Wireless Power Transfer (WPT) is a technology that enables the transfer of electrical energy from a power source to an electrical load without using physical wires. Instead, it uses electromagnetic fields or radiowaves to transmit power wirelessly over a distance. The transfer can occur through a variety of methods, such as inductive coupling or resonant coupling for short-range transfer, and focused beam microwave power transfer or energy harvesting from broadcasted radiowaves for long-range transfer. The choice of method depends on the distance and power requirements of the application. The field of WPT is a combination of electrical and radio sciences and is a rapidly developing area with a wide range of potential applications.
Short Range Wireless Power Transfer Technologies
The inductive and resonant coupling WPT technologies are used for short range wireless power transfer. Both the inductive and resonant coupling WPT rely on electromagnetic theory, where power is transmitted wirelessly through an electric field, magnetic field, or electromagnetic field between a transmitter and receiver that are electromagnetically coupled. For short range distances, technology using coils for inductive or resonant coupling is effective, but the coupling distance has limitations due to coupling theory, even in resonant coupling.
Inductive & Resonant Coupling Wireless Power Transfer
Maxwell combined Ampere's law and Faraday's law into his equations, unifying the knowledge that a current generates a magnetic field and a changing magnetic field creates a current. Two conductors that are arranged in such a way that a change in the current flow in one conductor induces a voltage in the other through electromagnetic induction are referred to as magnetically or mutually-inductively coupled. This phenomenon, known as inductive coupling, is utilized in power generators and transformers. Unlike WPT via radiowaves, WPT through inductive coupling typically uses lower frequencies in the kilohertz to megahertz range.
The following picture represents the inductive and resonant wireless power transfer technology diagrammatically.
The following picture represents Resonant Wireless Power Transfer diagrammatically.
The main distinction between inductive and resonant coupling WPT being the presence or absence of resonance.
Long Range Wireless Power Transfer Technologies
For long range wireless power transfer radiowaves are used. Herein microwave power transfer or energy harvesting from broadcasted radiowaves technologies are used for long range power transfer. To increase the power transfer range, radiowaves are required. Antennas are used for both power radiation and receiving in wireless power transfer (WPT) via radiowaves, serving as resonators to effectively radiate the radiowaves. There are some variations in their applications, with the use of higher frequency radiowaves, such as microwaves in the gigahertz (GHz) range, now possible to provide focused and efficient wireless power.
The diagram below depicts Microwave & Broadcast Wireless Power Transfer.
The diagram above shows multi-transmitting and multi-receiving antennas for WPT, as they are not coupled electromagnetically, similar to broadcasting and wireless communication systems. Low power WPT systems do not require battery storage and can operate using energy harvested from ambient radio frequency (RF) and microwave radiation. The reliance on battery storage will also decrease as wireless power becomes more widespread, as batteries can be charged wirelessly, eliminating concerns about battery storage shortages. The WPT via radiowaves differs in that it doesn't require coupling and instead uses radiated electromagnetic waves. The use of higher frequencies such as microwaves is necessary to effectively focus the wireless power.
Conclusion
The use of WPT technology to charge batteries in mobile phones, notebooks, EVs, and other equipment through radiowaves is becoming a reality. This convenient and valuable technology will soon make it possible to produce stable, CO2-free electric power from space. The concept of a space-based solar power satellite, supported by MPT, is a giant power station in space that is essential to the "humanosphere," which refers to the space where human activity takes place. Humanospheric science, an interdisciplinary field of study that focuses on the humanosphere, is a crucial development for the future of the human race.
To ensure human welfare and maintain our standard of living, it's important to address the issues of energy, food, and the environment. Currently, the increasing demand for electricity is conflicting with the need for a clean environment, as fossil-based power production contributes to environmental and pollution problems worldwide. While electricity has traditionally been generated through hydroelectric power, fossil thermal power, and atomic power, these methods are causing environmental and pollution issues. Hence, the idea of building power stations in space to transmit electricity to Earth through radiowaves is being researched. WPT technologies support this vision of a bright future.
