Thermal engine capable of utilizing low-temperature sources of heat

A method of operating a heat-driven engine, comprising

• (a) providing a heat spreader, to permit a heat path into said engine, from a heat source;
• (b) providing a working medium of thermostrictive material, having a first temperature of transformation, positioned adjacent to said thermally conductive path;
• (c) providing a heat pump of phase change material positioned adjacent to said working medium;
• and
• (d) an actuator controlled to apply a stimulus to said heat pump, causing a phase change and an associated release of thermal energy, to drive said working medium above its heat of transformation and alternately removing said stimulus from said heat pump, causing a reverse phase change and an associated intake of thermal energy to drive said working medium below its heat of transformation;
• and
• (e) permitting heat flow through said thermally conductive path to maintain said working medium at a temperature range that permits said heat pump to so drive said working medium temperature above and below its temperature triggers.

A heat-driven engine comprising

• (a) a thermally conductive path into said engine, from a heat source;
• (b) a working medium of phase change material, having a first temperature of transformation, positioned adjacent to said thermally conductive path;
• (c) a heat pump of phase change material positioned adjacent to said working medium;
• and
• (d) wherein a stimulus is applied to said heat pump, causing a phase change and the associated release of thermal energy, to drive said working medium above its low-to-high temperature of transformation and then said stimulus is removed from said heat pump causing said phase change to reverse, along with an associated intake of thermal energy, further causing heat flow through said thermally conductive path and maintaining said working medium at a temperature range that permits said heat pump to so drive said working medium temperature;
• and
• (e) wherein said thermally conductive path includes a heat flow constricting element, to avoid heat flow that does not conform to desired characteristics.