## 4 Results and Discussion
### Discussion  
According to the results obtained by implementing the sharing strategies in three districts in London, the sharing system can be seen to benefit both C/D ratio improvement and carbon emissions savings, but the sharing potential is different under various district situations. There are two main reasons for this: the building type contained in the district and the number of building types. In District 1, there are three types of building: residential, retail and office buildings. The residential and retail buildings have a relatively high C/D ratio and consume more energy for heating than cooling, while the office buildings have a low C/D ratio range and require more energy for cooling. The sharing improvements on capacity and carbon are significant in this district, and Strategy 2 shows an advantage over Strategy 1. In District 2, there are mainly two types of building: office and retail. The sharing also shows a good result, but this is weaker than in District 1. In District 3, only office buildings are present; the sharing potential is less efficient compared with the other two districts, and the results of the two strategies are closer to each other. Therefore, it can be seen that more building types and a  
Figure 8: CO\({}_{2}\) emissions of district sharing systems (Scenario 2). high variety of building types can lead to better sharing potentials for both strategies. In addition, the central district system (CS, Strategy 2) performs better in for a higher potential sharing range, and the individual system with borehole sharing (ISBS, Sharing Strategy 1) performs better in a lower range. Based on the findings from case studies, it can be suggested that combining more building types can increase the application potential of district GSHP sharing systems; in particular, residential buildings are preferred in combination with others as they mainly require heating. Regarding the strategy selection, for a district containing more building types, it is better to employ a central district system (CS, Sharing Strategy 2), while for a district with only a single building type, an individual system with borehole sharing (ISBS, Sharing Strategy 1) is considered to be a better choice. Therefore, it can be seen that, in the UK, the sharing application of GSHP systems can not only benefit the application capacity and carbon savings but also lead to a predictable economic improvement potential due to the Renewable Heat Incentive (RHI). To the best of our knowledge, the UK's RHI is one of the most advanced initiatives worldwide to encourage the district sharing of GSHP applications, featuring detailed and specific inventive categories. There are also other financial incentives dedicated to district sharing support as well; for example, in France, for geothermal district heating, the national funding grants a bonus of \(\upcategor{250}\) per ton of CO\({}_{2}\) emissions avoided, and the regional council provides a bonus of \(\upcategor{350}\) per ton of CO\({}_{2}\) avoided for connecting new dwellings to existing geothermal heating networks [26]. In the USA, qualifying residential GSHP systems are eligible for a 30% credit of the installation cost, and qualifying commercial systems can have a 10% credit [27]. In Shandong Province in China, the incentive is \(\upcategor{20}\)/m\({}^{2}\) for GSHP, and in Henan Province, the incentive is \(\upcategor{15}\)/m\({}^{2}\) for either heating or cooling and \(\upcategor{19.5}\)/m\({}^{2}\) for both heating and cooling [27]. However, in some other areas and counties, small-scale GSHP systems seem to be the main promoted target. In Germany, in new buildings, the support for GSHP is \(\upcategor{10}\)/m\({}^{2}\) of the used building area, up to \(\upcategor{2000}\), and in refurbishment, the support is \(\upcategor{20}\)/m\({}^{2}\) of used building area, up to \(\upcategor{3000}\)[26]. These maximum amounts (\(\upcategor{2000}\) or \(\upcategor{3000}\)) apparently demonstrate that this is a program which is primarily meant for small homes.