Cheap Drinking Water from the Sun, Aided by a Pop of Pencil Shavings | Hacker News Reader

Cheap Drinking Water from the Sun, Aided by a Pop of Pencil Shavings

npr.org

69 pointssizzle18 comments

This should be the paper mentioned in the article

http://app.mnt.metu.edu.tr/system/files/images/ncomms5449.pd...

So why not just focus the sun on the surface of the water in a narrow necked container? (This is not a rhetorical question, I really would like to know.) High tech materials are not likely to be available in the environment where such things are needed. Someone needs to re-read Viktor Papanek's book on the subject of appropriate technology.

The article does address it. Read the text around this quote:

"It creates steam at a low concentration of solar energy," Ghasemi says. "So you don't need such expensive optical systems to concentrate the solar energy."

Not really, he is still referring to the small holes in the graphite.

Graphite is not exactly a high tech material. Maybe you're thinking of graphene? The process they use to create the small holes is also very cheap.

Graphite is high tech if you are living in a place where there is no mains electricity. And if you had mains electricity you would be able to use a simple electric still. So I'm still not convinced that this is actually useful in the real world.

There are plenty of places in Africa (and no doubt Asia too) with shops selling factory-made goods, but no electricity.

Graphite is more portable than mains access.

My guess would be that your approach would go faster, assuming that the cold water around the focused area doesn't suck the heat out too quickly, but perhaps not fast enough to be of practical use. Also, the maximum temperature that you could get would be 100 deg C; after that the water evaporates.

I suspect they use the graphite because the graphite can get much hotter than 100 deg with a simple lens. Coupled with its ability to wick up water into it, you could evaporate a substantial amount of water quickly.

>a narrow necked container?

You mean, like .. a pencil you can turn upside down, attach a lens to, and it'll make a steamy cup of tea for you?

Sign me up!

I bet they can solve the salt problem with some kind of pulp-based filter wrapping around the graphite-corn solar layer which, when it too dries out, allows salt crystals to fall .. or at least, there's gotta be a third cheap material to add to the mix which would assist salt extraction by osmosis, or whatever ..

It seems like you could easily solve the salt problem every time it clogs up just by putting a lid on the jar, shaking it up a bunch to re-dissolve the salts in liquid and then add new liquid into keep the overall salinity down. Assuming these pores don't clog very quickly, it seems that "rinsing" the graphite could work.

"We took graphite and put it into the microwave for seven seconds," Ghasemi says. The gases in the mineral cause the outer layer to expand and pop. "It's exactly like a popcorn!"

Is this a safe experiment to do at home? Is there a chance of sparking?

microwave and blender are the future of the nanotechnology. I wonder how such popcorn would work in a battery.

Oh, common! Where's your spirit of scientific discovery? Next thing you say you never microwaved a burning match to get the plasma sparks :)

Or a grape cut in half.

or a CD

> Is this a safe experiment to do at home? Is there a chance of sparking?

Even if, so what? In the very unlikely worst case scenario, you'll have to shell out $50 for a new microwave. Just stay frosty and keep your finger on the "Cancel" button :).

i guess putting graphite in an inverted container made of glass should make it a bit safer.

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