Chief Operating Officer for OxEon Energy
Growing demands for clean energy solutions and energy storage which require the use of ceramic materials are creating an exciting area of growth for the ceramics industry. Solid Oxide Fuel Cells (SOFCs) are one such technology, and we spoke with COO of OxEon Energy, Jessica Elwell, to find out a bit more about this.
What are solid oxide fuel cells and what role do ceramics have in this?
SOFCs are energy conversion devices. They transport oxygen ions from air through a membrane that oxidizes a fuel on the opposite side, making them electrochemical reaction based and not chemical combustion. They operate near isothermally and thus not subjected to Carnot cycle efficiency limits (i.e. Delta T). Thus, the efficiency of conversion is very high. System level efficiency of 70% has been demonstrated (Siemens Westinghouse). They use a variety of fuels, hydrogen and hydrocarbon fuels and are more tolerant to contamination than low temperature PEM fuel cells.
Some designs use ceramic conductors to connect cell to cell, but metal is more common. But the metal surface is treated with a ceramic to limit volatilization of Cr from the metal that could lower the performance of air electrode.
Key elements of SOFCs entirely use ceramic components. The membrane, which is an oxygen ion conductor in the commonly used design, is made of yttria or scandia stabilized zirconia.
The electrode materials are perovskite ceramic (Lanthanum manganite or lanthanum cobaltite) for air electrode and a mixture of nickel metal with zirconia or ceria ceramic with for the fuel electrode. In the cell (fuel electrode-membrane-air electrode trilayer), it has 90% ceramic. Other ceramic materials include current distribution layers (of similar compositions to air and fuel electrodes) that are also ceramic containing. The need for ceramic ionic and electronic conducting materials comes from their stability at the high temperature. In high temperature as SOFCs operate in the range of 700 to 1,000 C.
What are the benefits of using SOFCs over alternative storage systems?
Efficiency is one primary advantage. SOFCs can operate at higher efficiency compared Carnot limited devices or lower temperature polymer membrane-based fuel cells. Another benefit is the ability to operate our systems reversibly to produce hydrogen through steam electrolysis, or hydrogen/syngas through co-electrolysis of steam with carbon dioxide. In the electrolysis mode the efficiency can be 100%, unmatched by any other devices. PEM electrolyzer operate at a much lower efficiency, more in the 60+%.
The materials for air and fuel electrodes in SOCs function well for both modes (fuel cell and electrolysis) unlike PEM based devices where the electrodes are specifically optimized for electrolysis or fuel cell operation.
What are the currently the key challenges of developing this technology?
High temperature operation causes materials interaction between layers to introduce performance degradation over time.
Cost is high as it becomes a manufacturing challenge to make large footprint cells. Generally, it is limited to 6 in x 6 in or at best 8 in x 8 in to have good manufacturing yield. In addition, the interconnect materials (specific metals that can withstand the temperature) also can have manufacturable size limits.
If you were sent to live on a desert island, what one item would you take?
Unfortunately, there are 10 essential items, so if only one… I suppose I need to bring a very long playlist to keep me company!
Jessica will be joining a panel of leading speakers at the Ceramics Expo conference, including experts from OneJoon and Special Power Sources. If you want to find out more on this and many other topics, join us in Cleveland at the free-to-attend event from August 30-31. Register here for your pass.