A turbogenerator having a gas turbine engine powering generator and a cooling system and an annular heat exchanger powered by a fan disposed across an outer fan duct of the engine. Fan variable inlet and outlet guide vanes may be used to vary power between the fan and the generator which are drivenly connected to a low pressure turbine. Inner and outer portions separated by a rotating shroud of the fan are disposed in annular inner and outer fan ducts respectively. A directed energy weapon may be powered by the generator and cooled by the cooling system. A refrigeration apparatus may be operably disposed between the annular heat exchanger and the directed energy weapon for cooling the directed energy weapon and conditioning power electronics for the weapon. The refrigeration apparatus may include a vapor cycle cooling system and a cold storage containing a phase change material.