An energy harvesting system in thermal communication with a hot region and a cold region includes a hot end heat engine in thermal communication with the hot region, a cold end heat engine in thermal communication with the cold region, and an intermediate heat engine disposed between the hot end heat engine and the cold end heat engine. The hot end heat engine includes a hot end shape memory alloy (SMA) element, the cold end heat engine includes a cold end SMA element disposed, and the intermediate heat engine includes an intermediate SMA element. A hot side of the intermediate SMA element is in thermal communication with a cold side of the hot end SMA element. A cold side of the intermediate SMA element is in thermal communication with a hot side of the cold end SMA element.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
 This invention was made with U.S. Government support under ARPA-E Contract number DE-AR0000040, awarded by the Department of Energy. The U.S. Government may have certain rights in this invention.