Materials Characterization for Concentrated Solar Power
Thermal shock analysis was used to characterize materials subjected to concentrated solar power, which offers clean renewable energy. Research at the National Renewable Energy Lab's High Flux Solar Furnace was conducted to determine the limiting factor for thermal fatigue. Optimal materials are heat and corrosion resistant because of the high temperature oxidative environment of the furnace. Failure and lifetime assessment was gathered via power measurements and flux profiling. Specimens tested included nickel-based superalloy Haynes 214, CoorsTek Alumina, and Hexoloy Silicon Carbide. Alumina is inherently resistant to corrosion and fatigue, while the other materials form protective oxide layers at elevated temperatures. Materials were thermally cycled and thermal shock behavior was analyzed. The cycling was meant to imitate conditions when optimal power is not available due to atmospheric conditions, i.e. cloud coverage or stormy weather. Factors include cycle time, max power levels, and number of cycles. Experimental testing of ASTM standardized specimens involved Vickers's hardness testing, tensile testing on Instron 5869 and a fully articulated four point bend fixture for ceramics, and vertical furnace corrosion testing. Testing for residual strength helps determine the material characteristics that contribute to thermal failure and the material properties needed for various applications using concentrated solar power.