4 ms·
From the paper: "For instance at a distance of 2 feet the battery charging system has 100 µW available compared to 10 µW at 10 feet." The Popular Science and UW
by jimrandomh 11y ago
From the paper: "For instance at a distance of 2 feet the battery charging system has 100 µW available compared to 10 µW at 10 feet." The Popular Science and UW Today articles both completely avoid numbers. But the numbers are vital, and if you do a little fermi math, you'll discover that's not enough to compete with watch batteries.
(The first watch battery I found with numbers on it had 240mAh*3V=720mWh, so one such battery could in theory provide 10 µW for 7.2e4 hours or 8 years.)
- imglorp 11y agoThat's not going to charge your notebook so fast, but that's plenty to power your thermostat, your tv remotes, your burglar alarm sensors, and some of the other lesser IoT bits floating around.
- vdnkh 11y agoMost of those items are fixed and can be powered more efficiently and reliably by wall power
- freehunter 11y agoWhether this technology is a winner or not, being able to install a thermostat without having to hire an electrician, shut down power to the room, and knock a hole in your wall would be great. For new construction it's easy. To retrofit older buildings, or to install something in an apartment, the requirements for wall power kinda suck.
- olympus 11y agoIt's not enough to power a thermostat. µW is microwatts. WiFi radios need milliwatts. As jimrandomh mentioned, the levels of power here are the same as what a watch battery can provide for eight years. Watches don't even run off of a watch battery for eight years.
- imglorp 11y agohttp://www.energyharvestingjournal.com/articles/1966/harvesting-power-from-wifi-signals http://www.energyharvestingjournal.com/articles/1966/harvest...
- jacquesm 11y agoIt is more than enough to power a thermostat. Just not all the time. The trick is to wake up from deep sleep often enough to do the job.