Solar Heat Storage

Scheffler has deployed at least one heat storage system consisting of an iron mass in an insulated container. One end of the iron mass is exposed to the focus of the heliostat during the day, then capped with an insulated lid to save the collected heat for cooking or frying up to 24 hours later.

More heat can be stored by using a metal with a low melting point like tin or lead enclosed in a steel container and well insultated. The state change from solid to liquid absorbes more energy while maintaining a more usefull range of temperature. When the unit cools, the change of state back from liquid to solid releases that energy and maintains a working temperature for a longer period of time.

See also:

• http://www.pcmproducts.net/Phase_Change_Material_Products.htm Commercial source of phase change materials over many temperature ranges.
• http://engineering.ucsb.edu/~yuen/references/ref-2.pdf Heating at 100-200'C will drive off up to 98% of water. The Zeolite can then cool to room temperature, as long as it is kept perfectly dry. Then, adding water as a mist releases the stored heat quickly. Perfect for cooking.
• http://en.wikipedia.org/wiki/Latent_heat
• http://www.engineeringtoolbox.com/latent-heat-melting-solids-24_96.html