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| Fig. 1: Above depicts the process in which energy is produced in a solid oxide fuel cell. The reformed fuel crosses the anode,and it attracts oxygen ions from the cathode. The oxygen ions combine with the reformed fuel to produce electricity, water, and small amounts of carbon dioxide. (Courtesy of the U.S. DOE) |
Clean, affordable, accessible energy is something that is heavily sought after. Lots of the energy we are currently using creates a high carbon footprint that is harmful for our environment. There are several different forms of alternative energies that don't have this same footprint, but face their own issues. One of the largest issues at hand is that it is hard to generate the quantity of energy that fossil fuel generators create. Also, many renewable energy sources, such as wind and solar, rely on resources that aren't always present. Additionally, these alternative energy resources are typically more expensive when comparing them to fossil fuel costs. [1] However, solid oxide fuel cells seem to have an answer to most of these problems.
Solid oxide fuel cells are made of three things: an electrolyte, an anode, and a cathode. Fuel and air are converted into electricity, through a chemical reaction. Since solid oxide fuel cells are high temperature cells, warm air enters the cathode and steam mixes to form reformed fuel. This reformed fuel is key to the reaction process because it attracts oxygen atoms from the cathode. Then the oxygen and reformed fuel combine to create electricity. This process can be repeated as many times as possible as long as there is fuel, air and heat. [2] These fuel cells operate at an efficiency level of around 60%, which means that only 40% of energy is lost during the chemical reactions, which is relatively good levels for a fuel cell. The cells operate at a temperature of 1,800 degrees Fahrenheit, and wasted heat can be used to create extra energy. [3]
Solid oxide fuel cells have a larger range of applications due to the materials involved in the cells. Other fuel cells, such as "proton exchange membranes (PEMs), phosphoric acid fuel cells (PAFCs), and molten carbonate fuel cells (MCFCs), have all required expensive precious metals, corrosive acids, or hard to contain molten materials". [2] Solid oxide fuel cells have low cost ceramic materials, so the benefit of these cells exceeds the costs, unlike other fuel cells. Therefore, solid oxide fuel cells can be used for commercial use. One such company using this technology is Bloom Energy, with their product called the Bloom Box. This is essentially a box the size of a refrigerator that uses solid oxide fuel cells for energy. One unit costs from $700,000 to $800,000, and is very easily installed. Companies such as Wal-Mart, Google and eBay are using this product. [4]
The amount of CO2 released from solid oxide fuel cells is still noticeable. "Bloom Energy Servers release 773 pounds of CO2 per megawatt-hour while the average U.S. grid emission rate is 1,555". [5] There is clearly a lower level of CO2 emissions compared to other sources, but these cells are not completely carbon dioxide free. Additionally, ensuring the correct temperatures for operation is pivotal. If temperatures are not ideal, then efficiency of the solid oxide fuel cells will not achieve maximum efficiency. [6] If maximum efficiency isn't achieved, then the cost of these fuel cells may surpass the benefit.
Solid oxide fuel cells have some obstacles, but we are starting to see how the application of these cells can have huge applications for our countries future with energy. Potentially these solid oxide fuel cells may be replacing all other fuel cells in the future. [7]
© Tom Fawcett. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] A. B. Stanbouli and E. Traversa, "Solid Oxide Fuel Cells (SOFCs): A Review of an Environmentally Clean and Efficient Source of Energy," Renew. Sust. Energy Rev. 6, 433 (2002).
[2] S. Kaul and R. Edinger "Efficiency Versus Cost of Alternative Fuels from Renewable Resources: Outlining Decision Parameters," Energy Policy 32, 929 (2004).
[3] Gaylord, "Bloom Box: What 60 Minutes Left out," Christian Science Monitor, 22 Feb 10.
[4] R. M. Ormerod, "Solid Oxide Fuel Cells," Chem. Soc. Rev. 32, 17 (2003).
[5] S. C. Singhal and K. Kendall, Eds., High-temperature Solid Oxide Fuel Cells: Fundamentals, Design and Applications, 1st Ed. (Elsevier, 2003).
[6] E. D. Wachsman and K. T. Lee, "Lowering the Temperature Of Solid Oxide Fuel Cells," Science 334, 935 (2011).
[7] E. D. Wachsman, C. A. Marlowe, and K. T. Lee, "Role of Solid Oxide Fuel Cells in a Balanced Energy Strategy," Energy Environ. Sci. 5, 5498 (2012).