Abstract: A plurality of wire elements for use in an energy recovery device comprising Shape Memory Alloy or other Negative Thermal Expansion (NTE) material, wherein at least one wire element is fixed at one end and free to move at a second end, such that the wire elements are arranged adjacently and are in friction or interference contact with each other and are secured at the outer perimeter of wires utilising a securing means. In such arrangement, during the operation of the bundle arrangement in a heat engine system, the plate elements act to transmit the aggregated force generation of the wire grouping and thus usefully recover and transmit power.