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What I don't understand is that they dumped black balls in the reservoir. If you want to keep the water cool to lessen evaporation wouldn't it make sense to use
by Bootvis 11y ago
What I don't understand is that they dumped black balls in the reservoir. If you want to keep the water cool to lessen evaporation wouldn't it make sense to use white or reflecting balls so the water stays slightly cooler?
I would be glad to know why black balls are chosen.
- cengizkrbck 11y agoblack is best suitable color to deflect UV rays.
- erikb 11y agoNow you just said the opposite of what intuition suggests without any evidence, or even argument. Please elaborate and don't just heat up the discussion!
- DanBC 11y agoBlack is the best colour to absorb UV. You want the UV to not reach the water, so you want whatever is on top of the water to not allow UV past.
- Implicated 11y agoUV + Chlorine = Bromide
- erikb 11y agoDoes that look like an explanation to you? I don't see anything about black. I don't see anything about white. I don't see anything about reflecting materials. I see something from chemistry, maybe? Customer: "Why should I buy the product?" Developer: "Here we had a problem with the inheritance tree. We worked around it with a factory method."
- throwaway_yy2Di 11y agoAccording to a chemist on /r/askscience, the plastics probably contain carbon black [0] as a UV protectant. So it might not be deliberate. (/u/Platypuskeeper) Although I have not seen a specification of what the balls are made of, what I know from polymer chemistry is that the black is quite likely from carbon black (essentially soot), which is used as an additive/filler in polymers (e.g. tire rubber) for multiple reasons but not least UV protection. Carbon black is one of the most (if not the most) effective UV-protective additives, precisely because it absorbs the UV and prevents it from penetrating deeply into the plastic. Plastic without some UV protective additive would degrade pretty quickly in the California sun, not least HDPE which has pretty bad UV resistance. https://www.reddit.com/r/askscience/comments/3gpu6x/why_are_the_shade_balls_in_los_angeles_black_and/cu11268?context=3 https://www.reddit.com/r/askscience/comments/3gpu6x/why_are_... [0] https://en.wikipedia.org/wiki/Carbon_black https://en.wikipedia.org/wiki/Carbon_black
- PhasmaFelis 11y agoBlack absorbs more light (and, yes, heat), which means less light penetrates through it to heat the water directly. If you block one bright light with a sheet of thin white plastic, and another with a sheet of thin black plastic, you'll see a lot more light shining through the former. And do remember that the primary purpose is to block UV, not heat, so you want maximum light absorption even if it means greater heat transfer. Chrome-mirrored balls would certainly be even better, but the whole reason they're using plastic balls is because they're dirt cheap. If you have enough money to fill your reservoir with disco balls, you'd be better off just building a gigantic awning.
- Bootvis 11y agoThanks for making a bit of sense of this!
- deleted 11y ago[deleted]
- thaumaturgy 11y agoThe primary purpose of these is not to slow down evaporation. In fact they have a negligible effect on the rate of evaporation. Their primary purpose is to absorb the light spectra that drives chemical reactions in the treated water to prevent carcinogenic bromate from being formed. Most of the reporting on this, including this article, is pretty bad, and causing a lot of laymen to ask questions like yours, because it doesn't make sense as described in the reporting.