Energy supply concepts based on shallow geothermal energy for existing urban districts

In order to achieve climate targets in the building sector in Germany, a significantly greater market penetration of heat pumps in existing buildings is necessary. In this respect , the conversion of existing heat supply structures to geothermal-based heat pump systems plays a central role due to their high efficiency, especially for small and larger districts. Using model-based potential studies, the feasibility of central and decentral heat pump systems has been investigated for five existing districts spread out over Ger-many. Starting with the evaluation of the existing buildings and the energetic quality of their building envelopes and supply systems, a demand-consumption adaptation has been done using provided energy consumption reports. Geothermal properties, regulatory conditions as well as the area availability within the districts are describing the potentials of the geothermal energy sources and represent the basis for designing the energy supply concepts. Hereby, centralized concepts with cold and low temperature grids, both with and without active regeneration using solar thermal collectors, are compared to decentral geothermal concepts and air-to-water heat pump systems. In a first step, the assessment of the concepts is focusing on energetic, ecologic and economic aspects. Especially regarding economic aspects, different operating models of energy suppliers have been evaluated considering flexible energy prizing and investment sharing between the different stakeholders as well as the impact of the different heating supply concepts on the maximum grid load. In a second step, a multi-criteria analysis has been established considering further aspects like preferences of building owners or future retrofit plans. Based on this, design criteria considering different district properties have been developed and integrated into a design guide for geothermal systems for the heat supply of existing districts.