1. Background to heat (and cold) storage

1.1 Importance of heat (and cold) in the economy

Energy as we use it every day covers three main areas of use:

• electricity and its many specific fields of application;

• mechanical energy, mainly in the form of transport;

• heat and cold, for building heating and air-conditioning, as well as specific refrigeration applications.

In France, the residential – tertiary sector uses almost 45% of the energy consumed, two-thirds of which is used for heating and air conditioning