Reduction of prime energy consumption by ground source heat pumps in a warmer world

Abstract: SUMMARY Much of the energy used worldwide is supplied by fossil fuels (~85 %) while renewable energy sources supply approximately 6 %. A sustainable future urgently requires worldwide efforts to reduce primary energy consumption and increase use of renewable energy sources. Heating and cooling in the industrial, commercial, and domestic sectors accounts for more than one third of the world’s total energy consumption. Consequently, the implementation of more efficient heating/cooling systems has clear potential to save both energy and the environment. However, the use of renewable energy systems for heating and cooling applications has received relatively little attention compared with other applications such as renewable electricity or biofuels for transportation. Up until now, renewable energy sources supply only around 2-3% of the annual global heating and cooling demand (excluding traditional bioenergy). Heat pump systems are becoming more common for heating and cooling purposes. Such systems extract energy from a relatively cold source to be injected into the conditioned space in winter or alternatively, extract energy from conditioned spaces to be injected into a relatively warm sink in summer. The driving energy of the heat pump strongly depends on the temperature difference between the conditioned space and the heat source/sink. More specifically, extracting heat from warmer source during the winter and injecting heat into colder sink during the summer leads to a better coefficient of performance (COP) and, consequently, less energy use. Since the ground under certain depth is warmer than the air during winter and colder during summer, using the ground as the heat source/sink of the heat pump results in better COP. Due to their high thermal performance compared to conventional heating and cooling systems, ground source heat pump (GSHP) systems are increasingly being used to reduce energy consumption. Essentially GSHP systems refer to a combination of a heat pump and a system for exchanging heat from theground. The GSHPs move heat from the ground to heat buildings and houses in the winter or alternatively, move heat from the buildings and houses to the ground to cool them in the summer. It is worth mentioning that the operating temperature of a borehole field depends on the annual mean air temperature and the ratio of heating to the cooling demand of the buildings. Hence, the ongoing global warming and improvement of the thermal quality of the building envelope have a direct impact on the performance of GSHPs. No GSHP system has yet been built in Syria despite the fact that the local conditions in many ways are more favorable than in for example Sweden, which has the world’s third biggest installed facility. In addition to emphasizing the importance of using ground source heat pumps in reaching the renewable energy goals of mitigating the climate change, the current work: • Reported the first thermal response test (TRT) that was performed in Syria that is required in order to determine the ground thermal properties, which are needed for the proper design of borehole heat; • Provided a simple method that gives the change in ground temperature as a function of the surface warming; • Showed the impact of GW in combination with the building envelope quality on the thermal performance of GSHP and, consequently, on the driving energy of GSHPs; • Introduced a method that can be implemented to improve the thermal characteristics of ground heat exchanger. In order to calculate the effective thermal conductivity of the ground and the thermal resistance of the ground heat exchanger, a computer model was built, which can be used to analyze the experiment data. Furthermore, a new method that can be used to calculate the thermal load of buildings was developed and a computer model was built too.