Wind-powered Wi-Fi Sensors
Glenn Fleishman writes "According to an article at Indolink a 10-centimeter diameter windmill can produce the 7.5 milliwatts needed for a wireless sensor. The paper was published earlier (available as a PDF), but Nature magazine has apparently picked up the tidbit. The process flexes piezoelectric crystals to create a current. Although flywheels aren't mentioned in this article, it seems like a windmill, a flywheel, and a solar cell could in combination produce effective power in a range of conditions for remote wireless devices, including network relays obviating batteries entirely."
Flywheels? The simplest way to store power would be an electric double layer capacitor. No moving parts. They can come in up to 70F at 2.1V - that's 140 C of charge. At 10 mW of power, 2.1V is 5mA of current; that means that it can stay above 1.5V for 2 hours. If a higher voltage is needed, put the capacitors in series. And these are not huge devices. Here's a datasheet for one
How about bring them back with a geeky Wi-Fi vengeance?
Possibly even attach an LED headband to it to tell others how close to a hotspot they're in. C'mon, I see profits galore!
Propeller Beanie hats :)
A sensor need not be on the network 24/7. When it's onboard memory has been filled to a certain capacity (say 80%) if fires up the transceiver and transmits to the network. You only need peak power on occasion. Give your windmill plenty of time to charge up a big capacator (or a small battery.)
Blessed are the pessimists, for they have made backups. -- 0 1 My two bits
Also found on the internet: " The piezoelectric generator is a much more efficient way of converting wind energy on a small scale than the conventional generators that create energy for the national power grid from wind turbines.
A conventional generator that used a 10-cm turbine would convert only 1 per cent of the available wind energy directly into electricity. A piezoelectric generator ups that to 18 per cent, which is comparable to the average efficiency of the best large-scale windmills, says Priya. "
Blessed are the pessimists, for they have made backups. -- 0 1 My two bits
10cm?!?! You'll decimate the local Japanese beetle population! We can't have that. Somebody alert PETA!