For the sake of simplicity, as the name indicates, you can compare a solid oxide fuel cell (SOFC) with an ordinary dry cell or battery. They are similar as both produce electricity by electro chemical reaction, but the difference is, unlike the traditional dry cell, an SOFC requires a continuous supply of fuel (typically hydrogen, hydrocarbons, carbon monoxide, and oxygen) in order to operate.
Construction of Solid Oxide Fuel Cell
- Like other fuel cells, SOFC have three main sections: a cathode (positive electrode), an anode (negative electrode) and the (solid) electrolyte (media in which ions flow).
- The fuel and air flows over the anode and cathode respectively. The fuel must be a compound of hydrogen.
- Some of the fuels used for SOFC are natural gas, alcohol, and pure hydrogen. The Rolls-Royce fuel cells use natural gas.
- The hydrogen molecule from the fuel is ionized at the porous anode at high temperature and releases free electrons. These free electrons then run from anode to cathode through the external circuit, generating electricity.
- On the other hand, the oxygen from the air is reduced at anode to an oxygen ion with the help of the received electron from the cathode.
- The oxygen ion then travels through the electrolyte and reacts with the hydrogen ion at the cathode to produce water.
- Typically the anode is made up of a composite made up of nickel and a ceramic material. The ceramic material is same material as the electrolyte.
- Typical cathode material for the a commercial SOFC is lanthanum strontium manganite.
- The electrolyte layer is made up with a solid dense ceramic layer. The electrolyte layer is made up of solid materials, and that’s why it is so named.
Why SOFC is Most Suitable for a Commercial Stationary Power Plant
- Higher efficiency: SOFC has relatively high efficiency, typically around 60%.
- Fuel flexibility: Lots of fuel options are possible for SOFC.
- Cost Effective: The solid oxide fuel cell is made up of normally available materials, hence is low in cost.
- Waste heat regeneration: Co-generation of steam is possible due to higher operating temperatures.
- Low pollution: This fuel cell has minimal emissions and noise, and also the materials of the cell are totally recyclable after the end of useful life.
Rolls-Royce believes that solid oxide fuel cell is best for stationary power generation applications. Mark Fleiner, President of Rolls-Royce Fuel Cell Systems (US) Inc., commenting on the acquirement of the assets of Ohio-based SOFCo-EFS Holdings LLC from McDermott International, Inc. said, “From the beginning, our strategy has been to engage the best skills and technology around the world to create the first cost-competitive, highly-efficient fuel cell systems."
The higher efficiency and the availability of the construction materials make the SOFC an ideal candidate for commercialization. And the companies like Rolls Royce and Bloom energy are working hard at tapping the future of this segment of green energy.