Linear electromagnetic electric generator for harvesting vibration energy at frequencies more than 50 Hz

Introduction

Studies on energy harvesting technology are being carried out to help address environmental and energy depletion issues.¹ Energy can be harvested from wasted sources such as solar thermal energy, vibration energy, and pressure energy, which can be converted into usable electricity.² Mechanical vibration has high energy density, it is not affected by climate conditions, and it is not constrained by space. Vibration energy can be harvested from ambient micro-vibrations, from body activities, and from mechanical equipment.³ It is not influenced by the environment since a device can be built without being exposed to the outside, so it can be applied as a plug-in type device, unlike other harvesting systems.⁴ The vibration energy harvesting systems are electrostatic, electromagnetic, piezoelectric, and so on. Electrostatic harvesting systems are advantageous for miniaturization, but they have low energy conversion efficiency. Systems that use piezoelectric ceramics are expensive, and it is fragile.⁵ Electromagnetic harvesting systems have lower production cost, longer lifetime, and higher power efficiency.^6,7 Electromagnetic methods include linear generators and rotary generators. In a rotary-type generator, linear vibration motion is converted into rotary motion using screws, chains, or gears. This increases the weight of the generator and complicates the structure and maintenance, in contrast to a linear generator.⁸

Park et al.⁹ carried out a study to charge a mobile phone battery by harvesting and applying dormant vibration energy to a linear generator. Kim and Choi¹⁰ carried out a feasibility study for a self-powered wireless emergency call button using an electromagnetic energy harvesting mechanism. Lim et al.¹¹ developed a tubular electromagnetic linear generator. Linear electromagnetic generators could be useful for harvesting vibration energy in various industries.

Figure 1 shows a common transformer which vibrates at a frequency of 60 Hz with displacement of approximately ±1.5 mm. A wireless load monitoring system which is circled in the figure helps prevent failures by detecting abnormalities.¹² The monitoring system measures the voltage, current, and temperature of the transformer and delivers information to an administrator.

Figure 1.

Transformer and wireless load monitoring system.

[Figure omitted. See PDF]

An electric battery is essential for supplying electricity to the monitoring. However, it requires periodic management for charging and replacement on a 2-year basis. If the transformer is...