Electricity to heat technologies with salt storage for use in industry and PV CSP hybrid power plants

Project duration: May 2018 – July 2021

The industrial sector accounts for about 30 % of the final energy demand of the Federal Republic of Germany. Of this, about 66 % is used for the generation of process heat, often resulting in large amounts of waste heat. With a new innovative technology - a high-temperature heat pump in combination with a salt storage tank - waste heat is brought to a temperature of over 500 °C and stored. The discharge of the storage tank takes place depending on the demand. As a reference to the electricity-to-heat technology under investigation, a commercial resistance heater is used to generate heat, which is also temporarily stored in a molten salt storage. In this way, both technologies make it possible to use surplus electricity from renewable energies and ensure grid stability.
In the SWS project, it was demonstrated that P2H systems combined with molten salt storage can be used advantageously for waste heat utilization, reduction of fuel demand and grid stabilization at the industrial site NRW. This main objective was achieved in the project, among other things, on the basis of a market study and by simulating real and theoretical application cases.
As part of a market study for the NRW location, potential industrial companies that could benefit from these systems were first identified. Subsequently, the use of P2H systems with molten salt storage and the combination with waste heat recovery strategies was simulated for selected industrial companies and industrial processes and the economic efficiency as well as the fuel savings were calculated for these cases.
Furthermore, it was demonstrated that a thermodynamically coupled PV-CSP hybrid power plant with P2H system can be economically viable, thus contributing to an accelerated implementation of CSP technology. A favored circuit design for each P2H unit was developed and verified by simulations.
High-temperature heat pumps for medium- and high-temperature applications are not commercially available, but show economic and environmental potential. The project determined that the working fluids of air, nitrogen, and argon in a Joule cycle have very high potential for use in such systems.
The economic analysis showed that the high-temperature heat pump systems investigated in this project are only competitive with electric resistance heaters if the specific investment costs of the high-temperature heat pumps are not significantly higher than the investment costs for electric resistance heaters (by a factor of 2 to 2.5 at most).

Project partners:
- Solar Institut Jülich of FH Aachen
- German Aerospace Center e. V.
With funding by the Ministry of Economic Affairs, Innovation, Digitization and Energy of North Rhine-Westphalia using ERDF funds.

German Aerospace Center e. V. Solar Institut Jülich of FH Aachen