Energy recovery apparatus for recovering and using thermal energy comprises multiple series of shape memory elements having decreasing transformation temperatures from one element to the next in the direction of a heating fluid to extract heat over a range of fluid temperatures to effect a shape change of each element. Cooling fluid is flowed alternately through each series of elements to cool the elements and effect another shape change. The cooling fluid exiting a preceding series of elements is used as the heating fluid of the next series of elements to extract further heat indirectly from the original heating fluid. The shape changes of the elements are converted to mechanical work.