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Wireless charging from 15 feet: can WattUp deliver on the promise?

Energous’ WattUp technology will let you wirelessly charge your smart phones and watches with a radius of 15 feet. Prototypes and products should arrive next year.
August 19, 2014
WattUp wireless charging Wearables

Wireless charging for mobile devices has been around for a little while now, but you’re still dependent on cables in some form, be that through a USB connected charging mat or Qi inductive docking station. Wouldn’t it be so much better if you could just walk in through the door and have your smartphone begin charging?

This is exactly what Energous’ WattUp technology aims to let you do, by offering wireless charging up to 15 feet in any direction from the hub. WattUp transmits power from a wireless hub, which can send energy over a distance of 30 feet in diameter, or from a smaller transmitter to plug into your nightstand that can be used to charge wearables and phones whilst you sleep. Combined with a case that collects the signal and converts it into a usable charge, WattUp allows for truly wireless charging.

As well as wireless charging cases and ideas like chargeable battery backpacks, Energous wants manufacturers to build its technology directly into devices, much like Qi chargeable handsets currently on the market. To do this, Energous aims to license its technology out to a wide range of manufacturers. The company currently has 7 partners in total, 5 of which have been publicly announced.

“Our collaboration with Dialog Semiconductor will provide consumer electronics manufacturers with a superior technology that will differentiate their products with the freedom of charging without wires,” – Stephen R. Rizzone, CEO of Energous Corporation

The latest partner to team up with Energous is integrated circuit manufacturer Dialog Semiconductor, which produces some of the lowest cost Bluetooth chipsets on the market, a key technology used in WattUp. Together with Dialog, Energous plans to bring reference designs and prototypes of its technology to other partners and consumers over the coming year.

How it works

Looking at the technology at a high level, it essentially transmits energy over the air, which is then converted back into a DC charge by the receiver. WattUp operates over the unlicensed WiFi ISM band between 5.7 and 5.8 GHz, and uses the same open-frequency transmitters as typical WiFi hubs, to comply with the FCC’s regulation on interference with other devices.

Of course that’s not all it does. WattUp also uses a Bluetooth connection between the transmitter and receiver to scan for nearby gadgets and to direct the ratio waves towards the receiver with more accuracy. Combined with a management app, you can also control when to charge your devices.

The transmitter contains around a hundred small antennae which send out radio waves with relatively small amounts of power, which are then accumulated by a smaller number of antennae in the receiver. The receiver converts the radio frequency power into a DC signal to charge the handset, tablet, or smartwatch.

As with all wireless signals, the power decreases over distance. The end result is roughly 4 watts of power when the receiving device is located within 5 feet of the transmitter, which is not far off what you will get by plugging your phone into the wall. The power available decreases to 2 watts at a range of 5 to 10 ft, and falls off to a single watt of power at 10 -15 feet. But this should still be enough to slowly charge up your smartphone or tablet whilst using it.

Although home spaces will be able to get by with a single hub, the technology also lends itself nicely to public spaces. Energous envisions businesses and coffee shops making using of a “mesh” type network, which uses several transmitter hubs to cover a larger area.

Public Wireless Charging

The trade-off with wireless over cables is that power transmission is less efficient, and WattUp won’t be as quick at charging your gadgets as plugging in directly to the mains. However, being able to charge your device wirelessly means that users will be able to keep using their devices whilst charging, putting an end to the “wall-hugger” problem.

Similarly, wireless charging methods are going to cost a lot more than the few dollars that you’ll pay for a USB cable, although Energous doesn’t have a price for its products yet. Still, the convenience might be worth the setup cost, especially if it means less time spent worrying about how much juice your phone has left.

Say goodbye to charging docks, WattUp will let you charge your phone from within your pocket.

“Great, but is it safe?”

Whenever we talk about wireless power, you can bet that there’ll be a comment questioning the safety of sending power over the air. To address these concerns, Energous gave us a few details about the regulations that they have to adhere to, and the level of testing that’s going into WattUp.

For starters, part 18 of the FCC’s wireless regulations deals with the emissions, power, and safety of wireless transmissions. The regular wireless communications from your mobile device sends and receives rather absorptive signals with about 2 watts of power. WattUp is a more reflective WiFi based technology, which utilises hundreds of antennas in the transmitters and 10 or so in the receiver, each transmitting just microwatts of power each. In other words, WattUp’s signals are highly distributed, making it no more of a risk than your smartphone’s more concentrated signal.

Furthermore, WattUp will also be undergoing an absorption rate test, to see how much energy is absorbed by tissue and what impact that has on the user. As WiFi signals are generally quite reflective, you’ll probably have noticed how signal strength drops off through walls, most of the energy would be reflected off human tissue. Again, the absorption rating should be a fraction of any normal cell phone.

Energous will be showing off a prototype of its WattUp technology at CES in January, where we will certainly go and take a close look at it in action. The first wave of commercial products, such as smartphone cases and chargers for wearables, should be ready for next year’s infamous Black Friday.