UC Berkeley

The electric grid began its service over 100 years ago and accumulated many safety concerns

regarding its infrastructure and nearby environment. The wireless sensor network has been

deployed to monitor the condition of both the grid infrastructure and environment, and

non-interrupted power sources with minimal maintenance has been an engineering challenge.

Here, design of an inexpensive and durable electromagnetic energy harvester coupled with

the magnetic field from the power line conductors for powering the wireless sensor network is

documented. A prototype of the energy harvester is first built to evaluate the device’s output

power by placing it against the power line conductor which carries an AC current of 30 A.

The power output is measured up to around 120 milli-watts with the use of a magnetic flux

guide made of electrical steels. This result shows that the electromagnetic energy harvester

is promising for most sensor applications whose power consumptions are usually from several

micro-watts to a few milli-watts.

A simulation model is developed to calculate the output power based on critical parameters

of a specific harvester configuration for an optimized energy harvester system. This model

includes the saturation e↵ect in the magnetic material as it has significant impact on the

harvester’s power output observed from the experimental results. Circuit analysis with

consideration of nonlinear saturation e↵ects is conducted using a current transformer model,

and it provides good approximations to the experimental measurements. Furthermore, a

finite element model is also developed to improve the accuracy of the circuit model, and it

is used to optimize the energy harvester designs. Several parameters of the energy harvester

are investigated in di↵erent configurations to maximize the output power, and up to 0.4

watts is obtained with three pieces of flux guides when the AC current in the power line

conductor is 30 A.