WiFi Hotspot Power Harvester
Since this is a website called GreeneComputing, I thought I ought to have something related to “green” computing. So, I did find this interesting account at OhGizmo of a new battery charger that gets it’s power from capturing WiFi signals. It’s from RCA and it’s called the Airnergy Charger. “The Airnergy has a battery inside it, so you can just carry it around and as long as you’re near some WiFi, it charges itself. Unlike a solar charger, it works at night and you can keep it in your pocket. Of course, proximity to the WiFi source and the number of WiFi sources is important, but at the rate it charges, if you have a home wireless network you could probably just leave anywhere in your house overnight and it would be pretty close to full in the morning.”
Sounds pretty darn cool to me and it’s supposed to cost around $40.
January 21, 2010 - 1:34 PM
There’s nowhere close enough energy that passes through that widget to charge a battery. Even if it totally enclosed an access point, managed a 100% conversion rate, and had a perfect battery…. still not even close.
February 4, 2010 - 7:44 PM
BoingBoing (http://boingboing.net/2010/01/12/rcas-wifi-power-harv.html)
had an interesting article questioning whether it is a hoax product: “Here’s some math. Long story short, by my calculations, 100% efficiency and absorption at 5 feet away from a 100mW home router, (reasonable figures), it would take 34.5 years to charge that blackberry battery.
It’s not a Dyson Sphere, so you only get the power that hits the antenna.
Surface of a sphere = 4pir^2, r = 60″ (5 feet).
Surface area of a 5′ sphere = 45,216 square inches.
The device appears about 2″ x 3″ = 6 square inches.
The device then picks up, best case, 0.000133 of the power out from the router, which is 100mW, so.. 0.0133mW
If you leave it there for 24 hours, 0.0318 mWh are stored.
According to Will’s battery, it has ~4,000 mWh capacity.
So, it would take 12,579 days, or 34.5 years, to charge your blackberry battery once, presuming 100% absorption, no losses.
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