Design and experimental evaluation of a linear thermomagnetic motor using gadolinium: Preliminary results

Thermomagnetic motors are based on the effect of heat on the magnetic properties of ferromagnetic materials around their magnetic phase transition (Curie) temperature. The main components of these motors are the magnetic material and the magnetic circuit. Changing the magnetic ordering by heating or cooling the magnetic material it is possible to generate power when the magnetic material interacts with an external magnetic field source. If the magnetic material temperature transition is around room temperature, it may have potential to be applied in thermomagnetic motors using low-grade thermal waste as heat source. In this way, the present work proposes a novel concept of a linear thermomagnetic motor using a double-C shape permanent magnet magnetic circuit to convert thermal energy into mechanical energy. The double-C magnetic circuit has two high field regions able to host, at least, two magnetic material heat exchangers connected to each other, but operating in opposite magnetic phases: if the first material heat exchanger is at a non-magnetic phase, the second is ferromagnetic. Thus, when the force equilibrium of such configuration is not satisfied, a linear motion is created. An experimental apparatus of the proposed concept was designed and built. Gadolinium spheres were used as magnetic material. Experimental tests for static forces and generated power were performed. Preliminary results presented a maximum generated power of 0.41 W at an operating frequency of 0.5 Hz.