How Far Is Far Enough? The Social Constitution of Geothermal Energy through Spacing Regulations

: This article argues that the sociotechnical context in which near-surface geothermal energy is embedded draws out its characteristic of being temporarily depletable. Thereby, the minimization of unavoidable side effects, such as cold plumes, which result from the social constitution of geothermal energy, is a crucial area of consideration. Using the situation in Germany as a touchstone, we discuss how cold plumes and interferences from neighboring ground source heat pumps test the limits of the existing regulatory framework, requiring negotiations between different knowledge sets stemming from areas as diverse as planning law, geology, cultural habits, and engineering. This makes the operation of geothermal energy highly uncertain and continuous negotiations on sustainable modes of extractions a pressing issue.


Introduction: The Transition to Low Carbon Heating in Germany
Growing awareness of the negative consequences of fossil fuel-based energy production has led Germany to plan taking all coal-fired power generation off-grid by no later than 2038 and to meet its energy demand with mainly non-fossil energy sources. At the same time, the country aims to reduce energy consumption and increase energy efficiency [1]. The Federal Ministry for Economic Affairs and Energy ("Bundesministerium für Wirtschaft und Energie"-BMWi) sees great potential both in reducing energy consumption and in switching to non-fossil alternatives in the heating sector. Thus, the Renewable Energies Heat Act ("Erneuerbare-Energien-Wärmegesetz"-EEWärmeG), which came into force on 1 January 2009, obliges citizens and companies in Germany to incorporate renewable energy sources, such as solar thermal, biomass, or geothermal energy, into the heating supply for new buildings if their floor space exceeds 50 m 2 [2,3]. The use of renewable energy for heating and cooling purposes is also subsidized by the federal government under the Market Incentive Program (MAP) in accordance with §13 of the Renewable Energies Heat Act [3]. This program funds technologies that use renewable energy for heating or cooling, including heat pumps (air source heat pumps, ground source heat pumps, and exhaust air heat pumps), as well as deep geothermal systems and heat storage systems. These government incentives have contributed to the rising popularity of near-surface geothermal energy, and by 2020 there were over 440,000 ground source heat pumps (GSHPs) installed in Germany [4]. In the same year, heat pumps (both ground and air source) made up about 10 percent of renewable heating (17.5 billion kWh). As Figure 1 illustrates, the installed capacity of GSHPs considerably varies between German federal states. This is not only caused by differences in geological conditions or population sizes, but also by varying regulations and incentive programs [5]. Heating transitions are currently taking place in many industrialized countries all over the world and they can be understood as transformations of social, technological, and material configurations in the heating sector. As outlined above, the political goal in Germany, as well as elsewhere, is to transform the sociotechnical system of heating in such a way that it becomes less CO2-intensive. Thus, heating systems which rely on fossil fuels need to be phased out, while renewable heating systems, such as heat pumps, are expected to spread throughout society. However, the integration of new elements into a larger sociotechnical system almost always goes hand-in-hand with unforeseen and unintended side effects [6]. Unexpected issues come to the fore, brought about by the interplay of social, technological, and material elements of the respective sociotechnical systems. With regard to geothermal energy, one such unexpected issue is the technology's temporary depletability when it is used in specific ways. This temporary depletability becomes observable in the form of so-called cold plumes, which represent a cooling of the subsoil due to the extraction of heat by GSHPs and will be explained in depth below.
With reference to science and technology studies (STS) as a conceptual perspective, and by drawing on issues of GSHP spacing regulation in Germany, we argue that the Heating transitions are currently taking place in many industrialized countries all over the world and they can be understood as transformations of social, technological, and material configurations in the heating sector. As outlined above, the political goal in Germany, as well as elsewhere, is to transform the sociotechnical system of heating in such a way that it becomes less CO 2 -intensive. Thus, heating systems which rely on fossil fuels need to be phased out, while renewable heating systems, such as heat pumps, are expected to spread throughout society. However, the integration of new elements into a larger sociotechnical system almost always goes hand-in-hand with unforeseen and unintended side effects [6]. Unexpected issues come to the fore, brought about by the interplay of social, technological, and material elements of the respective sociotechnical systems. With regard to geothermal energy, one such unexpected issue is the technology's temporary depletability when it is used in specific ways. This temporary depletability becomes observable in the form of so-called cold plumes, which represent a cooling of the subsoil due to the extraction of heat by GSHPs and will be explained in depth below.
With reference to science and technology studies (STS) as a conceptual perspective, and by drawing on issues of GSHP spacing regulation in Germany, we argue that the renewability of geothermal energy depends on the sociotechnical context in which geothermal energy is embedded and where it is used as a resource. The embedding in specific sociotechnical contexts brings certain characteristics of geothermal energy to the fore in the form of unintended side effects which had previously been unknown, ignored, or regarded as irrelevant. This may also result in social conflicts. Near-surface geothermal energy development in Germany offers a case study for this.
In the following section we briefly outline a science and technology studies-(STS) inspired perspective on the social constitution of geothermal energy as a resource. We then turn to our case study of spacing regulations and cold plumes in Germany, digging deeper into the legal and scientific issues which serve as a crucial knowledge base for the regulation of geothermal energy. After this, we utilize our STS perspective in order to discuss how the renewability of geothermal energy becomes contested within specific sociotechnical contexts. We then end with a short summary and outlook.

Conceptual Considerations: How Geothermal Energy Obtains Its Characteristics
From an STS perspective, a crucial question regarding energy sources is why and how they become resources in the first place [7]. Thereby, resources can be understood as something that serves the realization of human interests, and thus are considered useful and valuable [8] (p. 1219). Humans draw on biophysical materialities in order to satisfy and pursue individual or collective needs, aspirations, or projects. For example, natural materials are indispensable as sources of food, building materials, and for the production of everyday utensils. Similarly, geothermal energy, like any energy source, is a resource that we harness for a specific purpose-in this case, for heat generation-and to which we thus assign a certain significance and value. This process can be understood as a form of social constitution that presupposes various forms of knowledge and involves integration with larger sociotechnical systems so that the resource can be exploited at scale and in a useful way. According to Thomas P. Hughes, the concept of sociotechnical systems denotes a set of complex components: "Among the components in technological systems are physical artifacts, such as the turbogenerators, transformers, and transmission lines in electric light and power systems. Technological systems also include organizations, such as manufacturing firms, utility companies, and investment banks, and they incorporate components usually labeled scientific, such as books, articles, and university teaching and research programs. Legislative artifacts, such as regulatory laws, can also be part of technological systems" [9] (p. 51). However, through the integration with a specific sociotechnical system, certain characteristics of a resource come to the fore. In the context of an energy system that is fed with significant amounts of volatile renewable energies, for example, the base load capability attributed to geothermal energy gains particular relevance: since heat pumps can generate a stable supply of heat, the fluctuation of other renewables used for heat generation (e.g., solar thermal collectors) can be counterbalanced. By contrast, in a fossil fuel-based energy system, the base load capability of a heat source becomes largely irrelevant, and thus "invisible." Moreover, resources that are integrated into a sociotechnical system can also change that system's configuration. This is the case, for example, since resources are an element of the co-production of energy. They are part of a process involving different actors, technologies, and materialities that produces certain outputs, such as heat. The heating produced by heat pumps is the outcome of a complex process of co-production between homeowners, heating system installers, drilling companies, geologists, environmental administrations, energy production technologies, underground heat, and others [10]. In addition, the integration of heat pumps (which require electricity to operate) increases both the load on the power grid and its peak demand, which, in turn, may require further reinforcement of the grid and other redesigns of the system on a wider scale, such as the integration of energy storage solutions to mitigate peak load [11] (p. 13). As a consequence, heat pumps also alter the configuration of the energy system.
The crucial point here is that the CO 2 balance of a heating system, questions of base load capability, and the issue of peak loads are only of technical and political relevance in the sociotechnical context of an energy system that increasingly relies on fluctuating renewables, as well as in the face of aspirations to decarbonize the energy system. Thus, the characteristics of resources such as geothermal energy arise in part from their embeddedness in larger sociotechnical systems featuring specific social, technological, and material configurations.
One important "way of knowing" the characteristics of geothermal energy is through their representation by science; in particular, through measurements, quantifications, and modeling. Sheila Jasanoff coined the notion of "ways of knowing" [12] in order to describe the methods used to produce those things which are considered to be facts. In this stream of thought, technoscientific knowledge is central for understanding and thinking about resources. Technoscientific ways of knowing are both normative and functional: "For example, ideas of risk and opportunity are pervasive in the energy sector, and these calculations often reflect the biases of particular groups. The desirable path forward often looks very different depending on whether one is a policy-maker, an energy entrepreneur, or a local citizen" [13] (p. 142). Thus, we are always dealing with a kind of situated knowledge that is dependent on the circumstances under which it is produced and which, therefore, varies from context to context. Models, for example, produce different outputs depending on the often implicit assumptions that are built into them. Specific "ways of knowing" are, therefore, vehicles for the production of facts and always entail predefined (normative and descriptive) ideas of the object under study. These "ways of knowing," nevertheless, also shape our ideas of the characteristics of resources.

Ensuring Renewability through Spacing
As we will elaborate in the following case study, the design of boreholes for GSHPs seems to affect geothermal energy's status as a renewable energy resource, with the science, laws, rules, and regulations which govern the integration of geothermal energy in the sociotechnical system of energy also playing a crucial role. Our considerations emerged partly out of eight expert interviews of about one hour duration each with researchers, urban planners, and officials from Germany, Austria, and Switzerland dealing with near-surface geothermal energy. The interviews were conducted over the course of half a year in 2021 as part of the German Research Foundation-(DFG) funded project on "Wind harvest and heat theft as indicators of new ownership structures" (2021-2024) (for further information see here: https://sfb294-eigentum.de/en/subprojects/windernte-und-warmeklau-alsindikatoren-neuer-eigentumsordnungen/ (accessed on 29 December 2021)). The interview material was subjected to a thematic analysis [14] with the help of the computer program MAXQDA. Since the interviews are part of a larger research endeavor, only parts of them were relevant for the scope of this paper. Additionally, we have reviewed official documents, such as legal codes and spatial planning schemes, in order to supplement and deepen the insights gained from the expert interviews.

Geothermal Energy as Depletable Resource?
One of the main aspects that distinguishes renewables from fossil fuels is their ability to renew themselves, ideally at the same rate as they are being consumed. From a natural science perspective, an energy resource can be considered renewable when three crucial parameters are in an equilibrium: the inflow of energy, the outflow of energy, and the stability of the energy reservoir. The inflow of energy has to be equal to the outflow of energy, so that a specific energy reservoir can remain in balance [15] (p. 1). In this sense, "geothermal resources can be considered renewable on the time-scales of technological/societal systems and do not require the geological times of fossil fuel reserves such as coal, oil, and gas" [16] (p. 469).
Near-surface geothermal energy systems utilize geothermal heat at depths of up to 400 m and temperatures of up to 25 • C. At this depth, heat sources can be renewed by the natural vertical flow of energy from below, by lateral flows from the side, and from groundwater. However, if more energy is extracted than can be renewed in a particular time frame, the energy reservoir gradually depletes [17] (p. 1). The decline of geysers in New Zealand serves as a prime example of such geothermal resource depletion. In this particular case, extensive extraction of heat caused an irreversible depletion of geothermal resources in certain areas of New Zealand [18] (p. 803). So-called cold plumes are more common and less severe phenomena which can develop as a negative side effect of the application of GSHPs [19]. Even though deep geothermal heat extraction can also cause the heat reservoir to cool down [20], for this paper, the focus lies solely on the near-surface geothermal energy use, which, unlike deep geothermals, is an integral part of the German heating transition. Cold plumes emerge because GSHPs extract underground energy for utilization within heating purposes. In order to do this, they require groundwater (in open systems such as wells) or brine (in closed systems such as probes) to absorb the geothermal heat. GSHPs transfer the heat via heat exchangers and return the cooled water or brine back underground. The liquids can then reheat again due to the stable heat stored in the subsoil. This cyclic extraction-and, in particular, cold liquid or water reinfusion-can cool down the heat reservoir, thus potentially causing cold plumes to emerge [19] (p. 495). These cold plumes develop differently depending on the geothermal extraction system used and the conditions under the ground. If the heat transfer takes place via conduction, then the cooling spreads around the GSHP probe in a radial pattern. If the heat transfer is convective in nature, then a plume-like spreading in the direction of groundwater flow can be observed [21] (p. 70). The speed at which the cooling spreads depends on several factors. These include "soil characteristics, moisture content, building load, initial ground temperature, borehole spacing, etc." [22] (p. 222).
Plumes can accumulate if boreholes are located too close to each other. Meng and colleagues [23] investigated cold plumes in a neighborhood in Cologne (Germany) which is characterized by a high density of GSHPs. The adverse placing of real estate and the spacing of GSHPs in partial alignment with the groundwater caused the emergence of cold plumes affecting several households. Whereas property lines clearly denote the boundaries of individuals' property, no physical barrier exists under the ground in order to enforce these. Thus, thermal anomalies can traverse property lines with ease. As a result, cold plumes can cause several issues. As the study by Meng and colleagues shows [23] (p. 10), the most obvious of these is the decreasing efficiency of GSHPs when placed close together, requiring higher electricity input into the heat exchanger. Cold plumes can also result in social costs, such as litigation, if home owners feel negatively affected by neighboring GSHPs [24] (p. 482). These disputes are already part of public debates on geothermal energy extraction, often framed in terms of "heat theft" [25] (p. 37). Furthermore, heat extraction constitutes an artificial interference with the temperature regime that can potentially affect the groundwater ecosystem. Microorganisms, such as bacteria, provide important ecosystem services through filtering or cleaning the groundwater, but they are likely to be affected by changes in temperature [26]. To avoid such interferences, as well as unintended side effects in the form of cold plumes, the proper spacing of heat pumps is crucial.

Keeping GSHPs at a Distance
With the growing, politically subsidized diffusion of GSHPs, the density of GSHPs is also increasing in Germany, particularly in urban areas, leading to shorter distances between installations. This makes the cold plume phenomenon more relevant and interference more likely. If geothermal energy as a renewable resource is supposed to contribute to the German heat transition in an optimal way, the phenomenon of cold plumes could become an issue of growing relevance with regard to the planning of GSHPs. For this reason, the different German federal states have implemented distancing guidelines for near-surface geothermal energy systems. Depending on the state and/or municipality, these vary between 5 and 10 m [27] (p. 123). However, it remains unclear on which knowledge base these distances have been established. Furthermore, in an international survey of national legislation, temperature limits, and distances between near-surface geothermal energy systems, Hähnlein and colleagues found that regulations vary widely from country to country and are not solely derived from scientific considerations and evidence, but also from supposed best practice examples and rules of thumb [28]. Furthermore, plumes not only depend on spacing, but also on the characteristics of the underground environment. For example, in gravel aquifers, cold plumes can exceed 10 m within a single heating period at average withdrawal rates, as water can flow through the ground quicker [29]. Conditions under the ground vary regionally, making general distancing guidelines partially useless.
Since distancing guidelines do not necessarily meet the actual requirements for the efficient use of geothermal energy, they are a subject of controversial debate among experts: "The existing legal frameworks all over the world have failed to some degree to provide a scientific-based solution to this problem and aimed to use simple approaches, often with their roots in groundwater resource management, that have ended in disperse incoherent legal enforcements" [29] (p. 10). To avoid "significant errors," simple models can help to determine suitable spacing for boreholes based on "all geometrical parameters" [19] (p. 497). However, despite modeling, problems can arise, especially when geothermal probes do not run directly downwards, but run at an angle, extending beyond the boundaries of individual property [30] (p. 2). Moreover, the results produced by computer models are always and inevitably affected by uncertainties, since they are simplifications of a complex reality.
It follows from the above discussion that sound spacing of GSHPs seems fundamental to guaranteeing the sustainable extraction of the resource without causing interference with adjacent GSHPs. However, as we have laid out, thresholds and distancing regulations are contested and both seem to be somewhat arbitrary and, in general, to be constituted through contingent social processes. This not only holds true for distancing recommendations, but also, in part, for formal regulations for geothermal energy extraction more broadly as they are implemented in German law.

Governing Geothermal Energy Extraction by Law
In Germany, the extraction of geothermal energy is subject to several legal preconditions. In general, the German Civil Law Book ("Bürgerliches Gesetzbuch"-BGB), which allows landowners to make use of their land, includes in this permission both the sky above and the land underneath a piece of property ( §905 I 1 BGB). However, this does not hold true on all accounts. Even though the book suggests that natural resources in the ground can be exploited by landowners, the Federal Mining Act ("Bundesberggesetz"-BBergG) further defines under which conditions resources may be extracted. The Federal Mining Act distinguishes between two types of extractable resources under the ground. On the one hand are the "grundeigene Bodenschätze," that is, mineral resources that belong to landowners ("grundeigen") and can be extracted without any formal permission ( §3 II 1 BBergG). On the other hand are "bergfreie Bodenschätze" that do not belong to the landowner, and thus require permission to extract ( §3 II 2 BBergG). The adjective "bergfrei" in connection to mineral resources is a reference to the geological subsoil free for mining. Moreover, the Federal Mining Act explicitly states that land rights do not extend under the ground in the case of "bergfreie Bodenschätze" [24] (p. 477). In general, private installations by homeowners do not require mining permission in Germany, unless the boreholes exceed a depth of 100 m or the scope of the permitted field extends beyond the boundaries of the property [25] (p. 37). Then they require a permission in accordance with §127 Federal Mining Act ("Bundesberggesetz"-BBergG). Thus, up to a depth of 100 m, formal permission for the extraction of geothermal energy is only required if the geothermal energy system extends beyond the property boundaries or if the neighboring property is thermally or materially affected [21] (p. 71).
There is no formal reason or scientifically grounded justification for the 100-m threshold. Nevertheless, it has a direct impact on the installation, efficiency, and functioning of GSHPs. When it comes to the active regeneration of underground heat reservoirs, existing cold plumes could be mitigated more easily with boreholes exceeding 100 m. Thus, boreholes from different neighboring GSHPs could more easily be placed at different depths. However, this would be associated with higher financial costs (as the cost of drilling increases with depth), even though it is generally cheaper than actively regenerating underground reserves in the long term [31] (6f). Deeper drilling is also more time consuming and involves higher bureaucratic hurdles since the relevant permissions must first be obtained from the State Mining Office ("Landesbergamt"). Nevertheless, considering the level of heat under the ground which increases with every meter, deeper boreholes-depending on underground characteristics-could improve efficiency and reduce thermal interference between adjacent heat pumps [32] (p. 35). Accordingly, in Germany, the Federal Association of Heat Pumps ("Bundesverband Wärmepumpe") is already demanding a reconsideration of the 100-m threshold. The association suggests expanding the limit to a depth of 400 m, the maximum depth for near-surface geothermal energy systems (VDI-The Association of German Engineers 4640, Blatt 1, 2010, as referenced in [26] (p. 26)). Interestingly, in the neighboring countries of Austria and Switzerland, no comparable regulations in terms of depth of drilling have been imposed. Rather, drilling is carried out until a suitable geothermal heat reservoir has been reached. This can be at a depth of 50 m or 200 m.
Of course, the embedding of GSHPs into a regulatory framework is necessary for the prevention of conflicts and to steer the further development of geothermal energy usage. However, as we have seen, regulatory frameworks do not necessarily serve to promote the expansion of GSHPs in an efficient way. They can also serve as obstacles or contribute to the formation of negative side effects, such as cold plumes. In Spain, for example, García-Gil and colleagues have concluded that the present regulatory framework is slowing down the development of geothermal energy. They describe a similar ambiguity and arbitrariness with regard to the depth of boreholes as we have found to be the case in Germany [33].

Discussion
We have suggested above that geothermal energy can only be regarded as a fully renewable resource if the spatial layout of GSHPs is appropriately regulated. This means that, when geothermal heat is extracted from under the ground, it must be ensured that at least the same amount of heat can be returned or regained through natural or technical processes. This is due to the physical characteristics of geothermal energy as a renewable energy source. If this is not guaranteed, the ground will gradually cool down, making the operation of affected GSHPs inefficient. Thus, proper distancing between individual GSHPs is necessary in order to avoid interferences. In the context of the German energy transition, the demand for GSHPs is growing and thus spacing regulations are becoming increasingly important. As has been illustrated above, the distance that should be maintained between individual GSHPs is based on an understanding of cold plume formation and propagation that is barely adequate in the context of contemporary scales of geothermal energy usage. That existing spacing regulations appear to have arbitrary origins, and yet they continue to be followed, indicates that they have become part of general "knowledge" about geothermal energy to a point where they are hardly ever questioned. German distancing regulations were established before geothermal energy was considered to be an important part of the energy transition, with other kinds of resources in mind, and at a time when underground resources remained relatively unexplored. Further, different knowledges based on specific "ways of knowing" geothermal energy compete with each other for being incorporated in spatial planning practices and regulations [34]. These knowledges become incorporated in these practices and regulations, to different extents. Present regulations seem to be mainly derived from practical knowledge, conventional wisdom, and past experiences. However, these knowledges seem to blend out or underestimate geothermal energy's ability to produce cold plumes when being used by GSHPs. At the time when these knowledges have become embedded in practices and regulations of distancing, they may have been sufficient to ensure an appropriate management of geothermal energy as a resource. However, under conditions of density between geothermal probes, these knowledges seem to fail the test of practical applicability. Most interestingly, other countries, such as Switzerland and Austria, have adopted these guidelines despite different soil conditions and use patterns in either country. Switzerland's largest city, Zurich, for example, has a vast amount of aquifers and, therefore, relies heavily on groundwater and open geothermal systems, whereas Germany installs mostly geothermal probes [35]. Still, the German distance regulation of 10 m has been adopted. This transplantation of regulations [36] has also resulted in a transplantation of the congealed knowledges incorporated in the regulations and, thus, in a transfer of the boundaries of these knowledges. Modeling and measurements as ways of knowing the underground may appear to produce more robust knowledge since they are able to capture the cold plume phenomenon. However, each way of knowing produces certain blind spots and is affected by uncertainties. Furthermore, as Brian Wynne has famously pointed out [37], technoscientific knowledges are not necessarily superior to knowledges grounded in practical experience or conventional wisdom.
It is not only different ways of knowing which constitute certain characteristics of geothermal energy. As we have seen, the embedding of heat pumps within the specific configurations and expectations of the present energy system brings the (temporary) depletability of geothermal energy to the fore. Thereby, the material world exerts its own influence on the constitution of energy system characteristics. As Bruno Latour [38] has elaborated in detail, biophysical materialities follow their own trajectories, and thereby intervene in the flow of events in the world. That is, the characteristics of resources are not arbitrarily malleable, but exhibit moments of unruliness. As shown above, these moments of unruliness are revealed by the complex and partially arbitrary interplay between different knowledges formed by different knowledge-producing institutions and the biophysical entity of geothermal energy [39]. In our case, the main knowledge-producing institutions are law and science. As we have seen, law is a crucial knowledge-producing institution when it comes to the installation of GSHPs, while science and its inherent ways of knowing [12] (p. 249) are crucial for understanding the biophysical characteristics of geothermal energy. This understanding, however, also changes over time. Nevertheless, law and science are central to our understanding of geothermal energy and its characteristics. Miller et al. [13] thus speak of "energy epistemics" in order to denote the cognitive representation of energies on the part of different knowledge-producing institutions. These energy epistemics, together with the material world, co-produce [40] the cold plume phenomenon. These cold plumes, however, only come to the fore and become problematized through the reconfiguration of the sociotechnical system of energy and the growing diffusion of heat pumps in order to decarbonize heating. All in all, it is the constellation of different knowledge sources (which have partly sunk into oblivion), the resource's inherent unruliness, and the political project of decarbonization that brings cold plumes into being, which makes them a debated issue, and which reveals geothermal energy's characteristic of temporary depletability. This is what we understand to be the social constitution of geothermal energy.

Conclusions
Drawing on the example of cold plumes and regulatory issues of spacing in Germany, we have elaborated the unruly nature of geothermal energy, which reveals novel characteristics when exploited at scale. The scope of our research is mainly limited to Germany. However, the phenomenon of cold plumes and accompanying regulatory issues are not Germany-specific. If geothermal energy is intended to become an important component of a decarbonized energy mix in Germany and other countries around the world, careful management of the resource will become increasingly necessary. Thereby, regulatory frameworks and distancing regulations which draw on various knowledges grounded in distinct ways of knowing play a crucial role [41,42]. As we have seen, the sociotechnical context in which geothermal energy is currently embedded in Germany draws out its characteristic of being (at least temporarily) depletable. Unintended side effects are a common issue in complex sociotechnical transformations, such as the German energy transition. Thus, when it comes to dealing with such side effects, it is not so much a question of whether these unintended side effects could have been foreseen (since they cannot be avoided) as of how these effects can be minimized after they became perceivable. In the case of cold plumes and interference between neighboring GSHPs, a carefully balanced regulatory framework for locating GSHPs seems to be the obvious solution. However, this regulatory framework must be based on extant sets of knowledge stemming from the areas of planning, law, science, and engineering. Even when drawing together these different areas, such knowledge will never be complete, and the generation of new knowledge often includes the awareness of new knowledge gaps that foster new uncertainties, risks, and ignorance [43][44][45]. Whenever knowledge grows, so does the perception of ignorance. Uncertainties in geothermal energy operations will thus appear as soon as the sociotechnical context in which the use of geothermal energy is embedded changes.
Ultimately, this article throws into relief the social constitution of geothermal energy. It is intended to illustrate the relevance of the issue and whet appetite for further research to gain a deeper understanding of which actors-ranging from natural scientists and energy suppliers to NGOs and governments-contribute in what way to the epistemics of energy surrounding geothermal heating.  Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.

Data Availability Statement:
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy restrictions.