High Temperature (750 to 800 C) Silicon Carbide Receiver Assembly for High Efficiency Gen3 Molten Salt Concentrating Solar Power

In 2011, the US Department of Energy (DOE) launched the SunShot Initiative with the goal of making solar electricity cost-competitive with conventional power generation by 2020. Since 2011, research funded by the DOE has resulted in substantial progress toward meeting the aggressive SunShot performance and cost targets, but significant technical hurdles remain. In particular, the Gen3 CSP Roadmap concluded that achieving the target plant thermal efficiency of ≥50% will require the use of a supercritical CO2 Brayton cycle power system operating a temperatures > 700°C. For molten salt CSP plants, this will require solar receiver salt exit temperatures in excess of 720°C, and possibly approaching 800°C. It is unlikely that commercially available high-temperature metal alloys will have adequate strength and corrosion resistance for use at such temperatures. Consequently, the CSP Roadmap identified the need for the development of new solar-receiver materials having superior high-temperature mechanical properties and corrosion resistance, along with a high solar absorptivity that is stable in air at high temperatures. Ceramic Tubular Products (CTP) proposes to develop multilayer SiC composite receiver tubes that will enable the design of molten chloride salt CSP systems that achieve the SunShot performance and cost targets. The multilayer SiC tubes, which are comprised of an inner monolithic SiC layer and an outer continuous-fiber SiC composite outer layer, possess thermomechanical properties and corrosion resistance that are superior to metal alloys at high temperatures. Furthermore, with the use of engineered surface coatings, the SiC tubes are expected to have absorptance (> 0.95) and emittance (< 0.50) properties that are stable in air at surface temperatures in excess of 900°C. And, unlike commercially available monolithic SiC tubes, the incorporation of the composite layer into the multilayer tubes result in non-brittle failure behavior when mechanical loads exceed the tube strength. Initial testing of CTP composite SiC specimens performed by Sandia under a Small Business Voucher project yielded promising results. However, demonstration of better optical properties (i.e., reduced emittance) and superior corrosion resistance at 800°C will strengthen the case for SiC receiver tubes. Consequently, Phase I will be directed at fabricating multilayer SiC tubes with engineered surface coatings, followed by solar spectrum testing at Sandia. Molten chloride salt corrosion testing will also be performed at Sandia at 800°C. Finally, a conceptual design for a 2 MWt SiC receiver assembly will be developed and a production cost model will be prepared.Successful demonstration of the breakthrough multilayer SiC receiver tube will justify further investment in the development and manufacturing of the SiC receiver tubes and associated receiver assembly components, and production of receiver assemblies. This will enable the development and testing of molten salt CSP demonstration plants that can meet the SunShot goals, and follow-on scale-up to commercial CSP power plants. The resulting benefit to US citizens will be the creation of new jobs and reduced CO2 emissions.