Enhance of photovoltai̇c thermal system performance usi̇ng a spectral splitting

Photovoltaic systems (PV) are systems used to produce electrical energy. Photovoltaic cells have low electrical conversion efficiency. Overheating caused by high ambient temperatures reduces electrical conversion efficiency. The spectrum wavelength range coming from the sun to the photovoltaic panel is between 200 nm and 2500 nm. The range in which photovoltaic silicon cells produce is between approximately 380 nm and 1100 nm. The part outside the wavelength range is converted into heat in photovoltaic cells. The part converted to heat reduces the electrical conversion efficiency. Photovoltaic thermal systems (PV/T) have been developed as a solution to increase electricity conversion efficiency. Heat transfer fluid is used to reduce panel temperature. These fluids, circulating adjacent to the back side of the cells, absorb heat and enable the heat produced to be used as useful energy. However, in these systems, PV is exposed to the intense solar spectrum. The lifespan of overheated PV cells is shortened. Spectral discriminators are used as a solution to these problems. Before solar radiation reaches the photovoltaic silicon cells, it filters the incoming beam within the working range of the photovoltaic cells. Thus, electrical conversion and thermal efficiency losses caused by high temperatures are eliminated. In this study, two different experimental comparisons were carried out. First, an experimental comparison of PV and PV/T systems is given. In the PV/T system, 58% more electrical efficiency and an additional 33% thermal efficiency were achieved compared to the PV system. In total average efficiency, the PV/T system performed better with 46.95%. Five fluids were selected based on the physical properties of the spectral discriminators. The optical properties of the fluids were tested on the spectrophotometer device. Among these five fluids, water and mono ethylene glycol were determined as the spectral working fluids, considering their cost, specific heat, thermal conductivity and optical properties. It was determined that pure water had the lowest cost, highest specific heat (4180 J/kg. K) and highest thermal conductivity (0.6 W/m. K) values. Mono ethylene glycol is easily accessible and is thought to be the best alternative after pure water in terms of both its physical and optical properties. In the second experimental comparison, the spectral discriminator performances in the PV system and PV/T systems were compared. Spectral decomposers showed that mono ethylene glycol and pure water performed close to each other (11.58%-11.59%) in electrical efficiency. In comparing thermal efficiency, mono ethylene glycol was advantageous with an average efficiency of approximately 70%. In total average efficiency, mono ethylene glycol showed 81.59% performance, pure water 71.58% performance and PV system showed 9.14% performance. Increasing the electrical efficiency of the system, utilizing thermal energy, reducing maintenance costs due to cleaning, considering the advantages such as preventing damage to the PV system due to high temperatures, the PV/T system designed and analyzed will enable more effective use of solar energy, reduce energy costs and expand the use of renewable energy. Keywords: Photovoltaic system, solar radiation, spectral splitting