Abstract: The invention internal energy engine is a power machine that makes use of the shape memory effect of shape memory alloy members. The member can be made from a Ni-Ti alloy, for example. It generates great force on a movable part when its transformation is constrained while undergoing temperature changes. The generated high pressure or high speed fluid working medium stream can be used for many practical functions, such as to drive a generator. An important advantage is using waste heat as the energy source. Thus using no fuel and creating no pollution.