I think everyone at one time or another had wished that there were available sources of wireless power when dealing with electronics, mobile phones, personal computers and other tech devices. Of course, one such ubiquitous source is the sun, but for those nations, such as the U.K., in which there is scarce sunshine, solar energy to power our devices might not work at all, especially during the winter months.
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).
WiTricity couples together objects with the same resonant frequency for uninterrupted power transfer without affecting the surrounding environment or other objects
In comparison, MRI (magnetic resonant imaging) is a different sort of process in which uses near-field resonant magnetic fields to create images, so that all objects in this near field are affected. Microwaves are also types of energy transmission that affects all objects within that radiation field using EM waves like radio frequency signals. Wifi is also a type of energy transfer using EM waves via radio frequency signals. The main problem with wifi is that because it is based in near-proximity, objects that are further away will have a weaker signal than objects that are closely located, therefore wasting a lot of energy on the radiation (the entire area affected). Whereas, WiTricity uses a method of coupling objects together using electromagnetic (EM) induction via a resonant field, so that the strength of the power transfer is not compromised, as long as all objects are located within that resonant field.
WiTricity was founded by a professor at MIT, Marin Soljačić, a Croatian-American physicist and electrical engineer who was said to come up with the idea for wireless energy as he was standing in his kitchen late at night looking for his mobile phone charger.
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.
Whereas WiTricity only connects to objects with the same resonant frequency, uBeam sends a directional ultrasound to all objects in the range, potentially affecting the entire surrounding environment, in addition to creating a variable and perhaps, inconsistent 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:
The ultrasound energy penetrates the body tissue and is absorbed by the tissue. The effect on the tissue can be
-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
(source: Membranes for Life Sciences: Membrane Technology, Volume 1 edited by Klaus-Viktor Peinemann, Suzana Pererira Nunes; pp. 208)
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.
Dogs can hear up to 60kHz and cats can hear up to 80kHz. uBeam's ultrasound is within the 50-110kHz range according to their patents. Ultrasound has been found to be harmful to animals and humans with prolonged exposure, potentially leading to illness and death.
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.
Meredith Perry, Founder of uBeam explaining the concept of how ultrasound energy will be transmitted via ceiling fixtures in 2015.
In 1903, Marie Curie was the first woman to win the Nobel Prize in regards to the discovery of radioactivity and the use of radiation in the death of cancer cells. However, it was not known at that time of the detrimental effects of radiation, and Marie Curie died in 1934 of long-term exposure to radiation. However, currently in our era, we do know the potential detrimental effects of ultrasound via the study of workers who have been exposed to airborne ultrasound.
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.
The ubiquitous criss-crossing power cables in San Francisco.
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