High-Performance Coatings for Turbomachinery in Supercritical CO2 Cycles for Concentrated Solar Power Plants

Statement of the Problem or Situation that is Being Addressed: Concentrated solar power plants heat a working fluid that can be stored and used to generate power non-intermittently and on-demand. Such a technology is an ideal complement to intermittent renewable energy sources like solar and wind. To make Concentrated Solar Power plants more efficient and cost effective, supercritical carbon dioxide, a form of CO2 which occurs at high pressure and relatively low temperature having flow properties like a gas and the density of a liquid, has been proposed as a new working fluid. As a result, the turbines can be made much smaller (10X), and respond to varying power demands more rapidly, while maintaining efficiencies out-performing steam and gas turbines. To ensure effective and reliable operation of supercritical CO2 turbines, thermal barrier coatings are required that have low thermal conductivity and can survive the chemically hostile environment of high-pressure carbon dioxide. Statement of how this Problem or Situation is Being Addressed: Thermal barrier coatings for supercritical CO2 turbine have shared requirements as typical gas turbines, including having lowest possible thermal conductivity and acceptable mechanical properties. However, they are subjected to chemical attacks of the high-pressure hot carbon dioxide, and thermal stress challenges due to the 2.5X greater heating rates than in a standard turbine. Promising candidate materials will be explored for such applications, including materials for which no commercial source is available. The coatings of the novel compositions will have the specially engineered feature of stress-relieving cracks, and will be produced by the performing organizationĺs pioneered plasma spray process that uses solution precursors instead of the conventional powder feedstocks. The novel thermal barrier coatings will be evaluated under high-pressure high-temperature carbon dioxide environments, and the results along with other measured properties will enable the choice of an improved thermal barrier coating as desired by the industry. Planned Phase I Effort: In the Phase I program, multiple thermal barrier coating compositions will be selected from successful materials used for internal combustion engines and traditional gas turbines along with new promising candidates. The coatings of target compositions will be deposited by the solution-based plasma spray process, and used as rapid screening of multiple candidate compositions and microstructures. Thermal barrier coatings of down-selected compositions and microstructures will be tested in a high temperature, high pressure carbon dioxide rig and measured for other properties, upon which a winner will be selected. Commercial Applications and Other Benefits: The novel coatings developed here has great potential to advance the concentrate solar power technology, and facilitate the adoption of renewable energy by providing a robust and low-cost non-intermittent supplementary power source. The projected gains in operation efficiency and durability enabled by the new coating technology will bring economic benefits to US consumers and businesses, resulting in new good-paying domestic jobs. The advanced concentrated solar power technology will also strengthen the US energy independence and resilience in face of Climate Change.