A few years back a wireless charging device that was approved by the FCC. It sounds like a cool space age technical device, doesn’t it? Well, it is really just a repackaging of an old principle. Nikola Tesla did experiments with wireless power transmission long ago, which despite his accomplishments, which were ground-breaking at the time, showed a lack of understanding of power distribution. The claims then were free wireless power to the world. I worked on building a version of this when I was 13 years old and my son did a science project on it when he was in middle school. The range is nothing like what was imagined.
Basically the power from a radio transmitter can be collected, rectified and used to charge a battery, or run a small device. What the FCC just approved was the operation of the transmitter, and it really doesn’t indicate an endorsement of the effectiveness, usability or efficiency of the device. The stated range is very limited, but despite that fact, it captured the imagination of the public and the investment money from investors who thought that they were funding a revolution in technology. Some of the modern additions included a carbon nano crystal antenna to be able to create a resonant antenna in a smaller space, and beam steering to increase the efficiency of the power transfer.
What was not taken in to account is the power loss. The transmitter sends the power out but despite the attempts to focus the energy, only part of it is recovered by the receiving device. There is loss because of spreading of the energy over the increasing larger surface of the sphere as the energy travels further from the source, loss in radiating the energy, and the loss of power along the transmission path as physical obstructions are encountered. This is why Tesla’s original design failed. The physics have not changed.
Imagination rather than physics took over and claims were made about being able to power portable appliances, cars, and even houses. I got a call from someone wanting to use wireless technology to distribute power to a neighborhood. A microwave oven is a form of wireless power transmission and it is easy to see what it does to item in the field. Now imagine the power for the whole house, plus enough energy to make up for the loss transmitted through the air. What would happen to anything that got in to that path? It would be fried to a crisp by the power being transmitted.
There is some irony that in a world where people are worried about global warming, exposure to power line fields, and cell phone exposure that there would be such a rush to embrace a device that transmits energy in to the room just to save a few feet of cable. Wireless communications technologies are great tools for mobility, but there are times to just plug-in the device.