Techno-economic evaluation and environmental benefit of hybrid evaporative cooling system in hot-humid regions

Reducing the energy consumption of buildings is of great importance to achieve carbon neutrality targets. The air conditioning (AC) system in buildings, as a large energy consumer, should be taken into account as one of the main building service systems for energy saving integrated with energy-efficient and environmental-friendly technologies. Indirect evaporative cooler (IEC), constrained by its cooling principle, originally exerts energy saving potential in hot-arid regions. Recently, progress has been made in expanding its application to hot-humid regions. However, due to the large cooling load in hot-humid regions, an IEC-integrated hybrid system should be developed as an improved solution to effectively save energy and maintain the indoor thermal comfort. In view of the lack of a complete hybrid IEC system being reported thus far, in this study, the IEC is combined with a cooling coil unit as a primary air handling unit (IEC-PAU) for fresh air handling and supply. Accordingly, the model of the IEC-PAU with indoor fan coil units (FCUs) is constructed and incorporated into a typical office building, and the results are compared with a baseline case under hot-humid climate conditions. Comprehensive energy, economic, and environmental benefits are analyzed considering different setpoint temperatures in typical cities of the Great Bay area (GBA) of China. Results show that the proposed system could reduce the energy consumption of 4.6 kWh/m2 on average, with the acceptable thermal comfort level as they are in the reference cases. The greatest energy saving ratio is 8.3%, while the performance of the proposed system declines under the higher setpoint temperature. The saved electricity expenses can lead to the average discounted payback period of 8.2 years in the GBA cities. Furthermore, an annual greenhouse gas emission of 4.8 t on average can be diminished. In summary, this work demonstrates the feasibility of the hybrid IEC system as an effective approach for energy saving in hot-humid regions, which is promising to prompt the carbon neutrality in China.