Research Of Thermal Energy Harvestor Based On Magnetic-Phase-Transformation Alloy And Piezoelectric Material

Nowadays,growing energy demand and environmental issues are forcing people to look for more sustainable energy sources and use them efficiently.However,more than half of the energy generated by renewable and non-renewable sources is dissipated as heat.Therefore,developing and exploring methods for converting waste heat into electricity can effectively solve today's growing energy and environmental issues.In this paper,a magnetic phase change alloy is creatively used in combination with other functional materials to design and build a thermal energy harvestor.Compared with traditional thermal energy harvesting devices based on ferromagnetic materials,the devices designed in this paper have better practicability.The specific research results are as follows:Firstly,a magnetic phase transformation alloy Ni₄₅Co₅Mn₃₇In₁₃ and a piezoelectric polymer polyvinylidene fluoride(PVDF)were used to prepare a thermo-magnetic-electric energy harvestor.In this device,thermal energy is first converted into mechanical energy and then into electrical energy.Thanks to the special magnetic phase transition of Ni₄₅Co₅Mn₃₇In₁₃ alloy(the magnetic structural phase transition from weak magnetic martensite phase to ferromagnetic austenite phase induced by temperature increase),the structural design of the device becomes more reasonable.When the PVDF is 50 mm in length and 110?m in thickness,the maximum short-circuit current and open-circuit voltage of the device are 0.44?A and 10 V,respectively.When the cantilever beam has double-layer PVDF,its maximum short-circuit current and open-circuit voltage increase to 1.27?A and 25 V,respectively.Compared with traditional thermal energy harvesting devices based on ferromagnetic materials,the advantages of this device are:(1)no additional input of energy is needed;(2)the lack of function loss caused by high-temperature heat sources is avoided;(3)no temperature fluctuations are required for device operation.Secondly,the effects of the thickness of PVDF,the distance between permanent magnets and heat sources,and the length of PVDF on the output performance of the device are analyzed.Based on the experimental data,the movement of the cantilever beam is analyzed and theoretically simulated.The free vibration of the cantilever beam on the maximum output current of the device is revealed.The resulting contributions are given by physical formulas that provide theoretical guidance for optimizing device performance.After the final optimization design,it was found that 4 cm-long PVDF can maximize the instantaneous output power and average output power.Finally,a magnetic phase transformation alloy Ni₄₇Co₂Mn_37.1In_13.9 and a manganese-doped lead niobium magnesium magnesium-lead titanate piezoelectric single crystal were combined to design and prepare a thermal energy harvestor based on the pyroelectric effect.This design overcomes the shortcomings of traditional pyroelectric energy harvestors that rely on temperature fluctuations in their operation.The device can stabilize an open-circuit voltage with an output amplitude of 2.3 m V in the presence of a stable heat source,which lays the foundation for the application of the pyroelectric energy harvestor in practical environments.