved by CHP over centralised power generation and separate heat generation.
Fuel cells offer more efficient energy conversion than power stations (since fuel is chemically converted) and eliminate energy losses that occur when electricity travels over power lines (unlike electricity, gas is transported into homes without significant energy losses).
Transportation – range extenders
Fuel cells can power vehicles with as little as zero tailpipe emissions (if we use renewably produced hydrogen), whereas a petrol engine produces 130g/km of CO2.
Fuel cells are already being used in large fleets where extensive use helps offset the initial capital cost and where fuelling services can be managed at a central depot. They have found uses in ships, buses and even aircraft (so far only for taxiing, though fuel cell powered planes are in development).
Whilst PEMFCs are likely to be the fuel cell of choice for cars, SOFCs are finding uses in larger vehicles and as range extenders for battery electric vehicles, converting fuels such as ethanol into electricity which can charge the car battery even when driving and avoid the need for time-consuming battery charging from power outlets.
SOFCs can operate in reverse mode, as a Solid Oxide Electrolyser Cell (SOEC), turning energy and water back into hydrogen. By using the energy from renewables when they are not feeding into the grid, fuel cells can run in reverse, producing hydrogen gas through electrolysis.
Hydrogen allows a huge amount of energy to be stored for long periods, so the energy from the sun could be used in summer to create hydrogen, which becomes a fuel source in winter. SOECs are the most efficient means of electrolysis and can electrolyse water to hydrogen at close to 100 per cent efficiency.