The technological history of human can be said to be that of energy and energy conversion.
In this paper the various kinds and shapes of energy and their natural resources are clasified in several categories through various view points, then the total energy conversion system of today is graphically explained in one block diagram.
The energy conversion system is said to be consisted of the primary energy resources, the primary energy conversion method, the secondary energy shapes as the working fluids, the final energy conversion method at the out put points, and the final energy shapes for utilisation, and each parts is discussed from wide and general looking point.
At the end of this paper, the recent topics and some author's dreams on energy conversion including energy storage systems are shown, where the idea of “reversal stove” should be very interesting.
