A wireless replacement for all those pesky power cables
BENEATH your correspondent’s desk is a cat’s cradle of tangled cables linking a pair of computers to numerous peripherals and laptops around the office. On the credenza opposite is another jumbled nest of wires for recharging mobile phones, cameras, netbooks, MP3 players and other portable gizmos. When everything is humming, there are no fewer than 15 transformers plugged into various wall sockets and power strips, along with all the other electrical cables for powering computers, monitors, printers and still hungrier office gear.
Lately, your correspondent has taken to unplugging the power adaptors—at least those he can lay his hands on—when they are not being used to recharge their tethered friends. As it is, his office becomes a veritable Christmas tree of fairy lights at night with all the red, green and amber standby diodes twinkling in the dark.
Running the numbers, he has found that a five-watt adaptor used to recharge a device for one hour a day will consume at least as much power on standby during the remaining 23 hours. In some cases, up to seven times as much juice is used during standby versus normal operation, says Fulton Innovation, a Michigan company that specialises in developing electrical technology.
Anyone doubting such a claim should check with the adaptor-maker to see what the conversion efficiency is for a typical small transformer and how much it consumes when on no-load compared with full-load. Your correspondent has found many of these so-called “wall warts” to have conversion efficiencies of little more than 30%. In other words, two-thirds of the electricity they draw goes to waste. And there are an awful lot of them around. Some 730m such adaptors were shipped in America during 2008, with more than 370m finishing up as landfill. That is a profligacy the world can manage without.
The obvious answer is to cut the cables and go wireless. Today, we take for granted that wired communication—whether voice, data or multimedia—has largely gone wireless. But wired power, even for portable gizmos, remains the rule.
One of the few exceptions is the rechargeable toothbrush. A coil in the charging unit that is connected to the electricity supply generates a magnetic field, which induces an electric current in a coil in the base of the toothbrush handle for replenishing the battery. A handful of electric razors are recharged in a similar fashion. Your correspondent is not alone in wishing to see similar inductive couplings used to replace the various recharging units cluttering up his office.