An accurate knowledge of aquifers properties is important 2 in many disciplines, from hydrology to site characterization in order to designing and implementing remediation strategies, as well as geothermal ground source technologies. In par5 ticular, the groundwater flow rate is a fundamental parameter to be considered in the ground-coupled heat exchangers (GCHEs) design, together with the thermal properties of the ground. In fact, even relatively low flow rate entail temperature changes considerably lower than in the case of pure heat conduction (Gehlin and Hellström, 2003; Fan et al., 2007) and then relatively stable underground temper10 atures which allow heat pumps to operate with very efficient performance coefficients, thereby reducing energy costs (Lee et al., 2012). Moreover, an accurate knowledge of groundwater velocity and ground thermal properties allows a better design and dimensioning of the GCHE, with further reduction of costs. The objective of this paper is to propose an expeditious, graphical method to estimate the groundwater flow velocity from TRT analysis.  

The large-scale borehole layer (BTES) in Emmaboda was commissioned in 2010. Its aim was to make use of waste heat from the industrial processes at the Xylem plant. During all the years since its inception, additional heat sources have been included, and only now can the predicted annually amount of stored heat (3.6 GWh/year) be achieved. The average storage temperature is now 40-45oC. Very little of the injected heat has so been recovered (200 MWh) because the storage temperature was lower than expected. The reason for this is mainly that the amount of stored heat (12,000 MWh) is less than expected and that this heat also held a lower temperature than expected. Performed simulations based on actual storage data and presumed future operating data, show that the simulation model reasonably well predicts the future storage function. Initial circulation problems in the storage have been solved with the use of vacuum pumps for degassing of the liquid. The BTES has reduced the amount of annually purchased district heating by about 4 GWh. To further improve the system and reduce the heat losses, it is proposed to install a heat pump to heat withdrawal. This would enable the system to deliver high enough supply temperature for heating of the buildings. The system could then be operated according to planned annual heat injection/ extraction (3.6 GWh/2.7 GWh).

The increasing popularity of ground-coupled heat pumps has resulted in almost20% of all Swedish family houses being heated this way. To avoid undesirableinteractions between neighboring boreholes and disturbance of the ground temperature, the general rule and recommendation of Swedish authorities is that the distance between two neighboring boreholes must be ≥ 20 m. However, according to previous studies, relatively low groundwater flow rates may significantly reduce the borehole excess temperature compared to the case of pure heat conduction. In this work the Influence Length is defined and its relations with flow rate, real thermal conductivity of the ground and effective thermal conductivity obtained by thermal response analysis are investigated. The aim of this study was to find a way to use the thermal response test as a means to determine the groundwater flow influence in order to reduce the borehole spacing perpendicular to groundwater flow direction. The results confirm that very low groundwater flow rates are enough to significantly reduce the Influence Length, hence this is a crucial parameter which should be considered. Moreover, a first estimation, even before the thermal response test analysis, of the Influence Length is possible if the knowledge of hydrogeological conditions of the site allows good predictions about real thermal conductivity of the ground and flow rate.

The Emmaboda HT-BTES was taken into operation 2010. Since then ~10 GWh has been stored, only a fraction has been extracted, and a storage temperature of 40-45 oC has been reached. The purpose of the BTES is to utilize waste heat from the industrial processes. Heat sources have been added annually and in 2015 the predicted heat injection (3.6 GWh/year) will be reached. Performed simulations are based on actual heat injection and extraction. The simulation model can reasonably well predict the future operation of the BTES. Initial problems with circulating the heat carrier at a slight vacuum pressure have been solved by using vacuum pumps to degas the fluid. The BTES has reduced the amount of bought district heating by approximately 4 GWh/year. To improve the system further, and reduce heat losses, it is suggested that a heat pump should be installed for heat extraction.

The Emmaboda HT-BTES was taken into operation 2010. Since then ~10 GWh has been stored, only a fraction has been extracted, and a storage temperature of 40-45 oC has been reached. The purpose of the BTES is to utilize waste heat from the industrial processes. Heat sources have been added annually and in 2015 the predicted heat injection (3.6 GWh/year) will be reached. Performed simulations are based on actual heat injection and extraction. The simulation model can reasonably well predict the future operation of the BTES. Initial problems with circulating the heat carrier at a slight vacuum pressure have been solved by using vacuum pumps to degas the fluid. The BTES has reduced the amount of bought district heating by approximately 4 GWh/year. To improve the system further, and reduce heat losses, it is suggested that a heat pump should be installed for heat extraction.

In this work, the transient forced convection from vertical boreholes is investigatedby numerical simulation. The actual borehole geometry is accounted for, resultingin perturbed flow and temperature fields. The present results are compared withthe analytical line heat source model derived by Diao et al. (2004). A wide rangeof viable Peclet numbers is considered.

Groundwater advection is commonly neglected in the design of ground-coupled, vertical borehole heat exchangers. In this work, the efficiency of heat transfer from a vertical borehole with groundwater advection is investigated by numerical simulations. The actual borehole geometry is accounted for, resulting in a perturbed flow field. The present results are compared with the analytical solution for the transient, two-dimensional heat convection around a line heat source derived by Diao et al. (2004). A wide range of viable Peclet numbers is considered.