Abstract
Thermomagnetic energy harvesters are one form of technology that can be effectively used to extract energy from low grade heat sources, without causing damage to the environment. In this study, we investigated the output performance of our previously designed thermomagnetic heat engine, which was developed to extract thermal energy by exploiting the magnetocaloric effect of gadolinium. The proposed heat engine uses water as the heat transfer fluid, with heat sources at a temperature in the range 20–65 °C. Although this method turned out to be a promising solution to extract thermal energy, the amount of energy extracted through this geometry of thermomagnetic engine was limited and depends on the interaction between magnetic flux and magnetocaloric material. Therefore, in this paper we carry out an in-depth analysis of the designed thermomagnetic heat engine with an integrated approach of numerical simulation and experimental validation. The computational model improved recognition of the critical component to developing an optimized model of the thermomagnetic heat engine. Based on the simulation result, a new working model was developed that showed a significant improvement in the rpm and axial torque generation. The results indicate that the peak RPM and torque of the engine are improved by 34.3% and 32.2%, respectively.
Highlights
Different sizes of the rectangular magnet were studied to follow up the output performance of the thermomagnetic engine (TME) for the applied magnetic field
The actual length of the rectangular magnet is considerably larger than the diameter of the rotor, which causes an overall distance of 22 mm between the magnet poles and the edges of the cubic gadolinium blocks
The distance between the magnet poles and the gadolinium blocks is 12 mm, which is comparatively closer to the rotor than the previous existing model of the TME
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Various methods have been validated for thermal energy harvesting, which underpins the pyroelectric effect [2,3,4], thermoelectric [5], shape memory alloys (SMA) [6,7], and the magnetocaloric effect [8] Among these choices, the thermomagnetic heat engine has proved to be a promising approach to harvest thermal energy at low temperature differences. Another study was reported, in which a piezoelectric and electromagnetic generator was used in conjunction with the same design of a thermomagnetic heat engine [28] These approaches turned out to be promising solutions to harvest low temperature waste heat, the lower torque of the thermomagnetic heat engine is one of the biggest challenges to develop an efficient methodology to improve the overall efficiency of the system. The designed thermomagnetic heat engine exploits the magnetocaloric effect of gadolinium, which undergoes a phase shift from magnetic to nonmagnetic state with the altering heat near the Curie temperature
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