Ultra-high temperature thermal energy storage. Part 2: Engineering and operation

The storage of energy at ultra-high temperatures offers many benefits including high energy density and efficient conversion to and from electricity that can be further enhanced by cogeneration. In addition to this, an Ultra-High Temperate thermal energy Storage (UHTS) system would be clean, closed, and reversible and could be built with abundant low cost materials. However, operation at ultra-high temperature is challenging due to the reduced strength and increased reactivity of materials. This paper discusses how a storage system with useful performance can be engineered. In many cases UHTS components and systems can be created by using existing techniques, but in some areas there are engineering challenges that need to be solved before UHTS can become operational. Once the technical and practical feasibility is investigated, there is a brief assessment of the likely capital cost of implementing the storage system at grid scale. As a compact and closed system, UHTS would be inherently suitable for supplying heat at the point of demand. This offers an opportunity to increase the effective roundtrip efficiency to 95%, which far exceeds most other storage methods Beyond this UHTS could be used to aid the transition of a national energy system to all electric renewable operation. The paper closes with a discussion of the complexities and opportunities brought about by the flexibility of configuration and the transient thermal nature of UHTS.