The sun is a radiative form of light energy. Although there are many sun worshippers out there, too much exposure can be harmful to humans. Another source of radiative energy is the laser, such as IPL (intense pulse light) which is a directed form of light energy and can have therapeutic uses for certain skin conditions. However, excess radiative energy can burn and potentially damage cells and interfere with biological processes.
Although many companies around the world have been attempting to solve the wireless energy demand, I wanted to examine two companies based in the U.S.: WiTricity and uBeam.
WiTricity powers electronic devices via non-radiative transfer of power via electromagnetic coupling of objects within a resonant field. We are surrounded by electromagnetic fields as anyone who has used a compass will know that the needle will point north, where the magnetic center of the earth's gravity will pull objects. Although there has been safety concerns about electromagnetic (EM) radiation, especially those being emitted by our mobile devices and computers and wifi signals, WiTricity bypasses the safety concerns of EM radiation via resonant magnetic coupling in which essentially connects objects with the same resonant frequency and transfers energy without affecting surrounding objects nor the surrounding environment. This is referred to as ICPT (inductively coupled energy transfer).
In a parallel story, Meredith Perry, the founder of uBeam, was said to be in her dorm room at the University of Pennsylvania, and was surrounded by a chaotic mess of wires and adapters, before moving onto research the possibilities of wireless energy transfer.
uBeam (founded 2011), although identical in concept of wireless energy transfer as WiTricity (founded 2007), utilises a completely different sort of technology. Instead of inductively coupled energy transfer (ICPT), uBeam utilises directional ultrasound to transmit energy. Most people understand ultrasound via medical devices, especially in female gynecology in order to create images of ovaries and also in pregnancies to detect images of developing fetuses. The development of ultrasound technology began in 1870 with the discovery of echolocation used by bats then was primarily utilised by the military in WWI, with applications of sonar devices to detect submarines, then starting in 1965, ultrasound became available for commercial use in medical devices for body scanning and detection of tumours.
Although, ultrasound is generally considered safe in medical usage, there are many problematic issues with ultrasound in the transmission of energy. Firstly, ultrasound can negatively affect biological tissues and create cavities within the skin with prolonged exposure:
-Thermal: owning to ultrasound the temperature of the tissue increases. The rise varies with the ultrasound intensity and exposure time.
-Cavitational: owning to ultrasound-induced pressure, gaseous cavities are formed in the tissue. The cavities can collapse causing significant changes in the surrounding tissue.
-Acoustic streaming: As a result of the sound waves, a one-dimensional flow current that affects the surrounding tissue develops
Ultrasound-assisted sonophresis can be utilised between low frequencies (18-100kHz) to high frequencies (3-10 MHz). According to uBeam patents: Sender communications for wireless power transfer US 20120299540 A1 and Receiver transducer for wireless power transfer US 20120300593, the company has outlined the usage of its ultrasound energy transmitters between 50kHz to 110kHz. Although this is considered in the low range for human usage, and typically in the range of medical devices, the effects of long-term exposure to continual ultrasound exposure may be potentially dangerous as outlined above. In addition, since animals, such as cats and dogs hear in the 20Hz-80kHz range, with dogs being able to hear up to 60kHz (source: Metrics and Methods for Security Risk Management by Carl Young, pp.114) and cats up to 80kHz (source: The Neuroethology of Predation and Escape by Sillar, Picton and Heitler, pp.108), this might also have a detrimental effect on pets that people might keep in their homes. However, in the press, and on their website, uBeam has been reported that their ultrasound energy power transfer device will not affect pets, despite information to the contrary in their patents filed above in 2012, which clearly shows a range that will indeed affect pets.
Curiously, uBeam also states on their website that 99.9% of the emitted ultrasound will bounce off skin and the uBeam description makes a comparison to flourescent lights. However, florescent lights are an entirely different sort of energy source than ultrasound, and ultrasound has been proven to absorb into skin tissues even at a very low setting of 50kHz. Airborne ultrasound in the 20-50kHz range have caused a number of people who work in industrial applications to suffer from fatigue, headache, nausea, tinnitus and disturbance of neuromuscular coordination. The Canadian government recommendation for exposure limits of ultrasound range are given in 1/3-octave bands from 16 kHz to 50 kHz. Again, in the 2012 uBeam patents, their ultrasound power transmission range is between 50kHz-110kHz, a range that is potentially harmful to humans under continual exposure. In addition, pets will also be detrimentally affected at this range as mentioned above.
uBeam has also said in the press that the directional ultrasound waves will not be transmitted if it is not in the direct line of sight for the charging of electronic devices, such as the mobile phone and other devices, but because ultrasound waves penetrate skin at the 50kHz-110kHz range, a range clearly stated in their patents, there will have to be a way for the transmitter and receiver to recognise skin tissue and other objects so that the directional ultrasound waves will not affect humans. This will be exceeding problematic especially if as uBeam had outlined, they plan to construct an overhead ceiling fixture transmitting directional waves below, affecting entire areas instead of isolated locations where electronic devices can be charged.
From a cursory standpoint, I think what Meredith Perry is doing is pretty brilliant- she, like Marie Curie, is attempting to solve a scientific and commercial problem in which a solution is in high demand. She is also an interesting figure and a cult of personality who should be lauded for her work as an entrepreneur, and not simply because she is a woman. She, like Travis Kalanick, has a kind of charisma that VCs typically are attracted to and both have been stalwart in the defense of their companies under heavy criticism. However, upon a closer analysis of the comparison between technologies, I think the problem of wireless energy is better solved by WiTricity's more private and reclusive founder, Marin Soljačić.
In the future, I predict WiTricity will potentially change the landscape of our wired present, so that we may no longer see twisted cables in the sky everywhere we go, and instead of those utility poles and cell phone towers, we might see an entirely different landscape, one that will perhaps be replaced by WiTricity's inductively coupled energy transfer.
By Sierra Choi