A New Global Standard for at-a-Distance RF Wireless Charging is Here

The AirFuel Alliance has announced the release of AirFuel RF, a new global standard for wireless power transfer (WPT) with the potential to give designers more freedom in designing and implementing new IoT devices. This news comes at a welcome time as IoT devices become more commonplace in both the home and workplace, with an expected 22 billion devices by 2025.

With an ever-increasing number of devices, providing power is no longer a simple task. Batteries offer an on-device solution but require manual replacement when depleted, while traditional power cables can quickly create a rat’s nest of cords. Wireless power offers a viable method of powering devices without batteries or cords but is typically limited in range or efficiency. However, with the release of the AirFuel RF standard, wireless power in the IoT space has suddenly become an attractive potential solution.

 

Wireless charging landscape. Screenshot used courtesy of AirFuel (Click image to enlarge)

 

This article overviews the AirFuel Alliance and the AirFuel RF standard alongside the technical backbone that makes AirFuel RF an effective wireless power source. In addition, we'll discuss some target use cases for AirFuel RF to help designers understand how they may incorporate the standard in the next generation of IoT designs.

 

From Tesla to Today

Ever since Nikola Tesla built his tower in Pikes Peak, Colorado, engineers have been chasing the dream of universal wireless power. While we now understand the physics behind Tesla’s experiments, we also know that WPT is not as simple as erecting Tesla coils throughout cities. To develop wireless power that is both efficient and effective, a group of organizations formed the AirFuel Alliance with the goal of standardizing WPT.

At the time of writing, there are numerous mechanisms through which power may be transferred wirelessly. The most common method relies on electromagnetic (EM) induction and is typically used in applications where power must only be transferred over millimeter-scale distances. EM induction relies on two coils, one in the source and one in the load, to transfer energy in the form of magnetic fields.

 

The WattUp system block diagram from Energous shows how RF WPT can be used to transmit power across longer distances compared to other methods. Image used courtesy of Energous

 

Another common form of WPT is radio frequency (RF) transmission, which is commonly used to send information globally. While it is true that RF does have the ability to send power across the world, it is typically not sufficient to power a load at long distances and relies on active amplifiers to extract any useful information. RF-based short-range wireless power devices have existed for some time but, until now, have not been united under any one standard.

 

AirFuel RF: Extending the Reach of WPT

Since it’s often not practical to confine devices within a few millimeters of a power source, the AirFuel Alliance developed the AirFuel RF standard to unify RF-based WPT development under a single standard. Quantitative results of the standard are still unavailable, but the AirFuel Alliance has reported promising metrics such as multi-device charging “several feet” away from the charger without requiring precise placement.

 

The AirFuel RF system architecture illustrates the basic system-level components for an RF WPT system. As the distance (and path loss) increases, the system's efficiency decreases. Image used courtesy of AirFuel

 

While high-power applications such as wireless mobile phone charging are still out of reach for AirFuel RF, low-power devices common in the IoT space are poised to benefit greatly from the standard since low power can be quickly transferred and harvested. In addition, the AirFuel RF standard is scalable, ensuring an easy deployment regardless of the environment.

 

Phasing in AirFuel RF

As with any new standard, time will be the ultimate test for AirFuel RF to determine its effectiveness as a low-power energy source. One major unknown for the standard is efficiency since transmitting RF energy over long distances inherently increases wasted power. It’s also unlikely that AirFuel RF can work as a standalone system because prolonged power loss at the source may create a system-wide shutdown. Organizations interested in testing the AirFuel RF standard in a practical setting may consider using the evaluation kit from AirFuel.

Regardless, expanding the range of WPT can provide a ubiquitous power source that designers can use to shrink existing designs or spark new innovations. As practical results using AirFuel RF become widely available, designers can weigh the benefits and tradeoffs of the standard to decide if cutting the cord is right for their projects.