The Economist has an article on the increasing popularity for using USB connectors for DC power distribution, declaring "The humble USB cable is part of an electrical revolution. It will make power supplies greener and cheaper" - Edison’s revenge.

Most phones and other small gadgets can charge from a simple USB cable plugged into a computer or an adaptor. Some 10 billion of them are already in use. Hotel rooms, aircraft seats, cars and new buildings increasingly come with USB sockets as a standard electrical fitting.

Now a much bigger change is looming. From 2014, a USB cable will be able to provide power to bigger electronic devices. In the long term this could change the way homes and offices use electricity, cutting costs and improving efficiency. ...

The big change next year will be a new USB PD (Power Delivery) standard, which brings much more flexibility and ten times as much oomph: up to 100 watts. In his London office Simon Daniel, founder of Moixa, a technology company, charges his laptop from a prototype souped-up USB socket. The office lighting, which uses low-voltage LED (light-emitting diode) lamps, runs from the same circuit. So do the monitors, printers and (with some fiddling) desktops. Mains power is only for power-thirsty microwaves, kettles and the like.

That could presage a much bigger shift, reviving the cause of direct current (DC) as the preferred way to power the growing number of low-voltage devices in homes and offices. DC has been something of a poor relation in the electrical world since it lost out to alternating current (AC) in a long-ago battle in which its champion Nikola Tesla (pictured, left) trounced Thomas Edison (right). Tesla won, among other reasons, because it was (in those days) easier to shift AC power between different voltages. It was therefore a better system for transmitting and distributing electricity.

But the tide may be turning. Turning AC into the direct current required to power transistors (the heart of all electronic equipment) is a nuisance. The usual way is through a mains adaptor. These ubiquitous little black boxes are now cheap and light. But they are often inefficient, turning power into heat. And they are dumb: they run night and day, regardless of whether the price of electricity is high or low. It would be better to have a DC network, of the kind Mr Daniel has rigged up, for all electronic devices in a home or office.

This is where USB cables come in. They carry direct current and also data. That means they can help set priorities between devices that are providing power and those that are consuming it: for example, a laptop that is charging a mobile phone. “The computer can say ‘I need to start the hard disk now, so no charging for the next ten seconds’,” says Mr Bhatt. The new standard, with variable voltage and greater power, enlarges the possibilities. So does another new feature: that power can flow in any direction.

This chimes with another advantage. A low-voltage DC network works well with solar panels. These produce DC power at variable times and in variable amounts. They are increasingly cheap, and can fit in windows or on roofs. Though solar power is tricky to feed into the AC mains grid, it is ideally suited to a low-voltage local DC network. When the sun is shining, it can help charge all your laptops, phones and other battery-powered devices.

TreeHugger has a post celebrating Nikolai Tesla's birthday - Happy 157th birthday, Tesla!.

These days, when we hear "Tesla" we might first think of electric cars, but the Californian company's namesake also deserves our attention. Well known among scientists, engineers, and geeks of all kinds (I say that in the most positive way), uber-inventor Nikola Tesla is still overlooked by too many people, and that's too bad because his contributions to our civilization were immense.

The Economist has a look at wireless energy distribution and efforts to power devices using ambient energy - Power from thin air (there is also an accompanying video).

ANYONE whose mobile phone has ever run out of juice—which means, these days, more than half the world’s population—will like the idea of getting electrical power out of the air. The notion is far from new. A little over a century ago, the inventor Nikola Tesla drew up ambitious plans to transmit electrical power without wires. He carried out a series of experiments in which electric lights were illuminated via electrostatic induction, by connecting them to metal sheets suspended in a strong electric field produced by a distant transmitter. In 1898 he proposed a “world system” of giant towers that would form both a global wireless communications network and a means of delivering electricity over large areas without wires.

The construction of the first such tower, the Wardenclyffe Tower, on Long Island, began in 1901. Tesla’s backers included the financier J.P. Morgan, who invested $150,000. But before the tower was completed, Morgan and the other backers pulled out. They worried that the delivery of electricity through the air could not be metered, and there would be nothing to stop people from helping themselves.

But has Tesla had the last laugh after all? Today several firms—including Fulton Innovation, eCoupled, WiTricity and Powercast—are pursuing various technologies that deliver electrical power without wires (though over shorter distances than Tesla had in mind). WiTricity has demonstrated the ability to send enough energy across a room to run a flat-screen television using its approach, called “resonant magnetic coupling”. This is different from Tesla’s approach, but the firm’s founders have acknowledged his pioneering work.

In the long run, however, it may be Morgan who is vindicated, as researchers find ways to pull power out of the air without paying for it—a technique known as “energy scavenging” or “energy harvesting”. It is already possible to power small electronic devices, such as wireless sensors installed in buildings and industrial machinery, using a dedicated microwave transmitter nearby. The sensors pick up the microwaves with an antenna and convert the signal into electrical energy. But as power requirements drop and energy-scavenging technology improves, it will become increasingly practical to power these and other devices using just “ambient” energy—the sea of existing radio waves produced by television, radio and mobile-phone transmitters. ...

Ambient radio waves have largely been ignored as a potential power source until recently, because the power of a broadcast radio signal rapidly decreases with distance. That is not to say that radio waves cannot pack a punch from a distance. Advocates of “satellite solar power”, for example, dream of beaming gigawatts of solar power down to Earth from geostationary satellites more than 35,000km up. The same approach has been used in ground-based experiments to beam one kilowatt of power over a distance of several kilometres, notes Peter Fisher, a physicist at the Massachusetts Institute of Technology. But ambient radiation is much weaker.

One way to address this problem is to harvest radiation from multiple sources. Last year Nokia, the world’s largest handset-maker, raised eyebrows with research showing that this approach could scavenge nearly 100 times as much energy as Dr Smith’s approach. Markku Rouvala, an engineer at Nokia Research Centre in Cambridge, England, harvested as much as 5 milliwatts of power using a “wide band” receiver capable of mopping up radio signals between 500MHz and 10GHz—including radio, TV, Wi-Fi and mobile-phone signals—from nearby transmitters. It takes at least 20 milliwatts to keep a mobile phone operating in standby mode, but Nokia hopes that power scavenging might eventually deliver 50 milliwatts, enough to trickle-charge a phone.

At the Consumer Electronics Show in January, RCA showed off a gadget designed to harvest energy from nearby Wi-Fi transmitters, which can then be used to recharge a mobile phone. RCA says it plans to launch the device, dubbed Airnergy, later this year.

The first devices to be powered entirely by ambient energy are likely to be sensors, calculators and clocks. But the hope is that music-players, e-readers and mobile phones will eventually follow, says Dr Smith. There are other means of harvesting ambient energy, from vibrations, movement or heat. But the attraction of radio waves is that they are pretty much everywhere. It’s like recycling energy, says Dr Fisher. “It’s energy that’s around, and is not doing anything else,” he says.

Inhabitat has a post on a Nikolai Tesla inspired wind turbine design - Ultra-Efficient Bladeless Wind Turbine Inspired by Nikolai Tesla.

SolarAero recently unveiled a new bladeless wind turbine that offers several advantages over current wind turbines — it emits hardly any noise in operation, has few moving parts, and since it doesn’t use spinning blades it’s much less of a hazard to bats and birds. The whole assembly is inside an enclosed housing, with screened inlets and outlets to keep animals safely out. It also can be installed on sensitive locations such as radar installations or sites under surveillance where the rotating blades cause detrimental effects. Read on to learn what makes it work.

Whether they are vertical axis or horizontal axis, typical wind turbines work by catching moving air with blades, and using that force to rotate the axle, which turns a generator to produce electricity. Instead of pushing on blades, SolarAero’s turbine is based on the Tesla turbine originally developed by Nikolai Tesla. The principle of the Tesla turbine is to set up an array of closely-spaced, very thin, and extremely smooth metal disks. The viscous flow of air moving in parallel to the disks is what propels the turbine, instead of buffeting blades with moving air. This makes for a more compact mechanism with only one moving part: the turbine-driveshaft assembly.

According to the company, this turbine should cost around $1.50 per watt of rated output, and have a lifetime operating cost of about 12 cents per kilowatt-hour — comparable to, or even better than, current retail electrical rates in many parts of the country. This would make the SolarAero turbine about 2/3 the price of a comparable bladed unit, and because of the significantly lower operating costs, lifetime maintenance could be just 1/4 the cost. At this point the project is still under development, and no manufacturer has been lined up as of yet.