A Feasibility Study on Harvesting Rainwater from Large Solar Panel Canopies to Supplement Makeup Water for Cooling Towers by Using Remotely Controlled and Self-Cleaning Rain Cistern

Rainwater collected from rooftops can be a safe, low-cost alternative source for non-potable water uses, thereby reducing tap water usage. In climates with adequate rainfall during cooling seasons, rainwater can compensate for evaporative water loss in cooling towers. Central chillers and cooling towers play an essential role in removing heat from large commercial, institutional, and industrial buildings. Water losses from evaporative cooling in the towers increase the concentration of minerals in the water system loop, and scaling occurs within the system, decreasing the heat exchange's effectiveness and damaging equipment. Freshwater must be added to the cooling tower water system loop to make up for water losses. This paper presents a feasibility study on harvesting rainwater from solar panel canopies as an alternative water source for a cooling tower water makeup. A remotely controlled and automatically self-cleaning rain cistern is demonstrated in this study. In addition, a water quality analysis including the concentration of chemicals relevant to cooling tower operation was conducted on tap water and rainwater samples. The results show that the total dissolved solids concentration of the rainwater was significantly lower than tap water, indicating that an increase in the number of cycles of concentration (COC) could be achieved by using rainwater as part of the water makeup source. The predicated COC values for the rainwater/tap water blends were calculated, and the tap water reductions, financial benefits of using rainwater, and the pay-back period of the application of the remote control technology are analyzed in this study.

Automated summary

This study investigates the feasibility of using rainwater as an alternative water source for cooling tower makeup. Water quality analysis shows that rainwater has a lower total dissolved solids concentration than tap water, which can increase the cycles of concentration and reduce tap water usage, resulting in economic benefits. The study also examines the application of remote control technology.