A pilot borehole heat exchanger field in Egypt: Subsoil investigation, thermal response tests and sensitivity analysis

Abstract

Information regarding the shallow geothermal energy potential is lacking in Egypt. Few studies were conducted to study the applicability of shallow geothermal energy in such hot and dry areas. In Cairo, a site investigation was carried out to provide insight into using shallow geothermal energy for cooling, for the first time in Egypt by collecting the ground's geological and thermal properties. A 40-m deep exploratory borehole (piezometer) was drilled at Cairo University- Faculty of Engineering (CUFE), Egypt. A shallow geothermal pilot plant at CUFE was designed and installed with the aid of data gathered during this initial phase. Second, three borehole heat exchangers (BHEs) underwent thermal response tests (TRT) to obtain the equivalent thermal properties of the ground. Data collected from both phases were compared to assess the importance of carrying out TRT and its effect on the accuracy of BHE sizing. TRT resulted in 20.47 % and 4.15 % higher values of the ground thermal conductivity and the undisturbed ground temperature (UGT) respectively. A sensitivity analysis was carried out to test the most effective factors on borehole sizing. UGT, building thermal load, BHE configuration, and ground thermal conductivity had the greatest effect. The results of the sensitivity analysis were significantly impacted by the project scale with increasing thermal loads. Several parameters had a greater impact at larger-scale projects. According to the results, using TRT to accurately determine the ground thermal properties saved several drilling depths.