## 4 Results and Discussion
### Comparison of District Sharing Strategies on C/D Ratio and Required Borehole Number  
Two district GSHP systems with different sharing strategies were applied to the three selected districts for analysis. Two scenarios--Scenario 1 (boreholes under buildings) and Scenario 2 (borehole around buildings), shown in Figure 4--were analyzed for comparison. The C/D ratio and required borehole number were used as indicators to demonstrate the performance of the two proposed district GSHP systems. Figure 5 shows the C/D ratio and required borehole number of the three target districts with different sharing strategies under Scenario 1 (boreholes under buildings). For District 1, more than half of the buildings had C/D ratios in yellow and red colors with the individual GSHP system. With borehole sharing (Strategy 1, Figure 1b), although the required borehole number remained the same, the C/D ratio of the whole district turned to a green color, which showed that heating and cooling demands could be fully satisfied by sharing the land for borehole installation. The performance of implementing a central district system (Strategy 2, Figure 1c) showed an even better result, in that the required borehole number could be reduced from 71 to 51 while still satisfying all energy demands. In District 2, the results are quite similar to those of District 1. Sharing can allow the energy demand of the whole district to be fully satisfied, and a central district system can save a further 13 required boreholes, reducing the number from 46 to 33. As for District 3, mainly office buildings are present, and this type generally has a low C/D ratio range, which can be also seen from the figure. However, the district sharing also brought benefits to meeting the energy demand of the district, but the influence is not as significant as other two districts. The C/D ratio of the whole district turns to a yellow color with borehole sharing, and a district central system can only save 4% of the required boreholes, reducing the number from 135 to 130. Figure 4: Borehole allocation for districts. Figure 6 shows the C/D ratio and required borehole number of the three target districts with different sharing strategies under Scenario 2 (boreholes around buildings). In a similar manner to Scenario 1, for District 1, borehole sharing (Strategy 1, Figure 1b) could enhance the C/D ratio of the whole district, shown by the green color, which means that heating and cooling demands can be fully satisfied by sharing the land for borehole installation. Employing a district central system (Strategy 2, Figure 1c) saves 20 boreholes--reducing the number from 71 to 51--while still satisfying all energy demands. For District 2, the results are quite similar to those of District 1; sharing allows the whole district's energy demands to be fully satisfied, and a central district system can further reduce the required number of boreholes from 46 to 33. As for District 3, borehole sharing makes the C/D ratio of the whole district turns to a yellow color, and a district central system reduces the number of required boreholes from 135 to 130. As Scenarios 1 and 2 describe the borehole allocation methods, they can only influence the maximum borehole number which is allowed to be installed for the building (\(BN_{Max}\)), but not the required borehole number by the building to satisfy its heating and cooling demands (\(BN_{Req}\)). Therefore, in Figures 5 and 6, the required borehole numbers for various sharing strategies are exactly the same under both scenarios. However, the different influences on \(BN_{Req}\) lead to the differences in the C/D ratios of the district. Table 3 shows C/D ratios with various sharing strategies under Scenario 1 and Scenario 2 for Districts 1, 2 and 3, respectively.