Company at https://cellcius.com/en/

They envision charging container-sized units at heat sources such as industry, data centres and horticulture and transporting them to places where heat is needed.

This doesn’t need very high temperatures, so heat that currently is typically wasted can be taken to where it’s needed.

They claim a m³ can store 361kWh (https://cellcius.com/en/warmtebatterijen-vol-zout-kunnen-mil...). I don’t dare say whether they can store it, or estimate whether that’s good enough.