Improving Thermal Distribution in Water-Cooled PV Modules and Its Effect on RO Permeate Recovery

Abstract

Among the most notable emerging hybrid technologies for water treatment are those that combine reverse osmosis (RO) membrane systems with alternative energy sources such as solar photovoltaic (PV). Solar PV modules can enable systems disconnected from the electricity grid, and in some locations can also be used for water heating as photovoltaic-thermal (PVT) units, a process in which water removes heat from the PV module, increasing its electrical generation efficiency. When combined with RO, the higher temperature feed water can increase RO permeate flux, improving recovery but decreasing the rejection of dissolved salts. Although the decrease in efficiency of PV modules at higher temperatures is a well-known issue, this is usually under conditions of uniform temperature. However, the temperature distribution in water-cooled PV modules is usually not uniform and, given the anisotropy of the distribution and electrical connection of the PV cells in the module, this factor has not been the focus of much study. In this context, a PVT unit that focuses on increasing the output water temperature with a high global heat transfer coefficient will not necessarily be the most electrically efficient system. This study experimentally assesses several proposed heat-exchange configurations for PVT systems where the PV modules are cooled by forced convective water flow. A simulation model of PVT performance is then validated and used to predict the productivity of the PVT-RO coupling, both in terms of electrical generation and permeate flux of the hybrid system under different conditions. The results suggest that water-cooled PV modules have several potential applications for off-grid and remote water treatment, as well as water transportation systems.

Keywords

• solar energy
• PV modules
• reverse osmosis
• solar desalination
• PVT