Peter Bayer

Martin Luther University Halle-Wittenberg | MLU · Institute of Geosciences and Geography

The thermal response test (TRT) in an aquifer establishes a relationship between the groundwater flow rate and the recorded temperature response curve of temporal ground heating. A major challenge for achieving a mature hydrogeological field test is to minimize borehole effects by smart practical solutions of in situ heating and temperature sensing...

In this study, we infer the structural and hydraulic properties of the highly fractured zone at the Grimsel Test Site in Switzerland using a stochastic inversion method. The fractured rock is modeled directly as a discrete fracture network (DFN) within an impermeable rock matrix. Cross-hole transient pressure signals recorded from constant-rate inj...

Vertical water flow is a decisive factor for slope stability and instability, but its characterization in the field remains a challenge. Quantifying flow rates in slopes is commonly impeded by insufficient resolution during field investigations or the limited insight obtained from near-surface geophysical methods. This study aims to develop a conve...

Snowfall and ice formation on road surface significantly impact the safety of driving conditions. To resolve this, every year salt and de-icing chemicals are sprinkled on roads. However, use of salts and snow ploughing have environmental as well as economical disadvantages. To resolve these problems, hydronic road heating systems are valid alternat...

Aquifers contain the largest store of unfrozen freshwater, making groundwater critical for life on Earth. Groundwater temperatures infl uence stream thermal regimes, groundwater-dependent ecosystems, aquatic biogeochemical processes, water quality, and the geothermal potential. Yet little is known about how groundwater responds to surface warming a...

Precise information about the spatial distribution of hydraulic conductivity (K) in an aquifer is essential for the reliable modeling of groundwater flow and transport processes. In this study, we present results of a new inversion procedure for induced polarization (IP) data that incorporates petrophysical relations between electrical and hydrauli...

Shallow temperatures down to a depth of 100 m were measured over one year in 19 closed boreholes located in Nanjing, China, to reveal the conditions and factors influencing the subsurface thermal regime. A monitoring concept with distributed temperature sensing, fiber Bragg grating-based sensor, and a type of Resistance Temperature Detectors, is im...

Pumping optimization under uncertainty is a powerful approach for the management of groundwater resources, and its implementation would be valuable in island aquifers where freshwater lenses are affected by seawater intrusion. Sharp‐interface numerical models are especially well suited for the task as they offer fast simulation times, but to date t...

Meeting the rising energy demands of cities is a global challenge. Exploitation of the additional heat in the subsurface associated with the subsurface urban heat island (SUHI) has been proposed to address the heating demands. For the sustainable use of this heat it is crucial to understand how SUHIs evolve. To date, there have been no comprehensiv...

Despite the global interest in green energy alternatives, little attention has focused on the large-scale viability of recycling the ground heat accumulated due to urbanization, industrialization and climate change. Here we show this theoretical heat potential at a multi-continental scale by first leveraging datasets of groundwater temperature and...

In this study, we infer the structural and hydraulic properties of the highly fractured zone at the Grimsel test site in Switzerland by a stochastic inversion method. The fractured rock is modeled directly as a discrete fracture network (DFN) within an impermeable rock matrix. Cross-hole transient pressure signals recorded from constant rate inject...

Anthropogenic warming of the atmosphere is one if not the most pressing challenge we face in the 21st century. While our state of knowledge on human drivers of atmospheric warming is advancing rapidly, little so can be said if we turn our view toward the Earth’s interior. Intensifying land use and atmospheric climate change condition the changing t...

Seasonal thermal energy storages are considered a central element of modern, innovative energy systems and help to harmonize fluctuating energy sources. Furthermore, they allow for an improved coupling between the electricity and heating sectors. Despite recent improvements of planning processes and enhanced models, significant discrepancies betwee...

Groundwater fauna (stygofauna) comprises organisms that have adapted to the dark subterranean environment over a course of thousands and millions of years, typically having slow metabolisms and long life cycles. They are crucial players in the groundwater of oxygenic aquifers, and contribute to various ecosystem services. Today's knowledge of their...

Interpretation of tracer tests in geothermal reservoirs is carried out by fitting the measured data either with simplified two-dimensional (2-D) analytical solutions or with complex numerical models. Available analytical solutions commonly only describe isotropic conditions in 1-D or 2-D, which is generally unsatisfactory to construct realistic res...

We introduce an approach for the stochastic characterization of the geometric and hydraulic parameters of a three‐dimensional (3D) discrete fracture network (DFN) and for estimating their uncertainty based on data from hydraulic tomography experiments. The inversion approach relies on a Bayesian framework and the resulting posterior distribution is...

Subsurface flow rates are critical for hydrology and geothermal research, while field characterization remains a challenge. There are several analytical solutions for calculating the vertical water flux based on measured temperatures. Heat is a popular natural tracer to estimate subsurface flow rates. However, quantifying flow rates is impeded by i...

The objective of this study is to assess the suitability of the analytical infinite moving line source (MLS) model in determining the temperature of vertical grouted borehole heat exchangers (BHEs) for steady-state conditions when horizontal groundwater advection is present. Therefore, a numerical model of a grouted borehole is used as a virtual re...

Aquifer Thermal Energy Storage (ATES) is an open-loop geothermal system allowing long-term storage of thermal energy in groundwater. It is a promising technology for environmentally friendly energy generation that can reduce greenhouse gas (GHG) emissions. In the literature, there are few studies on the greenhouse gas emissions caused by ATES syste...

Thermal use of the shallow subsurface and its aquifers (< 400 m) is steadily increasing. Currently, more than 2800 aquifer thermal energy storage (ATES) systems are operating worldwide alongside more than 1.2 million ground source heat pump (GSHP) systems in Europe alone. These rising numbers of shallow geothermal energy (SGE) systems will put addi...

Thermodynamic coupling between atmosphere and ground yields increasing aquifer temperatures as a consequence of global warming. While this is expected to manifest as a gradual warming in groundwater temperature time series, such continuous long-term recordings are scarce. As an alternative, the present work examines the use of repeated temperature-...

The slug test is a common field technique for obtaining local hydraulic parameters near wells, applied, for example, for the hydrogeological investigation at contaminated sites. Although many slug test models have been developed for interpretation of measurements, only a few of them have considered heterogeneous conditions, and water column inertia...

Every technology and anthropogenic activity affects the environment. This even applies to renewable, green energy forms, such as geothermal energy, which are often labelled as being climate neutral. Yet, a second glance reveals that this is not the case, as the construction, operation and decommissioning of geothermal power plants implies a consump...

Decarbonising the heating sector is crucial for reducing CO2 emissions. This is in particular true for Central European cities such as Vienna, where 28% of the total CO2 emissions are caused by the energy supply for buildings. One promising option for environmental friendly heat supply is the use of shallow geothermal energy. To determine whether s...

Heat transport in natural porous media, such as aquifers or streambeds, is generally modeled assuming local thermal equilibrium (LTE) between the fluid and solid phases. Yet, the mathematical and hydrogeological conditions and implications of this simplification have not been fully established for natural porous media. To quantify the occurrence an...

Accurate estimation of thermal ground properties is needed to optimally apply shallow geothermal energy technologies , which are of growing importance for the heating and cooling sector. A special challenge is posed by the often significant heterogeneity and variability of the geological media at a site. As an innovative investigation method, here...

Drilling costs, induced seismicity, scaling and corrosion, emissions, and assessment of the inherent uncertainty associated with the reservoir properties for long-term sustainable provision of thermal energy are the major challenges of deep geothermal systems. In particular, the cost of drilling typically comprises 50-70 % of the total capital inve...

Seasonal heat storage is considered as one of the key elements on the path to a low-emission economy. Embedded in local district heating networks, they raise the share of renewable energies and balance out highly fluctuating supplies of e.g. solar systems or windmills. The technology of seasonal heat storage can be described as almost technically m...

This supplement to the article "Paraffin wax as self-sealing insulation material for seasonal sensible heat storage systems – A laboratory study" contains the temperature data recorded in the laboratory for section 2.1 "Enhancement of thermal performance".

The number of worldwide installed groundwater heat pump (GWHP) systems is approaching one million units. This increase in GWHP systems creates an increasing competition for groundwater use. Thus, we have simulated the long-term thermal impacts of such open-loop geothermal systems with numerical heat transport models, by studying the role of flow an...

As groundwater is competitively used for drinking, irrigation, industrial and geothermal applications, the focus on elevated groundwater temperature (GWT) affecting the sustainable use of this resource increases. Hence, in this study GWT anomalies and their heat sources are identified. The anthropogenic heat intensity (AHI), defined as the differen...

Actively stimulated temperature changes are common in many groundwater applications. A widely used concept to determine water fluxes, mean transit times, and other parameters from heat tracer tests is the use of the thermal retardation factor. Different methods are available to determine the thermal velocity from thermal breakthrough curves (BTCs)...

Fractures serve as highly conductive preferential flow paths for fluids in rocks, which are difficult to exactly reconstruct in numerical models. Especially, in low-conductive rocks, fractures are often the only pathways for advection of solutes and heat. The presented study compares the results from hydraulic and tracer tomography applied to inver...

Subsurface temperature data is usually only accessible as point information with a very limited number of observations. To spatialize these isolated insights underground, we usually rely on interpolation methods. Unfortunately, these conventional tools are in many cases not suitable to be applied to areas with high local variability, like densely p...

The growing interest in shallow geothermal resources leads to dense installation areas, where interference and decrease in efficiency might occur. To optimize geothermal use in cities which prevents interference between neighbouring and future installations, we present a novel concept relying on the definition of thermal protection perimeters (TPP)...

Continuous use of fluctuating renewable energy resources is facilitated only by temporal storage solutions. For long-term and seasonal heat storage, many large-scale closed seasonal thermal energy storages (TES) have been built in the recent decades. Still there is no consistent picture available that contrasts the different technologies and summar...

The number of groundwater heat pump systems (GWHPS) is growing in many countries and dense installations of urban areas lead to thermal interference among neighboring wells. The assessment of the thermal plumes caused by GWHPS is a necessary step to manage the geothermal potential beneath cities and to validate the feasibility of a project. The pre...

Thermal energy for space heating and for domestic hot water use represents about a third of the overall energy demand in Germany. An alternative to non-renewable energy-based heat supply is the implementation of closed and open shallow geothermal systems, such as horizontal ground source heat pump systems, vertical ground source heat pump (vGSHP) s...

What is the heat beneath our feet? There is a growing interest in the geothermal resources available at shallow depth beneath cities. However, there exists no general procedure for quantifying the low-temperature geo-thermal potential in urban ground and groundwater. This review categorizes previous work based on different definitions of the geothe...

This study presents the first field validation of using DNA-labeled silica nanoparticles as tracers to image subsurface reservoirs by travel time based tomography. During a field campaign in Switzerland, we performed short-pulse tracer tests under a forced hydraulic head gradient to conduct a multisource-multireceiver tracer test and tomographic in...

Information on structural features of a fracture network at early stages of Enhanced Geothermal System (EGS) development is mostly restricted to borehole images and, if available, outcrop data. However, using this information to image discontinuities in deep reservoirs is difficult. Wellbore failure data provides only some information on components...

Groundwater heat pump (GWHP) systems have gained attention for space heating and cooling due to their efficiency and low installation costs. Their number is growing in many countries, and therefore in some areas, dense installations are expected. This might lead to thermal interferences between neighbouring groundwater wells and a decrease in effic...

Climate change is one of if not the most pressing challenge modern society faces. Increasing temperatures are observed all over the planet and the impact of climate change on the hydrogeological cycle has long been shown. However, so far we have insufficient knowledge on the influence of atmospheric warming on shallow groundwater temperatures. Whil...

Link to characterization factors datasets: https://doi.org/10.3929/ethz-b-000253177 Link to code: https://github.com/ethz-esd/compaction_stoessel_2018

Maintaining biotic capacity is of key importance with regard to global food and biomass provision. One reason for productivity loss is soil compaction. In this paper, we use a statistical empirical model to assess long-term yield losses through soil compaction in a regionalized manner, with global coverage and for different agricultural production...

In this work, we present the application of a fully-coupled hydro-mechanical method to investigate the effect of fracture heterogeneity on fluid flow through fractures at the laboratory scale. Experimental and numerical studies of fracture closure behavior in the presence of heterogeneous mechanical and hydraulic properties are presented. We compar...

Table 2 and Eq. 3 of the original article are reported incorrectly. The correct Table 2 and Eq. 3 are shown.

Climate change is one if not the most pressing challenge modern society faces. Increasing temperatures are observed all over the planet and the impact of climate change on the hydrogeological cycle has long been shown. However, so far we have insufficient knowledge on the influence of atmospheric warming on shallow groundwater temperatures. While s...

This work studies the roughness characteristics of fracture surfaces from a crystalline rock by analyzing differences in surface roughness between fractures of various types and sizes. We compare the surface properties of natural fractures sampled in situ and artificial (i.e., man-made) fractures created in the same source rock under laboratory con...

Zusammenfassung Die Kenntnis der hydraulischen Durchlässigkeit (kf-Wert) ist die Grundvoraussetzung für das Prozessverständnis der Grundwasserbewegungen im Untergrund. Daher existieren zahlreiche Labor- und Feldmethoden zur Bestimmung der hydraulischen Durchlässigkeit, deren Anwendung allerdings zu deutlich unterschiedlichen kf-Werten führen kann....

In the summer of 2015, a series of thermal tracer tests were conducted at the Widen field site in northeast Switzerland to validate travel time-based thermal tracer tomography for reconstruction of aquifer heterogeneity. Repeated thermal tracer tests and distributed temperature observations were used to obtain a multisource/multireceiver tomographi...

Fracture network geometry is crucial for transport in hard rock aquifers, but it can only be approximated in models. While fracture orientation, spacing, and intensity can be obtained from borehole logs, core images, and outcrops, the characterization of in situ fracture network geometry requires the interpretation of spatially distributed hydrauli...

Monitoring the migration of sequestered CO2 in deep heterogeneous reservoirs is inherently difficult. Geophysical methods have been successfully used, but flow conditions are only indirectly linked to the measured properties. Besides geophysical methods, pressure tomography (PT) is proposed as an alternative method to depict the structure of deep s...

Human activity directly influences ambient air, surface and groundwater temperatures. The most prominent phenomenon is the urban heat island effect, which has been investigated particularly in large and densely populated cities. This study explores the anthropogenic impact on the thermal regime not only in selected urban areas, but on a countrywide...

Transport processes in a fractured aquifer are mainly controlled by the geometry of the fracture network. Such a network is ideally modelled as discrete fracture network (DFN), which is composed by a skeleton of hydraulically conductive fractures that intersect the impermeable rock matrix. The orientation and connectivity of the fractures are highl...

Only meters below our feet, shallow aquifers serve as sustainable energy source and provide freshwater storage and ecological habitats. All of these aspects are crucially impacted by the thermal regime of the subsurface. Due to the limited accessibility of aquifers however, temperature measurements are scarce. Most commonly, shallow groundwater tem...

Borehole temperature logs in urban areas often show deviation from the regional geothermal gradient that increases towards the land surface in the top ∼100 m. This deviation is the sum of two effects: atmospheric global warming and urban heating. To invert the temperature profiles (T-logs), a novel analytical model is presented to distinguish effec...

Many cities leave a considerable thermal footprint in the subsurface. This is caused mainly by accelerated heat fluxes from warmed basements, pavements and buried infrastructures. Even though rough estimations of the theoretical heat content in urban ground exist, there is no insight available on the technical potential of such subsurface urban hea...

Borehole heat exchangers (BHEs) utilize the shallow ground to extract geothermal energy. Mostly they are installed in urbanized areas, where the thermal regime is strongly influenced by pavements, buildings and other urban infrastructures. In order to account for the spatial and temporal variability in the above-ground urban temperatures, a new sem...

Increasing fracture aperture by lowering effective normal stress and by inducing dilatant shearing and thermo-elastic effects is essential for transmissivity increase in enhanced geothermal systems. This study investigates transmissivity evolution for fluid flow through natural fractures in granodiorite at the laboratory scale. Processes that influ...

This work presents a review of the studies applying life-cycle assessment (LCA) methodologies to evaluate the environmental performance of enhanced geothermal systems (EGSs). Due to the scarcity of commercially installed EGS power plants such studies are rare and usually represent very site-specific conditions and plant characteristics. A detailed...