The project HyStEPs is part of the NEFI Energy Model Region for the Decarbonization of manufacturing and energy-intensive industry. Therein, novel efficient thermal energy storage technologies for industrial processes are developed. The motivation for new innovative solutions is, on the one hand, the increase in the share of renewable energy sources in the power grid and, on the other hand, ongoing decarbonization efforts. Both factors will require a drastic increase in the capacity of thermal energy storage in existing industrial plants or industrial processes in the future.

With HyStEPs, an innovative hybrid storage concept was developed and tested in order to increase the storage capacity of so-called „Ruths steam accumulators“ by up to 40%. To this end, a storage unit was encased in latent heat storage elements as a laboratory prototype. These special storage elements contain phase change material (PCM), in this case salt hydrates, which feature a high storage density. The PCM containers make it possible to store significantly larger amounts of energy with approximately the same size. The loading and unloading behavior of the steam accumulator should remain as unchanged as possible even with the increased storage capacity.

A prototype of the novel hybrid storage was built and tested at the steel production facility voestalpine Stahl Donawitz GmbH in Leoben, Austria. For this purpose, steam was diverted from the existing steam network and fed into the storage unit under laboratory conditions. Both the steam accumulator and the PCM elements are connected to a large number of measuring devices in order to be able to record the thermodynamic state of the accumulator at any time and to determine its dynamic behavior. On the basis of the findings obtained here, the concept is to be further developed and transferred to other storage facilities.

The following aspects were the main focus points of the project:

  • Thermal connection of the latent heat storage elements to the steam accumulator
  • Increase of the thermal conductivity of the phase change material by heat conduction structures
  • Corrosion behavior of the material combinations
  • Strength calculations
  • New methods for mathematical modeling, simulation and control of the behavior of hybrid storage systems
Hybride storage concept

© voestalpine & AIT/ Kiedl & Drexler-Schmid

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HyStEPs - A novel hybrid thermal energy storage prototype for efficient industrial processes

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