Phase Change Materials (PCM) or latent heat storage materials use a physical effect to store large amounts of energy as heat or cold with nearly no loss and release them again later. When PCM are heated and reach their melting temperature, the temperature stays nearly constant until the melting process is completed. The temperature only rises again afterwards.
The best-known example is water which has its phase transition from solid to liquid state at 0°C and has been used as cold storage in the form of ice and snow to keep food cool for centuries. Melting 1 kg of ice requires the same amount of energy as heating the water up from 0°C to 80°C afterwards. PCM are of particular interest for a number of applications because of their high storage capacity and the extremely low losses compared to other storage technologies.
There is a huge spectrum of different PCM today, so that almost all temperature ranges can be covered and storing heat or cold, stabilising the temperature or increasing the comfort is also interesting from an economic perspective.