Technoeconomics of a molten salt/supercritical carbon dioxide heat exchanger with fractal-textured corrosion resistant coatings for concentrating solar thermal systems

Abstract

Molten salt/supercritical carbon dioxide heat exchangers are integral to the operation of Generation 3 concentrating solar thermal systems, which play a key role in facilitating the decarbonization of power generation and industrial sectors by reducing reliance on fossil fuels and curbing greenhouse gas emissions. At the targeted operating temperatures of about 750 °C, molten carbonate and molten chloride salts are two viable heat transfer fluids and thermal energy storage media. However, their extreme corrosivity at high temperatures limits the containment materials choice to expensive alloys such as Haynes 230, which increases the levelized cost of energy. Toward addressing the materials and cost challenge, this paper presents a detailed technoeconomic analysis of a molten salt/supercritical carbon dioxide heat exchanger made of low-cost ferrous alloys with novel fractal-textured corrosion-resistant coatings as tube and shell materials. The coatings impressively reduce the corrosion rate on the alloys to be lower than or on par with Haynes 230. Considering different alloy materials, the study systematically demonstrates that the levelized cost of a heat exchanger with coated low-cost ferrous alloys is lower than that with Haynes 230 by 60 % and 63 % for molten carbonate and chloride salts, respectively. The study establishes for the first time that low-cost ferrous alloys with fractal textured corrosion-resistant coatings are technoeconomically superior alternatives to Haynes 230 in Gen3 CSP systems, with broader application to molten salt nuclear reactor systems as well.