Sustainable subtropical hotel operations: A time series analysis of waste heat recovery potential

The waste condenser heat from chiller systems in hotels is typically discharged into the environment, leading to energy waste and plume generation. However, the recovery of this waste heat is not common. Therefore, this study presents a time series analysis to evaluate the potential for waste heat recovery for sustainable hotel operations. The case study focuses on a prototype hotel in subtropical Hong Kong and its engineering systems are modeled using EnergyPlus. By incorporating heat exchangers and thermal storage systems, waste condenser heat can be recovered to fully meet the heating demand for daily service water, which was originally supplied by boilers for 79.32 % of the total time. This application offers several benefits. Firstly, it reduces annual carbon emissions by 40.23 kgCO₂e/m² (equal to 27.36 % of the baseline emissions) associated with water-cooled chiller systems by maximizing energy efficiency and minimizing waste heat. Secondly, it decreases the operating capacity of cooling towers at high heat rejection, which reduces the chance of plume emissions by 30.9 %. Finally, it lowers the annual gas consumption of boilers by 153.11 MJ/m² (equal to 79.32 % of the baseline consumption) and can serve as an alternative to renewable solar thermal systems. Challenges and opportunities for recovering waste condenser heat are also discussed in detail. Notably, this study introduces a new approach of using outdoor enthalpy to normalize the cooling demand for improved energy management. Overall, this study provides a comprehensive assessment of waste condenser heat from chiller systems to promote sustainable development.