Some of the heat generated by STEAG New Energies GmbH’s cogeneration plant Wellesweiler is supplied to a plastic film manufacturing plant. The uninterrupted supply of steam required for this has so far been provided through the continuous operation of a boiler under minimal load. In the event of a failure, this steps in until the boiler has started up again - an energy- and fuel-intensive concept.

Within the scope of the research project TESIN (Thermal Energy Storage for Increasing the Energy Efficiency in Cogeneration Plants and Electric Steelworks), a new latent heat storage system with a capacity of 1.5 MWh was developed, whose high performance and fast switching time meet the high, specific demands of the CHP plant. The idea is that, within just two minutes, it is able to produce and supply its superheated steam for a period of at least 15 minutes. Based on the concept of a tube heat exchanger, water or steam in the tubes absorbs heat in the form of sodium nitrate. This melts at approx. 305 degrees Celsius and can absorb large amounts of energy which is released as heat upon discharge. A high yield is ensured by the ribbed structure on the tubes, which was co-developed and produced by the project partner F.W. Brökelmann.

Extensive planning and analyses, for instance to explore its technical-economic potential, preceded the design of the storage tank. Finally, precautions had to be taken to ensure the safe transportation of a newly developed latent storage tank from the Bavarian production site to the CHP plant in Saarland. In autumn 2018, the project partner Steag New Energies GmbH will start physically connecting the storage unit with the CHP plant. Commissioning and the first trials are scheduled for 2019.

The project is being funded between May 2013 until January 2020 by the Federal Ministry for Economic Affairs and Energy (BMWi) within the scope of the Energy Storage Initiative.