HEATbucket - Urban underground thermal energy storages to enable energy transition

Starting point / motivation

The very positive development in the expansion and extension of renewable energy sources in terms of sustainability will sooner or later result in a considerable deficit in storage options, which in turn can potentially Iead to a waste of available primary energy.

For example, energy obtained from photovoltaic systems in the form of electricity is often not used at the time it is generated, which usually results in unwanted voltage peaks in the local supply grid caused by the feed of excess energy.

This can currently be remedied mainly through the use of battery systems. Alternatively, it would be possible to store the energy generated as heat using power-to-heat or to convert the power of the sun directly into thermal energy using solar thermal energy. However, new developments are also needed in the area of sustainable heat storages.

Contents and goals

The HEATbucket project addresses this problem and focuses on the development of possible heat storage solutions for urban areas based on a practical approach. The problem is primarily considered from a structural, thermodynamic and hydrogeological perspective, taking into account the technical equipment required for heat storage systems.

The aim of the project is to explore the possibilities of underground heat storage in urban areas and to make the best possible use of them. The evaluation of different system combinations plays a key role here.

Methods

A feasibility study and potential analysis of underground heat storage systems in densely populated areas is to be carried out. On the one hand, the possibility of a pure hot water storage system and, on the other hand, the use of the existing subsoil (soil & groundwater) as a storage medium will be investigated.

Furthermore, different forms of construction, i.e. individual larger storage units, parallel connection of several smaller battery storage units and the serial connection of several individual storage cells, depending on the footprint and the space available, will be examined.

The project thus achieves the presentation of several proposed solutions for the inner city application of underground heat storage systems. Due to the extremely valuable groundwater resources in Austria, a comprehensive study on the influence of the storage systems on the surrounding groundwater is also being considered. The extent to which the groundwater can or must be protected in order not to damage it will be discussed. Concerning this, solutions are to be developed which make it possible to keep the temperature of the groundwater within an acceptable range.

ln addition, the technology of thermal component activation, which is becoming increasingly widespread in geotechnical engineering, will also be examined. All these investigations will be realized by laboratory scale tests as well as by the use of numerical calculation models.

Expected results

The findings from the evaluation of different system combinations should provide the necessary planning basis for future structures of the respective type. ln addition, the focus is on supporting the creation of future regulations, with Stakeholders already being involved in the ongoing project in order to raise their awareness and initiate the process.

Project management

Dr. Matthias Rebhan, Graz University of Technology - Institute of Soil Mechanics, Foundation Engineering and Computational Geotechnics

Project or cooperation partners

• ACI Monitoring GmbH
• AEE - Institut für Nachhaltige Technologien (kurz: AEE INTEC
• AIT Austrian Institute of Technology GmbH
• BAUER SPEZIALTIEFBAU Gesellschaft m.b.H.
• Herrenknecht AG
• University of Graz – Department of Earth Sciences

Graz University of Technology
Institute of Soil Mechanics, Foundation Engineering and Computational Geotechnics
Rechbauerstraße 12
A-8010 Graz
Tel.: +43 (316) 873 6738
E-mail: soil@tugraz.at
Web: www.soil.tugraz.at