**6. Conclusions**

The global energy oil production is unstable and will peak within a few years. Therefore, the energy prices are expected to rise and new energy systems are needed. In addition to this energy crisis the fossil fuels seems to be the main reason for climate change. There is a global political understanding that we need to replace fossil fuels by renewable energy systems in order to develop a stable and sustainable energy supply.

About half of the global energy consumption is used for space heating and space cooling systems. Ground source heat pump systems are considered as an energy system that can make huge contributions to reduce energy consumption and thereby save the environment.

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