## 1 Introduction
According to the regional application analysis of GSHP in Shenyang, China [1], significant efforts have been made to increase the adoption of this technology to 59.41 million m\({}^{2}\) from 780 projects, and policies have been implemented to plan GSHP technology at the urban district and county level. Regional application could contribute to an anticipated 4.18% of CO\({}_{2}\) savings in Shenyang's building sector. The city-scale analysis of GSHP application in London [15; 16] showed that a high proportion (over 60%) of buildings have a C/D ratio (the ratio of ground capacity to energy demand) of over 1.0, meaning that many houses and buildings have sufficient space to install a GSHP and thus fully satisfy their own heating demands. In addition, it was found that buildings demonstrated significant spatial heterogeneity in C/D ratios due to variations in heating demand and available space. If a spatial sharing strategy can be introduced, buildings with high C/D ratios will be able to share their surplus capacity with their neighbors, allowing the heating and cooling demands of a greater number of buildings in the area to be satisfied. [PERSON] et al. [17] built a utility model of a district hybrid GSHP system combining multiple commercial/industrial buildings to show that intelligent chosen combinations can reduce the required ground loop length and thus diminish the drilling space. [PERSON] et al. [18] conducted a study on a heating and cooling district in a mild climate based on GSHP and specifically analyzed the influence of the district heating layout and population density in the district on the most suitable solution. From both energetic and economical points of view, sharing can be a good way to bring benefits and, in some cases, splitting a district centralized system into two sub-systems can reduce the financial risks. In fact, in addition to the cost consideration, [PERSON] et al. [19] simulated a case study at the city scale in London to investigate the influence of district size on the application potential of GSHP systems, which demonstrated that the use of a \(50\) m \(\times\) 50 m area can greatly improve the potential compared with individual system planning, but the improvement rate decreased as the district sharing size increased. According to the existing research, it can be seen that district sharing can benefit GSHP applications, and sharing performance can be changed by building types and demand intensity. However, researchers have mainly focused on the utilization of a centralized GSHP system on specific cases including certain building types, but no investigation has been made into a systematical analysis to evaluate how the mix of typical building types can influence district system performance. Moreover, GSHP systems have unique characteristics, so it is worthwhile to compare several specific sharing strategies under different district scenarios to demonstrate their application capacity and carbon-saving ability. Accordingly, this study makes a number of contributions to the literature:  
1. We develop two district sharing models specific for GSHP system application. The two sharing strategies in the models are (i) individual systems with borehole sharing and (ii) a central district system. 2. The performance of the models is tested on three selected districts in London. These districts are a representative \(50\) m \(\times\) 50 m size and show the variety in the combination of typical building types. The results demonstrate the good performance of models regarding the sharing potentials and, according to the comparison analysis, the potentials vary according to the different building type combinations. 3. We evaluate the carbon-saving potential of the developed GSHP district systems, and the results show that the sharing strategies can significantly reduce carbon emissions compared with individual systems, which is beneficial in the attempt to create a low-carbon city.