Impact of climate change on outdoor design conditions and implications to peak loads

This study exams the impact of climate change on outdoor design conditions and peak loads of five Chinese cities over the five major climate zones for the winter and summer conditions. The design dry-bulb temperature (DDBT) and the coincident wet-bulb temperature (CWBT) for two 30-year periods; 1971–2000 and 1984–2013 were analysed. It was found that the DDBT of the period 1984–2013 was higher than that of the period 1971–2000, whereas the CWBT and the corresponding outdoor enthalpy of the period 1984–2013 was lower than that of 1971–2000 at the various cumulative frequencies. This trend implies that the increment in conductive heat gain through the building envelope due to the rising temperature can be lower than the reduction in fresh air load due to the lower outdoor air enthalpy. In this case, the peak cooling loads may reduce in all five cities under study, and this is different from the widely held view that global warming will lead to more stringent outdoor design conditions, higher peak cooling loads and larger heating, ventilation and air conditioning (HVAC) plants than the current or historical status. The implications to the “free-cooling” of HVAC systems with enthalpy control are discussed as well.