Session: 10-02: Photovoltaic, Photovoltaic-Thermal, and Electrochemical Technologies II

Paper Number: 168370

168370 - Efficient and Sustainable Heat and Power Cogeneration Using Evacuated Flat Plate Photovoltaic-Thermal Systems 

Abstract: 

Photovoltaic thermal systems (PVT) have been introduced to utilize waste heat from Photovoltaic systems, as more than 80% of solar energy is converted into heat in Single junction PV systems. However, many PVT systems suffer from low thermal performance because of high heat transfer resistance between PV and the absorber, high thermal losses from the surface of the PV, low optical efficiency, etc. This low thermal performance limits the ability of the PVT system to supply the required energy for high thermally demanding processes such as desalination. Accordingly, an evacuated flat-plate photovoltaic thermal system has been designed and built for cogeneration of heat and electricity at high thermal and electrical efficiencies. The system was tested under different mass flow rates and solar irradiance levels during September 2024.

Additionally, the electrical efficiency of PV cells decreases as their surface temperature increases. Accordingly, hybrid photovoltaic thermal (PVT) systems have been developed to extract heat from PV panels and utilize it for applications such as domestic hot water, desalination, or space heating. PVT systems not only prevent the waste of thermal energy from PV panels but also enhance the electrical efficiency of the system. Such hybrid systems can achieve total efficiencies above 80%, and a recent study showed that PVT systems can reduce global carbon dioxide emissions up to 18% by 2050.

In this research, we have designed and fabricated an advanced Evacuated Flat Plate PVT system for highly efficient and sustainable cogeneration of heat and electricity. Monocrystalline PV cells, measuring 21.5 by 52 cm^2, are mounted on an absorber plate to generate electricity while simultaneously transferring heat to the plate. Thermal paste enhances heat conduction between the PV cells and the absorber plate, which is constructed from Aluminum 6061 with a black coating to increase sunlight absorptivity. Below the absorber plate, a water channel extracts heat from the system. We selected borosilicate glass for the glazing due to its high resistance to thermal shocks. To minimize convection losses and boost thermal efficiency, the space between the absorber plate and the glass is maintained under vacuum pressure. The bottom and sides of the PVT system are also well insulated to minimize heat loss. The evacuated design, combined with robust insulation, is expected to mitigate the impact of ambient temperatures on system performance, ensuring the provision of required water temperatures even in cold conditions when sunlight is available. This hybrid PVT system could be utilized for water desalination or space heating.

The impact of various nanoparticles, including SiO2, Al2O3, CuO, and TiO2, on the thermal efficiency and Nusselt number of the system is explored. Tests are conducted under varying conditions, such as different mass flow rates of water, solar irradiances, and nanoparticle volume fractions, to evaluate the electrical and thermal performance of the system.

Presenting Author: Behnam Roshanzadeh University of New Mexico

Presenting Author Biography: Behnam Roshanzadeh is a PhD candidate at the University of New Mexico, specializing in thermal sciences with applications in solar thermal technologies, thermal power plants, and cooling systems. He has authored five papers published in accredited journals within this field and has presented his research at several conferences, including ASME 2024.