A control system for controlling the temperature in a high-temperature battery to which hot air is supplied via an air duct system or in a high-temperature electrolyzer to which hot air is supplied via an air duct system is provided. The control system includes at least two temperature probes designed to detect the temperature at two different points in the air duct system, at least one first air-conditioning unit for physically conditioning the air, mounted in the air duct system upstream of the high-temperature battery or high-temperature electrolyzer, and a recirculation duct which recirculates hot air discharged from the high-temperature battery or high-temperature electrolyzer to a point in the air duct system upstream of the high-temperature battery or high-temperature electrolyzer and feeds the hot air back into the air duct system. The control system controls the first air-conditioning unit in accordance with the temperatures detected by the temperature probes.