The field is strongest at its center. At 10, it's just like, nothing. If you had a coil the size of a desktop, you could probably hold it a foot above the desk, but you'd be using a lot of power.
That's the big problem with wireless charging in general. The research is trying to increase the efficiency of charging, or make our phones more energy efficient. While this makes wireless charging limited for phones that use a lot of power, it isn't as challenging for smaller devices like Radio-frequency identification RFID tags that use less power. The difference in energy between the two, if you thought about them in terms of mass, is like an African elephant versus an ant, Hester said.
In other words, although wireless chargers are relatively weak now, they'll get better every year. Business Insider contributor Simon Hill recently ranked a few of his favorites after testing about 40 of them. For you. World globe An icon of the world globe, indicating different international options. Get the Insider App. The receiver s retrieve the power and convert it back to DC or AC electric current to be used by an electrical load. An antenna or coupling device at the receiver converts the electromagnetic energy to electric current.
The electromagnetic field that radiates from an antenna takes on characteristics that depend on the distance from the radiating element. Two areas of wireless power techniques can be distinguished: near field area and far-field area. In near field wireless power transfer, power is transmitted over short distances by magnetic fields through inductive coupling electromagnetic induction between coils of wire, or by electric fields through capacitive coupling electrostatic induction between metal electrodes.
The first stage is basically an inverter, which converts DC current into AC current at the appropriate frequency. After the inverter is an impedance matching network which adjusts the impedance seen by the transmitting coil according to the load.
The next stage is composed of the transmitting and receiving coils, coupling to generate the magnetic field and intercept it. A second impedance matching network ensures that the load sees the appropriate impedance. Finally, a rectifier converts the alternating current to a stable DC current through a voltage regulator. To make it possible, Emrod uses rectifying antennas, a.
It sounds futuristic and fantastic but has been an iterative process since Tesla. The link to Nikola Tesla , Kushnir admits, is more of an imaginative, feel-good tale than a true genealogy. Emrod, by contrast, can keep the beam of electricity tight and focused with two technologies. The first is transmission-related: Small radio elements and single wave patterns create a collimated beam, which means that the rays are aligned in parallel, and will not spread much as they propagate.
Second, Emrod uses engineered metamaterials with tiny patterns that effectively interact with those radio waves. Kushnir envisions placing Emrod technology on difficult terrain that links with the sunniest, windiest, or most hydro-friendly points on Earth as these often rural places have the widest gap in electrification. The team is making progress -- in June , the MIT team published a paper detailing a successful demonstration of their prototype.
They used resonating coils to power a light bulb over a distance of about seven feet two meters [Source: PhysOrg ]. Other wireless power theories involve enormous distances -- like from space to the Earth. We'll look at those next. NASA has also developed long-distance power sources for unmanned planes. Scientists at Marshal Space Flight Center used an invisible, infrared laser to activate photovoltaic cells on a small airplane.
The photovoltaic cells -- essentially solar cells -- converted the light to electricity. A similar system could also power devices that climb a space elevator 's tether. However, systems like this require a direct line of sight between the laser and the solar cells. Whether or not it incorporates resonance, induction generally sends power over relatively short distances.
But some plans for wireless power involve moving electricity over a span of miles. A few proposals even involve sending power to the Earth from space. In the s, Canada's Communications Research Centre created a small airplane that could run off power beamed from the Earth. Rather flying from point to point, the SHARP could fly in circles two kilometers in diameter at an altitude of about 13 miles 21 kilometers. Most importantly, the aircraft could fly for months at a time.
A large, disc-shaped rectifying antenna , or rectenna , just behind the plane's wings changed the microwave energy from the transmitter into direct-current DC electricity. Because of the microwaves' interaction with the rectenna, the SHARP had a constant power supply as long as it was in range of a functioning microwave array.
They are usually made an array of dipole antennae, which have positive and negative poles. These antennae connect to semiconductor diodes. Here's what happens:. Other, longer-range power transmission ideas also rely on rectennae. David Criswell of the University of Houston has proposed the use of microwaves to transmit electricity to Earth from solar power stations on the moon.
Tens of thousands of receivers on Earth would capture this energy, and rectennae would convert it to electricity. Microwaves pass through the atmosphere easily, and rectennae rectify microwaves into electricity very efficiently. In addition, Earth-based rectennae could be constructed with a mesh-like framework, allowing the sun and rain to reach the ground underneath and minimizing the environmental impact.
Such a setup could provide a clean source of power. However, it does have some drawbacks:. As the Earth's population continues to grow, however, the demand for electricity could outpace the ability to produce it and move it around.
Eventually, wireless power may become a necessity rather than just an interesting idea. Sign up for our Newsletter! Mobile Newsletter banner close.
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