Nowadays Ground Source Heat Pumps (GSHP) are widely used to provide heating and/or cooling as well as domestic hot water in commercial and residential buildings. The Swedish GSHPs market is the first one in the European Union with more than 378,000 units installed until 2010 according to the Swedish Heat Pump Association (SVEP). This thesis focuses on the improvement of a Thermal Response Test (TRT) apparatus available at KTH Royal Institute of Technology – Energy Technology Department. This equipment aims at improving Borehole Heat Exchanger (BHE) design in terms of size. Its key purpose is to evaluate two main BHE properties: the ground thermal conductivity and the borehole thermal resistance. A new command software is developed in order to control the TRT equipment and run TRT measurements. This new software is developed using Python as programming language and replaces an older program which needed LabVIEW to run. The TRT command software designed in this thesis provides the user with a simple and user-friendly interface to control each device of the equipment. Measurements are exported and saved to files which can be open with both Microsoft Excel and the analysis tool also developed in this thesis. The stand-alone evaluation tool can be used to analyse TRT and/or DTRT measurements. This analysis tool helps the user to compute large amount of data with few data manipulation and low computation time. Model parameters and TRT/DTRT measurement can be imported from files into it and different fitting settings are available to run the optimization, i.e. account for baseline variations (early activities in the borehole, different optimization periods, analysis during thermal recovery of the ground, single/multi-sectional analysis along the depth, among others). This report covers a theoretical description of TRT experiments and its models, the objectives of such a project and the development of the control and evaluation tools.

<p>The sales of Ground Source Heat Pumps in Sweden and many other countries are having a rapid growth in the last decade. Today, there are approximately 360 000 systems installed in Sweden, with a growing rate of about 30 000 installations per year. The most common way to exchange heat with the bedrock in ground source heat pump applications is circulating a secondary fluid through a Borehole Heat Exchanger (BHE), a closed loop in a vertical borehole. The fluid transports the heat from the ground to a certain heating and/or cooling application. A fluid with one degree higher or lower temperature coming out from the borehole may represent a 2-3% change in the COP of a heat pump system. It is therefore of great relevance to design cost effective and easy to install borehole heat exchangers. U-pipe BHEs consisting of two equal cylindrical pipes connected together at the borehole bottom have dominated the market for several years in spite of their relatively poor thermal performance and, still, there exist many uncertainties about how to optimize them. Although more efficient BHEs have been discussed for many years, the introduction of new designs has been practically lacking. However, the interest for innovation within this field is increasing nowadays and more effective methods for injecting or extracting heat into/from the ground (better BHEs) with smaller temperature differences between the heat secondary fluid and the surrounding bedrock must be suggested for introduction into the market.</p><p>This report presents the analysis of several groundwater filled borehole heat exchangers, including standard and alternative U-pipe configurations (e.g. with spacers, grooves), as well as two coaxial designs. The study embraces measurements of borehole deviation, ground water flow, undisturbed ground temperature profile, secondary fluid and groundwater temperature variations in time, theoretical analyses with a FEM software, Distributed Thermal Response Test (DTRT), and pressure drop. Significant attention is devoted to distributed temperature measurements using optic fiber cables along the BHEs during heat extraction and heat injection from and to the ground.</p> / QC 20100517 / EFFSYS2 / Efficient Use of Energy Wells for Heat Pumps

The sales of Ground Source Heat Pumps in Sweden and many other countries are having a rapid growth in the last decade. Today, there are approximately 360 000 systems installed in Sweden, with a growing rate of about 30 000 installations per year. The most common way to exchange heat with the bedrock in ground source heat pump applications is circulating a secondary fluid through a Borehole Heat Exchanger (BHE), a closed loop in a vertical borehole. The fluid transports the heat from the ground to a certain heating and/or cooling application. A fluid with one degree higher or lower temperature coming out from the borehole may represent a 2-3% change in the COP of a heat pump system. It is therefore of great relevance to design cost effective and easy to install borehole heat exchangers. U-pipe BHEs consisting of two equal cylindrical pipes connected together at the borehole bottom have dominated the market for several years in spite of their relatively poor thermal performance and, still, there exist many uncertainties about how to optimize them. Although more efficient BHEs have been discussed for many years, the introduction of new designs has been practically lacking. However, the interest for innovation within this field is increasing nowadays and more effective methods for injecting or extracting heat into/from the ground (better BHEs) with smaller temperature differences between the heat secondary fluid and the surrounding bedrock must be suggested for introduction into the market. This report presents the analysis of several groundwater filled borehole heat exchangers, including standard and alternative U-pipe configurations (e.g. with spacers, grooves), as well as two coaxial designs. The study embraces measurements of borehole deviation, ground water flow, undisturbed ground temperature profile, secondary fluid and groundwater temperature variations in time, theoretical analyses with a FEM software, Distributed Thermal Response Test (DTRT), and pressure drop. Significant attention is devoted to distributed temperature measurements using optic fiber cables along the BHEs during heat extraction and heat injection from and to the ground. / <p>QC 20100517</p> / EFFSYS2 / Efficient Use of Energy Wells for Heat Pumps