Ground source thermal loop with two-phase carbon dioxide (CO2) as heat carrier fluid to manage thermal energy in buildings

根据《泛加拿大清洁增长和气候变化框架》，加拿大承诺通过减少化石燃料的使用和更多地采用可再生能源来实现低碳未来。在所有其他部门中，建筑业对减少加拿大温室气体(GHG)排放和能源消耗的影响最大。通过整合有效的终端使用技术和可再生能源来开发高性能建筑，可以大大减少建筑部门的能源消耗和温室气体排放。这项研究计划提出了一种新的建筑热能管理概念。它促进了热泵和地热等可再生能源的整合。它由一个以两相二氧化碳作为热载体流体的热循环组成，所有加热和冷却组件(如热泵机组、蓄热系统和空气通风系统)都将通过该热循环进行热量交换，无论它们在建筑内的物理距离如何。恒温两相二氧化碳循环通过利用热回收和提高本地供暖和制冷机组的性能系数(COP)来确保高效的建筑能效。由于与水中水循环系统等其他替代品相比，二氧化碳具有更好的热物理性能，因此循环具有潜在的额外优势，例如减少循环能耗、增加热能传递强度以及减小循环的管道尺寸。该研究项目解决了地源两相二氧化碳热循环的建模和性能评估问题。将开发模拟模型，并在实验室中根据测量结果进行验证。地源CO2环路的模拟需要建立耦合的地热响应系数以及环路和地热交换器中的两相CO2流体流动和换热。模拟技术的改进将允许开发计算量较小的直接膨胀式地下换热器(DX-GHE)模型，并准确评估该概念的潜在能源、环境和经济效益。还将开发和测试一种工具，以测量连接到环路的每个本地热泵机组的热能使用情况，以评估建筑区、办公室或公寓的制冷/供热份额。这一新概念以及热能表的发展也将促进建筑实时智能监控、诊断和排除建筑暖通空调系统的故障。这项拟议的研究还将通过提高建筑能效，为加拿大建筑业的脱碳做出重大贡献。

Under the Pan-Canadian Framework on Clean Growth and Climate Change, Canada has committed to a low-carbon future through reduced use of fossil fuels and increased adoption of renewable energy. Buildings can have the greatest impact among all other sectors towards reducing Canadian greenhouse gas (GHG) emissions and energy use. Developing high performance buildings by integrating efficient end-use technologies and renewable energy can contribute to significant reductions of energy consumption and GHG emissions in the building sector. This research program proposes a new concept to manage thermal energy in buildings. It facilitates the integration of heat pumps and renewable energy sources such as geothermal. It consists of a thermal loop with two-phase CO2 as the heat carrier fluid through which all heating and cooling components (e.g. heat pump units, thermal storage systems, and air ventilation systems) will exchange heat, regardless of their physical distance within the building. The constant temperature two-phase CO2 loop ensures efficient building energy performance by exploiting heat recovery and improving the Coefficient of Performance (COP) of local heating and cooling units. Due to superior thermophysical properties of CO2 compared to other alternatives such as water in water loop system, the loop potentially offers additional advantages such as reduced circulation energy consumption, increased thermal energy transfer intensity, and reduced pipe sizes of the loop. The research program addresses the modeling and performance evaluation of a ground source two-phase CO2 thermal loop. Simulation models will be developed and validated against measurements in laboratory. Modeling of the ground source CO2 loop requires the development of coupled ground thermal response factors and two-phase CO2 fluid flow and heat transfer in both the loop and the ground heat exchanger. Improvements in simulation techniques will allow for development of a less computationally intensive direct expansion ground heat exchanger (DX-GHE) model and accurate evaluation of the potential energetic, environmental and economical benefits of the concept. A tool will also be developed and tested to measure thermal energy use of each local heat pump unit connected to the loop for evaluating cooling/heating shares of building zones, offices or apartments. Development of this new concept along with the thermal energy meter will also facilitate the building real-time intelligent monitoring, diagnostics, and troubleshooting of building HVAC systems. The proposed research will also contribute significantly towards the decarbonisation of the Canadian building sector by increasing building energy performance.