A device for storing and restoring electrical energy comprising: - water electrolysis means supplied at the inlet with water and electrical energy and producing at the outlet at least dihydrogen (H 2) and dioxygen (O 2) in gaseous form; - means for storing said dihydrogen (H 2) in gaseous form; - a fuel cell supplied at the inlet with at least the stored dihydrogen (H 2) and producing at the outlet at least the electrical energy; - monitoring/control means to control the operation of said device in fuel cell mode or in electrolyzer mode; - an autonomous chamber type in which said water electrolysis means, said fuel cell and said monitoring/control means are arranged; - said chamber comprises standard communication interfaces (112, 114, 116) enabling a detachable connection of an electrical power supply, a detachable connection of a water supply and/or a detachable connection of a pipework for circulating gas; - said communication interfaces comprises an inlet interface with a detachable connection of an electrical power supply and a detachable connection of a water supply, an outlet interface with a detachable connection of an electrical power supply and a detachable connection of a water supply, and a communication interface with storage means of said dihydrogen comprising a detachable connection of electrical control and a detachable connection of dihydrogen pipework; - connection means connected to the interface communication with storage means of said dihydrogen, said connection means enabling said chamber to be connected to said storage means for storing said dihydrogen (H 2) outside of said chamber, said connection means (141, 142) comprise a plurality of interfaces distributed over the length of connection means enabling an impermeable and detachable connection of storage means (210, 220) so as to make the means modular; - each interface of said chamber and each interface of connection means comprising valves electrically connected to the monitoring/control means. - water electrolysis means supplied at the inlet with water and electrical energy and producing at the outlet at least dihydrogen (H 2) and dioxygen (O 2) in gaseous form; - means for storing said dihydrogen (H 2) in gaseous form; - a fuel cell supplied at the inlet with at least the stored dihydrogen (H 2) and producing at the outlet at least the electrical energy; - monitoring/control means to control the operation of said device in fuel cell mode or in electrolyzer mode; - an autonomous chamber type in which said water electrolysis means, said fuel cell and said monitoring/control means are arranged; - said chamber comprises standard communication interfaces (112, 114, 116) enabling a detachable connection of an electrical power supply, a detachable connection of a water supply and/or a detachable connection of a pipework for circulating gas; - said communication interfaces comprises an inlet interface with a detachable connection of an electrical power supply and a detachable connection of a water supply, an outlet interface with a detachable connection of an electrical power supply and a detachable connection of a water supply, and a communication interface with storage means of said dihydrogen comprising a detachable connection of electrical control and a detachable connection of dihydrogen pipework; - connection means connected to the interface communication with storage means of said dihydrogen, said connection means enabling said chamber to be connected to said storage means for storing said dihydrogen (H 2) outside of said chamber, said connection means (141, 142) comprise a plurality of interfaces distributed over the length of connection means enabling an impermeable and detachable connection of storage means (210, 220) so as to make the means modular; - each interface of said chamber and each interface of connection means comprising valves electrically connected to the monitoring/control means.