A magnetostrictive system in smart cities converts mechanical vibrations into electricity through the use of a technology called magnetostriction. Magnetostriction is a property exhibited by certain materials that causes them to change their shape or dimensions when exposed to a magnetic field. This phenomenon occurs due to the reorientation of magnetic domains within the material, leading to mechanical strain.
The basic working principle of a magnetostrictive energy harvesting system can be summarized as follows:
Material Selection: The system uses a magnetostrictive material with appropriate properties. Commonly used materials include Terfenol-D (terbium, dysprosium, and iron alloy), nickel, and some other rare-earth alloys.
Mechanical Vibrations: In a smart city environment, various sources of mechanical vibrations exist, such as traffic movements, pedestrian footsteps, machinery, and other sources of kinetic energy.
Transducer or Harvester: A transducer or harvester device is employed to convert these mechanical vibrations into mechanical stress in the magnetostrictive material. This device can take different forms, such as a cantilever beam, a piezoelectric element, or a magnetic-coil-coupled structure.
Magnetic Field: A magnetic field is applied to the magnetostrictive material. This field is usually provided by a permanent magnet or an electromagnet.
Magnetostrictive Effect: When the mechanical vibrations cause the magnetostrictive material to experience strain, the magnetic domains within the material realign, leading to a change in the material's dimensions.
Induction of Electrical Current: The changing dimensions of the magnetostrictive material induce an electrical current in nearby coils or conductors through electromagnetic induction (Faraday's law). This generated electric current can then be captured and used for various purposes, such as powering sensors, transmitting data, or charging batteries in the smart city infrastructure.
The efficiency of a magnetostrictive energy harvesting system depends on the properties of the magnetostrictive material, the design of the transducer, and the characteristics of the mechanical vibrations present in the environment. These systems offer the advantage of being able to harness energy from low-frequency vibrations, making them suitable for various applications in smart cities where mechanical vibrations are abundant.
It's worth noting that there are other methods of converting mechanical vibrations into electricity, such as piezoelectric and electromagnetic induction systems, which have their own advantages and applications. The choice of energy harvesting technology depends on the specific requirements and environmental conditions of the smart city project.