Solar-Thermal energy is generally stored in the form of heated water (sensible heat). Due to time-dependent and unpredictable characteristics of sun exposure, the efficiency of solar-thermal systems relies on the efficiency of thermal energy storage technology.
Solar-Thermal energy can be stored in the form of latent heat by using a suitable Phase Change Material (PCM). This offers a higher heat storage capacity per volume/mass and a higher temperature stability of stored hot water.
Utilization of solar-thermal energy storage tanks with PCM based latent heat storage technology is expected to enhance the efficiency of available solar-thermal systems. The higher efficiency is achieved by bridging the gap between solar heat availability and hot water demand.
Phase change material (PCM) absorbs heat during its phase change cycle from solid to liquid during the daytime solar cycle. The amount of heat that a tank of water can absorb is much higher with the presence of phase change material. SavEnrg PCM58P is a non-toxic & non-flammable, inorganic PCM, that can be encapsulated in 75mm polypropylene or high density polyethylene balls. They are then added to insulated, atmospheric water storage tanks. This PCM operates from 52 degrees C to 63 degrees C (126 degrees F to 145 degrees F) with a phase change temperature of 55 degrees C to 59 degrees C (131 degrees F to 138 degrees F). This latent heat stored in PCM maintains the temperature of stored water for longer periods and also pre-heats cold inlet water during the absence of solar heat. Latent heat storage technology also reduces water temperature fluctuations in solar thermal system as PCM stabilizes temperatures.
Key advantages of PCM based latent heat storage for solar-thermal systems:
- Temperature of stored water decreases at a much slower rate.
- PCM can pre-heat cold inlet water during extreme consumption of evening hours.
- Total heat storage is more efficient with PCM in solar-thermal storage tanks.