1. Field of the Invention
The present invention relates to an installation and a method for producing cold and/or heat by a sorption system.
2. Description of the Related Art
When the production of energy is not located near the place where the energy is required, it is necessary to provide for transport means. The most widespread energy transport means are the electricity distribution grids. It is nonetheless well-known on the one hand that the conversion efficiency of a primary energy into electricity barely exceeds 50%, and that furthermore, the transport of the electricity is accompanied by losses of about 15%. It is also known how to transport energy in thermal form for the distribution of cold or heat, particularly in urban or industrial networks, using heat transfer fluids (such as water or steam for example) which exchange heat with the medium to be heated or to be cooled. In most cases, these types of exchange involve an exchange of sensible heat or latent heat, which causes the recirculation of large fluid flows and consequently heat losses associated with the high or low temperature of the heat transfer fluid, as well as a high consumption of pumping energy.
Installations for producing heat or cold are known based on thermochemical systems, which employ reversible processes between a gas, called the working gas, and a liquid or a solid. In these systems, the combination step between the gas and the liquid or the solid (absorption of the gas by the liquid, adsorption of the gas on the solid, reaction between the gas and the solid) is exothermic, and the reverse step is endothermic. A large number of reactors and methods based on these principles have been described. They are described in particular in U.S. Pat. No. 4,531,374 (Alefeld) which describes many variants of a device for producing cold or heat based on reversible reactions. These devices operate by reversible absorption of a working gas by a liquid in two working gas circulation circuits operating at two or three pressure levels. Owing to the various operating modes described, the use of such a reactor requires the circulation of the liquid absorbent between one of the reactors of one of the working gas circulation circuits and one of the reactors of the other circuit. This circulation of large quantities of liquid demands pumping means which consume non-negligible quantities of energy, and considerable insulation means to prevent heat losses during the transport of the liquid. The energy supplied to the device during a complete operating cycle is added sometimes to the evaporator supplying the working gas, sometimes to the reactor containing the liquid enriched in gas, in order to liberate the gas, said input therefore taking place at temperatures higher than the gas evaporation temperature and consequently incurring a higher cost. Furthermore, U.S. Pat. No. 4,523,635 and U.S. Pat. No. 4,623,018 describe systems which operate by reversible insertion of hydrogen in hydrides. The systems comprise at least two operating units each consisting of two reactors containing a hydride and connected by a pipe for circulating hydrogen. According to U.S. Pat. No. 4,523,635, during an operating cycle, hydrogen is liberated from a first hydride by adding heat at high temperature to the reactor of one operating unit which contains the hydride whereof the equilibrium temperature is the higher. In the operating mode described in U.S. Pat. No. 4,623,018, each cycle includes at least one step during which heat is added by an external source to a “high temperature” reactor of one of the operating units.