[nitsuaeekcm]

Even better imo than all the chemical energy we could store when we have excess solar, think about all the water we could create. Creating fresh water from sea water is extremely energy intensive, but there's nothing easier to store than giant bodies of water. Once the energy term is the reverse osmosis opex equation is erased, large scale water plants wherever it's sunny are going to start looking awfully attractive.

[bruce511]

As a corollary to that, a lot of deserts terminate in coastline. Generating desalinated water from solar in these areas has the side benefit of "creating useful land".

What's left to figure out is the ratio of panels to water to land, and in turn whether the long term value of the land is worth the investment. (Dubai would argue it is.)

[abdullahkhalids]

This will destroy the near shore ecosystem, because desalination dumps brine that kills everything, while at the same time destroying the desert ecosystem because it gets converted into something local flora and fauna can no longer live in.

[bruce511]

I don't think we need worry too much about desert habitats being removed. Deserts are large (and getting larger) and the amount of land which could realistically benefit from desalination is a tiny fraction of that.

While brine can impact local salinity, so does treated-effluent outflows (mixed together they are neutral.) Regardless elevated brine levels drop off sharply from the point of outflow.

[ehnto]

We are really good at mis-estimating scale. So we know brine decreases sharply from the point of outflow, but do we know what 50 years of brine outflow at tens of thousands of locations around the world would do?

If it's profitable, it'll be implemented all over, and underestimating that cumulative effect is something we would plead willful ignorance on as we have done with other industries in the past.

Second point I will try to make, habitats are often unique and small, we would just want to make sure an ecosystem is truly ubiquitous before destroying a small pocket of ecosystem.

Especially now, there are animals that live in just one or few specific spots. We should be careful.

[tzs]

I'd expect that long term the brine would do bad things near the places it is released but would not have any noticeable long term consequences much farther away as long as we don't discharge it somewhere where it destroys something local that turns out to be a dependency of something far away.

That's because almost all the water that is taken out of the ocean will make its way back to the ocean. We just borrow it for a while.

If all the water used by humans were taken from the ocean, we'd take about 1/300000th of the ocean's water per year. Most of that will be back in the ocean within 200 years. That puts the cap on the amount of water that would be missing from the ocean of 1/1500th of its volume, which means that the steady state increase in salt concentration would be less than 0.1%, which is much less than the natural variation in ocean salt levels.

[jdjdjsgwiwj]

With all the talk of rising oceans... Taking some sea water out might be a good thing ;)

[nullc]

The brine levels can be greatly reduced by pumping more water to dilute the brine. RO desal projects tend to optimize for an energy efficient local optima that targets minimum energy subject to maintenance constraints. But if energy is nearly free you can instead pump a lot of extra water to solve the issue by moving more volume over more area further from shore.

[sliken]

Well keep in mind:

  1) cheaper energy means you can mix more water in to get whatever salt level you want.

  2) you can mix in the output of your sewage plants

  3) most water is borrowed and returned, not a huge net loss.  Every toilet full returns to the ocean, every washing machine run, etc.

Solar powered desalination doesn't make the list for things to worry about over the next 100 years.

[fasa99]

>This will destroy the near shore ecosystem, because desalination dumps brine that kills everything,

WRONG WRONG!!!

No, we used the brines to create even more batries which store our solar charge Now we have POWER at day and at NIGHT. 24/7. 247 we are producing the brines, but then that goes onto make more batries. Ain't no ecosystem destroyed here (though I'm sure people will try to perform a regression of muh bad event unto muh new technology because that is a timelessly vogue thing to do)

[burnished]

How in sweet salty fuck is brine being used as a battery?

[zelo]

Like this https://en.m.wikipedia.org/wiki/Molten-salt_battery

Btw touristic heaters are based on https://en.m.wikipedia.org/wiki/Sodium_acetate and that's also energy storage

[woleium]

useful land at the expense of dumping brine in the ocean, which would have unforeseen consequences at scale, i am sure.

[bruce511]

I think there might be local effects from elevated brine levels, but overall nothing substantial.

Compared to the amount of water that is naturally desalinated every day (ie via evaporation), even large scale desalination is a drop in the bucket.

Desalination is already operating on a massive scale in the middle east, and we're not seeing any medium scale effects there. Elevated salinity dissipates very quickly from the point of outflow.

[containedgravel]

>Elevated salinity dissipates very quickly from the point of outflow.

I've not seen any evidence supporting this is the case, but the opposite; large swathes of high-saline concentrated blobs sweeping accross the sealife, killing it. We've had to build specialized very long outflow pipes to give the brine even a change to level

[woleium]

Its also denser, so will settle in basins underwater (search for helocline)

[burnished]

If convenient could you link to such?

[raffraffraff]

Could that not also be stored, or have some use?

[thenthenthen]

Molten salt reactor?

[pshirshov]

Sodium batteries?

[credit_guy]

Unfortunately, most of the cost of water desalination is capital cost. You simply can't afford to build a desal plant and run it only 25% of the time.

Take the Carlsbad plant in San Diego. It cost $1 billion to build, and it produces about 200k tons of fresh water per day. Let's say you build a similar plant and to finance the build you use municipal bonds that have a yield of 3.6% (the current level for 30 year muni bonds). That's 0.30% per month, or 0.01% per day. So only the interest on these bonds is $100k per day, which is 50 cents per ton of fresh water. According to wikipedia, it takes about 0.3 kWh to desalinate 1 ton of water [2]. In my state (NY) the average cost of electricity for industry consumers was about 7 cents for 2023 [3], so that would mean 21 cents per ton of water. If that cost goes to zero, you save 21 cents for each ton of water. But if you reduce the plant utilization from 100% to 25%, you increase the interest cost by 150 cents.

In order for desalination to be a useful target for peak electricity consumption, we need to find ways to massively reduce the capital cost of building desal plants. By "massively", I mean a factor of 10 or more. Is it possible? Yes. Is it guaranteed? No.

[1] https://en.wikipedia.org/wiki/Claude_%22Bud%22_Lewis_Carlsba...

[2] https://en.wikipedia.org/wiki/Desalination

[3] https://www.nyserda.ny.gov/Energy-Prices/Electricity/Monthly...

[bsder]

> Creating fresh water from sea water is extremely energy intensive, but there's nothing easier to store than giant bodies of water.

You also generate brine, you know, and that is its own environmental disaster that must be disposed of. In addition, maintenance of facilities in contact with salt water is murderously labor intensive.

Desalinization is economically useful up until you provide everybody with drinking water. Once you pass that point, desalinization is way, way, way less useful.

[SoftTalker]

Mix the brine with the treated sewage you are discharging. You're probably discharging a little less than you take out, but that gets you closer to the original salinity.

[xbmcuser]

Well if electricity is so cheap/free. Then brine left behind is not a problem as you can get a lot of chemicals out of it by processing it. Doing that though needs a lot of energy so it's not viable currently but would be with cheap/free electricity

[karmakurtisaani]

You cannot just process salt out of salt water. Eventually you're left with a lot of salt.

[xbmcuser]

yes you can https://www.nature.com/articles/s41929-018-0218-y the brine left behind is just not salt but many other minerals like lithium which require a lot of energy to separate out. But when you have free energy/electricity a lot of other things become viable.

Most people so far don't comprehend the kind of huge change free/extremely cheap electricity would bring to the world. We have the tech to do a lot of stuff but it is not cost effective cheap electricity will change that.

[throttlebody]

Well, money is, in essence, an exchange for energy, so if energy is free we'll see a significant change in our economy system and my guess it's gonna be a wild ride

[more_corn]

Yes, and that free energy will be seeking an equilibrium (where excess energy converts back into liquid capital) through clever uses and previously non-economical activities like separating lithium from brine. The great news is that each niche is a business opportunity. We, the clever ones, can spot those opportunities, build the tech to make them possible and build the companies that live in those new energy niches.

[karmakurtisaani]

I'm not a chemist nor have access to the paper. Can you summarize what happens to the seawater salt if that's applied? Surely it will still need to be deposited somewhere.

Apparently seawater has 3.5% salinity. So desalinating enough to water crops/supply cities leaves you with a lot of salt.

[xbmcuser]

A lot of this is possible already but not economical as most of the process to extract minerals from sea water require a lot of energy/electricity where as it is extremely cheap comparable to mine them directly. But free energy electricity would change that.

Metals that can be extracted from seawater include:

Sodium (Na): One of the most common metals found in seawater, sodium can be extracted through solar evaporation or electrolysis.

Magnesium (Mg): A metal that can be extracted from seawater.

Calcium (Ca): A metal that can be extracted from seawater.

Potassium (K): A metal that can be extracted from seawater.

Lithium: A metal that may become more important in the future as demand for lithium batteries and fusion energy increases.

Copper: A high-value metal that is often present in seawater.

Nickel: A high-value metal that is often present in seawater.

Cobalt: A high-value metal that is often present in seawater.

[tzs]

I wonder if the salt extracted during desalination could be dumped on top of underwater salt domes? Salt domes are one of the sources of the salt in the ocean [1].

The idea is that our salt would cover part of the salt dome, preventing that part of the salt dome from providing salt to the water. Instead, the salt that would have come from that part of the dome comes from our salt.

[1] https://oceanservice.noaa.gov/facts/whysalty.html

[dialup_sounds]

Dumping salt water into salt water doesn't immediately strike me as an environmental disaster.

[more_corn]

Dramatically increasing the saltiness of salt water can have some negative effects. If you’ve ever kept an aquarium you’ll know that sudden changes in water composition kill your pets pretty quickly. A solvable problem, but a problem that requires a bit of careful consideration.

[ulkhf]

Capital cost of these plants is significant, which is why most of them run 24 hours per day. If you only run them 8 hours per day, you triple the capital cost.

[nine_k]

How do you power such plants? Good thing if you're an oil-rich country that can just readily burn what flows from the wells anyway (say, UAE). A bit harder if you don't have anything like that (say, Namibia or West Sahara).

[more_corn]

There are small scale desalination designs like the slingshot.

[nwellinghoff]

You also have to consider the material cost. RO membranes require continuous maintenance , are expensive, and generate a massive amount of brine waste water. So while having cheap energy definitely helps, there are many expensive problems with RO filtering at scale.

[jondwillis]

I have run a dehumidifier off of excess solar before to collect water and use on plants. It was mostly for fun, and not ideal bc of possible contaminating chemicals from the dehumidifier involved, mold, and lack of minerals for the plants, but hey, it worked.

[ars]

> and lack of minerals for the plants

Are you doing hydroponics or something? Because the soil has more minerals that you could ever possibly get from water. I mean the ground is where those minerals in regular water come from in the first place.

[whycome]

What possible contamination?

Easy enough to add minerals/nutrients after the fact!

What kind of wattage was the device?

[jondwillis]

I just don’t trust my random chinese amazon brand dehumidifier’s internals to be totally food-safe. At the very least the water is condensing onto some unknown (to me) metal, touching some mystery plastics.

It was a peak ~700W device, and quite efficient for its price. It’d produce a few gallons overnight in summer in southern california when attached to a rather large battery.

[Izkata]

> I just don’t trust my random chinese amazon brand dehumidifier’s internals to be totally food-safe.

Dehumidifier water in general isn't safe for consumption.

[pests]

But if you pour that water onto a plant, and then you eat the fruit or vegetables of that plant, is it safe?

I meant acid rain and contaminated water probably lands on crops all the time.

[rightbyte]

Probably not a bigger risk than using a no-name mug?

[M95D]

Why would plants need minerals in the water? Rain doesn't contain any.

[collinvandyck76]

hydroponics i'm guessing

[oska]

Fresh water is already naturally generated by surface evaporation of the oceans under the sun's rays, i.e. it's already a solar process done on a global scale.

[throwaway48476]

Or not build cities in deserts.

[mitthrowaway2]

Deserts are coming to you, at least seasonally. With less snowpack, many cities even in temperate climates are seeing their summer water supply dry up.