Ionic liquids as advanced heat transfer fluids in renewable energy systems

As the demand for efficient and sustainable heat transfer solutions continues to grow, ionic liquids (ILs) have emerged as a promising alternative to conventional fluids. This review explores the multifaceted role of ILs as heat transfer fluids (HTFs), emphasizing their classification, thermophysical property modulation through nanoparticle integration, and environmental sustainability considerations. The discussion includes the biodegradability and ecotoxicological profiles of ILs, alongside containment and recovery strategies, while also assessing their economic feasibility compared to alternative HTFs. The application of ILs in renewable energy systems, particularly in solar power and absorption refrigeration, is examined, highlighting innovations that enhance system efficiency and thermal energy storage integration. Additionally, the review addresses other industrial applications, including manufacturing, heat exchangers, and geothermal energy utilization, while identifying practical challenges such as crystallization, corrosion, and viscosity issues. Finally, future directions are outlined to overcome production costs, material compatibility, and safety concerns, positioning ILs as a promising solution in the quest for efficient and sustainable heat transfer technologies.