TOUCHSTONE RESEARCH LABORATORY, LTD. — Department of Energy SBIR Phase I: 18c

Description

Coal is recognized as a primary energy resource used in the production of electricity and heat. Furthermore, coal is a very versatile commodity used in industrial processes such as refining metals and refined into coal tar, phenol, creosote oil, naphthalene and other chemicals. The objective in this research is to develop a silicon carbide foam, produced from domestic coal that has an open pore structure for molten salt containment and used in thermal storage systems forthe concentrated solar power industry.In addition, the silicon carbide foam will have high thermal conductivity that enhances heat transfer. The high use temperature of silicon carbide, combined with high heat transfer properties, potentially overcomes technical barriers that prevent implementation of closed loop supercritical carbon dioxide recompression Brayton cycle technology. Moving from steam (Rankin Cycle) to super critical carbon dioxide (Brayton Cycle) potentially increases thermal efficiency by almost 45% resulting in concentrated solar powerplant output 40% or more. For thermal energy storage systems used in concentrated solar power technology, and molten salt phase change materials in general, molten salt systems represent the most familiar approach. However, the increase in hot salt system temperature from 565 centigrade to about 720 centigrade brings significant material challenges. First, salts used for phase change materials have low thermal conductivity that are typically less than 1.0 (watt/meter-kelvin). This corresponds to low heat transfer within the thermal energy storage system.The objective in this Phase I research isto develop and show feasibility that molten salt contained within the porosity of silicon carbide foam will significantly enhance heat transfer in thermal energy storage systems. Feasibility inPhase I will be demonstrated through defining the process and characterizing silicon carbide properties, which include thermal conductivity, corrosion resistance, microstructure and physical properties. In addition, cost feasibility will be demonstrated through the use of coal as feedstock and an innovative processing approach. The proposed technical approach is anticipated to significantly reduce silicon carbide production costs in contrast to current methods using petroleum-based foam feedstocks and chemical vapor infiltration or chemical vapor deposition conversion processes in the manufacture of silicon carbide. While the bulk of concentrated solar power electricity will come from large, on-grid powerplants, these technologies also show significant potential for supplying specialized demands such as process heat for industry, co-generation of heating, cooling and power, and water desalination. Concentrated solar power also holds potential for applications such as household cooking and small-scale manufacturing that are important for the developing world. Solar-generated hydrogen can help decarbonize the transport and other end use sectors by mixing hydrogen with natural gas in pipelines and distribution grids, and by producing cleaner liquid fuels.