NOVELTY - The apparatus (103) has a bent fin naturally convective heat exchanger (201) including fins attached to a side of a metal plate. An electrical insulation-clad vapor chamber (204) extends along surfaces of the metal plate and crosses a bend such that the vapor chamber transports heat away from a photovoltaic cell (202) during operation when the photovoltaic cell is attached to the first or second surface of the metal plate. A cladding material is provided between the vapor chamber and the heat exchanger, where the cladding material thermally couples the vapor chamber to the heat exchanger.    USE - High power cooling apparatus for cooling a photovoltaic cell i.e. triple-junction solar photovoltaic converter cell and single semiconductor photovoltaic cell such as silicon solar cell, utilized in a concentrating solar collector system of a photovoltaic system (claimed).    ADVANTAGE - The apparatus can cool concentrating solar collector systems that perform optimally at different elevation angles and provide electrical isolation to the photovoltaic cells in the photovoltaic system. The apparatus allows a wrapper to be open at a top and a bottom of the fins to permit formation of a convective airflow along the channel containing the fins so as to enhance flow of air past the fins and improve the cooling capacity of the system in areas in which wind is not usually present. The cladding material thermally couples the vapor chamber to the heat exchanger, where air tends to rise up along vertical direction, so that a portion of the heat exchanger is in vertical orientation when the heat exchanger is a naturally convective heat exchanger, thus enhancing convection of heat from the heat exchanger to the air.    DETAILED DESCRIPTION - The heat exchanger is a plate fin heat exchanger. The apparatus allows a thermal interface material that is selected from a group consisting of solder, liquid metal thermal interface, liquid metal alloy, thermal grease, conductive particle filled organic thermal paste, conductive particle filled organic thermal gel, particle impregnated polymer and phase change material. INDEPENDENT CLAIMS are also included for the following:    (1) a photovoltaic system    (2) a method for operating a photovoltaic system.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a configuration of a cooling apparatus.    High power cooling apparatus (103)    Bent fin naturally convective heat exchanger (201)    Photovoltaic cell (202)    Thermal spreader plate (203)    Electrical insulation-clad vapor chamber (204)