An energy storage system comprising a device for producing a first and a second secondary fluid by electrolysis of at least one primary fluid, and a storage device for secondary fluids in order to store the first and second secondary fluids separately, and a fuel cell for generating electrical energy by oxidation-reduction reaction between the first and second secondary fluids, the storage device for secondary fluids comprising at least two reservoir containing a pressurized fluid, the reservoirs being place inside an enclosure , the storage system also comprising an emptying system for emptying said reservoirs , the emptying system comprising, for each reservoir , a vent for discharging the fluid out of the reservoir and a discharge valve for connecting the reservoir to the vent , the discharge valve being movable between an open configuration, in which the discharge valve fluidly connects the reservoir to the vent , and a closed configuration, in which the reservoir and the vent are fluidly isolated from one another by the discharge valve , the emptying system further comprising, for each discharge valve , a return member for returning the discharge valve to the closed configuration, and a fluid control system for controlling the movement of each discharge valve to the open configuration by action of an operating fluid on the discharge valve , said control system comprising an operating station , and, for each discharge valve , a fluid pipe fluidly connecting the operating station to the discharge valve , each discharge valve of the emptying system being fluidly connected to a respective reservoir of the fluid storage device so as to be fluidly interposed between said reservoir and a vent of the emptying system , the operating station being placed outside the enclosure and comprising at least one reversible free connection for connecting to each fluid pipe of a supply device for supplying the control system with the operating fluid. the storage device for secondary fluids comprising at least two reservoir containing a pressurized fluid, the reservoirs being place inside an enclosure , the storage system also comprising an emptying system for emptying said reservoirs , the emptying system comprising, for each reservoir , a vent for discharging the fluid out of the reservoir and a discharge valve for connecting the reservoir to the vent , the discharge valve being movable between an open configuration, in which the discharge valve fluidly connects the reservoir to the vent , and a closed configuration, in which the reservoir and the vent are fluidly isolated from one another by the discharge valve , the emptying system further comprising, for each discharge valve , a return member for returning the discharge valve to the closed configuration, and a fluid control system for controlling the movement of each discharge valve to the open configuration by action of an operating fluid on the discharge valve , said control system comprising an operating station , and, for each discharge valve , a fluid pipe fluidly connecting the operating station to the discharge valve , each discharge valve of the emptying system being fluidly connected to a respective reservoir of the fluid storage device so as to be fluidly interposed between said reservoir and a vent of the emptying system , the operating station being placed outside the enclosure and comprising at least one reversible free connection for connecting to each fluid pipe of a supply device for supplying the control system with the operating fluid. <EOS>