Modeling and Performance Analysis of High Vacuum Flat Plate Hybrid Photovoltaic-Thermal Collectors

Abstract

We present a novel design for a High Vacuum Photovoltaic-Thermal (HV PV-T) device, which combines photovoltaics and thermal energy conversion in a flat-plane architecture. Our design aims to reduce convective heat loss via high-vacuum encapsulation, whilst maintaining high electrical efficiency even at elevated temperatures. This system is well suited for converting solar energy into thermal energy and effectively meeting thermal demands in industrial processes, especially those needing temperatures up to 150 °C, like boiling and pasteurization. The PV-T system consists of three primary components: a glass covering and a metallic vessel, which keep the device under high vacuum conditions (p < 0.1 Pa), and the central PV-T device. The PV-T device comprises four essential layers namely, a Transparent Conductive Oxide (TCO), a Perovskite-based PV cell, a Solar Absorber (SA), and a copper substrate. These layers are welded onto a copper piping to allow heat extraction via heat transfer fluid. For a comprehensive evaluation of the proposed PV-T device performances, we developed a one-dimensional numerical model in MATLAB. The observed performance outcomes are affected by radiative losses, which depend on both the operating temperature $\left( {T_{op} } \right)$ and the emittance of the TCO layer $\left( {\varepsilon_{TCO} } \right)$. Therefore, we conducted a performance analysis by changing these two parameters within the appropriate ranges of (25 $\div$ 175) °C and (0.05 $\div$ 0.45). The annual thermal and electrical outputs of our PV-T system were evaluated, employing hourly meteorological data from Amsterdam (Netherlands), Naples (Italy), and Doha (Qatar). In addition, a comparative analysis was conducted with commercial High-Vacuum Flat Plate Solar-Thermal (HVFP ST) collectors and PV panels. The results indicate that at a temperature of 100 °C and with emittance values below 0.21, the annual thermal yields surpass 503 kWh/(m² year) for Amsterdam, 941 kWh/(m² year) for Naples, and 1278 kWh/(m² year) for Doha. Furthermore, annual electrical generation stands at 158 kWh/(m² year) for Amsterdam, 234 kWh/(m² year) for Naples, and 288 kWh/(m² year) for Doha. In terms of economic viability, our study shows promising outcomes. In Naples’ climate, for an annual thermal demand of 26 GWh, a cost margin of 248 €/m² is granted to our suggested HV PV-T system to achieve the same Simple Pay-Back time as the HVFP ST solution. In such a situation, the HV PV-T option can lower annual CO₂ emissions by 58% more than the HVFP ST solution.