Nikola Tesla is known for many things besides inspiring the name of an electric car company -- the design of the alternating current (AC) electricity supply system and motor is perhaps the innovation that affects the most people to this day. However, his dream was to do away with the wires and distribute electric power wirelessly – his Wardenclyffe Tower on Long Island was perhaps the best-known monument to this unfulfilled quest. If Nikola were alive today, he would likely be excited about (and probably consulting on) a new system developed by researchers in South Korea to transmit electric power safely using a wireless laser. Does it work? How does a transmission of 30 meters (98 feet) sound? Will we get more use out of this than just wirelessly charging our cell phones?
“The demand for wireless power transfer (WPT) systems is increasing with the growing needs of portable electronic gadgets, internet of things devices, electric vehicle charging, and smart mobile phones. In addition, the advent of 5G mobile communication that consumes significant amounts of power is deriving the demand of, long-range, low-cost, and low-latency wireless power transfer techniques.”
In a new study published in the journal Optics Express, a research team led by Jinyong Ha from Sejong University in South Korea explains that the demand for wireless electrical power in 2022 is being driven by “gadgets” and “5G” – two universal things Nikola Tesla didn’t have to help him generate excitement and funding for his wireless electricity projects. While a few attempts at wireless transmission have been successful, they have been over short distances (well under a meter) and were dangerous to humans. To hurdle those challenging obstacles, Ha and his team turned to a technology called ‘distributed laser charging’.
“Recently, an erbium-doped fiber-based gain medium operating at a wavelength of 1550 nm based on the RBC technique also referred to as distributed laser charging (DLC) via free space was presented. To sum up, the design of an efficient WPT system requires an efficient light source with low divergence and high gain, low beam deviation for longer distances, smaller hazardous wavelength region, and high PV cell optical to electrical energy conversion efficiency.”
Fortunately, the press release puts this technology in terms those of us much lower in pay grades than Ha and his researchers can understand. While traditional lasers use optical components integrated in a single laser cavity, distributed laser charging separates the device into a transmitter and a receiver. When there is a clear line of sight between the transmitter and the receiver, a laser cavity is formed between them over the air and light-based power is delivered between them. For those who have watched laser beams cut through metal or laser swords cut through Jedi arms, there is a safety feature to distributed laser charging – if someone or something enters into the laser’s path, the system automatically switches to a “power-safe mode.” That sounds pretty rudimentary and susceptible to all kinds of blockage possibilities, but that appears to be the team’s definition of “hazard-free” wireless power delivery.
“When wireless is perfectly applied the whole earth will be converted into a huge brain, which in fact it is, all things being particles of a real and rhythmic whole.”
Nikola Tesla’s dream was more elegant, but Ha’s is demonstrable and safe in comparison to other wireless ideas of the past. The erbium-doped fiber amplifier (the optical power source) operates a wavelength which won't harm the human eyes or skin. For additional safety, the system used a wavelength division multiplexing filter that created a narrowband beam with optical power within the safety limits for free space (over the air) propagation. On the other end, the receiver has a retroreflector, a photovoltaic cell for converting the optical signal to electrical power, and an LED that is illuminated while the system is in power deliver mode. is being delivered. To meet the requirement that this be a system which can power “portable electronic gadgets, internet of things devices, electric vehicle charging, and smart mobile phones,” the receiver was designed to be small enough to fit into all of these devices. With transmitter and receiver operational, the researchers turned the system on and began moving them farther and farther apart to determine just how far this wireless power transmission system would work before the signal was too faint.
“The results showed that a single-channel wireless optical power transfer system could create an optical power of 400 mW with a channel line width of 1 nm over a distance of 30 meters.”
To put this in simpler terms, the transmitter was able to power devices 100 feet away using an extremely low intensity light that did not hurt the eyes of those watching it and did not burn through the hands, legs or pets that passed through it will in operation – instead entering a “safe power transfer mode” just as it was designed to do. While the distance is impressive, it is a long way from city-wide or world-wide as Nikola Tesla had dreamed of. Nonetheless, Ha and his team say this wireless power transmission system as is has practical applications today.
“Using the laser charging system to replace power cords in factories could save on maintenance and replacement costs. This could be particularly useful in harsh environments where electrical connections can cause interference or pose a fire hazard.”
For those who don’t work in factories, other practical applications include on-the-go charging for smartphones – instead of being anchored to chargers, phones and other devices could charge any time they are within sight of a power transmitter. That is a it awkward if your phone is in a pocket or purse, but it is definitely a step in the right direction. Would Nikola Tesla agree?
“I don't care that they stole my idea. I care that they don't have any of their own.”
OK, the “wireless” part is his idea, but Ha and his team didn’t get the laser idea from Tesla. They’re going to have to get beyond line-of-sight and the 30-meter distance for their system to be practical, but Nikola would certainly be happy that progress is being made towards his dream of wireless electricity delivery. That is … unless he was distracted by everything else going on in the world he was trying to illuminate. That is when the philosopher side of Nikola Tesla kicked in – a side we could use a little more of today.
“If your hate could be turned into electricity, it would light up the whole world.”