Wireless power: could Cota make it long-distance and mainstream?

Is power over Wi-Fi the future of cord-free tech?

 The power levels received from Cota changed as we stood in the way of the power beam
The power levels received from Cota changed as we stood in the way of the power beam

The only technology that claims to match Cota's 30 feet is charging by laser; that could go up to 300 feet but there are still potential safety issues and your phone has to be in direct line of sight. Ultrasound charging could reach up to ten feet and could deliver 40W (enough to charge a laptop) but you need a separate charger for every device and Hatem doesn't believe it's as efficient as Cota, which can send its 1W up to 30 feet in all directions and cover all the rooms in a two-storey house (at least in US buildings where brick walls are rare).

"Transmitting at 80KHz ultrasound loses half the energy for every metre it travels, and it doesn't go through walls well, it gets absorbed. It's like when someone has a party down the road and you can hear the bass from their music; you hear the low frequencies but it's the high frequencies you need for charging." He also believes his target $99 price for Cota will be cheaper than ultrasound equivalents.

 A USB adaptor to receiver power from Cota
A USB adaptor to receiver power from Cota; until phones have it built in, you'll need an adaptor but it will be much smaller

We've seen a lot of wireless power demonstrations and Cota is still a prototype, but it works – and it reuses enough existing components that manufacturing shouldn't be too pricy. In a couple of years time, you might be able to buy a Wi-Fi access point that not only gets your devices online but powers them as well.

Being able to charge devices without plugging them in has several advantages. The power port takes up a small amount of space, which could be used for a bigger battery or more memory; it's also another hole in the case that makes it harder to create waterproof devices. But if there will always be power available, designers can make different decisions.

A phone could be thinner and lighter with a very small battery that just gets topped up all the time, or a device could be more powerful instead of optimising for battery life. "Devices like remote controls are still dumb," complains Zeine; "the remote doesn't know the state of the TV or what buttons do when you're in different modes. The cleverer learning remotes drain so much power that you have to charge them far more often. The power needs stop remote controls from getting more useful."

Apply that to other things in your home; almost everything from smoke alarms to the clock on the oven to the future Internet of Things sensors could be easier to manage and more useful if you didn't have to worry about the batteries running out.