In the landscape of transitioning to clean energy sources, geothermal energy is likely to be a key player in the energy mix. Geothermal energy technology has expanded its scope from primarily serving the electricity market to encompass a wider array of applications within the energy sector. This evolution includes sustainable heating and cooling solutions, making geothermal energy a dependable and cost-efficient source of renewable power, unaffected by weather conditions. However, corrosion poses a significant challenge in numerous geothermal facilities, exerting a considerable adverse influence on the economic viability of the geothermal sector. The capacity to engineer surfaces to combat corrosion represents a valuable tool for both engineers and plant operators, enhancing maintenance and repair practices. This paper explores the possibility of using thermal spray coatings on steel substrates and modify its corrosion behaviour in phase change materials (PCMs) used in geothermal plants. The selection of thermal spray coatings was guided by factors such as their documented performance, applicability, accessibility, and cost-effectiveness. The philosophy was to select coatings that were anodic to the substrate in molten PCM that would protect the substrate in case of any damage to the coating. Carbon steel substrate with thermal spray coatings of Al was prepared, artificial defect was created, and the specimen were exposed to molten nitrate-nitrite PCM at 165°C for 168h. After testing, the specimen was visually examined and detailed post-test characterisation [light and electron microscopy (SEM/EDX) etc] of surface and cross-sections was carried out. These measurements provided an indication of performance of the coatings and allowed further understanding of the mechanism of degradation of materials in nitrate-nitrite PCM in the presence of artificially-introduced through-thickness coating defect. The study showed that thermally sprayed aluminium (TSA) could provide a possible corrosion mitigation pathway for carbon steel structures in nitrate-nitrite based PCM systems even when damaged.

Geothermal energy has been an integral part of the renewable energy mix for several decades. The total installed geothermal power generation capacity by the end of 2021 was 15,854 MW. Despite the challenges imposed by the pandemic, new capability was developed, and capacity was added in several countries. The capacity was increased by 246 MW from the figure in 2020.4