Étude d'une communauté solaire avec stockage thermique saisonnier par puits géothermiques

The energy performance of a solar community located in Calgary (Canada) which uses a one pipe district heating loop to supply 52 houses is evaluated. Compared to a classic double pipe heating loop, a one pipe system implies that the supply and return are done from the same pipe. Therefore, temperature drops along the pipe. The community uses a seasonal borehole thermal energy storage (BTES) made of 144 double U-tube boreholes with two independent loops. The first is the solar loop for charging the BTES and the second extracts heat to supply the district loop. The community is modeled in the TRNSYS simulation environment. The Drake Landing Solar Community (DLSC) located near Calgary (Canada), whose construction was completed in 2007 is used as the reference case. An energy performance comparison between the proposed community (named CS1T) and the DLSC shows that the solar fraction of the DLSC, which is the ratio of the supplied solar energy to the total energy requirement of the houses, is always greater than the solar fraction of the CS1T. The difference is relatively large during the first year of operation with a solar fraction of only 26 % for the CS1T, compared to 66 % for the DLSC. After 5 years of operation, the solar fraction of the CS1T increases to 85 % compared to 89 % for the DLSC. The one pipe system reduces the heat losses thanks to the reduction of the distribution loop's length; during the 5th year of operation, theses losses amount to 178 GJ and 250 GJ for the CS1T and DLSC, respectively. Also, the temperature level in the district loop of CS1T needed to be increased because of the temperature drop along the one pipe loop. The lack of a short term water tank thermal storage leads to a small solar fraction during the first year of the CS1T because the temperature level in the BTES is not high enough to provide heat to the district loop. The use of double U-tube boreholes for the CS1T increases the efficiency of the BTES to a range between 13 % and 62 % during the first 5 years of operation, compared to a range between 9 % and 41 % for DLSC. Finally, a cost analysis shows that 1 M$\$$ could be saved by selecting the CS1T configuration over the DLSC for a total estimated project cost of 3.4 M$\$$.