a PEM fuel cell (which i assume from the previous posts that i have read from you is the fuel cell that you are working on) generally is considered a fuel cell that works at low temperature, generating heat as high as 200o
here is a list of fuel cells available in the market:
-phosphoric acid fuel cells, these cells are generally used in nursing homes, hospitals, hotels, office buildings, utility power plants, etc., etc. and operate at about 190.2o
C, they have a 40% efficiency margin, the reason i bring this one up is because the heat that is produced is also used, it uses 85% of the thermal energy it gives up to steam water and be used in cogeneration, though i would also assume this system to be very expensive, bulky, and heavy.
-Molten carbonate fuel cells: they use molten carbonate at about 634.6o
C, however, the fuel cells are mostly for stationary applications, and use hydrogen, carbon monoxide, natural gas, propane, landfill gas, diesel, and simulated coal gasification products
-Solid Oxide fuel cells: the efficiency of this system is about 60% and can be used for very large applications, requiring high-power applications, they have hard ceramic materials instead of liquid electrolyte, and operate at 968o
-Alkaline fuel cells: They usually use potassium hydroxide as the electrolyte and are used by NASA on space missions with a 70% efficiency. (no mention on temperature though)
-Direct methanol fuel cells: they use a polymer membrane as the electrolyte, from the anode the catalyst draws the hydrogen from the liquid methanol, eliminating the need for a fuel reformer, and operate between 34.6-73.6o
at 40% efficiency. (now there is something interesting about these fuel cells and that is that they are being taken by the cell phone and laptop industry, they are going to be in the cell phones in the future and will increase the time that you can use your battery for example in a laptop by about 10 hours, they almost paper thin and the methanol is the catalyst)
-Regenerative fuel cell: basically this fuel cell uses a solar panel in a process of eletrolisys, to break water into hydrogen and oxygen, is used by NASA, pratically new technology, it uses if i am not mistaken the PEM fuel cell to generate the electricity and is basically a good method to create hydrogen and store the hydrogen for emergency use of some kind, as it is being implemented into ships
-there is another fuel cell that i can't recall the name, but it uses propane to gasify the water and then split it into Hydrogen and Oxygen using the hydrogen to generate electricity and has an efficiency of about 70%. it is the primary reason that platinum is used in fuel cells and that is because this process produces CO and CO2
both of which can cause damage to the fuel cell, the platinum will not let this happen.
-Now something interesting about PEM fuel cells, according to my teacher they have reached 90% margins, making them probably one of the most efficient energy application in current existence, off curse breaking the water does require energy, and i really do not know if she took that into consideration.
most of the information here was basically sumarized from a packet that my teacher handed out to us. though some i found from researching for my project also dealing with PEM fuel cells...
hope this helps