A cooling system includes an evaporator associated with a heat source. A condenser is located at a higher elevation than the evaporator. A heat pipe structure fluidly connects the evaporator with the condenser. A fan forces air through the condenser. A working fluid is in the evaporator so as to be heated to a vapor state, with the heat pipe structure transferring the vapor to the condenser and passively returning condensed working fluid back to the evaporator for cooling of the heat source. A plurality of thermoelectric generators is associated with the condenser and converts heat, obtained from the working fluid in the vapor state, to electrical energy to power the fan absent an external power source. The thermoelectric generators provide the electrical energy to the fan so that a rotational speed of the fan is automatically self-regulating to either increase or decrease based on a varying heat load.