Design and operation of a thermomagnetic engine for the exploitation of low-grade thermal energy

Gadolinium is a rare earth magnetocaloric material that has a Curie temperature close to room temperature. Due to this unique property, gadolinium can be effectively used in conjunction with a thermomagnetic heat engine to extract thermal energy from low-temperature heat sources. However, the amount of energy harvested by this method is often limited by the capability of the engine in relation to exploiting the interaction between the magnetic flux and magnetocaloric material, where the latter is subject to temperature change as the system is constantly exposed to hot or cold heat sources. In this study, a simulation model has been developed to establish a reliable working model for the analysis of the performance of a thermomagnetic heat engine. Results indicate that the model was capable of delivering an in-depth representation of the interaction between the magnetic field and the magnetocaloric material (Gd) as the engine runs by exploiting the temperature difference in heat sources. This work also highlights some of the limitations in the design of the engine, where the accuracy of the present model was tested by comparing its numerical results against experimental ones as appropriate. Based on the simulation results, the thermomagnetic heat engine was modified to test a new working model in the lab. The new model shows a significant improvement in the engine's output, especially when the heat source is at a low temperature. With the modification, the engine's peak RPM and power increased by 22.72% and 18.79%, respectively.