Wireless Power Transfer (WPT) is a technology that allows the transfer of electric power without wires. Based on technologies using electric, magnetic, or electromagnetic fields, WPT is capable of supplying power from a standard AC source to the batteries and devices which are compatible, without any physical connectors. This technology utilizes the electromagnetic field generated by the charged particles to transfer energy through the air gap, which is further converted into usable domestic current by the receiver. Wireless power involves the exchange of energy by two objects having a similar resonant frequency while dissipating relatively little energy to the extraneous off-resonant objects.
With rapid technological advancements, WPT technology, i.e., wireless transmission of electrical energy from a power source to an electrical load without connecting wires, is particularly useful in the wireless functioning or re-charging of various products such as smartphones, tablets, and laptops, transportation devices such as drones and electric vehicles (EVs), wearable electronics, transmitter applications, and solar cells. The technology has begun to find increasing acceptance in various domains such as consumer electronics, transport, heating and ventilation, industrial engineering, and model engineering.
WPT allows doing away with the limitation of a power cord while keeping electrical devices charged continuously. Reliable, efficient, fast, and with a low maintenance cost, it can also be used for short-range or long-range. At the same time, this kind of charging gives a far lower risk of electrical shock as it is galvanically isolated.
Evolution of WPT
The concept of WPT started in the late 19th century when Nikola Tesla, a Serbian-American inventor, best known for his contributions to the design of alternating current (AC) power supply systems, proposed and worked on wireless power. Tesla displayed wireless bulbs at World Columbian Exposition in the early 1890s. In early 1961s, William C Brown proposed possibilities of microwave power transmission by publishing an article exploring possibilities of microwave power transmission. In 2007, a team from MIT (Massachusetts Institute of Technology) successfully lighted a 60W bulb at a distance of 2 meters with ~40% efficiency. In 2009, Sony came up with a wireless electrodynamics induction powered TV set. In recent years, so many experiments and advancements have happened, leading to the advent of different wireless mobile chargers.
A demonstration test of a motor-assisted bicycle was initiated by a team functioning at Japan’s Kyoto University. It involved a bicycle capable of wirelessly receiving charge by merely parking it opposite a charger stand. Its front-wheel drew power in the form of microwaves with the help of a battery pack and a receiver. The testing that began early in March 2017 ensures that the charging is only done late at night to avoid potentially harmful contact of humans with microwaves equalling a 100 watts. It is designed in such a way that it stops as soon as anybody comes within a particular range.
Wireless Power Transmission Market by Type
Induction method
Induction charging is used to manufacture wireless charges for toothbrushes, mobiles, shavers, and portable devices. The same principle is used in both wireless charging and transformer, where there is no direct connection between primary and secondary coils. Mutual induction leads to energy transfer between primary and secondary circuits. In this method, the induction coil on the charger acts as a primary coil and makes an alternating electromagnetic field when power is supplied to it. The portable device (which needs to be charged) contains the secondary coil that receives power from this electromagnetic field when it is placed on the charger and converts it to electrical current and charges the battery. This fantastic principle is applied to charge devices within a minimal range.
It is advantageous, convenient, and safe as no hazardous conductors are exposed, entailing no risk of electrical shock. The same principle with resonant inductive coupling can be used for power transmission. Resonant inductive coupling increases the transmission range. Here, primary and secondary coils resonate at the same frequency. Electricity given to the primary coil generates an oscillating magnetic field and is picked up by a secondary coil, which is converted into electricity for the load.
Another type of coupling is capacitive coupling or electrostatic induction. The principle involves capacitive coupling between two or more electrodes or plates with high frequency, high potential AC current.
All the above principles are limited to small distances, and can’t be implemented for more considerable distances.
Microwave Power Transmission
It was William C Brown who demonstrated wireless power transmission over greater distances through this method using Rectenna, an antenna with rectifier device, in 1964. This method provides the feasibility of directional power transmission by a microwave transmitter, which generates microwaves utilizing an antenna. The receiver has a Rectenna that converts microwaves back to electricity. One of the major obstacles with this method is that it needs very large scale antennas.
Laser beam power transmission
This method uses photovoltaic cells, which convert light into electricity by the photovoltaic effect. Firstly, power is converted to a laser beam and transmitted from the source. Photovoltaic cells are used as a receiver, and they convert the laser beam back to electricity. The laser beam’s cross-section is small, and it is advantageous for transmitting over more considerable distances, but laser beams are harmful to human beings and animals. Also, it is highly directional as photovoltaic cells should be exposed to the transmitted laser beam; otherwise, complete loss of power could happen. Other difficulties that could affect the efficiency of this system include atmospheric absorption, environmental scattering effects, and weather difficulties.
Advantages of wireless power
Wireless power transmission and distribution has distinct advantages over wired connections and may achieve higher efficiency in the times to come.
Losses occurring during the transmission of electrical power constitute a significant problem in power systems. The loss of power during the transmission is estimated to be 26%. The prime reason for this loss during transmission can be attributed to the resistance of wires used in the grid. According to WRI (World Resource Institute), India’s electricity grid incurs the highest percentage (27-40%) of power transmission losses in the world. In this context, electricity transmission using an electromagnetic induction method can be highly useful.
Wireless power plays a major role in lifesaving endeavors. In disaster-prone areas, quick recovery is possible with wireless power, and also it is possible to stop significant equipment damage. Remote power receivers dug into the earth when the hazard level meets the threshold, later rising and receiving energy and distributing it to the required load.
WPT not only decreases the risk of shock and stops to plug often into the sockets, but higher efficiency is also one of the critical factors to consider in this technology.
Following are some other advantages of WPT:
- Simple design
- Lower frequency operation
- Potential for power transmission to remote areas where wiring is not feasible.
- Wireless power is not as hazardous as wired power where conductors are exposed.
- Transmission and distribution losses of existing system can furthermore decrease when high-efficiency wireless power transmission is implemented.
- Electric vehicles can be charged from anywhere.
- Customers can be free from requirements of power cords, plug in cables, and plug-in adaptors.
- WPT leads to reduction in expenses and maintenance costs on transmission and distribution assets.
- Devices can be charged from anywhere without the need for chargers.
- Not prone to theft with handshake from source to load.
- Growing possibility of the entry of more power vendors for more considerable distances with consequent increase in customer base.
- Competitive prices of power can be obtained when more vendors participate in the market.
Disadvantages of wireless power
WPT has its downside too. Besides difficulties in transmission and distribution of electrical energy, high capital cost and interference are also considerable bottlenecks in the commercial implementation of wireless power over long distances. 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.
The growth of the global wireless power transmission market may be affected to some extent due to the lack of common standards involving compatibility issues and trade-offs between safety, efficiency, and short-range of wireless power.
Outlook of global wireless power transmission market
According to the “Global Wireless Power Transmission Market 2020-2026 research report,” the market is expected to grow with a CAGR of 21.89% during the forecast period of 2020 to 2025.
Key markets and players
The key regions of the wireless power transmission market include North America, Europe, Asia-Pacific, South America, and the Middle East & Africa.
The Asia Pacific region is expected to receive significant traction in terms of wireless power transmission market size due to the snowballing presence of a large number of consumer electronics industries in countries such as South Korea, India, Japan, and China. The contributory factors for the wireless power transmission market in these countries include swift urbanization and aggressively increasing population, besides a mammoth manufacturing hub of consumer electronics.
Various companies operating in the global wireless power transmission market differ in terms of finances, R&D, strategies, expansion plans, and many more.
Headquartered in South Korea, Samsung Electronics possesses a powerful line of smartphones, such as Samsung Galaxy equipped with the capabilities of a wireless charging receiver. Google Nexus and Motorola Droid comprise some of the popular smartphone series that carry wireless charging capabilities. TDK Corp., Integrated Device Technology, Inc., Texas Instruments Inc., Witricity Corp., Semtech Corp.; Toshiba Corp.; Panasonic Corp.; Rohm Co. Ltd.; LG Electronics Inc.; Murata Manufacturing Co. Ltd., Texas Instruments Inc., and Qualcomm Inc. are some other leading companies in the worldwide wireless power transmission market.
Going forward
In the future, existing wired communication of electricity could be replaced with wireless power. Soon, users need not carry charging devices or a power bank.
The market is likely to expand on account of certain factors propelling its growth. The requirement of effective charging systems and surging consumer preference for wireless connectivity and the convenience offered are expected to boost the prospects of vendors operating in the global wireless power transmission market. In the future, the international wireless power transmission market could witness the rise of magnetic resonance technology, making way into the introductory phase and inductive technology into the growth phase.
Smartphones are emerging as the largest receiver application in the inductive wireless power transmission market. Among several technologies for transmitting electric energy from one point to another for shorter distances, inductive coupling is most commonly used for very short distances in mobile charging.
Of late, one of the leading mobile manufacturers has filed a patent based on RF-based wireless power for wireless charging of mobile devices. The scheduled charging of its appliances may prompt its competitors to do R&D on futuristic wireless charging facilities.
In the future, a mobile service provider could be successful in charging mobiles by delivering the required power from a mobile base station. The synergy between mobile inbuilt software and hardware and base station takes care of energy threshold level to charge, which may lead to higher efficiency.
Trends are towards wireless charging points at signals for EVs. Charging EVs while driving for longer distances may not be an obstacle to replace existing vehicles. Special roads can be constructed across utilities and maintained with inductive coupling to provide continuous charging for EVs. Each EV is identifiable from the source perspective. Alternative charging possibilities can emerge by constructing roads for constant charging for EVs.
Opportunities in various segmentation markets such as integrated implementation and induction technology are predicted to compensate for the effect of deterrents in the global wireless power transmission market. In this emerging technology, the distance of power transfer can be improved given continuous R&D efforts. Further, WPT is expected to mitigate the grave energy crisis confronting the whole world at present. As this technology is continually evolving, wireless power may become a more realistic proposition in the future.
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