Thermal Energy Harvesting using Nitinol Rotary Actuators

Nitinol tubes trained in torsion are a compact, fast acting actuator form that have been successfully demonstrated in high torque, light-weight applications such as hinge-line actuation for aerospace structures. Because of its small package size and high torque capability, Nitinol tubes are suitable for a wide range of other applications. Here we investigate rotary Nitinol tubes for their applicability to harvesting waste thermal energy using hot and cold water from industrial processes. A single-tube system with water flow in the center bore was built and tested to demonstrate feasibility. Hot and cold water were cycled through the interior of the tube and controlled with solenoid actuated valves. Initial testing demonstrated a heating cycle of 5 sec and a cooling cycle of 2.5 sec with up to 120 degrees of rotation and 14 N-m of torque. Results are presented for this initial, single-tube demonstration raising and lowering a weight as well as driving an electrical generator through a gearbox. Based on these results, a scaled-up system consisting of multiple tubes was developed. Initial results of this system will be presented to demonstrate scalability and applicability to industrial processes.

This work was supported by NSF SBIR Award Number (FAIN): 2013838 Iowa Energy Center Competitive Grant Program Grant 22-IEC-004.