Electronics has already cut the data cord. Can it now cut the power cord as well?

[dozer]

http://www.economist.com/news/science-a ... dytostrike

DRONES may one day transform the way parcels are delivered, crops monitored and suspects apprehended. Those who talk up these possibilities, though, often neglect to mention the drawbacks of such robot aircraft—one of which is that most cannot fly for more than a quarter of an hour before they need to find a human being to swap their batteries for them or plug them into an electrical socket.

Joshua Smith, a computer scientist at the University of Washington, in Seattle, hopes to change that. In May he started a company called Wibotic that plans to recharge drones (and also earthbound robots) without them having to establish an awkward physical connection with a plug. A ’bot whose batteries were low would simply manoeuvre itself to within half a metre or so of a recharging station to top them up. LaserMotive, another Seattle-based company, is even more ambitious. It is developing a system designed to replenish the batteries of drones that are still aloft, using lasers and photovoltaic cells.


The idea of wireless power-transmission of this sort goes back more than a century. In 1893 Nikola Tesla (pictured), who was one of the pioneers of industrial-scale electricity, illuminated light bulbs across a room in a demonstration at the Columbian Exposition in Chicago. And that was a mere fleabite compared with his grander ambitions. He claimed to believe it possible to broadcast power around the world using a system of towers and balloons, and even convinced J.P. Morgan to back a trial.

That failed, as most other physicists of the time predicted it would. (Tesla was a good scientist, but also an inveterate showman.) More modest remote power-transmission is, however, now attracting attention again. The technology Tesla pioneered is already being used to charge mobile phones, and researchers are working on similarly wirelessly powered kitchen appliances, military equipment such as heads-up displays, and medical devices ranging from heart pumps to brain monitors. IHS, a market-research firm, estimates that sales of such machines, now half a billion dollars a year, will grow 30-fold over the next decade.

A question of standards

Lasers aside, the principle behind most wireless power-transmission is a piece of basic physics known as induction. In this process an alternating current passing through a coiled wire creates an oscillating magnetic field. That field then induces another alternating current in a second, nearby coil. If the transmitting and receiving coils are close together and aligned in the same direction, almost all of the power will be transmitted. Separate the coils by more than a few millimetres however, or wiggle them around, and the efficiency of the process drops off quickly.

Inductively coupled systems like this thus work well for things like repowering electric toothbrushes. They would be impractical, though, for a drone trying to hover over a charging station. Wibotic’s answer is to use tuned electrical circuits in place of simple transmitting and receiving coils. When such circuits are tuned to the same resonant frequency, they exchange energy more efficiently. That permits power to be transferred over distances up to the diameter of the coils, or even slightly farther. Besides being used to power up drones, chargers that worked this way could be shaped into bowls, to accommodate things like smart watches, or simply built invisibly into desktops.

Like induction itself, resonant induction is not a new idea (Tesla’s Victorian demonstrations used it). But those demonstrations were optimised to work at one, specific distance. Modern resonant circuits are able to change their electrical properties on the fly. That, Wibotic claims, permits its equipment to cope with wobbly drones and windy days. Wireless charging also allows devices to be sealed against water or mess. Philips, a large electronics manufacturer, has, for example, demonstrated a cordless food processor powered by a coil sunk into a counter.

For remote charging to take off metaphorically as well as literally, though, devices employing it need to be interoperable. That means establishing industry standards. Unfortunately, in a competition reminiscent of that in the 1890s between alternating current (Tesla’s preference) and direct current (promoted by Thomas Edison), three main consumer standards have emerged.

One, from the Wireless Power Consortium, a group of around 200 technology firms, is called Qi. It operates up to about five watts—the sweet spot for charging mobile phones. A second, that of the Power Matters Alliance (PMA), is a direct competitor of Qi. The third, Rezence, devised by the Alliance for Wireless Power (A4WP), permits higher power levels. To make matters still more complicated, PMA and A4WP merged earlier this month, meaning that one organisation now promotes two standards. And Apple, ever idiosyncratic, made a wireless charger for its Watch that complies with none of the others.

Standards wars are often won not by the sweetest technology but by whatever comes out first and fastest, and thus rolls over the opposition. In this case all three contenders seem to have a chance. Qi is the standard of choice for phone cradles in a dozen models of car, and more than 80 models of smartphone can draw power from these cradles. Qi is also built into some flat-pack tables and bedside lamps sold by IKEA.

PMA, however, is beating it in the fast-food market. Chargers conforming to its standard can already be found in several hundred American branches of McDonald’s and Starbucks that hope to lure customers with the promise of refreshment for their gadgets as well as themselves. Even Rezence, which has virtually no existing applications, is in the running. Intel, the world’s biggest silicon-chip maker, is adopting it for the next generation of its microprocessors destined for tablet and laptop computers.

Luckily for confused consumers, receivers that can work with two or even all three standards are starting to be built into phones and other gadgets. And, whichever does come out on top, Alex Gruzen, boss of WiTricity, a remote-charging equipment company that is a founder member of A4WP, thinks Intel’s intervention will prove a turning-point. He compares it to the moment, in 2003, when the firm decided to incorporate wireless networking into its processors. This launched the Wi-Fi revolution. Something similar may now happen in the field of wireless power.

The Tesla exception

That something, moreover, may not be restricted to machines small enough to be picked up and carried. The rise of electric cars opens yet another market for remote power-transmission. Carmakers are keen to avoid the standards war that has broken out among makers of smaller gadgets. The Society of Automotive Engineers, an industry body, has consulted manufacturers, wireless-power companies and energy suppliers, and has already agreed on such things as the power level (around 20kW) and operating frequency (85kHz) of future car-charging systems.

The first cars to include such systems should arrive in 2017 or 2018. Ironically, models made by Tesla Motors will not be among them. Elon Musk, the firm’s boss, is no fan of wireless power. He thinks it inefficient and underpowered compared with the (wired) “Superchargers” that Tesla Motors has developed. These provide six times the wattage of wireless, and have already been installed at hundreds of places around the world.

Fixed-point recharging stations, whether wired or wireless, are not, though, the limit of some peoples’ ambitions. Qualcomm Halo, a company working with Daimler on automotive charging, envisages wireless chargers being integrated into the roadway itself. That would certainly help electric-car makers compete with rivals using other forms of power, for the batteries required to give a car a reasonable range are its most expensive component. Indeed, such technology already exists in a limited form. Electric buses in parts of South Korea, Italy, Britain and California are, today, recharging themselves from underground wireless chargers.

If convenient wireless charging lets carmakers halve the size of electric-vehicle batteries, it could slash thousands of dollars from their prices. That would make a huge difference to the economics of owning and running them. Nikola Tesla failed to beam power between continents but his tricks may yet succeed in something equally dramatic: decarbonising the world’s road vehicles.

From the print edition: Science and technology

[Bristolian]

As the article says for itself, there is not much new here. The issue as always is cost and profit. Can the technology be made affordable and where does the power come from? There is little point in moving the source energy from carbon fuels direct to carbon fuels indirect. There still needs to be a game changers in the equation i.e. Workable and affordable hydrogen cells,reductions in power transmission losses. For sure we'll get there but in what timescale and will we accept the costs, are at least two of the questions?