A main method to increase the solar energy utilization efficiency is to combine heat and power generation together. In this paper, a critical review of the literature on solar combined heat and power systems (CHP) is conducted, which includes solar photovoltaic/thermal systems, concentrated photovoltaic/thermal systems, and various combination with different solar collectors and applications. It shows that there are serious gaps in thi. A main method to increase the solar energy utilization efficiency is to combine heat and power generation together. In this paper, a critical review of the literature on solar combined heat and power systems (CHP) is conducted, which includes solar photovoltaic/thermal systems, concentrated photovoltaic/thermal systems, and various combination with different solar collectors and applications. It shows that there are serious gaps in this field, which calls for more research. The modeling and analysis of the electrical parts of the CHP systems are not adequate, and there are limited studies on the economic and exergy assessments of the solar concentrating CHP systems. The solar collectors for combined CHP were focused on optimizing the performance of the maximum average useful power generation and minimum total heat transfer area, little environment impact analysis was conducted. Careful exergy, economic and environmental analysis on both electronic and thermal performance is suggested, especially for large CHP system. Also, further studies are recommend for investigating the hybrids of concentrating collectors with CHP, with considering the economic issues.••••Solar combined heat and power systems including collectors and PVTs are reviewed.••Several gaps are identified and reported in the survey of the literatures.••Economic studies and exergy analyses are suggested for solar concentrating CHPs.••It is recommended to conduct more studies on large-scale solar CHPs.Combined heat and powerPhotovoltaic/thermalConcentrating collectorsFlat collectorsEnergy and environment are the two main concerns of our future, and developing sustainable renewable energy technologies becomes more and more imperative. Among all the renewable sources, solar energy is the most promising one due to its abundance and environmentally friendly nature. To resolve the reliability and accessibility problems of solar energy, hybrid power generations are used broadly. A main method of increasing the productivity of solar systems is to extend them to combined heat and power generation (CHP). Solar CHPs could reduce the greenhouse gas emissions far faster than the conventional solar energy devices, and maximize the economic and environmental value of the energy derived from the sun.Firstly, in 1976, Wolf analyzed the performance of a hybrid system of solar photovoltaic and flat plate thermal collector for residential applications in New Mexico. The performance of combined solar heat pump arrangements including series, parallel and dual source were analyzed by the TRNSYS software, which showed that the parallel configuration was the most practical combined setup, because of the higher thermal performance at a given collector area over the hot season. In 1986, a hybrid solar closed-cycle gas turbine, consisting of a parabolic dish reflector with focal-mounted heat exchangers and a centralized prime-mover, was analyzed to meet the needs of a small urban/industrial com. Obviously, solar energy can be used as the source of thermal energy and electrical energy. PVT systems are capable of converting solar radiation into electrical and thermal energy, simultaneously, which makes it more efficient compared to the current PV systems. Due to many advantages of PVTs such as supply both electrical and thermal demand at the same time, and being cost-effective, the applications of these systems are being expanded. The PVT systems consist of two parts: a solar cell which converts the sunlight into electricity and a solar thermal collector, mounted at the back of the PV panel, for collecting the thermal energy. Water or air are usually applied as the cooling fluids for the solar panels,,. Therefore, this configuration enhances the operation of the panels, and improves the efficiency. Utilizing the waste heat could improve the efficiency of the system up to 80%.It has established that increasing the solar cell temperature by one degree centigrade decreases the efficiency of monocrystalline (c-Si) and polycrystalline (pc-Si) silicon solar cells by about 0.45%, and about 0.25% for the amorphous silicon (a-Si) cells. Many researchers have analyzed the PVTs in terms of efficiency and the relation between the temperature of the panels and efficiency,,,. With this regard, Medrano et al. investigated the efficiency, and the economic and environmental aspects of the integration of t.
