Harvesting Energy From Humidity

rtoz writes: Last year, MIT researchers discovered that when water droplets spontaneously jump away from superhydrophobic surfaces during condensation, they can gain electric charge in the process. Now, the same team has demonstrated that this process can generate small amounts of electricity that might be used to power electronic devices. This approach could lead to devices that can charge cellphones or other electronics using just the humidity in the air. As a side benefit, the system could also produce clean water. The device itself could be simple, consisting of a series of interleaved flat metal plates. A cube measuring about 50 centimeters on a side — about the size of a typical camping cooler — could be sufficient to fully charge a cellphone in about 12 hours. While that may seem slow, people in remote areas may have few alternatives.

Comments

Moisture Farmers!

[Commontwist]

Power and water to produce... more power and water? Hmm... I wonder how much this could scale up

Re:Moisture Farmers!

[MrBigInThePants]

Err....

0.5m cubic of spaced sheet metal to charge a phone in a mere 12 hours and produce x litres of water.

Why on EARTH would you want to scale this up??

Perhaps on a distant, humid planet far from the sun?

uhh yeah they do...

[Anonymous Coward]

its called a solar panel. it'll charge your phone in about an hour

Oblig. StarWars

[psybre]

"What I really need is a droid who understands the binary language of moisture vaporators."

Re:Oblig. StarWars

[SuricouRaven]

Did you see any crops on the surface? It might be a humidifier for an indoor farming area.

Re:Oblig. StarWars

[demonlapin]

What you're saying is that Owen and Beru were running a massive grow op?

Dehumidifiers that PRODUCE power?!

[GenaTrius]

I'm from Florida and I'll take 30.

Where?

[Red Herring]

At ~1pW/cm^2, a 50x50cm verision of this will provide about 30mWh in 12 hours. Tiny cell phone battery. Heck, a tiny lithium coin cell will provide ~150mWh.

For contrast, a typical solar cell will give 130W/m^2 (-ish), so a 0.25m^2 solar cell will provide ~33W, while the sun shines, obviously.

I'm not sure where exactly on Earth is sufficiently "remote", dark, moist, and unreachable that this makes sense. (Yes, I though of that, but it's really uncomfortable to fit a camping cooler there...)

Re:Where?

[Ichijo]

At ~1pW/cm^2, a 50x50cm verision of this will provide about 30mWh in 12 hours.

That's just one 50x50 cm plate. They're suggesting a 50x50x50 cm cube of stacked plates.

Re:Where?

[viperidaenz]

A solar panel doesn't produce much clean drinking water.
.

How does it compare to a thermocouple

[American Patent Guy]

under the same conditions? That's what would really be interesting.

This new device needs a temperature differential and humidity to operate. A thermocouple only needs a temperature differential. The new device won't work anywhere where there isn't a humidity high enough to provide condensation (such as space).

It's a curiosity, but I'm not investing any money in it in the short term...

Twist on a very old idea?

[BillX]

While the "water droplets spontaneously jumping off superhydrophobic surfaces" effect is interesting in itself, the mechanism of stripping charge from those droplets as they leave the apparatus sounds like a variation of the Kelvin water-drop energy harvester from 1867. In this case, rather than charge separation via the cross-connected cups, electric-double-layer charge-separation occurs between the droplet and the hydrophobic surface, causing the two to come away similarly unbalanced when the droplet jumps away.