Proof of Concept: Pozzolan Bricks for Saline Water Evaporative Cooling in Controlled Environment Agriculture

Abstract. Control of indoor temperature and humidity is of critical concern for controlled environment agriculture systems in hot, arid regions. Evaporative cooling is a technology utilized for energy-efficient cooling and humidification of these systems. However, the evaporative cooling process consumes considerable amounts of water, as much as 80-90% of the water footprint for indoor food production in these regions. The use of saline water in place of fresh water in evaporative cooling systems offers a potential solution for greatly improving the sustainability of these systems. However, the use of saline water in industry-standard cellulose pad systems can cause premature clogging of the porous medium, leading to system failure and the need for porous media replacement. A new evaporative cooling technology consisting of crushed pozzolan volcanic rock formed into porous bricks was evaluated for use in controlled environment agriculture systems using saline water. Two brick designs were tested for proof of concept cooling of commercial-scale greenhouses. Temperature-based cooling efficiencies of the bricks were achieved that are comparable to cellulose pads. In addition, the pozzolan-based bricks showed impressive resistance to saline water and harsh environments, requiring no replacement over the duration of the experimental trials. The integration of the pozzolan evaporative cooling systems using sea or brackish water with a water-saving growing technology, such as recirculating aquaponics or hydroponics, shows promise for reducing the fresh water footprint of food raised indoors in hot, dry environments by as much as 80%-90%.