An off-grid solar district energy system with borehole thermal energy storage: Life cycle assessment in a subarctic region

Nunavik, a remote subarctic region covering the northern third of Quebec, Canada, relies heavily on diesel to meet residential heating demand. Solar district heating (SDH) with borehole thermal energy storage (BTES) has been developed there as one of the most promising solutions that can break the dependence on fossil fuels and develop renewable energy resources locally. Developing an SDH-BTES in Nunavik is not only a technical and economic consideration, but also an environmental deliberation. Therefore, in this study, a cradle-to-grave life cycle assessment (LCA) of both SDH-BTES and conventional systems are performed for this area. The SDH-BTES system is defined as a heating system for a community comprising 1500 m² gross solar area and 150 borehole heat exchangers with a depth of 30 m which is modeled to analyze its environmental performance. The results are presented comparatively with the conventional heating system consisting of local household diesel furnaces. Fifteen various impact categories are introduced for the comparison and contribution of main components (solar subsystem, auxiliary subsystem, transportation, and disposal) are analyzed individually. The present analyses show that SDH-BTES performs better than local diesel furnaces regarding human health, climate change, and resources. However, ecosystem quality impact of SDH-BTES system is slightly higher than the conventional domestic diesel furnaces due to the large land occupation of underground thermal heat storage and drilling process. The SDH-BTES system can improve environmental impact by 21 % compared to the conventional system and reduces CO₂ emission by 22.4 %.