Response testing and evaluation of groundwater-filled boreholes. Development and validation of a new caculation tool.

Sammanfattning: Ground source heat pump, GSHP, systems are an interesting alternative in the energysector compared to other heating and cooling systems due to the fact they areconsidered to be energy efficient technologies. The use of GSHP systems, in comparisonto the use of more conventional cooling and heating systems, could result in adecrease of emissions according to the U.S. Environmental Protection Agency, EPA.The design of a ground source heat pump system will depend on the groundthermal properties. These properties include ground thermal conductivity, boreholethermal resistance and the undisturbed temperature of the ground. These propertiesare commonly estimated from in-situ thermal response tests, TRTs. Numerous methodshave been developed to evaluate the experimental data obtained from thermalresponse tests.This Master's Thesis presents a comparison of some of the commonly used methodsfor the evaluation of ground thermal properties. A new method has also beenpresented to evaluate experimental data obtained from TRTs. The method is basedon mathematical models developed by Javed and Claesson and considers the thermalcapacities, resistances and properties of all the borehole elements. The newmethod has been programmed in the software MATLAB and has been comparedto the existing methods. The evaluation of these methods have been performed usingexperimental data obtained from dierent in-situ TRTs. The TRTs have beenperformed both for single and multiple injection rates, in increasing and decreasinginjection modes. The estimated ground thermal properties have then been used tomodel a GSHP system where the size of the system obtained from the dierent methodshave been compared to each other. The GSHP systems have been modeled inthe software, Earth Energy Designer, EED.The results show that the existing methods give similar results when the evaluationis performed for single injection rates. This is also true for the new method. Themultiple injection rates in increasing mode gave similar results as the values estimatedfrom the single injection rates. The multiple injection rate performed in decreasingmode showed that the existing methods give inconsistent results of the ground thermalproperties. The new method however, gave more consistent results. The EEDcalculations showed that the borehole lengths obtained from the new method can becompared to the existing methods already used today and that the borehole lengthvariations between the methods do not vary more than 10 % from each other. Javedet al. observed that uncertainties of this magnitude can be expected in this type ofcomparisons.The analysis in this Master's Thesis have showed that the new TRT evaluationapproach can be compared to the existing methods already used today. The newmethod show good evaluation properties for multiple injection rates compared to theexisting methods since they can have problems with the evaluation of groundwater-lled boreholes. Besides the results of the comparison a software tutorial is presentedof the new evaluation method.