SALTME PLUS

Molten salt metal for energy storage - increasing storage efficiency (SALTME PLUS)

Joint project coordination
TUD Dresden University of Technology - Chair of Hydrogen and Nuclear Energy Technology (TUD-WKET)

Motivation

Temporary storage of electrical energy is necessary in energy systems dominated by volatile sources in order to balance supply and demand. Intermediate thermal storage in molten salt is one way of ensuring that subsequent electricity generation is continuous and independent of daily cyclical fluctuations.

Molten nitrate salts are currently often used for high-temperature applications such as solar-generated heat. The reasons for this are the high volumetric heat capacity, the high boiling point, the relatively good temperature stability and the very low vapor pressure of these salts. Nitrate salts are inexpensive, readily available and neither toxic nor flammable. However, molten salts have a high viscosity and low thermal conductivity compared to other liquids. In addition, the maximum operating temperature of nitrate salts is limited. This restricts the achievable storage efficiency, as the conversion of heat to electricity is typically Carnot-limited.

To improve efficiency when using molten salts as heat storage, heat transfer media for higher operating temperatures are required. Chloride salts appear to be an alternative under these boundary conditions, as they allow significantly higher storage temperatures compared to nitrate salts, are inexpensive, readily available and non-flammable. However, their stronger corrosive effect on construction materials is a disadvantage. This increased corrosiveness means that the efficient use of chloride salts as a heat storage and heat transfer medium is offset by higher costs for the necessary structural materials.

Project objectives

The overall aim of the project is to develop methods for active corrosion protection by modifying the chloride salt. First of all, electrochemical cells are to be developed and constructed to investigate the planned approaches on a laboratory scale. The results are then to be validated in long-term static exposure tests. Based on this, scaling up to small-scale production and techno-economic evaluation will follow.

Project partners

The project is being carried out jointly by the Chair of Hydrogen and Nuclear Technology at TUD Dresden University of Technology, the Institute of Fluid Dynamics at the Helmholtz-Zentrum Dresden-Rossendorf and the Institut für Korrosionsschutz Dresden GmbH. The Chair of Hydrogen and Nuclear Energy Technology at TUD Dresden University of Technology is responsible for coordination.