Date of Award

Spring 2023

Project Type

Thesis

Program or Major

Earth Sciences

Degree Name

Master of Science

First Advisor

Matt Davis

Second Advisor

Anne Lightbody

Third Advisor

Vanessa Levesque

Abstract

Climate change is an existential threat to human society, and mitigating some of the worst impacts will require electrifying the energy sector and reaching net zero emissions by mid-century (Intergovernmental Panel on Climate Change, 2018). Geothermal energy, specifically ground-source heat pumps, can help to meet winter heating demand in the Northeastern United States. This technology, as well as the various mechanisms that would aid its expansion, are still underdeveloped but have vast potential. A central factor to consider in energy transition work is how energy decisions are made by people within the context of both social and physical system constraints and opportunities. This thesis used mixed research methods to identify key needs surrounding setback requirements and policies that might support the technology. We considered the social factors that might advance shallow geothermal energy, ground-source heat pump development in the northeast region and conducted a physical analysis of the spacing needs for geothermal boreholes and compared these needs to existing setback guidelines. From a social science standpoint, little research exists on geothermal planning and development. Such studies could inform much-needed policy frameworks to support emerging social-physical geothermal systems, including the technology, industry, decisionmakers, and end users. To that end, this thesis draws on social studies of science and resource management, including institutions theory, to begin a discussion about initial elements to consider in the development of such a framework. Development of an effective policy framework that recognizes both social and physical opportunities and constraints can benefit from systematic collection and analysis of data from social groups involved in various stages of policy development and implementation. My interview data suggest that key factors to consider include provisions for affordability and multi-level governance with participation by a range of decision makers, including system installers, scientists, engineers, architects, governmental officials, and end users. Borehole spacing and setback distances are of primary concern in maintaining the quality of the thermal reservoir through which the geothermal system provides heat or cooling. Spreading thermal demand (or load) over a large subsurface ground volume can aid in preventing adverse impacts to the surrounding subsurface ground. Spatial analysis of simulated subsurface temperatures under a range of conditions suggests that current setback guidelines and best practices are most likely sufficient for most residential applications but may need to be increased under certain situations or for industrial installations with unbalanced net annual ground loads. Generally, the subsurface thermal energy reservoirs with higher thermal conductivity show less impact for a given unbalanced annual ground load. Findings from both the social and physical areas point to some basic considerations which can aid in the advancement of ground-source heat pump usage. Collected interview data indicate that high installation costs hinder widespread adoption of the technology, and that minimal policy and/or regulatory frameworks exist for shallow geothermal, whether legally binding or recommended. Interviewees with highly specialized technical knowledge generally communicated that existing setback requirements are sufficient for most applications, given the current low density of geothermal installations. However, simulation data for various scenarios showed that cases of unbalanced load may not be sustainable for maintenance of the thermal reservoir. In such cases, increasing distances between systems and increased spacing between boreholes can help maintain the thermal reservoir.

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