Over the next decade, the most vibrant Wireless Power Transmission (WPT) markets will involve the contactless charging of portable and mobile equipment, in particular consumer electronics and electric vehicles. Today, development teams worldwide are stretching the boundaries of physics using available components to create systems that are able to compete with the efficiencies of wired solutions while offering the conveniences of wire free connections.

In the 1890's famous scientist and engineer Nikola Tesla dreamt of wireless transfer of power. He envisioned a world, in which all electricity is transferred wirelessly, but the idea was more or less abandoned and highly efficient copper cables became the basis for modern electricity infrastructure.

Then, a few years ago, Marin Soljačić, an assistant professor of physics at MIT, was dragged out of bed by the insistent beeping of a cell phone. In his exhausted state, he wished the phone would just begin charging itself as soon as it was brought into the house.
So, Soljačić started searching for ways to transmit power wirelessly.

Soljačić found magnetic resonance a promising means of electricity transfer because magnetic fields travel freely through air yet have little effect on the environment or, at the appropriate frequencies, on living beings. Working with MIT physics professors John Joannopoulos and Peter Fisher and three students, he devised a simple setup that wirelessly powered a 60-watt light bulb.

The MIT work has attracted the attention of consumer-electronics companies and the auto industry. The U.S. Department of Defense, which is funding the research, hopes it will also give soldiers a way to automatically recharge batteries.

Types of WPT

1) Inductive coupling or magnetic induction

Two conductors are referred to as mutual-inductively coupled or magnetically coupled when they are configured such that change in current flow through one wire induces a voltage across the ends of the other wire through electromagnetic induction.

In the above figure there are two coils. The red color coil is the primary coil, which is carrying an AC current, and is generating an oscillating magnetic field. Blue coil is the secondary coil and when brought close enough to the first, it captures a portion of the oscillating magnetic field and receives energy from the magnetic field due to mutual induction. In induction coupling both coils are kept very close to each other so that secondary coil can capture the magnetic field of primary coil without any leakage of power.

For example, wireless charging pad (WCP) and electric toothbrushes. On a WCP, devices like mobiles are to be kept, battery will be automatically charged. Electric toothbrushes also charges using inductive coupling.

2) Resonant inductive coupling

Resonant induction is an improvement on electromagnetic induction that increases the allowable distance between magnetic coils. Radial expansion of a standard magnetic field is possible, but it is also extremely inefficient. Researchers at MIT found that resonance; "a phenomenon that causes an object to vibrate when energy of a certain frequency is applied" can be used to extend the magnetic field and target only devices, which resonate at a certain frequency. Resonant induction could work within a range of a few meters. Furthermore, resonant induction only affects devices that resonate at the same frequency as the transmitting coil, so other electronic or wireless devices would not be affected. In this case additional capacitors are connected in parallel to both coils, which will make the primary coil to produce strong magnetic field with bigger diameter. And thus secondary coil can capture the magnetic field from a large distance.

Resonance inductive coupling is highly efficient and this cordless power technology uses wireless antenna to transmit power in house and requires no charging pads or wires.

Advantages:

* Need for wires are eliminated. * Need for battery is eliminated. * Efficient energy transfer using RIC * Harmless, if field strengths is under safety levels * Maintenance cost is less

Disadvantages:

* Distance constraint * Field strengths have to be under safety levels * Initial cost is high * In RIC, tuning is difficult * High frequency signal must be the supply

Conceptual Analysis of the technology

1. Adoption

Research has shown that a desire to simplify powering and charging experiences and add a new level of convenience to everyday life are driving the consumer expectation for wireless power. And, as the latest wave of wireless power products enter the marketplace and the viability of the technology expands into industry, a need to address the understanding of wireless power and how it will be incorporated into everyday life has also arisen.

Research has shown that, if consumers knew that an integrated wireless power solution was going to be offered in the future, they would support a pad and adapter solution today.

* Nearly half of consumers (surveyed) indicate that they would wait for two years for the product if they could have the technology built into electronic devices.

* About one-third would be willing to buy adapters.

* And about one-quarter would buy the stand-alone charger (pad) and use them until they replace their devices with ones with embedded technology.

However, this research also indicates that there is a specific price point that, once exceeded, no longer makes the adaptive solution attractive - even to early adopters. As the industry matures and more specific questions and concerns around wireless power technology develop along with it, there is a necessary sequence of events that is required for mass adoption of the technology worldwide. The first of these is a deeper understanding of the available technologies, their strengths and limitations and the importance of creating a global standard to serve as the most effective vehicle for the evolution of the universal wireless power solutions that is capable of answering the consumer demand for a universal, integrated solution.

2. Disruptive Innovation

Wireless Power is definitely a disruptive technology. Power has been an absolute necessity to human life for centuries, and the demand for power is greater than ever. Everything, from toiletries to high-tech Unmanned Aerial Vehicles, is wired to and powered by either external power source or a battery.

To meet the demand of customers, the power companies have been aggressive in developing the technology to transfer energy with more capacity and efficiency. Wireless power is a disruptive technology that underperforms in the mainstream market but has attributes that emerging markets value.

The value of the established wired energy transfer technology market consist of efficiency, energy consumption, and distance, and market that of the wireless power transmission technology is made up of safety, convenience, and mass transmission capability. In addition, its current rate of development shows a strong potential to move upward into larger markets and ultimately meet the mainstream demand for power, which is an essential element of a disruptive technology.

Conclusion