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Can we power the smart home with ambient radio waves?

At CES, we saw Samsung show off a TV remote that powers itself with nearby wireless waves, eliminating the need to even have a battery. While our own A/V Editor Phil Nickinson is skeptical about the prospect, I’m more hopeful for the broad implications.

If Samsung applies this tech at scale and includes this remote in all of its TVs from here on out, there’s going to be a marked reduction in the number of batteries that need to be made. That’s ultimately good news for the planet, and likely saves everyone a few bucks. The amount of power saved from charging those batteries is going to be fairly minimal, seeing as how TV remotes don’t use much juice to begin with. That said, is the air crackling with enough invisible power to keep other low-demand smart home devices operating?

After all, we’re being blanketed by more and more overlapping spheres of electromagnetic waves, including Wi-Fi, cellular, FM, and TV. Our devices are becoming more energy-efficient, too. If we’re using all this power to blast out signals, maybe we can recoup some of the energy by catching it on the other side. The idea isn’t new. Nikola Tesla dreamed of being able to power whole cities with wireless transmission. We aren’t anywhere close to being able to do that today, but we already have companies making battery-free electronics thanks to emerging tech in this arena.

Image used with permission by copyright holder

How would we use wireless power harvesting?

The further you get from the source of a transmission, the less power it has to be harvested. The power we’re able to pull at everyday signal strength is minimal. In theory, you would get less than 0.0001 of a watt harvesting 2.4 GHz power beyond 1 meter from its source. It’s not a lot to play with.

Despite those limits, Wiliot has been able to make a full-blown computer that runs on ambient power. It’s a printed sticker that can sense what’s going on nearby, communicate with other machines, and only costs a few pennies. These are primarily used for food, retail, and medicine to track shipment and storage.

Manufacturers like Atmosic can create Bluetooth 5 chips that run on ambient energy waves. As an example, it’s been able to power a keyboard and get it to communicate without needing any batteries installed. A commercially available battery-free keyboard using Atmosic’s chip is already in the works.

Atmosic Battery-Free Keyboard Using RF energy harvesting

For more high-demand devices, we’ll need to resort to dedicated transmitters and receivers. We’ve seen quite a few of these already, but their energy efficiency is still in question. Wi-Charge is one of the companies jumping in from this angle. It relies on targeted bursts of infrared to send power wirelessly. Its transmitter puck has 12-volt draw, but the receiver can generate 5V at the other end at most. Meanwhile Ossia is working with Spigen to make a phone case that can act as a wireless power receiver, but beyond a range of six feet, it’s receiving a 10th of what’s being transmitted. Along that vein, GuRu is working with Motorola to bake a power receiver right into a phone. Their current best-case scenario has efficiency dropping below 50% beyond 10 feet of range. Is it worth setting up a transmitter in your house if it’s going to be this inefficient? It may be needed until we close the gap between the ambient energy available and power demand.

So why aren’t we there yet?

There are a few reasons why we haven’t reached the nirvana of a smart home completely decoupled from the energy grid. For one, the power supply is constantly fluctuating. Location and obstacles are obvious X factors. Even for devices that are physically static, atmospheric conditions and time of day can influence how well radios waves can be transmitted or received.

There’s also the challenge of standardization. If transmission devices aren’t optimized for powering targets, it’s going to be hard to get this vision off the ground. The AirFuel Alliance is trying to bring multiple manufacturers onto the same page on this front.

A diagram showing power being sent wirelessly to a range of office devices.

Luckily, radio frequency harvesting doesn’t exist in a vacuum. Going back to the Samsung remote example, its primary feature was actually running on solar power. RF harvesting can function alongside a host of other passive energy-gathering techniques, like thermal and mechanical, in order to make up the total energy demand. Like Samsung, Disney Research has found use in combining ambient radio energy with solar panels to enable wireless data transfer. As the efficiency of these methods improves and manufacturers start adding in layers of ambient power harvesting, their need for batteries will gradually diminish. Maybe that won’t result in ditching batteries altogether, but even if it just means getting by with smaller batteries, that’s still an improvement.

At the consumer level, the amount of power we can get from ambient wireless is still very small and inconsistent. At best, these techniques are only useful for devices that need a small amount of power on a very occasional basis. Beyond TV remotes, it’s easy to imagine having independent radio-powered sensors peppered throughout your home’s most remote corners in order to provide ongoing reporting on humidity and temperature. This could very well expand the dataset your smart thermostat is working with.

The idea holds huge implications for the smart home. Though we are still likely years away from seeing widespread implementation, we can be hopeful that technology like this exists and the focus on research continues.

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Simon Sage
Simon has been publishing in tech since before the first iPhone was released. When he's not busy lighting a candle for the…
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