Student’s six-foot water and solar-powered lens purifies polluted water
buffalo.edu
buffalo.edu
That is, unless it's not really a technical problem.
Articles such as this don't often delve into broader issues of public health, education, or even poverty, but with an issue as complex as water access, perhaps we out to discuss it in a more complex context.
It isn't. This has the same problem as all the other solar sterilisers, it says "I'm poor." People are empirically not willing to use these things. You'd probably be better off with a public education campaign to normalise their use, something objectively ridiculous like having middle class families that actually have decent running water doing it, visibily and publicly.
Poverty and deprivation is tied up with a huge range if issues, from water table effects to climate change to local politics and public health and education and ... Well, if the infrastructure existed to build a million of these frames and organise water to be brought to them and then handed out to those without clean water, then any number of other technologies could easily substitute.
So not saying that supplying ten thousand of these to villages whose water tables just moved five miles won't be a fantastic use of our dollars, it's just that seems a small effect.
There is a good ted talk on tackling poverty amount at Maori I can't find it though. It walks through a lot of these issues.
"Due to the sun’s movement throughout the day, Henry needs to repeatedly shift the container to match the focal point. "
A 2x4 passed through the focal point would catch on fire pretty much instantly (as quickly as one could count to one).
We successfully fried an egg (more like instantly scorched an egg) by bouncing the beam pre-focal point off a high quality front surface mirror (also harvested from the TV) and focused it onto the bottom of a cast iron skillet.
Anyhow, the realization was that this thing was incredibly inconvenient and also dangerous to use. We built it into an articulated wooden frame with the explicit idea of being able to track the sun. Power output peaked and dropped off very quickly and was near useless during low-horizon times. You had to be super aware of where the focal point was at all times or risk a very serious accident. This is an obvious point but you don't fully comprehend how serious a point this is until you start setting wood on fire instantly. Even putting the thing away for the day we had to be sure to rotate it 90 degrees so that the sun hit the edge of the lens. Even then, we threw a black cloth over it just to make sure. This thing could set your house on fire in a fraction of a second.
We ended up destroying it after playing with it for a month or so. Just too dangerous to be around and pretty much useless for anything practical. After a while you get tired of demonstrating how quickly you can set a piece of wood on fire.
A long intro to say the following.
Neat trick by this student and a fantastic learning experience I am sure. Kudo's should be given. Kids learn tons of stuff doing off the wall scientific experiments like this one. In practical terms though, well, it isn't practical at all. But, who cares, this is about learning and on that point it is absolutely brilliant.
I remember seeing an article many years ago about using a folded-up t-shirt as a first-pass filter and then simple clear two liter plastic bottles left under the sun for 24 hours to make water safe to drink. People would fill these bottles with t-shirt-filtered water and either place them on a table outside or on the roof for a day. They'd rotate sets of plastic bottles for a continuous supply of safe drinking water. I couldn't think of anything simpler, cheaper or more effective.
Here's on version of that:
I'd expect ETFE to perform a lot better (and last longer) than PTFE, for instance.
Of course often times the trick is getting the water in the first place.
Wonder if the article considers the effects of sun ultra-violet radiation to help in that process.
Such temperatures are common in sous-vide (see e.g. http://www.douglasbaldwin.com/sous-vide.html - interesting headings to grep include "Pasteurized in Shell Egg" and "Computing the Destruction of Pathogens")
Though this does sound neat, and it's still much better to have than nothing at all.
It's like the old saying, it's easy to destroy HIV - the hard part is doing it inside a human body. In the case of sterilizing water, we don't have that problem, the water will remain usable.
So, 150 °F is not really all that hot as some organisms thrive at 250°F or well above boiling. However, I suspect organisms that thrive at 150+°F are unlikely to also thrive in the human body. A more important issue is the effort to sterilize water by hand is unlikely to be made with any real consistency.
That's what safety margins are for.
Point? Entropy is a bitch, but mankind carries a bigger stick.
For everyone who's saying that nothing could evolve to resist this, please look at Legionnaire's disease: http://en.wikipedia.org/wiki/Legionnaires'_disease
This is a disease which can be fatal, and is found in association with systems involving water, including hot water heaters.
I'll grant you as much as you likely that you're unlikely to get this or that, what I'm cautioning against is the idea that you've found a silver bullet. You've never found a silver bullet against bacteria, and it's better to go into use of systems like these with that assumption.
Thinking ahead to make "thoroughly rinse, clean, and dry this system at least once a week" part of the instructions for use as a precaution against bacteria isn't nay-saying, it could be quite valuable to the people we would have using systems like these in the future.
Our only hope, is all I'm saying, is in our ability to cross all boundaries and communicate under extraordinary duress, nevertheless, with effective results. So I fully support your position.
I'm encouraged by the community efforts being made to address this; there is, after all, a very large industrial powerhouse that can be directed towards these problems. If we see Ebola-bots on the horizon, better hope they're flying away and not getting closer, uh oh ..
How fast does the water evaporate ? Can oil or gas be floated on top to stop it?
Could one just put water in metal cans painted black? Had no idea it only took temps of 130F to kill the pathogens that harm.
The bit that gets purified is in a separate container held (manually?) at the focal point of the water lens, and gets hot. But as the sun moves so does the focal point, so a very patient person has to be shoving the heating container along every few minutes. This doesn't seem very practical to me.
http://www.who.int/mediacentre/factsheets/fs292/en/
Over 4 million people die prematurely from illness attributable to the household
air pollution from cooking with solid fuels.
More than 50% of premature deaths among children under 5 are due to pneumonia
caused by particulate matter (soot) inhaled from household air pollution.Pollution really is way, way down on the list of concerns for people in impoverished nations. Water, Shelter, Food are much more pressing concerns.
Okay, I'll bite. How does burning wood not result in a net increase in CO2? Are you assuming that for every cord of wood burnt, that someone is simultaneously planing and growing a cord's worth of tree (which, of course, pulls carbon out of the air?)
That's a pretty big assumption.
Carbon embodied in coal, oil, and gas was last part of the biosphere hundreds of millions of years ago. And that's precisely the problem: humans have re-introduced, mostly in the past 50 years (95% of all oil was burned since then, a large portion of coal and gas) carbon that was deposited over hundreds of millions of years. The biosphere portion of the carbon cycle (atmospheric uptake, oceans, plant growth) simply cannot keep up.
Yes, if you were to burn all forests at once, you'd run up CO2 a bit. That is, however, a pretty self-limiting prospect.
At one point, there was some n amount of CO2 in the air.
A tree was planted. Through a few biological cycles, CO2 is exchanged and stored as various sugars within the wood.
Burning the wood releases the CO2 back into the air.
This is a net zero process.