Solar-thermal energy conversion and storage: Conductive heat transfer using bulk graphite

Concentrated solar power (CSP) highlights the fact that there is substantially more energy in the sun´s heat than there is in its light. However, solar-thermal energy conversion and storage systems using CSP are handicapped by challenges associated with storage technologies, especially high pressures and corrosion. In assessing the possibilities for new materials and designs, issues of thermal properties and heat transfer must be considered. While current technologies largely utilise convective heat transfer of liquids, a promising approach is the use of conductive heat transfer with highly aligned graphite in air as the storage material at temperatures les600 degC. Modelling of a small domestic-scale system (4 m diameter concentrator; <200 kg graphite) indicates that, in only 3 h, sufficient heat can be stored to supply 25 % more than is required for a typical 24 h electricity usage cycle, operating at a storage temperature of les420 degC in air.