Energy and environmental implications of advanced chiller system under climate change

Full variable speed chiller systems are believed to have better energy performance in the long run compared with conventional chiller systems with constant speed control and yet their application is still limited. This paper elaborates on their energy performance and environmental impacts in terms of water consumption, carbon emissions and plume emissions under climate change. Hourly weather data under climate change scenarios in 2020, 2050 and 2080 were generated by using the program CCWorldWeatherGen, based on a typical meteorological year weather file for Hong Kong. The building simulation program EnergyPlus was used to model a hotel with an all-variable speed chiller system or a conventional system. Part load performance data from a chiller manufacturer were used to verify the modelling equations of the advanced chiller system. Results show that the full variable speed system can help maintain a higher coefficient of performance of chillers even under the warmer future climate, reducing carbon emissions by 24.0 - 32.4% and water consumption by 5.4 - 11.7% from 2080 to the typical meteorological year. The optimal speed control for the condenser water pumps and cooling tower fans helps lower the condenser water temperatures, reducing the chance of plume emissions. Such a comprehensive analysis on the environmental performance of advanced chiller systems is hardly found from previous studies.