To feed power in a simple construction from the natural air by detecting a temperature through the solidification and melting of a substance and driving a machine with the utilization of a volumetric change at the time.

This temperature detector comprises container 1, a water 2, a membrane 3, a mechanical part 4, a spring 5, a valve 6, a temperature- retaining part 7 and a temperature-adjusting valve 9. When a temperature of the outside air decreases to turn the water 2 to 0°C, the water 2 freezes. At this time, the volume of the water 2 is increased to press the membrane 3 down, and the force is transmitted to the valve 6 through the mechanical part 4, whereby the valve 6 is opened. When the water 2 becomes 0°C or higher, the frozen water melts and the volume is reduced. As a result, the spring 5 presses the mechanical part 4 up and the valve 6 is closed. The opening-closing of the valve 6 can be reversed in this case. The container 1 may be provided with a fin to transmit heat to the outside air well.