A well-known example of a latent heat accumulator is the hand warmer, which is cold in a liquid state and crystallizes and heats up after a metal plate is pressed. The latent heat energy contained in the liquid medium is released and converted into heat. The medium solidifies. When a latent heat storage unit is used again, the so-called phase change material (PCM) must first be melted. The medium stores the added energy in the liquid medium and releases the energy again in the form of heat when it solidifies later. The advantages of latent heat storage are the high storage density and the low energy losses. Latent heat accumulators are used in motor vehicles, where the excess engine heat is stored and released again during a cold start, in the catering industry or in the heating and building materials industry as heat-storing building materials.