An energy harvesting device for harvesting energy from a moving structure includes a housing allowing transmission of magnetic fields therethrough. A piezoelectric material capable of a phase transition and a magnetostrictive material capable of a structural change when subjected to a magnetic field are mechanically coupled to each other in the housing. An adjustable pre-stress means is positioned between the housing and the combination of the piezoelectric and magnetostrictive materials. Electrical contacts are positioned on the piezoelectric material. A magnet is mounted on the moving structure. The housing is mounted in sufficient proximity to the magnet for the magnetic field of the magnet to induce the structural change in the magnetostrictive material.