Energy audit and air-conditioning system renovation analysis on office buildings using air-source heat pump in Shanghai

Abstract

In the past, the building energy consumption was surveyed without distinction of air-conditioning system types, which caused large dispersal of the energy consumption of the same building type. To study energy consumption of office buildings using air-source heat pump, six office buildings using air-source heat pump in Shanghai were investigated through energy audit and field test. The energy use intensity (EUI) per annum ranged from 102 to 139 kWh/m2, with an average value of 126 kWh/m2. The EUI range of office buildings using air-source heat pump is much smaller than the EUI of office buildings according to the literature. Based on field test of the air-conditioning (A/C) system, it was found that the present main problem of A/C system included insufficient refrigeration capacity of A/C system, low A/C system energy efficiency, and small cold water temperature difference. Countermeasures were brought forward to solve the problems, including ① retrofitting part of the present air-source heat pumps to water-cooled cold water air-conditioners, ② retrofitting present air-source heat pumps into new air-source heat pumps, and ④ pump variable frequency renovation. The A/C load is estimated by Bin method. According to the case study in this paper, the pay back period are about two years for the first measure, five to seven years for the second measure, and 0.65–2 years for the third measure. Practical application: Generally, the energy consumption survey gives a wide range of data. To some extent, it is caused by the survey method which does not take the air-conditioning type into consideration. The work stresses on the energy consumption of office buildings using air-source heat pump. The result showed that the energy consumption was in a relatively small range, which will be more meaningful to industry. Energy saving measures concerning air-conditioning system is studied on the basis of the survey.