Design, optimization and operation of a high power thermomagnetic harvester

Converting low temperature waste heat to electricity is vital for the green transition. Here we present how to design and optimize a thermomagnetic energy harvester that can convert a stream of waste heat to electricity through Faradays law. In optimizing the design in the traditional figure-of-eight shape, we determine the ideal size of the magnet and the beds of magnetic material using a numerical model given an overall volume constraint for each of the thermomagnetic volumes of 20 cm³. The magnet is determined to ideally be 5 × 5 × 1.25 cm, the beds should have a height of 1.09 cm and contain about 120 g of Gd spheres, and we use coils with a wire diameter of 1.8 mm and 156 windings in each coil. Following the design study, the system is realized using off-the-shelf components and tested as a function of flow rate, frequency of operation and temperature span. At a temperature span of 40 °C and a hot side temperature of 40 °C, the device produces 9 mW of power at a flow rate of 1.4 L/min.