Tech Summary

Overview of Wireless Power Transfer

image001It is well known that electric power can be transferred wirelessly based on different electromagnetic phenomena. Wireless power transfer (WPT) always requires a transmitter () and receiver ()  which are physically detached from one another. The physical phenomena best suited for different applications varies and the system can be categorized as non-radiative/reactive/coupled, which includes capacitive and inductive coupling and radiative/radio wave/decoupled, where electromagnetic radiation is used, from radio to microwaves and lasers.


Coupled WPT

Inductive power transfer and capacitive power transfer based on magnetic and electric field coupling allow smaller distance WPT. These are associated with the highest WPT efficiency while being limited in range.

Work on this field usually includes system modelling and analysis, lumped circuit theories, magnetic and electric field distribution, Poynting vector analysis, power transfer mechanism, resonance and tuning/compensation design, bifurcated nonlinear WPT systems, system control and optimization, etc.

Most commercial applications found on the market belong to this category.


Radiative WPT

For achieving WPT for higher distances, the use of electromagnetic radiation is preferred, as it propagates freely through space. These waves suffer from divergence, and most of the energy radiated does not reach the intended target. To increase the beam efficiency, one needs to increase the directivity of the energy beam, which can be achieved by using focusing components, as well as increasing the frequency of operation. Hence, most of these systems are implemented in microwaves or lasers.

Additionally, the widespread use of electromagnetic waves in telecommunications results in a constant presence of energy, which can be harvested for powering devices. This is another important aspect of this technology.

The main topics included here are the energy conversion from DC to RF and RF to DC, antenna systems, focusing components, as lenses, reflectors and metasurfaces, quasioptics.


Electromagnetic Compatibility

Wireless power transfer technologies must consider the environment where it occurs, as well as the living beings in the surroundings. Electromagnetic compatibility (EMC), electromagnetic field (EMF) safety and biomedical engineering are important aspects when applying these solutions to real-world applications. 

Hence, EMF studies human exposure to reactive and radiative WPT systems, compliance assessment with international standards and guidelines, low and high frequency dosimetry, etc.

On the other hand, bioelectromagnetism, such as EMI with cardiac electronic implantable device or WPT system for charging biomedical devices is also considered. 



Multiple topics are considered: standards, measurement techniques and test procedures, instrumentation, equipment and systems characteristics, interference control techniques and components, field mitigation techniques, education, computational analysis, and spectrum management, along with scientific, technical, industrial, professional or other activities that contribute to this field.




WPT Applications

Wireless power transfer techniques have enabled many novel applications, with the main advantages of being nondestructive and noninvasive, while enabling mobility, convenience, efficiency. Some applications can replace existing solutions, others provide the possibility of previously impossible scenarios. Currently, WPT has been demonstrated for charging vehicles, drones, medical implants, consumer electronics, factory and industrial instruments, mobile sensors, and Internet-of-things (IOT) devices for smart cities.

Research has also been conducted for aerospace, satellite, energy distribution, sensor network, and city infrastructure applications, with one of the most known project being the solar power satellite (SPS) system. These applications are changing the technological landscapes and making significant impacts on our society. Finally, the integration of WPT with communications is known as simultaneous wireless information and power transfer.

The main goals are to identify stakeholders and common technology needs in several key application areas including (1) vehicles; (2) aerospace; (3) healthcare and medical devices; (4) wearables; (5) IoT devices and sensors; (6) energy industry and (7) emerging applications.

Interesting topics include synergy developments for best practices toward these applications; collaborative studies of fundamental issues; collaboration toward standardization among stakeholders; promotion of technologies; roadmaps for specific application fields; and establishment of industrial initiatives or consortiums.