USB is changing again in 2014. Not in a way that will make old devices incompatible, but in a way that will make USB an even more ubiquitous connection than it already is. USB PD, or Power Delivery, will increase USB's power throughput to 100 watts from its current 10 watts. While charging larger mobile devices like iPads currently pushes the limits of USB power, in a couple years we could power our lightbulbs and lamps via USB and charge bigger pieces of technology that currently require AC power bricks.
According to The Economist, USB PD will start showing up in 2014, with a full rollout arriving in 2015. Over the past decade, USB has revolutionized how we charge electronics, pushing proprietary cell phone chargers out the window in favor of universal mini or micro USB ports. The Economist predicts the same thing could happen with DC power in general, with USB as the delivery system.
"Turning AC into the direct current required to power transistors (the heart of all electronic equipment) is a nuisance," writes The Economist. "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...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 USB website expands on the important new features of USB PD, like its ability to provide bi-directional power--the host device (say, a laptop) can now charge from the peripheral device (say, a smartphone, or battery pack, or solar accessory) instead of the other way around. Devices will be able to draw variable amounts of power. For example, an external hard drive could survive on only a trickle, but ask for more juice when it needs to spin up and access files. And devices like hard drives and even printers which currently come with AC adapters will now be able to survive on DC USB power alone.
The Economist makes the point that solar power is ideally suited to powering a low-voltage DC network, which USB could provide. Check out the rest of the article if you want to dream big about the future of green energy running on USB. Even if it doesn't all come true, future USB plugs will at least be smarter and more powerful than they currently are.