We decided to store the energy produced by the heating element as latent heat in a substance called Calcium SulfoAluminate (or CSA). The latent heat can easily be extracted by hydration of the CSA, which is in powder form.

Storing the energy as latent heat rather than specific heat means the temperature of the material is constant while the energy is extracted, as so a constant voltage can be held. This also means insulation is less of an issue as the the material does not need to be kept hot for long.