Development of modified bentonite slurry for use in subsurface thermal storage and insulation

近年来，利用地源热泵(GSHP)作为能源汇/源来节约建筑物供暖和制冷所需的能源的情况越来越多。根据加拿大地热联盟的数据，从2005年到2009年，这些热泵在加拿大的市场年增长率约为44%。因此，对创新的方法/技术的需求很高，以使地源热泵在工业规模上更加高效和经济。此外，出于对地下地下水可能受到污染的环境问题的担忧，司法管辖区通常要求GSHPS系统中的钻孔填充几乎不透水的膨润土灌浆。膨润土浆的热工和水力性能对地源热泵的经济安全运行有重要影响。具有高导热系数的增强型膨润土灌浆可以将更多的热能转移到周围土壤或从周围土壤转移出来，从而提高系统的效率。同时，地下储能还需要具有低导热系数和低磁导率的材料作为绝缘材料。本研究将开发满足地源热泵不同热工和水力性能要求的新型复合膨润土灌浆。将进行理论研究，以帮助寻找不同类型添加剂与膨润土的最佳组合，同时将进行一系列实验室测试，以验证不同类型添加剂的最佳组合。然后，在全面实地实施之前，将在一个大型测试水箱中检查和验证这些发现。该项目的预期成果将适应行业需求，并为适当处理与地源热泵的设计和安全运行有关的特殊问题提供宝贵的工具，地源热泵被认为更经济，能够减少潜在的负面环境影响。

The use of ground source heat pumps (GSHPs) as an energy sink/source to save energy required for building heating and cooling has been increasing in recent years. According to Canadian Geothermal Coalition, the market in Canada for these heat pumps has been expanding approximately 44% per year from 2005 to 2009. As a result, innovative approaches/technologies are in high-demand to make the GSHPs more efficient and economical in industrial scale. In addition, because of environmental concerns about the potential for contamination of underlying ground water, jurisdictions commonly require boreholes in a GSHPs system be filled with nearly impervious bentonite grout. The thermal and hydraulic properties of such bentonite grout has significant impact on the economic and safe operation of GSHPs. Enhanced bentonite grout with high thermal conductivity allows more thermal energy to be transferred to or from the surrounding soil and hence increases the efficiency of the system. At the same time, materials with low thermal conductivity and low permeability are also required as insulation for subsurface storage of thermal energy. This research will develop new composite bentonite grouts that meet different requirements on thermal and hydraulic properties for ground source heat pumps. A theoretical study will be performed to help find the optimal combination of different types of additives with bentonite, while a series of laboratory tests will be carried out to verify the optimal combination of different types of additives. The findings will then be examined and verified in a large testing tank prior to full-scale field implementation. The expected outcomes of the project will accommodate the industry needs, and provide valuable tools to appropriately deal with special issues related to the design and safe operation of ground source heat pumps, which are considered to be more economical and able to reduce potential negative environmental impact.