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Geothermal energy - influence of the borehole geometry
Leiter, Augustin ; Frankovská,, Jana (referee) ; Hrubešová,, Eva (referee) ; Miča, Lumír (advisor)
Geothermal energy is one of the oldest forms of energy on our planet. Its use by humanity dates back to the beginning of the ages. The forms of this energy gradually changed from the direct heat of the hot springs, through the heating of the buildings and the baths to the later use of superheated steam for industrial use. Nowadays, there is a large share of the use of large number of ground geothermal boreholes with heat exchangers drilled in the matrix. The geometric arrangement of such system has a considerable impact on its operation. Specific examples show that, unlike the design, actual boreholes in such system can often be drilled non vertically or even curved. These imperfections then usually deteriorate the thermal properties of the system. This thesis demonstrates the influence analysis of the borehole geometry distortion on the system thermal properties, it also informs about the development of a special measuring device designed to obtain information about the actual geometric shape of the investigated borehole and about the development of software for in situ rapid borehole system properties evaluation. The theoretical part of thesis contains the derivation of a simplified numerical model of heat conduction in the vicinity of the borehole system. Its results serve to compare the different borehole variants and the inaccuracy of borehole shaping. Using the simulations, the influence of inaccuracies in the borehole system on its thermal properties is demonstrated in several model configurations. This effect does not occur in a single borehole, but it is significantly visible in organized geothermal borehole systems. It may deteriorate system properties, but under certain circumstances its properties may improve. Verification of the results of these simulations was performed by the FEFLOW simulation software. In the practical part the development of a special instrument for measuring the shape of a geothermal energy borehole is documented. ....
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Geothermal energy - influence of the borehole geometry
Leiter, Augustin ; Frankovská,, Jana (referee) ; Hrubešová,, Eva (referee) ; Miča, Lumír (advisor)
Geothermal energy is one of the oldest forms of energy on our planet. Its use by humanity dates back to the beginning of the ages. The forms of this energy gradually changed from the direct heat of the hot springs, through the heating of the buildings and the baths to the later use of superheated steam for industrial use. Nowadays, there is a large share of the use of large number of ground geothermal boreholes with heat exchangers drilled in the matrix. The geometric arrangement of such system has a considerable impact on its operation. Specific examples show that, unlike the design, actual boreholes in such system can often be drilled non vertically or even curved. These imperfections then usually deteriorate the thermal properties of the system. This thesis demonstrates the influence analysis of the borehole geometry distortion on the system thermal properties, it also informs about the development of a special measuring device designed to obtain information about the actual geometric shape of the investigated borehole and about the development of software for in situ rapid borehole system properties evaluation. The theoretical part of thesis contains the derivation of a simplified numerical model of heat conduction in the vicinity of the borehole system. Its results serve to compare the different borehole variants and the inaccuracy of borehole shaping. Using the simulations, the influence of inaccuracies in the borehole system on its thermal properties is demonstrated in several model configurations. This effect does not occur in a single borehole, but it is significantly visible in organized geothermal borehole systems. It may deteriorate system properties, but under certain circumstances its properties may improve. Verification of the results of these simulations was performed by the FEFLOW simulation software. In the practical part the development of a special instrument for measuring the shape of a geothermal energy borehole is documented. ....
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