Why Kyoto chose molten salt for Heatcube

By Camilla Nilsson, 17. Feb 2022

Recent research shows that up to 45% of all industrial heat demand could be electrified. At Kyoto we aim to promote renewable heat powered by renewable energy and stored in the Heatcube thermal battery which has a core of molten salt. But what exactly is molten salt, and why is it the optimal storage medium for our Heatcube?


Novel energy storage technologies present very different characteristics, making them suitable for different applications.[1] Within thermal energy storage technologies the types of storage media are sensible heat storage with molten salts, other rock materials or concrete; latent heat storage by means of inorganic and organic materials (e.g. salt compounds), and metals (e.g. aluminum alloys and zinc); and thermochemical heat storage based on reversible endothermic/exothermic reactions, such as the calcium hydroxide reaction.

Molten salt is currently the most mature technology for thermal storage at high temperatures. Compared to latent and thermochemical solutions, sensible heat storage with molten salt is a commercially proven technology for high temperature heat storage. Indeed, it is the second most used media for high temperature thermal storage after water and direct saturated steam, without the risks and costs associated with highly pressurized steam vessels. 


Stable and safe: highly suitable for thermal energy storage

Molten salts are an ionic compound solid at room temperature and atmospheric pressure, but liquid when heated above its melting point.[2] Molten salts are often used as a heat transfer fluid and thermal energy storage solution in concentrating solar power (CSP) plants. In liquid phase, salts have high volumetric heat capacities[3], which means we can store more heat while taking up the minimal amount of physical space, and are easy to transport. As a mature technology it is also cost-efficient and competitive with today’s energy prices. 

We at Kyoto believe in molten salts as the preferred heat transfer and storage medium for our Heatcube because they are highly suitable for storing and deploying a stable load of heat on demand, are reliable, cost-effective and have a good heat capacity in terms of the required volume and size of the tanks. Another key benefit is safety in operations, as molten salts are non-toxic when operated within their limits, and they are not flammable.

Together with world leading experts Kyoto is working on further developing our Heatcube molten salt thermal battery, and this knowledge and the latest research is applied to continuously improve the performance of our solutions.


Reference list:

1) https://www.ldescouncil.com/publication 

2) https://www.nmbu.no/en/faculty/realtek/research/groups/molten-salt-technology

3) Samuel C. Johnson, ... Michael E. Webber, in Storage and Hybridization of Nuclear Energy, 2019

4) M. Green, et al. "Nuclear Hybrid Energy Systems: Molten Salt Energy Storage," INL/EXT-13-31768, November 2013. 

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