Efficiency improvement of floating photovoltaic panels with natural convection cooling loops: Multi-physics thermal modelling

• Introducing a hybrid natural convection cooling loop with a radiation filter feature. • Numerical multi-physics conjugate and radiation heat transfer analysis. • Impact of cooling channel thickness on the floating photovoltaic performance. • Comparison of water vs. Ag-water nanofluid as a coolant in cooling loops. • Using a radiation filter to lower temperatures and increase electrical efficiency. This investigation focuses on the thermal modelling of floating photovoltaic panels with a natural convection cooling loop, which includes a transparent cooling channel on top of the photovoltaic cell. Using pure water and 5.3 ppm Ag-water nanofluid, the novelty lies in the development of a two-dimensional multi-physics numerical model, which couples conjugate heat transfer with thermal radiation analysis. The resulting novel numerical model is used to investigate the effectiveness of the cooling loop over the daily cycle and, for the first time, to explore the effects of the coolant channel thickness and the nanofluid application. The research affirms the efficacy of the proposed system in lowering the photovoltaic cell temperatures, ensuring continuous day-to-day functionality. The coolant channel thickness explorations demonstrate the link between channel thickness, buoyancy-driven coolant flow rate and the photovoltaic cell temperature. Pure water resulted in superior electrical efficiency with varying cooling channel thicknesses (15.45 %), compared to 5.3 ppm Ag-water nanofluid (15.08 %), while a standard floating photovoltaic panel without a cooling system achieved an efficiency of 14.98 %. Although the Ag-water nanofluid results in a lower temperature, the difference in efficiencies arises from pure water’s heightened transmissivity in the crystalline silicon photovoltaic cell’s useful wavelength range (325 nm to 1125 nm), whereas the Ag-water nanofluid absorbs more in the 340 nm – 510 nm. Therefore, reducing the operating temperature alone does not guarantee higher efficiency, as the cooling fluid’s transmissivity within the useful wavelength range also plays a crucial role.