Assessment of the ground source heat potential at building level applied to an urban case study
- Conference Paper
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Ground source heat pumps (GSHPs) are gaining popularity as urban energy systems move towards decentralization. As compared to the ambient air temperature, the ground remains at a higher temperature during the winter, and at a lower temperature during the summer, which makes GSHPs an ideal choice for both heating and cooling. The calculation of the amount of ground heat which is available for the design of borehole fields is a key input to perform an energy balance of a building and to effectively install GSHPs. Besides the net heating/cooling demand of the building, the design of GSHPs requires the ground properties and the type of technology employed. The installation of multiple GSHPs within the larger context of an urban energy planning exercise is however a challenging task, due to the influence of neighbouring buildings and cooling of the ground due to extensive heat extraction. Within the present study a GIS based workflow is developed for the design and spatial arrangement of boreholes for single buildings in a large urban area. The methodology is applied to a part of a district of Zürich city, called Altstetten, with approximately 170 residential buildings. The model takes as input the hourly net heating and cooling energy demand of each building. The heating energy demand includes space heating and domestic hot water requirements. The spatial variation of ground thermal properties and the spatial drilling depth restrictions by law are taken into account in the modelling process in the form of spatially differentiated GIS layers. A detailed thermal model based on the Eskilson’s g-functions is used to calculate the appropriate length for different values of the separation distance. The long term effects of cooling of the ground due to the heat extraction from the borehole is important for a sustainable operation of the system. These effects are modelled within the design procedure. The model also evaluates the operation of the GSHPs and the actual heat potential available for each building is derived. This study provides a general modelling technique which can be implemented in any GIS platform to outline the available GSHP potential for the respective urban area. It also demonstrates the developed method through its application on a large scale case study. Show more
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Organisational unitETH Zürich
NotesConference lecture on 8 September 2017.
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