Underground Thermal Energy Storage: Environmental Risks and Policy Developments in the Netherlands and European Union

Abstract

ABSTRACT. We present an overview of the risks that underground thermal energy storage (UTES) can impose on the groundwater system, drinking water production, and the subsurface environment in general. We describe existing policy and licensing arrangements for UTES in the Netherlands, as well as the capability of the current and future Dutch policy and legal framework to minimize or mitigate risks from UTES on groundwater resources. A survey at the European Union member state level indicates that regulation and research on the potential impacts of UTES on groundwater resources and the subsurface environment often lag behind the technological development of and ever-growing demand for this renewable energy source. The lack of a clear and scientifically underpinned risk management strategy implies that potentially unwanted risks might be taken at vulnerable locations such as near well fields used for drinking water production, whereas at other sites, the application of UTES is avoided without proper reasons. This means that the sustainability of UTES as a form of renewable energy is currently not fully understood, and the technology may be compromising the natural resilience of the subsurface environment. We recognize three main issues that should be addressed to secure sustainable application of UTES: Scientific research is required to further elucidate the impacts of UTES on groundwater; cross-sectoral subsurface planning is required to minimize negative conflicts between UTES and other subsurface interests; and EU-wide guidelines and standards are required for quality assurance and control when installing UTES systems.

Preface: Hydrogeology of shallow thermal systems

“…However, the current legal situation in many countries only allows a maximum injection temperature of 25°C (Haehnlein et al 2010). Furthermore, other associated environmental risks due to the operation of such systems also have to be considered (Bonte et al 2011). For example, the use of higher injection temperatures could substantially impact and alter the groundwater ecosystem (Brielmann et al 2009) and the hydrogeochemistry of the aquifer (Bonte et al 2013).…”

Consequences and mitigation of saltwater intrusion induced by short-circuiting during aquifer storage and recovery in a coastal subsurface

“…Furthermore, although the risks of short-circuiting by perturbation are acknowledged by scientists, it seems that the practical and regulatory communities are less aware (Chesnaux, 2012). This is underlined by the fact that certification for mechanical drilling (applied since the Industrial Revolution) in the Netherlands was not obligatory before 2011 (Stichting Infrastructuur Kwaliteitsborging Bodembeheer, 2013a), while for the subsurface design and operation of ATES systems (> 1500 systems since the 1990s; Bonte et al, 2011a;CBS, 2013), obligatory certification has only been enforced since early 2014 (Stichting Infrastructuur Kwaliteitsborging Bodembeheer, 2013b).…”

“…The impact of shortcircuiting on ASR has not been evaluated to date. However, reliably confined aquifers are vital to successfully store energy (Bonte et al, 2011a) and freshwater (Maliva et al, 2016;Maliva and Missimer, 2010;Missimer et al, 2002;Pyne, 2005;Zuurbier et al, 2013a) to bridge periods of surplus and demand, as inter-aquifer leakage may result in a loss of freshwater or undesirable admixing groundwater with a poorer quality, and therefore a reduced ASR performance. Furthermore, although the risks of short-circuiting by perturbation are acknowledged by scientists, it seems that the practical and regulatory communities are less aware (Chesnaux, 2012).…”

“…Confined and semi-confined aquifers are increasingly being used for storm water and (Ferguson, 1990), brine disposal (Stuyfzand and Raat, 2010;Tsang et al, 2008) and storage of freshwater (aquifer storage and recovery or ASR; Pyne, 2005), heat (aquifer thermal energy storage or ATES; Bonte et al, 2011a), and CO 2 (Steeneveldt et al, 2006). Additionally, they are perforated for exploitation of deep fossil and geothermal energy and traditionally used for abstraction of drinking and irrigation water.…”

Developing pathways for energy storage in the UK using a coevolutionary framework

“…For thermal energy storage, the most significant potential environmental impacts are from underground systems, which may pose risks to the ground water system if not managed properly (Bonte et al, 2011). …”