Reducing water footprint of indirect evaporative air-cooling systems through integration of passive and active water recovery techniques

Abstract

In the future, a large number of individuals are expected to take advantage of metropolitan life. The requirement for thermal comfort in highly urbanized areas, particularly in countries that are emerging, is projected to increase significantly. To fulfill the thermal comfort demands, the Maisotsenko cycle-based indirect evaporative air-cooling system is the prominent choice due to the improved performance of the system compared to conventional air-cooling techniques. However, fresh water is used as a cooling media in an indirect evaporative air-cooling system, presenting a major challenge to the implementation of this cooling technique in water-deficient regions. The current study investigates the performance of the indirect evaporative air-cooling system in terms of water recovery from exhausted working air or reducing the water footprints by using the two different configurations such as passive and active water reclamation techniques, utilizing the highly-effective hydrophobic sheets and dehumidifier (Peltier module). The results indicate that the dew-point and wet-bulb effectiveness of the indirect evaporative air-cooling system are 0.80 and 1.06, respectively. Moreover, the integrated indirect evaporative air-cooling system with water recovery techniques, reduces water consumption with the average recovery achieved 208.1 kg/year to 421.5 kg/year under the actual climate conditions. In addition, the amount of water recovered results in ultimate values of the energy efficiency ratio and specific reduction in water footprints, which range from 31.57 to 73.02 and 2.84–6.14 kg/h.ton, respectively. Furthermore, a cost-benefit analysis revealed that the levelized costs of energy for the passive and active water recovery systems are 7.4 × 10⁻⁵ and 3.8 × 10⁻⁵ USD/kWh, respectively. These values are significantly lower than the levelized cost of energy of the indirect evaporative air-cooling system without water recovery, which ranges from 2.4 × 10⁻² to 5.8 × 10⁻² USD/kWh, indicating a substantial improvement in energy efficiency. Besides, the operating CO₂ emissions of passive and active water reclamation techniques are 162.35 kg CO₂e/year, and 184.86 kg CO₂e/year, respectively. The findings demonstrate that the proposed techniques are viable, highlighting their significant potential in terms of reducing the water footprint of the system. Therefore, the developed strategies can be implemented in real-world applications for promoting the long-term sustainability.