Analysis of rainwater use in membrane-based semi-direct evaporative cooling of air

Abstract

The trend of seeking solutions to reduce energy consumption in buildings is evident in the context of heating, ventilation, and air conditioning technologies. One such solution with low energy consumption is direct evaporative cooling systems. However, the use of such systems is associated with an increase in fresh water consumption in buildings. The article presents a novel approach to air cooling, taking into account the sustainable building aims of designing buildings with low energy consumption and water conservation. The proposed system is a membrane-based semi-direct evaporative cooling system, which is fed by harvested rainwater. The study analyzed the potential of rainwater harvesting for direct evaporative cooling in ten cities. The cities selected for the analysis of system operation, are located in different climates according to the Köppen-Geiger classification. Water consumption for cooling at a base temperature of 26.7 °C was estimated using a mathematical model of the membrane module. Furthermore, the number of evaporative cooling hours per year was determined for this temperature. The system under analysis achieved a high coefficient of performance (COP) and a seasonal coefficient of performance (SCOP) of up to 183 and 133, respectively. Depending on the location of the building, the annual water consumption of the system ranged from 150 to 8859 dm3. The rainwater harvesting provided up to 100 % of the evaporative cooling requirements. The proposed solution reduces tap water consumption and lowers the temperature of fresh air supplied to indoor spaces while consuming low energy.