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

近年来，越来越多的人使用地源热泵作为能源汇/源，以节省建筑物采暖和制冷所需的能源。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以每年约44%的速度增长。因此，需要创新的方法/技术来提高地源热泵在工业规模上的效率和经济性。此外，由于对潜在地下水污染的环境担忧，司法管辖区通常要求地源热泵系统的钻孔填充几乎不透水的膨润土灌浆。膨润土浆液的热水力性能对地源热泵的经济安全运行具有重要影响。具有高导热性的增强膨润土浆液允许更多的热能从周围的土壤中传递或传递，从而提高了系统的效率。同时，还需要导热系数低、渗透率低的材料作为地下储热的保温材料。本研究将开发满足地源热泵不同热水力性能要求的新型复合膨润土浆料。将进行理论研究，以帮助找到不同类型的添加剂与膨润土的最佳组合，同时将进行一系列实验室试验，以验证不同类型添加剂的最佳组合。在全面的现场实施之前，研究结果将在一个大型测试罐中进行检查和验证。该项目的预期结果将满足行业需求，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有价值的工具，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.