Wireless Power Is Coming

Mobile World Congress is one of those events that make you realize the thin line between civilization and barbarism is the width of a single charging cable.

Anyone who's attended MWC (or any massive trade show) is familiar with the creeping dread caused by watching your phone's battery power seep away over the course of a very long workday. Tweet by tweet, photo by photo, text by text, the percentage points tick away, until you're scrambling in your bag for a battery packamid a tangle of chargers and cables or searching the packed halls and press lounges for a free plug point—an oasis in the desert.

Imagine you never had to seek out an outlet, carry a backup battery, or stuff an array of cables into your bag again; that all your devices were being charged continuously, no matter where you went. Someday you may not have to imagine it—because companies like Energous and Ossia are working to make it a reality.

Nikola Tesla first envisioned a wireless power transmission system in the early 1890s; he even attempted to build an experimental station, Wardenclyffe Tower, which he hoped would be the first in a worldwide wireless system. Today, phones, smartwatches, and other devices sometimes come with inductive charging coils, which let them charge wirelessly through resonant inductive coupling. But this method relies on direct contact between the device and a charging pad—hardly the untethered future Tesla imagined.

That's where Energous and Ossia come in. Both focus on developing "true" wireless charging that works over the air (OTA) so you can power up at a distance. This is the wireless charging we were promised over a century ago. Could our dependence on cables or tethered charging solutions finally be coming to an end?

Why Today's Wireless Charging Disappoints

Though wireless charging has been around for years, it had a big boost last year, when Apple announced that its new phones had the feature. Qi, used by most phones (including iPhones), and the lesser-known PMA are the two forms of wireless charging used by current consumer-oriented devices. Both standards require one or more induction coils in a charging pad to transmit power and another in the device that's being charged.

There are some minor differences between the two standards, but they share the same limitations: the need for very close contact between the device and the charging pad, as well as proper alignment of the induction coils, for power to be transmitted.

 The range can be slightly extended: The FCC Office of Engineering and Technology Laboratory Division recently approved an increase in distance of up to 20cm, potentially by using multiple charging coils. So far, though, no products currently utilize longer-range wireless charging for inductive charging coils.

Other potential problems with this type of wireless charging include heat buildup. "The circuitry in the wireless charger must be thoughtfully designed to prevent excess heat from building up in the charger and transferring to your smartphone," said Jack Norton, director of electrical engineering at Belkin. "Excess heat can lead to lower life spans for the wireless charger [and] your phone's battery."

The primary reason that wireless charging is slower than using a fast charge–enabled power brick is that a device will reduce its charging speed to manage heat and prevent damage to sensitive components. "Managing heat is definitely one of the challenges in wirelessly transferring power beyond 10 watts," said Charlie Quong, VP of product development and engineering for Zagg (Mophie).

Thermal dissipation can be managed in a variety of ways, including: passive airflow, which means putting holes or vents in strategic locations to transfer heat away from the device being charged; cooling fans; heat sinks made of metal or thermal glue; larger housing; specialized material; and more efficient component layouts. But even when you mitigate heat, inductive-charging speed for phones is limited. According to Pablo Valentin, global product manager at Belkin, "The fastest output realized in the market right now is 15W, both from charger side and phone side."

That means a device such as the Samsung Galaxy S9+$839.99 at Samsung, which is fast charge–compatible, can juice up to 50 percent in 1 hour and 34 minutes. That's not quite as fast as regular fast charging using an adapter (35 minutes to 50 percent), but it's a big step toward making wireless charging fast and convenient.

 For larger devices such as laptops, which have more surface area and ventilation options, wireless charging can go to 30W or more. But when it comes to phones, you're still likely looking at a charging speed of 10W to 15W for most wireless charging pads, with most of them dropping down to slower wattages (5W) to prevent heat buildup. That's quite a bit slower than a 27W Qualcomm Quick Charge 4.0+ power adapter or 29W USB-C Power Adapter for the iPhone X$999.00 at Verizon Wireless, for example.

Another and perhaps more significant downside of inductive wireless charging involves the size of the charging coils. "There are different coil designs that can be implemented, depending on the application, but the size of the coil must be optimized and calibrated correctly for a wireless charging system to work properly," said Quong.

Charging coils can be made to fit on small devices such as Bluetooth earbuds, but such coils are uncommon. According to Gary Gao, wireless charging leader for Anker, the most common coil design is 50mm in diameter as required by the Qi standard.

What Does This Look Like?

Though other companies are exploring this space, the Energous and Ossia wireless charging standards come closest to matching Nikola Tesla's vision. The two technologies operate using different radio frequencies, but they both let you charge a device from a distance, transmitting power over the air without using cables or inductive charging coils.

Energous: The Energous wireless charging technology works with the company's proprietary WattUp transmitter and receiver. It operates similarly to Wi-Fi by transmitting power in the 900MHz frequency to the receiver, which converts the RF signal into DC power.

Energous uses beamforming for the mid-field and far-field transmitters: a directional antenna array sends energy directly to the receiver. In the case of obstacles, it can reflect energy beams off walls and ceilings, although this results in some efficiency loss. The technology breaks down into three different types of wireless charging: near field, mid field, and far field, with varying ranges.

Energous WattUp mid-field transmitter design

Energous WattUp far-field transmitter design

In addition to charging at a distance, each transmitter would be supported by a software layer (app- or web portal-based) to allow power management of devices connected to the various WattUp transmitters. You'll be able to control which devices are charged and to prevent your transmitter from charging your neighbors' devices. The mid-field and far-field transmitters also allow you to set device priorities and rules for charging and authentication and to configure charging zones. The short-range transmitter is more traditional: You can't set priorities or charging rules, but once you drop the device on the charging pad, you're able to view its battery level and expected time to charge fully.

The transmitter "sees all the different Bluetooth devices that are within the room," said Rizzone. "It identifies which ones are close enough to be charged and also identifies [whether] they're authorized on the network, and then it actually monitors, with sensors, what the user's typically doing."

This type of software-based power management is vital, Rizzone said, because "under Part 15 rules, you can only send one watt of power out. That means that at a foot away, you're going to get … one milliwatt or lower. So a very, very small amount." (FCC Part 18 doesn't limit the amount of power).

With the widespread adoption of WattUp transmitters, though (however far off that might be), you'd be able to go to a coffee shop and even travel without having to carry adapters or cables: Various transmitters in public and private spaces would top up your various devices as you need them and according to your usage patterns.

As with Energous, the company's technology is similar to Wi-Fi and uses the 2.4GHz spectrum (it's considering the 5.8GHz spectrum for the future) under its proprietary "Cota" standard. Ossia's receiver sends a low-power beacon signal to the Cota Power Transmitter. The transmitter then directs power along the same pathway, with the receiver converting the RF signal to DC power. That allows Ossia's transmitter to send power to multiple Cota-enabled devices simultaneously and to send power to objects in motion. It also effectively bypasses objects that are in the way, since the signal doesn't pass through people, animals, or other organic matter.

The current implementation of Ossia's technology is currently showcased by two prototype devices—the Cota Forever Battery and the Cota Tile. The Forever Battery is a AA or AAA battery that wirelessly receives power from a Cota Power Transmitter on the 2.4GHz band. The Cota Tile is a transmitter capable of delivering several watts of power to Cota-enabled devices close to it and milliwatts at a distance of 30 feet. It operates at a greater range than Energous's far-field transmitter, but this requires the transmitter to be larger.

"We know that at a distance, signals drop off very quickly, and we don't really get much power in a far field," said Hatem Zeine, Ossia founder CTO. He explained that the company designs antennas and transmitters to be large enough to extend range of the near field.

Zeine was keen to point out that for consumers, the key to providing useful wireless power isn't necessarily to transmit a high degree of power to one or two devices. "The idea is that power has to be continuous, no matter how fast you go," he said. "This system [the Cota Tile] is running 2.4GHz with 20 watts coming out. At about a meter, we're receiving over 6 watts of power, and at two meters we're talking about a few watts, 2 to 3 watts, and then at the end of the room we're talking about 1 watt. So now, suddenly ... every cubic inch of this room has power."

The Cota Cloud software is able to define the priority of devices that get power and show the basic power usage of the device. When using the Cota Tile on a large scale, the administrator can set up and manage users. With prioritized charging, the Cota Tile first charges devices with lower battery levels; the Cota receiver communicates with the transmitter about how much power it needs. When there are no devices within range that need to be charged, the Cota Tile goes into sleep mode, so it's not wasting energy or transmitting power to devices that are already topped up.

The Cota Tile is able to power a variety of devices in a room because it doesn't have to operate on line of sight. A pair of Cota Tiles are twice as efficient and emit four times the power of a singla Cota Tile. So in a warehouse, for example, numerous Cota Tiles can join together to power hundreds or thousands of compatible devices.

An IoT Revolution

The ability of the WattUp far-field transmitter and the Cota Tile to transmit data along with power makes them particularly compelling for the Internet of Things. "There's no way you can get to a trillion IoT devices without wireless power," said Jennifer Grenz, Ossia's vice president of marketing, in a company blog post. "Wireless power is going to go hand-in-hand with the evolution of this entire market."

The best example of this is Ossia's Cota Forever Battery. It can be placed in smoke alarms, sparing you from charging them and also allowing for the transfer of data by giving you the Cota Cloud: cloud-based software that allows for power management of various devices.

"Let's say your smoke detector in the kitchen goes off," said Zeine. "The battery will notice that the smoke detector has changed its power-draw pattern and knows that this new pattern is actually the alarm going off. It sends a message to your phone; the Cota Cloud will tell you that, 'Hey, your smoke detector is going off.' This makes dumb devices smart. It brings them to the internet age."

With both Energous and Ossia, the software layer is a key component of what makes them so game-changing, since they allow for intelligent power management. We all have devices that need charging, and when we charge them is up to us. We might charge a phone every day, a wearable every few days, a game controller whenever we use it. With wireless power, the software will make that choice for you based on your usage patterns, lifestyle, and even the time of the day. 

Essentially, both the WattUp transmitters and Cota Tile take the burden from the user in deciding what device to charge and when, and take it on themselves. It's as close to a seamless, cable-free existence as you can get.

Cutting One Cord At a Time

In practical terms, this technology is still a few years from implementation for both consumers and enterprises, but potential use cases are already apparent. Both technologies will allow you to effectively cut the cord at home. Phones won't have to be plugged in. Game controllers will charge according to usage. Smoke detectors will never need their batteries changed.

Assuming widespread implementation in public spaces such as coffee shops and office buildings, the endless scramble for chargers, cables, and portable batteries could become a thing of the past. "In the future, you would go into a coffee shop. If it has the Cota logo, and you know your phone has Cota, that means you'll get power when you're in the coffee shop," said Obeidat. "That's the kind of standard that we're creating."

But the biggest impact is likely to be felt with low-power-consumption devices that need to be charged (or their batteries changed) infrequently. Rizzone cited the father of Gordon Bell, Energous VP of Marketing as an example of someone who would benefit considerably from Energous' technology, though he doesn't have many connected devices. "My colleague's father wears hearing aids ... What happens is, he's got these little tiny batteries that are the size of a pomegranate seed, and he's gotta put it in there and swap the battery out. It's a nightmare for an older person."

With a mid-field or far-field transmitter, hearing aids would be able to charge throughout the course of an entire day, according to the usage patterns of the individual user.

Of course, devices such as phones and Bluetooth headphones that are more frequently in need of power boosts are also going to see a shift to wireless charging, according to Rizzone: "A lot of devices that you're currently plugging in and plugging in every single day, eventually, that little tiny tip of your micro USB port breaks. It wears out, or you jammed it in the wrong way, salt water gets in there, sweat, etc. That's a failure part or a failure point for that product. So companies are trying to get rid of that."

Radio Beams Everywhere: Are We Safe?

Energous' longer-range transmission technology are certified under FCC Part 18 and Part 15 while Ossia has passed key tests for FCC approval of the Cota Transmitter, and approval is expected shortly. These rules impose RF exposure requirements and limit power transfer levels. RF exposure must be measured for users and bystanders under different wireless configurations. As a general rule, higher RF power is required to operate at a lower frequency.

In the electric vehicle industry, wireless charging has already been widely implemented and can indicate the kind of requirements we might see for electronics devices. According to an article by Joe Bablo, Ken Boyce, and Hai Jiang at Underwriters Laboratory, aside from the normal safety concerns that apply to any electrical transmission (fire, shock), the wireless charging system has to show it can operate in hazardous conditions and detect and shut down when an organic object enters, among other requirements.

Since the higher power Energous and Ossia technologies use the same radio frequencies as Wi-Fi, one would hope that there are no health impacts—but there are surprisingly few scientific answers to this question. The Nation has reported that the wireless industry has tried to limit the amount of research that can be done into the impact of wireless radiation on public health: "Lack of definitive proof that a technology is harmful does not mean the technology is safe, yet the wireless industry has succeeded in selling this logical fallacy to the world. In truth, the safety of wireless technology has been an unsettled question since the industry's earliest days," wrote authors Mark Hertsgaard and Mark Dowie. "The upshot is that, over the past 30 years, billions of people around the world have been subjected to a massive public-health experiment: Use a cell phone today, find out later if it causes cancer or genetic damage." 

 The Cota beacon signal bounces off walls and objects while avoiding people. Power is delivered along those paths.

According to Ossia, though, Cota technology is safe for people and pets and doesn't interfere with Wi-Fi or face the overheating issues of Qi wireless charging. "2.4GHz and above don't heat metal themselves; they reflect off the metal" Obeidat said.

Energous claims the same. "We're not blasting energy all over," pointed out Rizzone. "We're planting a small, unique pocket of energy just around the device, and it transmits [to] that device."

With FCC certification and no evidence to the contrary, the wireless transmission technologies should be no more dangerous or detrimental than Wi-Fi or any other RF spectrum we're exposed to daily. Perhaps not the most comforting answer, but the only one readily available.

Our Wireless Future

Energous partners with Dialog Semiconductors, a large electronics manufacturer, to produce their transmitters and receivers while Ossia partners with Motherson and Molex, and there have long been rumors about Energous technology ending up in a future Apple product. Neither company manufactures its own hardware, nor do they create consumer products themselves. 

Energous is primarily a licensing company, and its products are partner-based. Myant's Skiin fitness- and health-tracking clothes, expected to ship this summer, are the first WattUp-enabled products. And neither Ossia's Cota Forever Battery nor the sizable Cota Tile can be purchased. The company is working on getting the Tile into a smaller, more efficient form-factor.

The first place you might see the larger Tile is in your local Walmart. In this case, you'd have several Cota Tiles providing power to thousands of low-power RFID tags. And the tags, which could show prices, discounts, and bar codes, could all be managed by software. It's not the most exciting implementation, but it's the one most likely to happen soonest.

Ultimately, wireless charging technology needs a few more years, a few more product announcements and certifications, and some experimentation by large retailers. So don't throw out your cables and chargers just yet. But the widespread adoption of Qi inductive charging on phones and wearables is strong evidence that both manufacturers and consumers are eager to untether.

Anker's Gao takes a cautiously optimistic view. In one or two years, he said, we should see more and more phones that can charge wirelessly, and he expects that wireless-charging efficiency will have reached the level of wired charging. Gao also said he hopes that in as soon as three to four years, we'll have a "true position-free technology," likely debuting on a wearable device.

Wireless power has always seemed like a work in progress. From Nikola Tesla till now, the promise has always been "the wireless power revolution is coming," yet it never seems to arrive. It remains to be seen if Energous and Ossia can flip the script.

But there's a reason wireless power is an idea that refuses to die. It promises freedom from arranging our lives around all the many power-hungry devices we've accumulated, each one acting as a tether that limits our movement. And that promise is worth waiting for.