Thermal response tests (TRTs) are a common field method in shallow geothermics to estimate thermal properties of the ground. During the test, a constantly heated fluid is circulated in closed tubes within a vertical borehole heat exchanger (BHE). The observed temperature development of the fluid is characteristic for the thermal properties of the ground and the BHE. We show that, when the BHE is installed in an aquifer with significant horizontal groundwater flow, this test can also be used for hydrogeological characterization of the penetrated subsurface. An evaluation method based on the moving line source equation and considering the natural occurring variability of the thermal transport parameters is presented. It is validated by application to a well-controlled, large-scale tank experiment with 9 m length, 6 m width, and 4.5 m depth, and by data interpretation from a field-scale test. The tank experiment imitates an advection-influenced TRT in a well-known layered aquifer. The field experiment was recorded with a 100 m deep BHE, installed in a gravel aquifer in southwest Germany. The evaluations of both experiments result in similar hydraulic conductivity ranges as determined by standard hydraulic investigation methods such as pumping tests and sieve analyses. Thus, advection-influenced TRTs could also potentially be used to determine integral hydraulic conductivity of the subsurface.

Thermal conductivity and thermal borehole resistance are basic parameters for the technical and sustainable design of closed ground source heat pump (GSHP) systems. One of the most common methods to determine these parameters is the thermal response test (TRT). The response data measured are typically evaluated by the Kelvin line source equation which does not consider all relevant processes of heat transfer in the subsurface. The approach only considers conductive heat transfer from the borehole heat exchanger (BHE) and all transport effects are combined in the parameters of effective thermal conductivity and thermal borehole resistance. In order to examine primary effects in more detail, a sensitivity study based on numerically generated TRT data sets is performed considering the effects of (1) the in-situ position of the U-shaped pipes of borehole heat exchangers (shank spacing), (2) a non-uniform initial thermal distribution (such as a geothermal gradient), and (3) thermal dispersivity. It will be demonstrated that the shank spacing and the non-uniform initial thermal distribution have minor effects (less than 10%) on the effective thermal conductivity and the determined borehole resistance. Constant groundwater velocity with varying thermal dispersivity values, however, has a significant influence on the thermal borehole resistance. These effects are even more pronounced for interpreted effective thermal conductivity which is overestimated by a factor of 1.2–2.9 compared to the real thermal conductivity of the saturated porous media.

For ground-source heat pump (GSHP) systems, the thermal response test (TRT) is commonly used to determine the heat transport parameters of the subsurface. The main limitation of this approach is the assumption of pure conductive heat transport, which might result in significant deviations. Based on the moving line source theory, a parameter estimation approach is introduced, which is sensitive to conduction and advection. This approach is calibrated and successfully tested against three different test cases. The presented analytical approach therefore expands the field of application of the TRT to advection-influenced conditions beyond a Darcy velocity of 0.1 m day(-1). (C) 2012 Elsevier Ltd. All rights reserved.

W/m 2 , the computed effective thermal conductivity decreases by 0.14 W/(mK) meaning a decline by 6.4%. At the same time the calculated borehole resistance increases from 0.086 to 0.101 (mK)/W, i.e. it rises by 17.4%. The effect of the geometry is examined by varying the distance between the tubes in the BHE. This leads to no significant change of the calculated thermal conductivity. However, the computed thermal borehole resistance is highly sensitive. The values shift from 0.06 (mK)/W (for the closest arrangement of the tubes) to 0.17 (mK)/W (for the greatest possible distance between the tubes). The presented relationships clearly show the uncertainties in standard TRT interpretation and demonstrate that in many situations a more detailed evaluation concept is needed.

Shallow geothermal systems such as open and closed geothermal heat pump (GHP) systems are considered to be an efficient and renewable energy technology for cooling and heating of buildings and other facilities. The numbers of installed ground source heat pump (GSHP) systems, for example, is continuously increasing worldwide. The objective of the current study is not only to discuss the net energy consumption and greenhouse gas (GHG) emissions or savings by GHP operation, but also to fully examine environmental burdens and benefits related to applications of such shallow geothermal systems by employing a state-of the-art life cycle assessment (LCA). The latter enables us to assess the entire energy flows and resources use for any product or service that is involved in the life cycle of such a technology. The applied life cycle impact assessment methodology (ReCiPe 2008) shows the relative contributions of resources depletion (34%), human health (43%) and ecosystem quality (23%) of such GSHP systems to the overall environmental damage. Climate change, as one impact category among 18 others, contributes 55.4% to the total environmental impacts. The life cycle impact assessment also demonstrates that the supplied electricity for the operation of the heat pump is the primary contributor to the environmental impact of GSHP systems, followed by the heat pump refrigerant, production of the heat pump, transport, heat carrier liquid, borehole and borehole heat exchanger (BHE). GHG emissions related to the use of such GSHP systems are carefully reviewed; an average of 63t CO2 equivalent emissions is calculated for a life cycle of 20 years using the Continental European electricity mix with 0.599kg CO2 eq/kWh. However, resulting CO2 eq savings for Europe, which are between −31% and 88% in comparison to conventional heating systems such as oil fired boilers and gas furnaces, largely depend on the primary resource of the supplied electricity for the heat pump, the climatic conditions and the inclusion of passive cooling capabilities. Factors such as degradation of coefficient of performance, as well as total leakage of the heat carrier fluid into the soil and aquifer are also carefully assessed, but show only minor environmental impacts.

Different methods for the field-scale estimation of contaminant mass discharge in groundwater at control planes based on multi-level well data are numerically analysed for the expected estimation error. We consider "direct" methods based on time-integrated measuring of mass flux, as well as "indirect" methods, where estimates are derived from concentration measurements. The appropriateness of the methods is evaluated by means of modelled data provided by simulation of mass transport in a three-dimensional model domain. Uncertain heterogeneous aquifer conditions are addressed by means of Monte-Carlo simulations with aquifer conductivity as a random space function. We investigate extensively the role of the interplay between the spatial resolution of the sampling grid and aquifer heterogeneity with respect to the accuracy of the mass discharge estimation. It is shown that estimation errors can be reduced only if spatial sampling intervals are in due proportion to spatial correlation length scales. The ranking of the methods with regard to estimation error is shown to be heavily dependent on both the given sampling resolution and prevailing aquifer heterogeneity. Regarding the "indirect" estimation methods, we demonstrate the great importance of a consistent averaging of the parameters used for the discharge estimation.

Large-scale contaminated land and groundwater is a widespread problem that can severely impact human health, the environment and the economy at many urban sites all over the world. At these sites there are usually a great number of possible management solutions to be considered. A detailed investigation of all these options, however, is economically not feasible. Hence, the streamlining of the planning and decision process is a mandatory requirement. Decisions to be taken should be made as early as possible in order to reduce expenditures on site investigation. Therefore, a tiered decision-making procedure is required, including (i) an identification and prioritisation of focal areas (origin) of risks, (ii) a feasibility screening of remediation targets as well as of available management options to narrow the range of possible options for (iii) subsequent detailed investigations of only a few preferable options. For each of these elements tailored decision and investigation concepts are required. These concepts and employed methods should be specifically adapted to the type and scale of the particular decision to be taken - more target oriented, and cost- efficient investigation programmes as well as model-based assessment methods are needed (Rügner et al. 2006). A gap exists within this framework with respect to preliminary assessment methodologies streamlining the further planning process. To fill this gap, a new system dynamics approach has been developed to represent the source-pathway-receptor system and its dynamics by a mass flux model, describing the effects of possible remedial actions as mass flux change over time (Serapiglia et al. 2004). This concept has been implemented in the preliminary evaluation tool CARO-plus (Cost-efficiency Assessment of