To eliminate the attenuation of energy in cyclic process of temperature difference → work → temperature difference → work, etc., and to increase the energy.

Each of three linear expansion bodies is placed in its heat insulation environment, and formed so that the temperature difference exists between two out of the three linear expansion bodies. By alternately bringing the respective two linear expansion bodies into contact with a third linear expansion body, heat transmission therebetween is performed while utilizing the temperature difference therebetween at the contact. The alternate contact is repeated until the temperature difference among the three linear expansion bodies can be considered zero, and then dynamic energy is obtained from expansion or contraction phenomenons thereof caused by a change of temperature between the three linear expansion bodies due to the alternate contact. Bimetal can be also used in place of the linear expansion bodies.