Nanotechnology applications for green energy transformation: performance enhancements, trends, challenges and emerging opportunities

Renewable energy resources like solar, hydropower, wind, and geothermal energy are abundant in nature, and continue to be naturally replenished. With these resources, we address climate change and environmental deterioration. This review provides an extensive insight into recent trends in renewable energy systems, nanotechnology, and, in particular, the use of engineered nanoparticles and nanofluids in energy conversion and recovery. This review also analyses the recent breakthroughs in the conversion of biomass and the use of nanotechnology to capture carbon dioxide. The evaluation of the different nanofluids for heat transfer applications in renewable energy systems is done critically, and these heat transfer systems are used as a reference in selecting the nanoparticles to be used in a specific thermal management system. This review links the advances in nanotechnology to the deployment of nanotechnology in renewable energy systems by overcoming certain engineering challenges such as the reduction of viscosity, stabilization of the engineered nanoparticles, and integration of the system. However, although nanoparticle-enhanced systems have high potential, more studies are required to address the current shortcomings, especially in the domains of wind and hydropower where nanofluids are not widely used yet that, nevertheless, could make a substantial contribution to the enhancement of lubrication and energy recovery.