Abstract: In a cogeneration system that stores hot water heated by exhaust heat of a generator in a hot water storage tank, a situation in which there is a risk of freezing of water in a water circulating passage is accurately grasped, and thus anti-freezing control prevents the freezing from occurring and unnecessary anti-freezing control is reduced to suppress the drop in efficiency of the system. When determined that an environmental temperature Ta is lower than a lower-limit value Ta_min, it is determined whether or not a temperature difference ?T (=Tr1?Tr2) between a radiator inlet temperature Tr1 and a radiator outlet temperature Tr2 exceeds a predetermined value ?T0, and when determined that the temperature difference exceeds the predetermined value ?T0, it is determined that there is a risk of freezing of the water in the water circulating passage and an command to execute the anti-freezing control is output.

Abstract: In a cogeneration system that stores hot water heated by exhaust heat of a generator in a hot water storage tank, during return to normal control from anti-freezing control, the return to the normal control is rapidly performed and freezing of water in a water circulating passage is also suppressed, suppressing the drop in system efficiency. When a freezing condition, indicating a risk of freezing of the water in the water circulating passage such as a radiator unit, is met, the anti-freezing control is executed. When a cancellation condition of the anti-freezing control is met, a heat recovery temperature target value (first return target value) SVTf2 at the outlet of the generator is set to a minimum target temperature SVTf2_min.

Abstract: A fuel cell system including a PEFC stack in an inner space of a housing includes a sheathed heater, arranged in the inner space, for heating the inner space; the sheathed heater is placed on a bottom face side of the inner space of the housing, while a gap is provided between the bottom face and the sheathed heater; a mounting plate for mounting an inner device including the PEFC stack is provided in the inner space of the housing; and the sheathed heater is arranged between the mounting plate and the bottom face of the inner space of the housing.