To prevent freezing of floating crystal on a tube wall face of a cold source in a floating crystal manufacturing machine of a heat storage system and a cooling system utilizing an eutectic point of multicomponent mixed solution.

A tube wall secondary-side temperature is detected in the cold source of the floating crystal manufacturing machine of a floating crystal manufacturing unit, and a capacity of the cold source is controlled to prevent freezing of a tube wall surface according to the detected tube wall secondary temperature value so that the detected tube wall secondary-side temperature does not become lower than a lower limit in a floating crystal safety manufacturing range. Alternatively, an evaporating pressure (temperature) of a primary-side refrigerant is detected, and an evaporating pressure (temperature) control valve is used for indirectly controlling the lowest secondary-side tube wall temperature so that the evaporating temperature does not become lower than a set value. Thus inhibition of heat exchanging capacity and inability in stirring can be prevented.