EPFL scientists have used a steam turbine-driven recirculation fan to increase the efficiency of Solid Oxide Fuel Cells (SOFCs).
The novel fan which runs on steam-lubricated bearings and recirculates gases through the system, also helps increase the SOFC’s lifespan.
SOFCs are devices that produce both electricity and heat by oxidizing a fuel such as natural gas or biogas.
If adopted, this energy-efficient, zero-emission technology could help meet domestic and commercial power, heating and hot water needs.
While uptake is high in countries like Japan, SOFCs have yet to catch on in Europe – mainly on account of their steep production costs.
Now an EPFL-led team has found a way to increase the lifespan and efficiency of SOFCs at a fraction of their given cost.
According to the scientists, the system’s new design marks a clean break with previous systems.
The fan is equipped with steam-lubricated bearings developed at the LAMD and is driven by a miniature steam turbine that runs on the heat produced by the cell.
None of the parts come into contact with one another, which means they don’t suffer from wear and tear.
Using a steam turbine helps do away with SOFC outlet gases containing hydrogen and other potentially explosive compounds in the residual fuel.
The EPFL collaboration involved three partners: the Laboratory for Applied Mechanical Design (LAMD); the Group of Energy Materials (GEM) headed by Jan Van Herle; and private firm, SOLIDpower SA.
SOFCs only convert around 80-85% of input fuel, which only transits the cell once. However, by connecting the outlet to the inlet, the team was able to recirculate the gases through the cell a second time.
Because SOFCs operate at temperatures exceeding 600°C, “the recirculation fan raises the pressure of the outlet gases, bringing it to a level compatible with the pressure inside the cell,” notes Patrick Wagner, the paper’s lead author.
With the new system, the team observed impressive efficiency gains of as much as 10%.
“When we coupled the fan to a domestic-rated fuel cell running at part load, or 4.5 kWe, we achieved gross efficiencies of 66%,” says LAMD head, Jürg Schiffmann.
By comparison, the most advanced power plants achieve efficiencies of 63% without generating recoverable heat.
The fan system also helps extend cell lifespan because the recirculated gas mixture increases catalyst stability.
Image and content: EPFL
