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，加拿大致力于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。在所有其他行业中，建筑对于减少加拿大温室气体 (GHG) 排放和能源使用的影响最大。通过整合高效的终端使用技术和可再生能源来开发高性能建筑，有助于大幅减少建筑行业的能源消耗和温室气体排放。 该研究项目提出了管理建筑物热能的新概念。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载热流体的热回路组成，所有加热和冷却组件（例如热泵机组、蓄热系统和空气通风系统）都将通过该热回路交换热量，无论它们在建筑物内的物理距离如何。恒温两相 CO2 回路通过利用热回收和提高局部供暖和制冷装置的性能系数 (COP)，确保高效的建筑能源性能。由于与其他替代品（例如水循环系统中的水）相比，二氧化碳具有优异的热物理特性，因此该回路可能具有额外的优势，例如减少循环能耗、增加热能传递强度以及减小回路的管道尺寸。 该研究项目致力于地源两相二氧化碳热回路的建模和性能评估。将开发仿真模型并根据实验室测量进行验证。 地源 CO2 回路的建模需要开发耦合的地面热响应因子以及回路和地热交换器中的两相 CO2 流体流动和传热。模拟技术的改进将有助于开发计算强度较低的直接膨胀式地热交换器（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，用于测量连接到回路的每个本地热泵机组的热能使用情况，以评估建筑区域、办公室或公寓的冷却/加热份额。这一新概念与热能表的发展也将促进建筑暖通空调系统的实时智能监控、诊断和故障排除。拟议的研究还将通过提高建筑能源性能，为加拿大建筑行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.