Wireless Electricity

Imagine a world without wires, for instance, your home may be equipped with a small receiver that intercepts wireless power and then further distributes that power wirelessly to every device. What if our cars are powered by energy transmitted merely through the air? 

"Power can be, and at no distant date will be, transmitted without wires, for all commercial uses, such as the lighting of homes and the driving of airplanes. I have discovered the essential principles, and it only remains to develop them commercially. When this is done, you will be able to go anywhere in the world — to the mountain top overlooking your farm, to the arctic, or the desert — and set up a little equipment that will give you heat to cook with, and light to read by. This equipment will be carried in a satchel not as big as the ordinary suitcase. In years to come wireless lights will be as common on the farms as ordinary electric lights are nowadays in our cities.” 

(The American Magazine, April 1921).

These are the words of a great inventor of the 18th century, and a futuristic man, Nikola Tesla. This man with such a great vision of a worldwide wireless transmission of electricity was much ahead of his time, thinking of a world with free energy. 

Since those times, inventors and engineers have been seeing the same dream, to make it possible that large amounts of electricity could be sent for long distances all without wires. 

Recently, a New Zealand-based startup Emrod has developed a method of safely and wirelessly transmitting electric power across long distances without the use of copper wire, and is working on implementing it with the country's second-largest power distributor. 

But the concept of wireless power transmission (WPT) is not new to us. It was introduced to the world much before, back in the days of Heinrich Hertz and Nikola Tesla, who discovered that energy could be transported by electromagnetic waves in free space.   

"...Electricity could move for hundreds of miles uninterrupted, and anyone with a receiver could access it..." Tesla theorized.

Tesla's early experiments could only send power within a short distance. So to overcome this he thought whether the connection could be stronger if he went through the ground instead of the air. The idea was to send electricity deep into the ground and use the Earth as a giant conductor; i.e. transmission supported by natural electromagnetic resonance of the earth.

He experimented with transmitting power by inductive and capacitive coupling using high AC voltages generated with his Tesla coil. He attempted to develop a wireless lighting system based on the same principle.

In 1899 Tesla presented a wireless transmission field powered fluorescent lamps miles twenty-five miles from the power supply without the use of wires. He successfully lighted a small incandescent lamp by the current induced in the coil, using a resonant circuit grounded on one end.

Tesla also attempted to construct a large high-voltage wireless power station, the WardenClyffe Power plant, that could broadcast both information and power worldwide. But the project was abandoned in 1906. The idea remained alive in the minds of researchers which inspired them to dwell upon new theories towards achieving this.

Wireless Power Transmission (WPT)

It refers to the transmission of electrical energy without wires.  A wireless power transmission system includes a transmitter device, driven by electric power from a power source, generates a time-varying electromagnetic field, which transmits power across space to a receiver device, which extracts power from the field and supplies it to an electrical load.

So far inductive coupling or simply inductive charging has been the most widely used wireless power transmission technology and has contributed to many commercial products like wireless charging pads to recharge mobile and handheld wireless devices such as laptop and tablet computers, cellphones, etc.

Inductive coupling falls under the near-field category of WPT where the power is being transferred over short distances by magnetic fields using inductive coupling between coils.

Two conductors are said to be Inductively Coupled or Magnetically Coupled when a change in current through one wire induces a voltage across the ends of the other wire through electromagnetic induction. 

“...Wireless charging, also known as inductive charging, is based on a few simple principles. The technology requires two coils: a transmitter and a receiver. An alternating current is passed through the transmitter coil, generating a magnetic field. This, in turn, induces a voltage in the receiver coil; this can be used to power a mobile device or charge a battery…."

It comes with a major drawback that it can only achieve higher efficiency when the coils are very close together, usually adjacent.

This efficiency could be increased by using resonant circuits to achieve high efficiencies at greater distances than the conventional commonly used inductive coupling. 

In resonant inductive coupling, power is transferred by magnetic fields between two resonant circuits (one in the transmitter and one in the receiver) tuned to resonate at the same frequency. This increases coupling and power transfer. 

Recent Advancements of this century in WPT

In 2007, MIT researchers showed it was possible to wirelessly power a light bulb more than 2 meters away, raising the possibility that coils buried in a road could help charge electric vehicles on the move above them.

With this researchers of Standard University are also looking forward to bring, use of wireless power for moving electric vehicles to reality in near future.

The interest for WPT has been inflating over the last five to ten years among the specialists, especially in the mobile phone sector – where wireless phone chargers are trending in the market. In 2018, companies like Apple, Samsung, and Huawei have started hitting the market with wireless chargers compatible with the latest models of their mobile phones. 

Coming back to the New Zealand-based startup company, Emrod's idea of WPT. They are claiming to achieve, scaling up a wireless electric power transmission system on the idea which is quite similar to a radio system. 

Energy is converted into electromagnetic radiation by a transmitting antenna, picked up by a receiving antenna, and then distributed locally by conventional means..……. What's new here is how New Zealand startup Emrod has borrowed ideas from radar and optics and used metamaterials to focus the transmitted radiation even more tightly than previous microwave-based wireless power attempts.

The system consists of a transmitting antenna, a series of relays, and a receiving antenna which is a rectifying antenna that converts the microwave energy into electricity. Its beams use the non-ionizing industrial, scientific, and medical band of the radio spectrum, including frequencies commonly used in Wi-Fi and Bluetooth.

The power here is beamed directly between specific points, with no radiation around the beam. Also a "low power laser safety curtain" immediately shuts down the power transmission before any object, like a bird, drone, power thief, or helicopter, can touch the main beam.

Researchers, companies, and specialists are working towards new theories and models to propose an efficient idea for implementing WPT. More R&D efforts are required to implement a wireless power system with safe, secure, high efficiency, and optimal capital cost, ruling out high power loss, non-directionality, and inefficiency for longer distances. 

Now Answer this: How Wireless Electricity can lead us to a more sustainable future? 

To further explore the topic please refer to these links :

1.  https://spectrum.ieee.org/energywise/energy/the-smarter-grid/emrod-chases-the-dream-of-utilityscale-wireless-power-transmission

2.   https://news.mit.edu/2007/wireless-0607

3.  https://www.forbes.com/sites/davidbressan/2019/07/10/how-nikola-tesla-planned-to-use-earth-for-wireless-power-transfer/?sh=70a6b3767490