Phase change materials (PCM) are substances that absorb and release thermal energy during the process of melting and freezing. When a PCM freezes, it releases a large amount of energy in the form of latent heat at a relatively constant temperature. Conversely, when such material melts, it absorbs a large amount of heat from the environment. PCMs recharge as ambient temperatures fluctuate, making them ideal for a variety of everyday applications that require temperature control.
The most commonly used PCM is water/ice. Ice is an excellent PCM for maintaining temperatures at 0°C. But water’s freezing point is fixed at 0°C (32°F), which makes it unsuitable for most thermal energy storage applications.
To address that limitation, PCMs have been developed for use across a broad range of temperatures, from -40°C to more than 150°C. They typically store 5 to 14 times more heat per unit volume than materials such as water, masonry or rock. Among various heat storage options, PCMs are particularly attractive because they offer high-density energy storage and store heat within a narrow temperature range.