Abstract: A heat-driven adsorption cooling unit, comprising: —a condenser having an input end and an output end; —an evaporator having an input end and an output end, the input end being connected to the output end of the condenser via an operable valve; and —a series of sorption-desorption generators, each of which has input and an output ends for connection to the condenser and evaporator to create a refrigerant flow circuit, and a heat supply for operating each generator at high and low temperatures, the generators being operable to flow refrigerant through the condenser and evaporator to provide a cooling effect at the evaporator; wherein the series of generators comprises two pairs of generators, each pair comprising: —a first generator having an output end connected to the input end of the condenser via a first non-return valve arranged to prevent flow from the condenser to the first generator; and —a second generator having an input end connected to the output end of the evaporator via a second non-return valve