Record Efficiency for Solid Oxide Fuel CellsCategory: Science & Technology
Posted: June 6, 2012 07:04PM
In the effort to build 'greener' power sources for the US, researchers at the Department of Energy's Pacific Northwest National Laboratory (PNNL) have set a new record for Solid Oxide Fuel Cells (SOFCs). All fuel cells work by separating parts of a chemical reaction in such a way that for the reaction to finish, electrons have to travel through a circuit. The fuel for these reactions ranges from hydrogen and methane to purified diesel fuel and gasoline, with oxygen being used from the air.
Most researchers have been looking for ways to create massive fuel cells that can generate 1000 KW or more of power. Those at PNNL decided to aim a lower, as their new SOFC is only generating 2 KW of power, which is enough to power the average (meaning non-overclocking) home. Potentially the design could be scaled up to between 100 KW and 250 KW. Believe it or not but going smaller like this has some benefits that larger, more powerful, SOFC lack. Primarily, the smaller sized units can be placed closer to the end user, so there is less power lost during transmission.
Other small-scale SOFCs have been made before, normally with an efficiency of 30-50%, which is good compared to the 18% of portable combustion generators. This new SOFC however reaches 57% efficiency, which is largely thanks to its steam reforming design. Steam reforming mixes steam with the fuel to cause some chemical reactions that create intermediate products. In this case, carbon monoxide and hydrogen, which then react with the oxygen at the fuel cell's anode. To keep the steam's heat from destroying the fuel cell, the researchers used an external steam reforming setup which they improved with some PNNL microtechnology.
Heat exchangers are used to move heat from the fuel cell to the steam in the external unit. Instead of the usual single wall to the heat exchanger, the researchers used multiple walls with microchannels. These microchannels increased the surface area of the heat exchanger, allowing more heat to move.
More work still has to be done, as the current design is not economical for distributed power generation systems. By the time they can reduce the cost though, the researchers will likely also be able to push the efficiency to 60% or beyond, so it will be worth the wait.