Increasing effectiveness of evaporative cooling by pre-cooling using nocturnally stored water

In this paper, a multi-step system of nocturnal radiative cooling and two-stage evaporative cooling is studied. The feasibility and potential of this system is investigated for four cities which have different climatic conditions. During the night time in summer, water is circulated from a storage tank to two radiative panels. The temperature of the water from the radiative panels decreases because of radiative heat transfer between the water in panels and night sky. During the next day, the stored cold water in the storage tank is used as coolant for a cooling coil unit. Hot outdoor air is passed through the cooling coil unit and a two-stage evaporative cooler. The results obtained demonstrate that first, the multi-step system can be considered as an alternative cooling system in some hot regions that evaporative cooling cannot be used. Second, the multi-step system has higher effectiveness than conventional two-stage evaporative coolers. Third, an energy saving of the multi-step system is between 75 and 79% compared to mechanical vapor compression systems. Consequently, this environmentally-friendly and highly-efficient system can replace the mechanical vapor compression systems.

► The multi-step system meets the comfort conditions in various weather conditions.
► Adding nocturnal cooling to IDEC increases the effectiveness by 9%.
► The new system expands coverage of IDEC over hot and humid weather conditions.
► The energy efficiency ratio of the multi-step system is higher than 48.8.