Take another look at wireless charging
- 21 June, 2017 00:14
The market for delivering power wirelessly over short distances is potentially huge.
The most obvious application is wirelessly charging smartphones. We depend on our smartphones to work all day long. The need to charge them when their batteries are low is a fact of life, but connecting a wired charger is not always convenient or even possible. There are wireless charging pads for the home and office, and wireless charging docks for automobiles, and we are just starting to see wireless charging spots in coffee shops, restaurants, hotels, and airports.
In an ideal world, we wouldn’t even have to think about charging our mobile devices. Infrastructure embedded in the environment would automatically detect our devices, check their battery status, and charge them as needed. This concept is not as far-fetched as it might sound. Such infrastructure has been developed and is starting to be deployed. However, there still isn’t universal support for wireless charging in smartphones, laptops, and wearables.
(There is also another solution that doesn’t require a power outlet. A portable cell phone charger, such as the Flux, can fast-charge a smartphone. However, it’s an additional item to carry around and must also be recharged.)
Vertical and horizontal markets
How might wireless charging achieve broader acceptance? New technology solutions often succeed first in vertical markets. Business customers are willing to invest heavily in new technology if it solves a major problem or gives them a competitive advantage. That gives developers time to refine their solutions and squeeze out costs.
For instance, mobile robots are being used to automate warehouses and drones are being used to conduct dangerous inspections. However, to operate for long periods, robots and drones must periodically recharge their batteries. Wireless technology avoids the need for a physical connection so that recharging can be performed autonomously.
The use of IoT devices in factories presents an exciting opportunity. It’s not practical to run wires to hundreds of sensors scattered around a factory--particularly when many are attached to moving assemblies. Nor is it advisable to equip sensors exposed to heat or vibration with batteries. Seattle-based Ossia has developed wireless technology for powering sensors at a distance.
Pittsburgh-based Powercast has developed wireless power solutions for particularly challenging applications. For instance, large-scale cooking operations need to determine when meat has reached the desired internal temperature without opening the ovens prematurely and letting heat escape. Temperature sensors inserted into the meat can be queried wirelessly. Similarly, perishable drugs must be kept cool during shipment. Wireless power can be used to activate and read a temperature sensor inside the box without breaking the insulation and letting in warm air.
Office hoteling and business travel are two major horizontal markets for wireless charging. An employee who spends most of his or her time in the field can reserve an office and use wireless to access a desktop display, the local area network, and a charging pad. Likewise, business travelers will no longer need to carry chargers and power cables when wireless charging becomes a standard amenity at coffee shops, airports, and hotels. Powermat has begun deploying wireless charging infrastructure and to date has hundreds of locations in 11 states across the U.S.
Different flavors of wireless power
In theory, there are several technologies for delivering power wirelessly. However, most of the business activity is focused on two technologies: magnetic induction and radio waves.
Inductive wireless charging is already in wide use. The transmitter’s coil generates a magnetic field that induces a current in the nearby receiver’s coil. Electric toothbrushes use inductive charging: You can only place the toothbrush on the stand one way, and it ensures the two coils are right next to each. Powermat, the company that has begun deploying wireless charging infrastructure across the U.S., uses inductive wireless charging.
It would be nice to have a little more spatial freedom for wireless charging. This would permit coffee shops and restaurants to install wireless charging transmitters on the undersides of tables where they would be out of the way. A variant of inductive technology called “resonant” allows wireless charging over modestly greater distances (from about one inch to more than a foot away). However, there are tradeoffs: as the distance increases, the efficiency of the power transfer decreases and there is greater risk of producing electromagnetic interference. Witricity, a leading proponent of resonant wireless charging, points out that the technique is highly scalable and can be used in applications as diverse as smartphones, medical implants, mobile robots, and even electric automobiles.
The other major wireless charging technology uses radio waves and is called “RF” (radio frequency). RF offers the most spatial freedom, but it also poses challenges. Radio signals tend to fan out from the transmitting antenna, so a device with a small receiving antenna is likely to capture only a fraction of the power. There are ways to steer the radio waves, but care must be taken not to expose people to concentrated beams.
Energous is a proponent of RF wireless charging for consumers. The firm is pursuing a phased strategy that it says will ultimately enable charging mobile devices up to 15 feet away. The firm’s WattUp technology works with Bluetooth-enabled devices, using Bluetooth to check the device’s battery status and pinpoint its location. RF is a good solution for wearables, because RF receivers can be made small enough to fit into the smallest devices, such as hearing aids that are worn in the ear. Ironically, the wearable must be placed right next to the RF transmitter--much like inductive charging.
Ossia and Powercast use RF technology for both wireless charging and to power devices at a distance. Ossia has developed solutions for wirelessly charging Bluetooth-enabled devices and wirelessly powering battery-free devices such as digital price tags in retail stores and sensors in factories. Powercast uses its RF energy-harvesting technology to power sensors connected to RFID tags as well as to trickle charge battery-powered devices.
Wireless power industry associations
There are two industry groups developing standards and promoting the use of wireless charging/power. Several leading vendors are members of both.
The Wireless Power Consortium promotes the Qi (pronounced “chee”) standard for wirelessly charging smartphones. The WPC reports that there are more than 200 million Qi phones and chargers in use today. There are also 66 car models from 16 car manufacturers that feature factory-installed Qi chargers. The Qi standard includes both inductive and resonant options (though the latter extends range only about one-and-one-half inches). Members of the WPC include Apple, Dell, HTC, Huawei, iRobot, LG Electronics, Nokia, Qualcomm, Samsung, Sony, and Verizon Wireless.
The other major industry group is the AirFuel Alliance. In addition to inductive and resonant technology, the AirFuel Alliance supports RF, ultrasound, and laser technologies. The AirFuel Alliance was created through the merger of the Alliance for Wireless Power (A4WP) and the Power Matters Alliance (PMA). Members include Dell, HTC, Huawei, Intel, Lenovo, LG Electronics, Motorola Mobility, NTT DoCoMo, Qualcomm, Samsung, and Starbucks.
Inventor Nicola Tesla dreamt of wirelessly delivering large quantities of electric power over long distances. We can now see there is an even bigger opportunity for delivering small amounts of electric power over short distances. Five years from now we may shake our heads when we remember how people used to carry around their own battery chargers.