In heat supply systems with combined heat and power generation, thermal solar systems and industrial processes, surpluses of heat are available to a considerable extent. Via heat storage, this heat can be delivered to consumers at a later point in time. This time shift in heat use enables to significantly increase the efficiency of fuel conversion as well as the percentage of renewable energy sources in a heat supply system.
For this reason, efficient heat stores at low investment costs are required. Besides its energetic requirements, the thermal energy store is also supposed to handle tasks relevant to the complete heat supply system, e.g. pressure maintenance and emergency operation. These tasks will be very important in the future.
Objectives of the joint research project
A novel overground tank store covering the volume range 500...6000 m³ shall be developed within the research project. A segmental construction for thermal energy stores applicable for temperatures of up to 98 °C requires to cope with significant technical challenges, e.g. a temperature-resistant segment sealing and the lack of constructional solutions. In addition, the project partners pursue the objective to implement the following features for the thermal energy store:
- excellent functionality (e.g. low heat losses, high charging power, permanent tightness, preservation of water quality)
- relatively low costs for the build-up of the store
- minimum use of materials
- efficient execution process
- use at various sites, a broad range of applications
- simple adaption to short-term and long-term heat storage
The following main tasks are part of the thermal energy store's development mentioned above:
- tests of sealing and thermal insulation materials as well as tests of wall constructions
- further development of charging and discharging systems including hydraulic integration
- complete revision of the thermal energy store's construction and build-up technology
- development of a demonstration unit and practical tests of all its components
- measures for the improvement of planning, calculation and simulation
- public relations work
Explanation of technology
In heat supply systems with supply temperatures below 100 °C, it is advantageous to realize large (overground) thermal energy stores as flat-bottom tanks. The compact shape allows for very low build-up costs and low heat losses.
An interesting alternative for welded wall constructions is the assembly of screwed segments. In recent years, many projects with large cold water stores have shown the practical advantages of this store construction technology:
- flexible adaption to size and shape of the store
- highly dynamic charging and discharging power
- efficient use of the store volume with thermal stratification and adherence to scheduled supply temperatures
- adequate adaption to the respective case of application (public supply services, local supply systems, industrial supply systems)
- fast and efficient build-up with minimum use of materials
- low follow-up costs (simple legal permission, operation and monitoring, etc.)
- possibility for repair (compared to underground stores)
- excellent quality control during prefabrication and on bulding site
Currently, the main challenge is the fact that the store construction mentioned above is not applicable to stores with high store temperatures (up to 98 °C). This and further challenges are to be solved in this research project. As a proof of concept, a demonstration unit (pilot store for the execution of practical tests) has to be built up during the project.
The project started on November 1, 2014 und will end on May 31, 2018.
Coordination and lead of project part "Accompanying research A"
Prof. Dr.-Ing. habil. Thorsten Urbaneck
Technical University of Chemnitz
Faculty of Mechanical Engineering
Professorship for Technical Thermodynamics
Lead of project part "Accompanying research B"
Dr.-Ing. Harald Drück
University of Stuttgart
Institute of Thermodynamics and Thermal Engineering (ITW)
Research and Testing Centre for Thermal Solar Systems (TZS)
Lead of project part "Practical development and demonstration"
farmatic tank systems
Fechtelkord & Eggersmann GmbH
Financial support and project management
The project is funded within the energy storage initiative (German: Energiespeicherinitiative) of the Federal Government.
Energy stores for stationary and mobile applications - an initiative of the German Federal Ministry for Economic Affairs and Energy (BMWi) as part of the 6th Energy research programme of the Federal Government
Grant number: 03ET1230 A/B/C