625 Solid Oxide

Solid oxide fuel cells (SOFCs) are currently being demonstrated in various sizes from 1 kW up to 250 kW plants. SOFCs utilize a non-porous metal oxide (usually yttria-stabilized zirconia, Y2O3-stabilized ZrO2) electrolyte material. SOFCs operate between 650 and 1000°C, where ionic conduction is accomplished by oxygen ions (O). Typically, the anode of an SOFC is cobalt or nickel zirconia (Co-ZrO2 or Ni-ZrO2), and the cathode is strontium-doped lanthanum manganite (Sr-doped LaMnO3) (Singhal, 1997; Minh, 1993).

SOFCs offer the stability and reliability of all-solid-state ceramic construction. High-temperature operation, up to 1000°C, allows more flexibility in the choice of fuels and can produce very good performance in combined-cycle applications. SOFCs approach 60% electrical efficiency in the simple-cycle system and 85% total thermal efficiency in cogeneration applications (Singhal, 1997).

The flat plate and the monolithic designs are at a much earlier stage of development typified by subscale, single-cell, and short-stack development (kW scale). Companies pursuing these concepts in the U.S. are Allied-Signal Aerospace Company, Ceramatec, Inc., Technology Management, Inc., and Ztek, Inc. At least seven companies in Japan, eight in Europe, and one in Australia are developing SOFCs. Tubular SOFC designs are closer to commercialization and are being produced by Siemens Westinghouse Power Corporation (SWPC) and a few Japanese companies.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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