Large-Scale Geothermal Collector Systems for 5th Generation District Heating and Cooling Networks

Abstract

Low temperature district heating and cooling networks (5GDHC) in combination with very shallow geothermal energy potentials enable the complete renewable heating and cooling supply of settlements up to entire city districts. With the help of 5GDHC, heating and cooling can be distributed at a low temperature level with almost no distribution losses and made useable to consumers via decentralized heat pumps (HP). Numerous renewable heat sources, from wastewater heat exchangers and low-temperature industrial waste heat to borehole heat exchangers and large-scale geothermal collector systems (LSC), can be used for these networks. The use of large-scale geothermal collector systems also offers the opportunity to shift heating and cooling loads seasonally, contributing to flexibility in the heating network. In addition, the soil can be cooled below freezing point due to the strong regeneration caused by the solar irradiation. Multilayer geothermal collector systems can be used to deliberately generate excessive cooling of individual areas in order to provide cooling energy for residential buildings, office complexes or industrial applications. Planning these systems requires expertise and understanding regarding the interaction of these technologies in the overall system. This paper provides a summary of experience in planning 5GDHC with large-scale geothermal collector systems as well as other renewable heat sources.

Survey of 53 Fifth‐Generation District Heating and Cooling (5GDHC) Networks in Germany

“…Figure 3 ): In 23 of the 53 districts, horizontal geothermal collectors are installed. For a detailed review of geothermal collectors, we refer to ref [15]. If geothermal collector tubes are installed in multiple layers and in close proximity, the surrounding ground freezes in winter.…”

“…For a detailed review of geothermal collectors, we refer to ref. [15] If geothermal collector tubes are installed in multiple layers and in close proximity, the surrounding ground freezes in winter. This further increases the heat potential and is often described as earth ice storage.…”

“…Twelve systems are operated with fixed temperatures and 16 networks with seasonal shifting temperatures. In the article by Zeh et al, [ 15 ] the 5GDHC systems surveyed by Buffa et al are visualized on a map.…”

“…There are many theoretical studies on 5GDHC systems, which mainly focus on the development of simulation [ 4,8–11 ] and mathematical optimization models. [ 1,12 ] Some studies present operational optimization models, [ 13,14 ] while other publications provide real‐world experience from a practical planning perspective: Zeh et al [ 15 ] discuss the planning of the 5GDHC network in Wüstenrot (Germany) and their experience with installing the first large‐scale agrothermal collector with a used land area of 4400 m 2 and a depth of 1.5 m. The Wüstenrot district is also discussed by Brennenstuhl et al [ 16 ] They also provide detailed information about two other geothermal collector systems in the cities Neustadt am Rübenberge and Bad Nauheim. Then et al [ 17 ] provide a technical description of the 5GDHC network in the district Largarde‐Campus in Bamberg, in which geothermal probes and horizontal collectors as well as sewage water is used as the heat source.…”

“…

There are many theoretical studies on 5GDHC systems, which mainly focus on the development of simulation [4,[8][9][10][11] and mathematical optimization models. [1,12] Some studies present operational optimization models, [13,14] while other publications provide real-world experience from a practical planning perspective: Zeh et al [15] discuss the planning of the 5GDHC network in

…”