SALTME PLUS

Liquid metal-molten salt mixtures for energy storage – Increasing the storage efficiency (SALTME PLUS)

Motivation

The temporary storage of electrical energy is necessary in energy systems dominated by volatile sources in order to balance supply and demand. Thermal storage in molten salts is one option for ensuring continuous power generation regardless of daily 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, high boiling point, the high temperature stability, and very low vapor pressure of these salts. Nitrate salts are inexpensive, readily available, and neither toxic nor flammable. However, compared to other liquids, molten salts show high viscosity and low thermal conductivity. 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.

In order to improve the efficiency of using molten salts as heat storage media, heat transfer media for higher operating temperatures are required. Chloride salts appear to be an alternative under these conditions, as they enable significantly higher storage temperatures than nitrate salts, are inexpensive, readily available, and do not promote combustion. However, their greater corrosive effect on construction materials is a disadvantage. The increased corrosivity means that the efficient use of chloride salts as heat storage and heat transfer media is offset by higher costs for the necessary structural materials.

Project objectives

The overall objective of the project is to develop methods for active corrosion protection by modifying the molten chloride salt. The first step is to develop and build electrochemical cells that will be used to investigate the proposed approaches on a laboratory scale. The results will then be validated in long-term static exposure tests. Based on this, the methods will be scaled up to a small technical scale and evaluated in terms of their techno-economic viability.

Project partners

This is a joint project of the Chair of Hydrogen and Nuclear Energy (TU Dresden), the Institute of Fluid Dynamics (Helmholtz-Zentrum Dresden-Rossendorf) and the Institut für Korrosionsschutz Dresden GmbH, coordinated by the Chair of Hydrogen and Nuclear Energy (TU Dresden).