Introduction to Wireless Electricity

In yet another of my ramblings down a rabbit hole of technology articles, I came across a very brief (too brief) piece on wireless electricity. Now I needed to know more about it, so you get to come along with me on the exploration.

What is wireless electricity?

Essentially, wireless electricity is just what it sounds like, as unbelievable as it may be: transmitting electrical power without using wires. There are two techniques for putting it into practice: near-field and far-field. I’ll briefly explain each and give some examples.

In near-field, or non-radiative techniques, the power only travels a short distances. This technique uses inductive coupling, which involves magnetic fields generated by coils of wire. You may be using this already if you’re using a charging pad for your phone or tablet, or a smartwatch. It’s also the technique used for the charging base of your electric toothbrush. RFID tags and induction cooking use it as well. Some implantable medical devices like pacemakers use it, and some electric vehicles. Some near-field methods use capacitive coupling between metal electrodes rather than inductive coupling.

Far-field, or radiative techniques, sometimes called power beaming, use beams of electromagnetic radiation to transfer power. These could be microwaves or laser beams. Using these techniques, power can travel longer distances, but they require precise alignment to the receiver. Some of the proposed applications for this power transfer method are solar power satellites, and drone aircraft powered wirelessly.

Why is wireless electricity significant?

Well, for one thing, our devices will have greater mobility. We can charge our devices without a big tangle of cords and cables. That will make life simpler and easier in a big way. But one of the most significant uses is in powering implanted medical devices, like pacemakers and neurostimulators. No wires penetrating the skin means a reduction in infection risk, and it’s got to be more comfortable. We can also extend this technology to hearing aids, wearable health monitors, and even drug delivery systems.

Let’s also consider our smart infrastructure and the Internet of Things (IoT). There are myriads of devices communicating over the internet now, and a huge percentage of them still need constant battery monitoring or hard-wired power. Smart homes, offices, and cities can all benefit from the availability of wireless charging stations. The more interconnected our infrastructure becomes, and the smarter the grid becomes, the more of an enabler wireless electricity becomes.

Historical Context and Discovery

We have Nikola Tesla to thank for today’s wireless power transfer, along with all of his other contributions (maybe I’ll do one post just on him). For almost a decade at the end of the 1800’s, he performed experiments on wireless energy transmission using his Tesla coil – a radio frequency resonant transformer. Picture a tall coil with a bunch of wires wrapped around it, like a giant spring. Applying a jolt of electricity to the coil shoots electric arcs out the top, which is called the spark gap. Tesla was able to produce high voltage, high frequency alternating currents, demonstrating the possibility of transferring power over short distances without using wires between the two points. He had a vision of a world of wireless communication and power transmission. The plans he described in 1900 included wireless signal transmission to all parts of the globe, instantaneously and precisely. His concept involved a network of towers that would allow anyone to make use of the ubiquitous power availability, assuming only that they had the requisite equipment.

Although Tesla never saw the realization of his global vision, his coil is now a key element in wireless charging devices. He wasn’t able to bring free energy to all, but the resonant inductive coupling method remains in use in short-range wireless systems. Furthermore, the objective he had to use the earth itself as a medium to transmit wireless power has come resurfaced in research circles. We still don’t have global wireless power, but we’ve seen great advancements in wireless charging, smart grids, and connectivity for IoT devices.

Building on Tesla’s work, during the 1930’s, H.V. Noble from Westinghouse Labs was able to transmit power about 8 meters using the inductive coupling technique. Further advancements occurred in the 19260’s using microwaves, and in 1968, Peter Glaser introduced the idea of an Space-Based Solar Power system. Fast forward to today where we see wireless charging pads for smart device, which use inductive coupling, magnetic resonant induction, and electrostatic induction. Scientists are continuing to work toward long-distance wireless power transfer, using uncoupled radio frequency charging, so that the device wouldn’t have to actually touch the charger, as it does today.

How Wireless Electricity Works

Now I’m going to go into some really basic explanations of how wireless electricity works. These are really, really basic. I’m not a physicist, and I don’t have a strong enough backgound in science yet to be able to go deeper than I have here, but the links at the end of the article should take you further down the rabbit hole, if you want to know more.

Inductive Coupling

Imaging you have two coils of wire, like mini hula hoops. One is connected to electricity, and the other one is close to it. When electricity flows through that first hoop, it creates a magnet field around it. The magnetic field “talks” to the second hoop, even though they’re not touching. The second hoop picks up the magnetic field, turning it back into electricity.

Magnetic Resonance

Think of a swing at a playground. If you’re on it, you “pump” with your legs, arms, and back motion to make it go higher and higher, but it takes all those movements at the right time. If you get out of the timing, you’ll actually slow down, and your peaks will be lower and lower. If you’re on the ground pushing the person on the swing, you have to push it at just the right time to make it go higher. Finding that perfect timing is called resonance. Wireless power uses magnetic resonance to make sure that the coil for the sender and the coil for the receiver are synchronized.

Radio Frequency Energy Transfer

Radio Frequency uses radio waves, the same kind of radio waves that sound radio uses. The waves are actually a type of electromagnetic radiation, like a vibration of the air. The radio turns the vibrations into sound, but an RF receiver turns RF waves into electricity.

Wireless Charging

Wireless charging requires two components – the charging pad, and your device (smartphone, smart watch, etc.). The charging pad is the transmitter, and it creates a magnetic field around it. Wireless-charging-capable devices have a receiver coil inside of them, which can absorb energy from the magnetic field. The charging pad creates an oscillating (back-and-forth or up-and-down) magnetic field, and the receiver coil turns the magnetic field on its end into energy.

It all sounds like magic, but it’s more like a handshake.

Applications of Wireless Electricity

The easiest application of wireless electricity for most people is wireless charging of our personal smart devices. I haven’t found it to be particularly promise-fulfilling, as the charger still needs to be plugged into a power source, but I do like that the device itself doesn’t need to be decoupled from the power source, I can just pick it up and use it or carry it away. I may find it more useful in the future when I have a charging pad big enough to charge several devices at once, and I can charge a phone, a tablet, a watch and my airpods all at the same time.

The revolutionary utility is and will continue to be in medical devices – implants and monitoring systems. Pacemakers, defibrillators, and neuromodulators have a limited battery life, and those batteries often require yet another surgical procedure to replace them. As wireless charging progresses, patients may be able to charge the batteries at home without requiring a visit to the doctor. Additionally, there are some monitoring systems that patients wear all day, but wireless charging may enable patients to charge the devices while still wearing them. Both of these applications can provide greater mobility for the patients who need them, which can help produce a much-improved quality of life.

In development now is technology for wireless charging for Electric Vehicles (EVs). The power connectors for EVs right now are bulky and cumbersome. Wireless EV charging will involve a charging pad or stand, and the car will park over the pad or close to the stand (or the stand may be rolled to the car). The pad or stand will have a magnet coil that will send current to the matching coil on the car’s underside or the location close to that on the stand.

IoT devices could definitely benefit from wireless charging. We often have to place them in inconvenient locations because they need a power source. There are companies that are developing technology that can send electrical power to multiple devices at once, even as far as 30 feet away. Eventually, we may see our IoT devices receiving signals and power from the same source.

Challenges and Limitations

As magical as all of this sounds, it is not without its problems. Wireless power transfer systems often experience energy loss during transmission, due to resistance, electromagnetic radiation, and couplings that aren’t quite perfect between transmitter and receiver. The farther the power has to travel, the greater the loss of energy, and it’s an exponential decrease, rather than just a mathematical one. Inductive and capacitive coupling methods work fine over short distances, from a few centimeters to as much as a meter, but beyond that, their efficiency drops a lot. Near-field charging works great for smartphones, but for room-sale wireless power, it gets to be a challenge. When we look to far-field techniques, we get longer distances, but they face challenges due to beam divergence, atmospheric absorption, and problems aligning precisely. They can also pose safety risks from exposure to radiofrequency and microwave transmissions, but these risks occur at high exposure levels.

Potential Impact on Various Industries

The advancements to come with wireless power transmission will shape several sectors. Energy production, storage, and transmission will benefit from enhanced grid efficiency, renewable energy integration, and smarter grids. Healthcare will see leaps forward in telemedicine and remote monitoring, diagnostic innovations, and implantable devices. Public safety and emergency services will enjoy better predictive policing and real-time alerts, enhanced communication, and improved situational awareness.

What’s Your Vision for Wireless Power?

What haven’t I mentioned that you know about? What can you imagine for the use of wireless electricity? Drop a comment below and let’s continue the conversation.

Here’s a list of sources I used to satisfy my curiosity. They’ll give you more information than I was able to provide here.

https://arxiv.org/ftp/arxiv/papers/2003/2003.01240.pdf

https://blog.ugreen.com/stay-safe-and-secure-understanding-wireless-charging-safety/

https://circuitdigest.com/tutorial/different-types-of-wireless-power-transmission-technologies-and-their-working

https://electronics.howstuffworks.com/everyday-tech/wireless-power.htm

https://evchargingsummit.com/blog/everything-you-need-to-know-about-wireless-ev-charging/

https://guidehouseinsights.com/news-and-views/true-long-range-wireless-power-for-the-smart-home-is-almost-here

https://interestingengineering.com/culture/welcome-to-the-age-of-wireless-electricity

https://jelouis.commons.gc.cuny.edu/the-invention-and-evolution-of-wireless-power/

https://keutek.com/blogs/news/are-wireless-chargers-harmful-to-your-health

https://powermat.com/wireless-charging-for-medical-devices/

https://sites.suffolk.edu/xenia/2016/02/17/nikola-tesla-and-his-work-in-wireless-energy-and-power-transfer/