In this era of modernization, electricity is one of the needs without which you cannot live. Everything around us is getting electrified, electricity has become as important as blood in veins or oxygen in the air. In simple words, electricity is the most important basic need. With urbanization rising and cities being concentrated, electricity generating stations and consumers are far apart. Currently, the primary medium of electricity transmission is through wires. In geographically diverse countries like Nepal, a major portion of the economy is spent on transmission lines. Apart from that, we are surrounded by a lot of electric devices which add a lot of wires, and managing those wires is a tedious job. What if wires could never be used? What if we could transmit electricity without any wired medium? It is possible if we could get some development in Wireless Power Transmission.
Wireless Power Transmission is an efficient way of energy transmission from one point to another where the medium of transmission is a vacuum or atmosphere but no wires. With its help, energy can be transmitted to locations where it is practically difficult to reach. With advancements in wireless transmission, we might not be forced to use wires at least for a short distance.
Need for WPT:
With the help of Wireless Power Transmission, a lot of issues can be solved. Let’s just imagine the trouble we feel when you try to manage the wires of any electrical appliance. You should never see those wires hanging around the electric poles that are ruining the beauty of the country. You might not need to chew the remote batteries to work when they run out of power or in fact, you might never use batteries in remote as well.
Let’s point out some needs for WPT,
• A large portion of the world’s economy is spent on the manufacturing of wires,
• The amount of plastic insulations around the wires affects the environment,
• While working with wires, there always remains the danger of electric shocks leading to disabilities and even death,
• Wireless transmission can help in removing electric poles and wires that are affecting the beauty of many cities,
Working
Fig:Working diagram
Wireless Power Transmission works on the principle of Electromagnetic Induction which states that a coil generating a magnetic field induces a current in another coil when it is being placed in the field of the former coil. That means, whenever electricity passes through a coil a magnetic field is set up around the coil and vice-versa. At the source, electricity is converted into magnetic fields with the help of a transmitter and at the receiving end, the magnetic field is converted into electricity with the help of a receiver.
Techniques
There are two main types of Wireless Power Transmission techniques depending on the length of transmission.
• Near Field Techniques
The near field technique is also further classified into Inductive and Resonant Inductive Coupling.
ln inductive coupling, the source drives a primary coil creating a sinusoidally varying magnetic field which induces a voltage across terminals of the secondary coil, thus transferring power to load.
Magnetic resonance coupling is more advantageous since it has an extended range and potential to support multiple receivers
• Far-Field Techniques
The far-field technique is also classified into Microwave and LASER power transmission.
o Microwave Power Transmission
For microwave or radio frequency, the parabolic dish focuses radio waves which are typically long-range waves towards the intended target.
o LASER power transmission
For LASER transmission, laser light is focused on photovoltaic cells that convert light energy to
power
History
Wireless Power Transmission might look like new technology, but a lot of research work is being done for a long time. Many theories and counter theories were developed in the 19th century and the work of advancement is still going on. Some of the major timelines of WPT are listed below:
• In 1826 Andre-Marie Ampere found Amperes circuital law showing that electric current produces a magnetic field,
• Michael Faraday described in 1831 with his Law of Induction the electromotive for driving a current in a conductor loop by a time-varying magnetic flux.
• Two schemes of wireless signaling were put forward by William Henry Ward (1871) and Mahlon Loomis (1872) that were based on the erroneous belief that there was an electrified atmospheric stratum accessible at low altitudes.
• In 1894, Nikola Tesla used Resonance Inductive Coupling, also known as ‘Electro-dynamic Induction’ to wirelessly light up incandescent lamps.
• 1961: William C. Brown publishes an article exploring the possibilities of microwave power transmission.
• 2009: Sony shows a wireless electrodynamics induction powered TV set, 60 watts over 50 cm.
Nikola Tesla
After 1890, Nikola Tesla experimented with transmitting power by inductive and capacitive coupling using spark-excited radio frequency resonant transformers, now called Tesla coils, which generated high AC voltages. He attempted to develop a wireless lighting system based on near-field inductive and capacitive coupling. He found he could increase the distance at which he could light a lamp by using a receiving LC circuit tuned to resonance with the transmitter's LC circuit.
In 1899, he built an aerial tower called Wardenclyffe (also known as Tesla tower), his pilot plant for the “World Wireless System” to broadcast energy all all-round the globe. A 187 feet tall tower was built to broadcast energy so that all people can have access to free energy. He managed to light 200 lamps over a 40km radius. Tesla failed to make a commercial product out of his findings and the project could not go any further. But his RIC method is widely used in electronics applied to short-range wireless power systems.
WiTricity
In 2007, a group of engineers from MIT came up with the idea to use the Resonance Inductive Coupling method to transmit power wirelessly. They demonstrated an experiment powering a 60W light bulb located 2m far from the source giving about 40% efficiency. They carried out research for decreasing the field strength and increase the range. They are working on park and charge, a wireless car charging project. WiTricity is actively developing the core technology and additional intellectual property that will take this spectacular invention and apply it to electric vehicle wireless charging.
Pros
• Safe, efficient, and good range.
• Can get rid of cables,
• Secure; no risk of shocks,
• Need of battery eliminated,
• E-waste eliminated,
Cons
• Has got limited range,
• Efficiency up to 40%,
• Probability of energy theft,
• Refitting old equipment or purchasing new might not be economical,
Application
Fig: Mobile charging
Coming from the 19th century to the 22nd century a lot of advancement has been achieved in the Wireless transmission field. We have seen many companies developing and using the techniques in their products. We have seen a lot of mobile phone companies providing wireless chargers as well. Apart from that, there are a lot of areas where wireless transmission can help. Some of them are listed below:
• Near-field energy transfer can help in electrical automobile charging,
• Far-field technique can be used in solar-powered satellites
• Device with rechargeable battery can get a great relief from WPT,
• Energy to remote and difficult areas can be easily transferred,
References
- Nikola Tesla and his work in wireless energy and power transfer https://sites.suffolk.edu/xenia/2016/02/17/nikola-tesla-and-his-work-in-wireless-energy-and-power-transfer/
- A Conversation with WiTricity CEO Alex Gruzen https://ride.tech/electric-and-hybrid/a-conversation-with-witricity-ceo-alex-gruzen
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