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Simple, solar-powered water desalination (2020)

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Re: Simple, solar-powered water desalination (2020)

#201

Post by finiteloops »

kingsuper20 wrote: post #173
tromp wrote: post #14

Earlier quoted context omitted.

The article says "per hour", not per day. Although that would seem able to support dozens of users rather than just 1.

The average US citizen uses 82 gallons of potable water per day.

Sounded astonishingly high, but a quick search from a few sources (one cited [1]) checks out. Now to go down a rabbit hole of how this 82 gallons breaks down and what I can do to reduce my consumption...

[1] https://www.usgs.gov/special-topic/water-science-school/scie...

Re: Simple, solar-powered water desalination (2020)

#202

Post by dsr_ »

adrianmonk wrote: post #180
dsr_ wrote: post #131

Earlier quoted context omitted.

This chunk from the article is, unfortunately, an outright lie. By definition, removing salt from seawater leaves you with water and salt. The article handwaves the salt away by supposing that the desalinator will float on top of the ocean. In actual production configurations other than towing it behind your sailboat, you will end up with a brine pool that needs to be disposed of, or a concentration in the wicking ma…

I don't think they are talking about the impact on the environment. I think they are talking about the procedures for operating the equipment. The way I read it, they mean whoever operates this device does not have to periodically go empty some bin/tank of salt or brine. An analogy would be to a frost-free refrigerator. When you say the freezer compartment of your fridge is frost-free, you don't mean that it never ge…

If you operate it directly on the open ocean, towing it behind your sailboat, you don't have to do anything special.

If you operate it in a commercial, protected context where you pump water through it, you will generate brine.

If you operate it en-masse in the ocean, the things that are insignificant at the scale of 1 and 10 square meters may become significant at the scale of 1 and 10 square kilometers.

All of these things are true for other desalinization systems, too. Claiming "you don't have to worry about brine" because it floats on the water surface is misleading at best. You can put any system you want on the water and make it float -- we have concrete and steel hulls, no problem -- but that doesn't solve the concentration problem.

Re: Simple, solar-powered water desalination (2020)

#203

Post by kingsuper20 »

celticninja wrote: post #187
kingsuper20 wrote: post #174

Earlier quoted context omitted.

>I am pretty sure if you had to get your water from one of these devices you would not be using it to flush toilets or other non-essential use. Are you suggesting that toilets, showers, washing machines use salt water?

Is there a problem with flushing a toilet with salt water?

Offhand I'd say that you are doubling the plumbing system plus you are using a much more corrosive fluid.

It would be an interesting experiment, since toilets use a great deal of water. Take a beach town, build a separate pressure water and sewer system, see if it's worth it. It's certainly more complicated than a sailboat's set up.

Re: Simple, solar-powered water desalination (2020)

#204

Post by Covzire »

As I understand desalination, a huge bottleneck besides cost is what to do with the brine. Why can't they build a gigantic pool/lake out in the desert and pump the brine there and let it dry into salt and other minerals. A 10 square mile pit/pool with a clay or other barrier to prevent it from sinking into the aquifers would allow for a massive amount of brine to be safely contained in one place wouldn't it?

Re: Simple, solar-powered water desalination (2020)

#205

Post by okareaman »

Covzire wrote: post #204

As I understand desalination, a huge bottleneck besides cost is what to do with the brine. Why can't they build a gigantic pool/lake out in the desert and pump the brine there and let it dry into salt and other minerals. A 10 square mile pit/pool with a clay or other barrier to prevent it from sinking into the aquifers would allow for a massive amount of brine to be safely contained in one place wouldn't it?

brine disposable seems like a made up problem to me. We're not going to raise the salt content of the world's oceans by pumping the salt back from whence it came. I understand we don't want to put the high salt discharge near sea life, but that is not a hard problem.

Re: Simple, solar-powered water desalination (2020)

#206

Post by philwelch »

Covzire wrote: post #204

As I understand desalination, a huge bottleneck besides cost is what to do with the brine. Why can't they build a gigantic pool/lake out in the desert and pump the brine there and let it dry into salt and other minerals. A 10 square mile pit/pool with a clay or other barrier to prevent it from sinking into the aquifers would allow for a massive amount of brine to be safely contained in one place wouldn't it?

The logistics would be a challenge. You’d have to transport the brine from the coast to the desert. In some places this would be a relatively short trip (Israel, North Africa, California) but in other places you’d be shipping a lot of heavy fluid over long distances. And you don’t even have someone buying the stuff on the other end; you’re just disposing of it.

Re: Simple, solar-powered water desalination (2020)

#207

Post by Dylan16807 »

alpaca128 wrote: post #118
wcoenen wrote: post #30

Earlier quoted context omitted.

The 100% level refers to a system where all energy goes to heating up water in order to evaporate it, and then letting it cool down to condense it. All the energy that was spent to heat up the water, is lost to the environment in the "cooling down" step. If some of the heat is instead recovered during condensation to heat up the next batch of water, then you have >100% efficiency.

Unless you ignore energy sources from the environment you cannot exceed 100% efficiency. And that would be incorrect, applying that same standard to photovoltaic panels would result in infinite efficiency. That doesn't make any sense. Edit: Also, when you take heat/energy from a previous step in the process, you also need to account for the energy put into that previous step. In the end that will again be As someone…

> applying that same standard to photovoltaic panels would result in infinite efficiency

No it wouldn't. The equivalent for panels would be like... you want to run some number of watts through a diode, and you're using solar panels to collect this power. The diode happens to give off waste light. By aiming this light at your panels, you can recapture most of it back into electricity, and reuse it 2.85 more times.

Re: Simple, solar-powered water desalination (2020)

#209

Post by travisporter »

okareaman wrote: post #205
Covzire wrote: post #204

As I understand desalination, a huge bottleneck besides cost is what to do with the brine. Why can't they build a gigantic pool/lake out in the desert and pump the brine there and let it dry into salt and other minerals. A 10 square mile pit/pool with a clay or other barrier to prevent it from sinking into the aquifers would allow for a massive amount of brine to be safely contained in one place wouldn't it?

brine disposable seems like a made up problem to me. We're not going to raise the salt content of the world's oceans by pumping the salt back from whence it came. I understand we don't want to put the high salt discharge near sea life, but that is not a hard problem.

> We're not going to raise the salt content of the world's oceans by pumping the salt back from whence it came.

Sorry, maybe dumb question but why not? We're taking out water and leaving behind salt

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