A comprehensive review on renewable energy integration for combined heat and power production

Renewable energy sources have gained prominence due to sustainability and less environmental impacts. With increasing energy consumption and depleting fossil fuel sources, emphases have been given to develop environmental-friendly energy systems and expand renewable energy penetration. In this regard, energy integration systems, that can satisfy energy demands in various forms, are considered as a viable approach for increasing the utilization of renewable resources and improving the efficiency of generation. Over the past decades, combined heat and power systems have been associated with energy savings and less environmental consequences. To this end, these systems attracted research community for further investigations and developments of renewable-based combined heat and power configurations in residential as well as industrial sector. In this study, energy generation by means of renewable resources including: solar, wind, and geothermal when operated as a cogeneration system, or integrated with a combined heat and power system is reviewed. The primary objectives of this study are to analyze the performance of most recent state-of-the-art designs, and present a comprehensive review that underlines the current research trends in the field of solar, wind, and geothermal energies. This review attempts to elaborate on integration of single or multiple renewable energies in combined heat and power systems. In this regard, preliminary research works are classified based on utilization of renewable resources in single and multiple integration. Further classifications are carried out based on the most cited research trends in that particular renewable energy field, in order to realize the current research objectives and the challenges every renewable field is facing today. Every presented system is evaluated in terms of implemented components, employed methods, and the objectives as well as key findings. This method of classification results in three primary research focuses including: model development and application in solar- integrated systems, thermo-economic optimization in geothermal-integrated systems, and scheduling and minimizing curtailment in wind-integrated systems. Finally, the future perspective of this field is proposed based on the current status of renewable integration to facilitate more effective and feasible operation in the future.