An intro to Wireless Electricity

Khalil Alizadeh
Oct 12 · 5 min read

Imagine a world where wires are obsolete, with wireless electricity that’s possible! Just think about it though, NO WIRES. At this point, there are a few instances where you wish you didn’t have an annoying cord in the way. But the power of wireless electricity doesn’t just affect the more tedious types of using a device. There are so many applications for this technology. For example, charging an electric car would be way easier because you would have the ability to charge your car on the go, as in putting coils in both the bottom of the car and on several instances on a city road, freeway or highway. Well, those ideas are pretty cool but the question is How?

So then in this article, I will be giving a brief explanation of the what, how and where of wireless electricity.

Induction

It is the most commonly found form of Wireless energy transfer and is integrated into Qi’s wireless charging stations. The basic principles of this technology were created by Nikola Tesla, he said that when an alternating current (or AC for short) was put in a loop of wire it created an alternating magnetic field which would induce an AC into a nearby secondary coil. And when a load was added to the secondary coil a current would run through it. So to put this into an example say I had my wireless charging station when I turn it on it creates a magnetic field that can be picked up by my phones receiver coil which would charge my device.

Pros:

  • This is the most efficient form of wireless power transfer(WPT) at 75–85% meaning it will give the fastest charge to the receiver.
  • Induction is more widely accepted for smartphones and other wireless charged devices making it the most available and compatible.

Cons:

  • Because magnetic fields are weakened as the receiver moves farther away the range of induction is very small so its a little bit less convenient.
  • Usage of your product while charging is extremely limited because you can easily miss-align with the primary coil.

Inductive charging has been around for quite some time now. It was usually seen being used in electric toothbrushes but has recently applied to some smartphones as I’ve said. Also, Razer came out with a gaming mouse pad that uses induction to charge a wireless mouse.

As this type of wireless electricity is further developed and the design of some products being made improve, you could see more and more products being bought.

Radiofrequency charging

Radiofrequency charging(RFC) increases the range drastically of WPT but at the same time, it sacrifices the amount of energy that can be transmitted. Because RFC is at the same frequency and wavelength as your traditional internet connection you could think of it as using Wi-Fi to power your phone. So your not exposing yourself to gamma rays when trying to charge a device. Since RFC uses radio waves to charge loads, antennas are needed but also are harvesters that can convert these waves into usable electric current. The most recent development of RFC is Cota by OSSIA, they plan to create hardware that is based on this method and integrate it into other companies’ products.

Pros

  • The range is increased exponentially so convenience is key with this technology.
  • With induction, you are usually constrained to one device at a time, but with RFC this isn’t an issue. Therefore, multiple loads can be charged at once.

Cons

  • Since there is such little power being transferred using a trickle charge is necessary. So don’t expect to be powering your Console with RFC any time soon.

This technology is still widely undeveloped but still has massive potential. But right now the best applications for RFC are for devices that have both low power consumption and long charge cycles (months to years). So then I think this has the perfect use for gaming controllers because of the low power that is required for it to run.

Resonant Frequency Charging

Resonant Frequency is a mix of Induction and Radio Frequency, the range is increased and the power transferred stays high. Resonant charging works by tuning two coils to the same electromagnetic frequency which then can induce a current in the receiver coil. This is why Resonant charging is so familiar with induction. You can increase the distance capabilities by tuning a passive repeater at the same frequency as an electric coil so that energy can be transmitted over longer distances. Resonant charging is pretty obsolete from the wireless charging scene mostly because of how new it is. One manufacturer called Integrated Device Technology (IDT) is planning to create chips that have inductive and resonant charging capabilities that also comply with the WPC and Airfuel Alliance’s specifications.

Pros:

  • The range is increased and can grow further with the use of a passive repeater.
  • This technology also supports multiple device charging which is a great convenience.

Cons:

  • Although resonant charging can increase the distance for power transfer it is also very in-efficient compared to induction.

Any place that would need a little bit of longer range but also the same power output, is perfect for resonant charging. So like I said before about charging a car on the road, Qualcomm is planning to do that very thing. With resonant coupling, they plan to charge electric cars wirelessly whether it be on the road or at your house.

Alright, so with all of that out of the way I’d like to end off with a few key takeaways:

  • Induction has a very short range with little convenience but with the highest efficiency of power transfer.
  • Radiofrequency charging increases the range exponentially but also reduces the amount of power transmitted drastically.
  • Resonant charging is kind of a mix of the two, with high power transfer and longer range.
  • These three technologies have a lot of potential and will improve and will be better designed as time goes on.