Performance Evaluation Of A Coupled Photovoltaic-Thermal Solar Powered Desalination Pilot System

A pilot scale coupled photovoltaic-thermal solar powered desalination system was evaluated at the Brackish Groundwater National Desalination Research Facility (BGNDRF). The pilot system consisted of a 3-kW photovoltaic-thermal (PVT) solar panel array and a 2.3 kW photovoltaic (PV) array coupled with a 4 gal/min single-stage 4 membrane reverse osmosis (RO) desalination system. A heat exchange system was in place to provide simultaneous cooling for the PVT system and heating to the RO system feed water. This system was evaluated with three objectives in mind. The first objective was to identify whether cooling of the PVT panels resulted in a significant increase in energy production. Increased operating temperatures in PV panels result in decreased electrical conversion efficiencies. The second objective was to evaluate an increase in total daily permeate production when the heat exchange system was in operation and the feed water tank was heated. Higher feed water temperatures result in lower viscosity in the feed water allowing for increased water production. The third objective was to evaluate the impact of greater feed water temperature on permeate water quality. Higher feed water temperatures result in an increase in salt passage. Although the heat exchange system did result in lower operating temperatures in the PVT system, a significant increase in energy production was not immediately apparent, but rather a decrease in energy production was noticed. With the heat exchange on, a mean RO feed water temperature increase of 3.8°F during daylight hours (7 AM to 7 PM) was associated with a 0.8% increase in total daily permeate production. Permeate water conductivity was analyzed to evaluate the change in permeate water quality when the heat exchange system was on. Although an increase in conductivity was identified, it was not substantial enough to conclude that heating of the feed water to the system resulted in a significant increase in salt passage