Method for thermo-chemical energy storage

Abstract

A method for thermo-chemical energy storage involves carrying out reversible chemical reactions for the storage of heat energy in the form of chemical energy in one or more chemical compounds for later re-release in the form of heat energy using chemical equilibrium reactions. Equilibrium reactions of ammine complexes of transition metal salts are carried out for the storage and re-release of the energy. Specifically, ammine complexes of transition metal salts are formed and decomposed according to the following reversible total reactions: [Me(NH3)n]X+ΔHR⇄MeX+n NH3, wherein Me represents at least one transition metal ion and X represents one or more counterion(s) in a quantity sufficient for charge equalizing the complex, according to the valence thereof and that of the transition metal ion. Also, one or more transition metal salt(s), carried on a carrier material that is inert with regard to the reaction, is / are used.

Description

[0001]The present invention relates to a method for thermo-chemical energy storage by carrying out endothermic chemical reactions for the storage of heat energy in the form of chemical energy in one or more chemical compounds for later re-release in the form of heat energy by carrying out chemical equilibrium reactions of ammine complexes of transition metal salts.PRIOR ART[0002]Thermo-chemical energy storage, i.e. storage of heat energy in the form of chemical energy, is a method of energy storage by cycling at least one chemical compound between the states of at least one reversible equilibrium reaction, said method having been known for decades, but only been subject to more intense research in the last few years. For example, U.S. Pat. No. 4,365,475 discloses the combination of two equilibrium reactions for the purpose of thermo-chemical energy storage, namely the alternating reversible endothermic formation of two ammine complexes, CaCl2.8NH3 and ZnCl2.NH3.[0003]In general, the...

AI Technical Summary

Benefits of technology

The present invention is about a new system for producing ammine complexes of transition metal salts. Unlike previous systems, this invention only allows the ammine complex formation reaction to occur, rather than two parallel reactions that complement each other. This means that the entire enthalpy of formation of the ammine complex is recovered during the reaction, which is very high. However, the invention solves this problem by applying the metal salts onto a carrier simultaneously with the formation reaction, which prevents melting and agglutination of the salts. The use of a particulate carrier material with a specific grain size makes it easier to handle and react the materials. This results in increased working life of the carrier material and more efficient energy utilization.

Problems solved by technology

They are still at a very early stage in their development, though, and for most of them a practical or economic application is still years away.

In most known cases, however, the energy storage density of the systems named above is rather low, and the corrosivity of some of the salts used often presents a problem with respect to the equipment.

Additionally, transport and storage of the metal salts used cause problems, because the temperatures reached during the exothermic reaction are frequently near or even above the melting point of the salts / complexes, so that at least a part of the respective salts will melt, which leads to agglutination.

Furthermore, for all known systems for thermo-chemical energy storage, the quality of the thermal storage material used decreases as the number of cycles increases, so that it either has to be exchanged or, in some cases, cleaned expensively.

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