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The global climate crisis has led society toward cleaner energy sources. Another reason is the limited reserves of fossil energy resources. Efforts to increase the efficiency of photovoltaic modules (PVs) have gained momentum. The high temperature is the biggest factor causing a decrease in the efficiency of PVs. In this study, a commercial PV was cooled with distilled water, a multiwalled carbon nanotubes (MWCNT)/water mixture, and a graphene nanoplatelets (GNP)/water mixture. The environmental impact of electricity, total energetic efficiency, energy payback time, energy return on investment, and embodied energy of the PV/thermal (PV/T) system were compared using life cycle assessment and cumulative energy demand. The electrical efficiency of the PV/T changed between 13.5% and 14.4%. The total efficiency of PV/T changed between 39.5% and 45.7%. The energy returns on investment were 1.76, 1.80, and 1.85 for PV/T-distilled water, the PV/T-MWCNT/water mixture, and the PV/T-GNP/water mixture, respectively. Moreover, the embodied energy evaluation values were 3975.88 MJ for PV/T-distilled water, 4081.06 MJ for the PV/T-MWCNT/water mixture, and 4077.86 MJ for the PV/T-GNP/water mixture. The main objective of this research was to study the energy and environmental performances of PVs cooled with different nanofluids and draw general conclusions about the applicability of these systems.

The heat absorbed by the heat transfer fluid for cooling a concentrated photovoltaic thermal (CPVT) solar collector can be used for purposes such as residential heating and cooking. Because of the combined production of heat and power, these systems are proposed for individual or commercial use in rural areas. In this study, a hybrid system was proposed to increase the electrical efficiency of the system. Experiments were conducted in winter conditions. Two operational modes were compared, namely a CPVT system with HP (HP-CPVT) and without HP (CPVT). The evaporator of the heat pump was settled inside the triangular trough receiver. The effects of cooling the PV system with a heat pump in the bifacial CPVT system on the electrical and thermal energy efficiencies were investigated. The electricity and thermal energy efficiencies of the CPVT system were calculated as 12.54% and 38.37% in the HP-CPVT system, respectively, and 10.05% and 81.97% in the CPVT system, respectively. The electrical exergy efficiencies of the CPVT system with and without HP were 14.65% and 10.73%, respectively. The thermal exergy efficiencies of the CPVT system with and without HP were 82.47% and 85.63%, respectively. The thermal heat obtained from the HP-CPVT system can be used for heating needs. Thus, the bifacial HP-CPVT system was an example of the micro-CHP system.

The current paper proposes a novel multi-generation system, integrated with compound parabolic collectors and a biomass combustor. In addition to analyzing the comprehensive system in a steady state, the feasibility of using nanofluids as heat transfer fluids in the solar cycle and their effect on the overall performance of the system was studied. The multi-generation system is generally designed for generating electricity, cooling, freshwater, drying, hot water, and hydrogen, with the help of six subsystems. These include a double stage refrigeration system, an organic Rankine cycle, a steam Rankine cycle, a dryer, a proton exchange membrane electrolyzer, and a multistage flash distillation system. Two types of nanoparticles (graphene, silver), which have various high-quality properties when used within ethylene glycol, were chosen as absorbing fluids in the solar cycle. The performance parameters of the base case thermodynamic analysis and some of the variable parameters were calculated, and their effect on system performance was determined. According to the results, a spike in solar irradiation, ambient temperature, output temperature of biomass combustor and nanofluids’ concentration positively affected the overall system performance. The results also clearly showed an improvement in system performance when using nanofluids as working fluids in solar collectors.