Electrical Power Transfer with “No Wires” - Energy Harvesting Autonomous Sensor Systems - page 194

6.1.4 Summary

In this research work, the inductive coupling concept was utilized for wire-
less power harvesting from power lines. Based on Faraday's law of induction
and Ampere's law, a toroid-based surge coil wound with 500 turns of wires
was designed as a magnetic energy harvester. The magnetic energy radiated
by a 50 Hz, 4 A, 230 V ac current-carrying power line/cable was harvested
by the designed magnetic energy harvester via inductive coupling to power
a wireless sensor node. The prototype of the inductive energy transfer sys-
tem was designed and developed to convert harvested AC voltage into DC
voltage, which then charged the storage capacitor until the preset energy stor-
age level. After this, the stored energy was released to the linear regulator to
provide a constant 3.3 V to the RF AM transmitter which required 132 Jof

energy for communication. Finally, the self-powered wireless RF transmitter
working prototype was capable of transmitting 10 packets of 12 digital bits
information over a range of up to 70 m in an open field with line of sight.

6.2 Wireless Power Transfer (WPT) via Strongly Coupled
Magnetic Resonances
In recent years, mobile gadgets such as laptops, iPods, iPads, mobile phones,
and digital cameras have become common in the consumer world. These
electronic devices and gadgets are typically powered by either the AC main
supply through power cords or solely alkaline/rechargeable batteries that
need to be replaced or recharged regularly. People are getting tired of the
mess, as illustrated in Figure 6.14 , created by power cords and chargers of
multiple electronic devices and the trouble of not being able to locate these
accessories when there is a need to recharge. When people forget to replace
the alkaline batteries in some electronic products, it damages the product
due to leakage and chemical reactions, which may lead to the disposal of the
whole product. In other cases, extensive electrical wiring laid out from the
main power supply to the user is too expensive and hazardous. Apart from
the technical issues, people are also concerned about the environmental and
economical impacts arising from the disposal of batteries.
Because of these concerns, there is an emergence of interest in the WPT tech-
nology to deal with these challenges. WPT is neither a crazy idea nor a very
new concept. If WPT can be realized in practical applications, the outcome
of WPT technology could potentially revolutionize the way electrical energy
is used for consumer electronic devices and portable gadgets and thereby
reduce the dependence on plug-in power supply and disposable batteries to
achieve the ultimate goals of wireless and batteryless electronic products. There
are several wireless charger-based products [168] —Powermat, WildCharge,
Fulton Innovation's eCoupled, Powercast, and so on—already available on
the market. These radiative and nonradiative WPT products are mostly for