Deutsche Version  ACT
Thermal Storage
Industrial waste heat utilisation 12.9.2017

The figure shows solid material sampled to determine heat capacity.
© ZAE Bayern

Foundry using waste heat of the furnace

In energy-intensive industries, e.g. foundry industry or cement

industry, the use of waste heat for example as process or space heating

energy reduces the consumption of primary energy.  In the Project “IAST”

researchers are testing an energy storage system for discontinuous

industrial waste heat of a furnace at a foundry. The implementation and

commissioning is expected to start at the end of 2014.

Project status Development
Storage type Solid material in direct contact with the heat transfer medium
Research objective Storage material, steel storage construction
Temperature type High temperature
Storage/Charging Direct
Storage time Short (hours to days)
Number of cycles Daily
Charging temperature Up to 300°C
Discharge temperature < 100°
Storage capacity 10MWh
Energy storage density 0,6kWh/m³K
Project duration June 2013 until November 2018

In energy-intensive industries (e.g. foundry industry, cement industry, etc.) the use of waste heat for example as process or space heating energy reduces the consumption of primary energy and the greenhouse gas emissions. Especially the use of discontinuous waste heat (> 100 ° C) by thermal energy storage is an already frequently discussed and theoretically considered field in which only a few industrial applications can be found. The main reasons are the high investment costs of available storage technologies that can be used for temperatures above 100 ° C. Another reason is the comparatively low energy costs for gas and electricity in the field of the energy-intensive industry. If there is a low number of cycles (loading and unloading) of the thermal energy storage an economic operation is difficult to achieve. The development of an effective thermal energy storage, the recovery of as many waste heat sources as possible and the identification of suitable heat customers and their intelligent combination within an energy system is therefore a prerequisite for an economic use of waste heat by thermal energy storage.

  • Temperature characteristic of the available waste heat at the foundry Heunisch &copy; ZAE Bayern
  • Influence of the solid material packed bed on cost and storage capacity compared to a conventional thermal oil storage. &copy; ZAE Bayern
  • Schematic diagramm of a dual media thermal storage &copy; ZAE Bayern
  • The figure shows solid material sampled to determine heat capacity. &copy; ZAE Bayern
  • Thermal conductivity measurement of different rock types &copy; ZAE Bayern

In this collaboration project with the Giesserei Heunisch, the ZAE Bayern and the Fa. Küttner as plant constructor an energy storage system for discontinuous industrial waste heat recovery will be developed and tested in a pilot plant. The energy system stores the waste heat of a furnace at the foundry Heunisch. During the downtime of the furnace it allows to continue using waste heat for process/space heating and process cooling. This will be achieved through the use of innovative technologies in the field of heat storage (up to 300 ° C) and heat transformation and its effective linkage with heat sinks and sources controlled by a higher-level energy management system.

High temperature heat storage is the core of the system

In the collaboration project the development and implementation of an innovative energy storage system for recovering discontinuous industrial waste heat is planned. The Core component of the system is a high temperature heat storage (up to 300 ° C). This should be realized as a so-called dual-media thermal energy storage with a packed bed in direct contact with a heat transfer medium. This non pressurized design offers considerable advantages over alternative storage concepts (e.g. pressurized water storage or thermal oil -storage ) especially in terms of manufacturing costs by using inexpensive solid materials as packed bed (e.g. rock). Another focus of the project is the adaptation of an absorption heat pump for operating with thermal oil as heat transfer medium. This heat pump provides process cooling and space heating at various temperatures. Thereby the stored waste heat can be used in different ways.

During the development phase of the energy system and its components the economic viability and durability plays a decisive role. During the testing phase under real running conditions the economic evaluation of system will be focused.

The project is divided into 4 phases: concept and development phase, implementation and commissioning, testing phase, assessment phase. Currently, the project is in the design and development phase. The implementation and commissioning is expected to start at the end of 2014.

Sub-projects: Development, adaption and testing

Development and test of the high temperature thermal energy storage
At the ZAE Bayern laboratory tests are carried out for develop the high temperature thermal energy storage. For the identification of suitable solid materials a test facility to determine the chemical stability and thermal cycle stability is necessary. A thermal storage test facility to investigate the influence of solid materials on packed bed density, pressure drop and the characteristic of the thermal storage system in terms of performance and capacity is also planned. Open questions for example: how to fill in the packed bed, system for loading and unloading, how to control volume expansion / thermal stresses will be locked at and discussed and technical solutions will be developed.

Adaptation absorption chiller / heat pump
The absorption heat pump will be driven by thermal oil as heat transfer medium instead of hot water, steam or flue gas. Because of this, both the concept of the heat exchange in the absorption heat pump and the dimensions of the required heat exchanger must be adapted. In addition to this the absorption heat pump needs to be adjusted at the required temperature levels (cooling mode: ~5 °C, re-cooling at about 40 °C, heating mode: ~85 °C, low temperature source at about 30 °C).

Testing the energy system under real operating conditions
After the commissioning of the energy storage system the testing of the demonstration plant starts under real operating conditions. During this phase of the project a continuous technical and scientific support of the plant takes place. Based on a monitoring system the energy storage system will be analyzed. The aim is an ecological / economic assessment of demonstration plant as well as the identification of optimization potential and their implementation respectively the identification of further research and development aspects.

Supported by: The Federal Government on the basis of a decision by the German Bundestag


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  • Richard Gurtner
    ZAE Bayern - Bayrisches Zentrum für Angewandte Energieforschung e. V.
Other Addresses


Research funding

The information system EnArgus provides information on research funding, including on this project (German only).