a thermal accumulator configured to accumulate thermal energy supplied from a heating module, and heat a thermal medium as air with the thermal energy;

a steam generator configured to generate steam using heat of the thermal medium heated by the thermal accumulator;

a first flow path configured to convey the thermal medium from the thermal accumulator to the steam generator;

a second flow path configured to convey the thermal medium from the steam generator to the thermal accumulator;

an auxiliary module provided on the first flow path; and

a bypass flow path configured to convey the thermal medium flowing through the second flow path to the auxiliary module by bypassing the thermal accumulator,

wherein the auxiliary module is supplied with a first thermal medium as the thermal medium from the thermal accumulator via the first flow path, the auxiliary module is supplied with a second thermal medium as the thermal medium from the second flow path via the bypass flow path, the auxiliary module generates a third thermal medium as the thermal medium using the first thermal medium and the second thermal medium, the auxiliary module supplies the third thermal medium to the steam generator via the first flow path, and the steam generator generates the steam using heat of the third thermal medium.