621Alkaline

Alkaline fuel cells (AFCs) were the first type of fuel cell to be widely used for space applications. AFCs contain a potassium hydroxide (KOH) solution as the electrolyte and operate at temperatures between 100 and 250°C (211 to 482°F). Higher temperature AFCs use a concentrated (85 wt%) KOH solution, while lower temperature AFCs use a more dilute KOH solution (35 to 50 wt%). The electrolyte is contained in and/or supported by a matrix (usually asbestos) that wicks the electrolyte over the entire surface of the electrodes. A wide range of electrocatalysts can be used in the electrodes (e.g., Ni, Ag, spinels, metal oxides, and noble metals). The fuel supplied to an AFC must be pure hydrogen. Carbon monoxide (CO) poisons an AFC, and carbon dioxide (CO2) reacts with the electrolyte to form potassium carbonate (K2CO3). Even the small amount of CO2 in the air (about 370 PPM) must be considered for operation of an AFC (Hirschenhofer et al., 1998).

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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