U.S. patent application 20190041139 (applicant Climate Change Technologies Pty. Ltd., Adelaide, Australia):
"A thermal energy storage apparatus, including: a block of a heat-absorbing material, and a plurality of heat storage elements, the heat storage elements including a phase change material stored in a containment vessel; wherein each heat storage element is in thermal contact with the block of heat-absorbing material. ... The phase change material may include silicon metalloid or a eutectic, hypereutectic or hypoeutectic silicon composition."