The heat store (1) is a buried pocket (1a) containing a permeable material (1b) and water (1c).

The invention relates to a heating device comprising a low-temperature heat store (1) thermally coupled to a heat pump (3).

A high heat exchange capacity is thus achieved by exploiting both the high specific heat of the water and the high latent heat of liquefaction of the water contained in the heat store (1).

The fibers thus treated have the high ability to hold the chitosan fixed thereto and have satisfactory antibacterial and heat-reserving properties imparted thereto.

Zero-point energy is not a thermal reservoir, and therefore does not suffer from the thermodynamic injunction against extracting energy from a lower temperature reservoir.