RAPID: Distributed Temperature Instrumentation for Performance Assessment and Long-Term Implications of an Unconventionally Deep Geothermal Exchange Well

该项目的目标是安装一套全面的光纤(FO)分布式温度传感(DTS)仪器，以获得对威斯康星州目前正在建设的非常规深度(约300 m)地热地源热泵(GSHP)系统中的温度和热通量分布的短期和长期测量。与建造多个相对较浅(例如，约50-75米)的热交换井用于住宅/商业供暖和制冷应用的传统做法相比，建造一口非常深的交换井具有潜在的优势。然而，有一些鲜为人知的问题同时具有重要的实践和科学意义。首次在深埋地源热泵系统的整个(600 M)换热路径上进行了换热流体温度和热流密度的短期和长期测量。在使用该系统以满足单户住宅的季节性供暖/制冷需求时，将获得热通量分布的长期测量。短期测量将从一系列旨在调查对系统运行变量(例如交换流体流量或输入温度)的扰动而设计的“模拟”测试中获得。这些数据将被用来将热流分布与地质和水文地质中的地下非均质性(例如，地下水流动)以及自然地温梯度联系起来。结果还将被用于地面真实情况和校准基于有限元的数值模型，以对地源热泵效率、生命周期评估进行长期(例如20年)模拟，并将项目结果扩展到更一般的地下地质、井眼几何形状以及季节性供暖和制冷应用。项目成果将具有重大的实用和科学价值。信息还可用于解决有关将地球用作热源/热汇的潜在地球化学影响的基本科学问题，并更有效地校准从深层地下温度测量收集的气候变化自然记录。虽然这项研究预计将对地热行业产生广泛的影响，但对威斯康星州的地热行业的影响预计将是巨大的。威斯康星州93%以上的电力燃料从其他州进口，地热能越来越被认为是一种基本能源。项目活动将通过旨在影响K-12学生、本科生、研究生和执业专业人员的外展和教学活动，在多种教育环境中发挥作用。为对STEM领域感兴趣的中学生举办的著名的住校夏令营。

The objective of this project is to install a comprehensive suite of fiber optic (FO) distributed temperature sensing (DTS) instrumentation to obtain short- and long-term measurements of temperature and heat flux profiles in an unconventionally deep (~300 m) geothermal ground source heat pump (GSHP) system currently being constructed in Wisconsin. Construction of a single, but very deep, exchange well offers potential advantages over conventional practice of constructing multiple, but relatively shallow (e.g., ~50-75 m) heat exchange wells for residential/commercial heating and cooling applications. There are, however, a number of poorly understood issues having both important practical and scientific implications. Short- and long-term measurements of exchange fluid temperature and heat flux will be made along the entire (600 m) heat exchange path of a deep GSHP system for the first time. Long-term measurements of the heat flux profile will be obtained while the system is in use to meet seasonal heating/cooling demand of a single-family residence. Short-term measurements will obtained from a series of "stimulation" tests designed to investigate perturbations imposed to the system operating variables (e.g., exchange fluid flow rate or input temperature). These data will be used to link the heat flux profile to subsurface heterogeneities in geology and hydrogeology (e.g., groundwater flow), and the natural geothermal gradient. Results will also be used to ground-truth and calibrate a finite-element based numerical model to conduct long-term (e.g., 20-year) simulations of GSHP efficiency, life-cycle assessment, and to extend the project results for application to more general subsurface geologies, borehole geometries, and seasonal heating and cooling applications. Project results will have significant practical and scientific merit. Information from the instrumentation and modeling effort can be used to design better ground loop systems for unconventionally deep (as well as shallow) geothermal heat exchange systems, to quantify short- and long-term GSHP performance, and to assess the implications of seasonal load imbalance on system efficiency. Information can also be used to address basic scientific questions regarding the potential geochemical ramifications of using the earth as a heat source/sink and to more effectively calibrate natural records of climate change gleaned from deep subsurface temperature measurements. While the study is expected to impact the geothermal industry on a broad scale, the impact to the industry in Wisconsin in particular is expected to be significant. Over 93% of Wisconsin's electrical fuel is imported from other states and geothermal energy is increasingly being considered an essential energy source. Project activities will be leveraged across multiple educational environments through outreach and teaching activities designed to impact K-12 students, undergraduate students, graduate students, and practicing professionals. Activities will be integrated with: (1) a Research Experience for Undergraduates (REU) program on Energy Geotechnics currently ongoing at the University of Wisconsin-Madison (UW), (2) extension courses offered to the practicing engineering and science community through the UW Engineering Professional Development (EPD) program, including a short course on Design of Geothermal Systems, (3) a platform session with the Wisconsin Geothermal Association, (4) lectures in large freshmen-level courses at UW, (5) dissemination in journal and conference publications, and (6) a geothermal session and field tour for UW-EPD's Badger Camp(TM), a renowned in-residence summer camp for middle school students interested in the STEM fields.