Energy and Buildings 147 (2017) 90–100 Contents lists available at ScienceDirect Energy and Buildings journal homepage: www.elsevier.com/locate/enbuild Performance evaluation of existed ground source heat pump systems in buildings using auxiliary energy efficiency index: Cases study in Jiangsu, China Shuyang Zhang, Lun Zhang ∗ , Xiaosong Zhang School of Energy and Environment, Southeast University, Nanjing 210096, PR China a r t i c l e i n f o Article history: Received 15 February 2017 Received in revised form 12 April 2017 Accepted 18 April 2017 Available online 22 April 2017 Keywords: Ground source heat pump Performance analyses Post-evaluation a b s t r a c t The application and performance of ground source heat pump (GSHP) systems in Jiangsu, China are reported in this study. Fifty cases were selected from different areas including office, residence, and other building types. Half of the selected cases was measured in summer, and the other half was measured in winter. The water temperatures, energy efficiency, energy consumption and thermodynamic perfectibil- ity were analyzed statistically. The ground provided an average water temperature of 25.4 ◦ C in summer and 11.7 ◦ C in winter. The temperature difference between the inlet and outlet on the ground side in both the seasons was 3.07 ◦ C. The statistical average values of coefficient of performance (COP), energy efficiency ratio (EER), and thermodynamic perfectibility  were 4.62, 3.41, and 0.38 in summer and 4.34, 3.22, and 0.49 in winter, respectively. The energy used by heat pumps and water pumps was about 3:1 in both the seasons. Furthermore, a comprehensive evaluation was conducted based on the statistical base- line set by the collected data. This method included factors that influence the actual system performance and provided an approach to assess and compare the performance of the cases comprehensively. © 2017 Elsevier B.V. All rights reserved. 1. Introduction As a promising way to conserve fossil energy resources, shal- low geothermal energy has been utilized around the world. For worldwide direct use, the installed capacity of ground source heat pump (GSHP) has taken the first place since 2000 and increased to 50,258 MWt in 2015 [1]. The utilization of heat pumps has taken the first place since 2005 and increased to 326,848 TJ/year in 2015. The USA and China are the leading countries in terms of installed capacity and annual energy use. China achieved the first place in the world as for the direct utilization of geothermal energy with the total amount reaching 17,870 MWt in 2014 [2]. According to the shallow-depth geological data (within 200 m) supplied by the China Geological Survey, the shallow geothermal resources in China approach 77.1 × 10 12 kWh/yr in total. Among all the 31 provinces of the mainland, the resource capacity of Jiangsu approaches 7.13 × 10 12 kWh/yr, ranking in the second place. Because of the promotion and financial incentives offered by both the central and the local governments, as one of the renewable energy technolo- gies, GSHP is mostly installed and utilized in eastern area in China, ∗ Corresponding author. E-mail address: zhanglun@seu.edu.cn (L. Zhang). including Jiangsu Province [3].Jiangsu is one of the most developed provinces in China and leads in the development of GSHP. The build- ing application area of GSHP increased to 26.3 million m 2 in the last decade (2006–2015), and its proportion in the new energy-saving construction increased from 0.6% in 2006–14.6% in 2015 (Fig. 1 and Table 1). The wide use of GSHP in Jiangsu is related to its climatic con- ditions and many other reasons. The geographical coordinates of Jiangsu are within an east longitude of 116 ◦ 18 ′ to 121 ◦ 57 ′ and a north latitude of 30 ◦ 45 ′ to 35 ◦ 20 ′ . Most of Jiangsu has a humid subtropical climate and belongs to the Cfa climate zone accord- ing to the Köppen climate classification [4], corresponding to the Hot Summer and Cold Winter (HSCW) area of China. The HSCW area is defined according to the yearly cumulative data, 60–89 days with average daily temperature less than or equal to 5 ◦ C, or not less than 75 days with average daily temperature stably less than or equal to 8 ◦ C [5]. The coldest month in this area is January, and the hottest month is July. Compared to other countries or areas in the same latitude among the world, the average air tempera- ture is about 2 ◦ C higher in July and is 8–10 ◦ C lower in January [6,7]. The air temperature in Jiangsu fluctuated considerably in a year. The daily average outdoor air temperature was about −1 to 4 ◦ C in January and 26–29 ◦ C in July. The annual average rainfall is 800–1,200 millimeters, concentrated mostly in the early sum- http://dx.doi.org/10.1016/j.enbuild.2017.04.052 0378-7788/© 2017 Elsevier B.V. All rights reserved.