Fuel Cells offer a wide choice of power outputs dependent on the system chosen. These vary from smaller portable fuel cells which produce low power outputs from 1W to 150W running on gaseous hydrogen or methanol, to standby power units from 10kW to 100kW running on hydrogen through to prime power 250kW+ units mainly fuelled by natural gas, with alternative sources of methane such as biogas now becoming available.
Today’s fuel cell development continues apace with new technologies appearing on a regular basis. In terms of those systems which could be deemed commercially available, there are several variants all of which can be chosen, dependent on the requirement of the user.
Solid Oxide Fuel cell (SOFC)
– operating at 500-1000°C
Molten carbonate fuel cell (MCFC)
– operating at 600-650°C
Phosphoric Acid fuel cell (PAFC)
– operating at 150-200°C
These fuel cells have long start-up times and are generally higher power units from 200kW upwards. As such they are best suited to continuous use. Even though fuel cells in general are considerably more fuel efficient than other forms of power production, use of the high-grade heat produced by these types of fuel cell for combined heat and power (CHP) or cooling via absorption chillers, can increase efficiency further by up to 85% in total.
Alkaline fuel cell (AFC)
– operating around 80°C
Direct methanol fuel cell (DMFC)
– operating around 70°C
Proton exchange membrane fuel cell (PEM)
– operating around 75°C
These fuel cells have rapid start-up but produce little in the way of usable heat. They are generally of lower power output (up to 20kW) and are ideal for standby and low-power, long runtime, prime power applications.Fuel cell technologies are continuing to develop, but whilst they share the fundamentals and the technology adopted within them, their differing power outputs make each one suitable for differing applications.
In summary fuel cells generally offer the following benefits to the end user: