Phase Change Materials for Solar Heat Storage Phase Change Materials for Solar Heat Storage Passive solar space heating systems commonly use dense materials, such as brick, concrete, and adobe, as thermal storage materials. On a weight basis, these high-density storage materials cannot compete with water. Heat storage materials absorb heat through standard heat transfer mechanisms radiation, conduction, and convection. As the materials cool off at night or on cloudy days, they subsequently release the stored heat in the same fashion.
Water is the typical thermal storage medium in solar water heating systems.
This means as they absorb heat, their temperature increases and they become warm to the touch. They use chemical bonds to store and release heat. The thermal energy transfer occurs when a material changes from a solid to a liquid, or from a liquid to a solid. When the ambient temperature in the space around the PCM material drops, the PCM solidifies, releasing its stored latent heat. PCMs absorb and emit heat while maintaining a nearly constant temperature.