A review of heat recovery applications for solar and geothermal power plants

With depleting natural resources and the effects of conventional energy sources like coal and petroleum on the environment, clean energy sources have been gaining prominence in recent times. Renewable sources are abundant and improving the efficiency of renewable technologies will provide a viable solution to meet the ever-increasing energy demands of the modern-day world. One of the most effective and practical ways for improving the efficiency of renewable power plants and other possible energy sources is by recovering waste heat (vs. improving the power plant component efficiencies using new designs and materials). However, in many of the existing designs, the waste heat is merely rejected or not effectively utilized. Through a combination of sustainable and hybrid solutions and reusable waste heat methods, a sustainable future for power and advanced technology can be made a reality. Many independent review articles exist in the areas of solar power plants, geothermal power plants, and combined heat and power (CHP) plants. In this article, power generation using solar and geothermal sources when simultaneously operated as CHP plants for waste heat recovery (WHR) is reviewed with the focus on the current state of the art applications for this waste heat. Also, the thermodynamic performance and economics of these power plants when combined with the heat recovery applications are discussed. Finally, the future research direction for the field is suggested based on the current status and findings to pave the way for a more effective waste heat utilization from renewable thermal sources.