5 ms·

Desalination will be the new pumped hydro. I kid but I don't. (I don't actually know much about desal - there's details, but is it power in = water out, plus

Desalination will be the new pumped hydro. I kid but I don't. (I don't actually know much about desal - there's details, but is it power in = water out, plus a bunch of facility maintenance and operations?)

croddin 4y ago
Yeah we need good things to do with cheap power that don't always have to run and aren't too capital intensive (Making them need to use more expensive power). I'm not sure what is best between Desalination, Aluminum smelting, Crypto mining, or what other good alternatives are.
- brianwawok 4y ago
  You are putting crypto mining on the same level to humankind as making drinking water?
  - croddin 4y ago
    Desalination is higher priority overall then crypto mining. There are several factors which make something a good candidate to use excess solar power. Maybe it makes sense for desal to always be running? Crypto can more quickly be spun up or down to respond to the energy market. Crypto mining can be done anywhere with cheap power but desalination needs to be near salt water and where water is needed. We will probably need a mix of several industries to effectively use the cheap power.
    - RustyRussell 4y ago
      Indeed, we're seeing this happening. Bitcoin mining will pay $$$ for your waste power, and an increase in waste power is the problem with wind and solar. We need a shitload of green generation infrastructure, and Bitcoin is going to pay for it. Sometimes the world is weird, sorry.
- deleted 4y ago
  [deleted]
invalidator 4y ago
> but is it power in = water out, plus a bunch of facility maintenance and operations? Basically yes. I'm mostly familiar with Reverse Osmosis, where electricity to drive the pumps is about 40% of the TCO. There's another big chunk for consumables - chemicals, failed membranes, etc. Then the rest is capital costs to build the thing. It's not "free power == free water", but the power is a significant factor. > Desalination will be the new pumped hydro. Eh, no. Desal is a great place to dump surplus energy, but you can't get the energy back out. It pairs well with nuclear power, so you can use extra nighttime capacity. It's less useful with solar, unless you've severely overbuilt panels and can't find anything else to do with them on sunny days. It's a better tradeoff to buy fewer panels and use that money to pay for storage (pumped hydro, batteries, whatever).
- sbierwagen 4y ago
  Fun fact: the Mangyshlak atomic energy complex used low temperature steam from the first stage turbines for thermal desalination: https://inis.iaea.org/collection/NCLCollectionStore/_Public/29/067/29067742.pdf https://inis.iaea.org/collection/NCLCollectionStore/_Public/...
- ncmncm 4y ago
  Nothing pairs well with nuclear. A key fact about desalination is that it is totally OK for it to happen only when the sun shines or the wind blows.
- RangerScience 4y ago
  Neat, thanks for the additional details! My mind went "you can't do pumped hydro if you don't have enough water!" Although I guess you could just pump salt water, and we're not gonna run out of that.
zdragnar 4y ago
It's power in, water + brine out. You have to do something with the brine- dribble it into the ocean over a large area, pump it into old salt mines or below freshwater aquifers. It's too concentrated to just put back into the ocean in one spot without killing everything around it, and you don't want it contaminating what little fresh water you have under ground. Not an insurmountable problem, but it does add another cost in addition to maintenance and power
- robonerd 4y ago
  The dilution can be done in holding tanks. Fill a tank a tenth of the way with the hyper-saline brine (or whatever the right ratio is), flood the rest of it with sea water, stir it around for a while then dump it into the ocean. If the holding tanks are built in the tidal zone and are sized appropriate relative to the brine output of the desalination plant, then you wouldn't even need to do much pumping. The salinity of the tank could be tested before dumping it, an extra layer of safety in the system.
  - lstodd 4y ago
    What holding tanks? They would have to be by the volume about the equal of where you'd discharge them. This is just sad.
    - robonerd 4y ago
      I don't see the problem. The holding tanks would be concrete lined basins amounting to relatively small reservoirs. Not exactly unprecedented.
  - ncmncm 4y ago
    A long, leaky pipe achieves the same thing without the tanks.
    - robonerd 4y ago
      There is public opposition to building desalination plants in part because a lot of people don't like that solution. For starters, it just sounds bad; it sounds like a company brushing aside pollution concerns by saying they'll spread it out where you can't see it. That characterization isn't fair; but fair or not, poor public perception still stalls land development. More significantly, it requires more infrastructure under the water where it will be difficult to inspect and repair. Furthermore there is a financial incentive for plants to neglect these pipes. Suppose there is a break in the pipe that discharges concentrated brine straight into the ocean. Slowing or ceasing production until the pipe could be repaired would be very expensive to the plant operator. On the other hand if they ignore the problem, they wouldn't have to slow production and it would cost them nothing (unless they got caught.)

croddin 4y ago

Yeah we need good things to do with cheap power that don't always have to run and aren't too capital intensive (Making them need to use more expensive power). I'm not sure what is best between Desalination, Aluminum smelting, Crypto mining, or what other good alternatives are.

brianwawok 4y ago
You are putting crypto mining on the same level to humankind as making drinking water?
- croddin 4y ago
  Desalination is higher priority overall then crypto mining. There are several factors which make something a good candidate to use excess solar power. Maybe it makes sense for desal to always be running? Crypto can more quickly be spun up or down to respond to the energy market. Crypto mining can be done anywhere with cheap power but desalination needs to be near salt water and where water is needed. We will probably need a mix of several industries to effectively use the cheap power.
  - RustyRussell 4y ago
    Indeed, we're seeing this happening. Bitcoin mining will pay $$$ for your waste power, and an increase in waste power is the problem with wind and solar. We need a shitload of green generation infrastructure, and Bitcoin is going to pay for it. Sometimes the world is weird, sorry.
deleted 4y ago
[deleted]

invalidator 4y ago

> but is it power in = water out, plus a bunch of facility maintenance and operations? Basically yes. I'm mostly familiar with Reverse Osmosis, where electricity to drive the pumps is about 40% of the TCO. There's another big chunk for consumables - chemicals, failed membranes, etc. Then the rest is capital costs to build the thing. It's not "free power == free water", but the power is a significant factor. > Desalination will be the new pumped hydro. Eh, no. Desal is a great place to dump surplus energy, but you can't get the energy back out. It pairs well with nuclear power, so you can use extra nighttime capacity. It's less useful with solar, unless you've severely overbuilt panels and can't find anything else to do with them on sunny days. It's a better tradeoff to buy fewer panels and use that money to pay for storage (pumped hydro, batteries, whatever).

sbierwagen 4y ago
Fun fact: the Mangyshlak atomic energy complex used low temperature steam from the first stage turbines for thermal desalination: https://inis.iaea.org/collection/NCLCollectionStore/_Public/29/067/29067742.pdf https://inis.iaea.org/collection/NCLCollectionStore/_Public/...
ncmncm 4y ago
Nothing pairs well with nuclear. A key fact about desalination is that it is totally OK for it to happen only when the sun shines or the wind blows.
RangerScience 4y ago
Neat, thanks for the additional details! My mind went "you can't do pumped hydro if you don't have enough water!" Although I guess you could just pump salt water, and we're not gonna run out of that.

zdragnar 4y ago

It's power in, water + brine out. You have to do something with the brine- dribble it into the ocean over a large area, pump it into old salt mines or below freshwater aquifers. It's too concentrated to just put back into the ocean in one spot without killing everything around it, and you don't want it contaminating what little fresh water you have under ground. Not an insurmountable problem, but it does add another cost in addition to maintenance and power

robonerd 4y ago
The dilution can be done in holding tanks. Fill a tank a tenth of the way with the hyper-saline brine (or whatever the right ratio is), flood the rest of it with sea water, stir it around for a while then dump it into the ocean. If the holding tanks are built in the tidal zone and are sized appropriate relative to the brine output of the desalination plant, then you wouldn't even need to do much pumping. The salinity of the tank could be tested before dumping it, an extra layer of safety in the system.
- lstodd 4y ago
  What holding tanks? They would have to be by the volume about the equal of where you'd discharge them. This is just sad.
  - robonerd 4y ago
    I don't see the problem. The holding tanks would be concrete lined basins amounting to relatively small reservoirs. Not exactly unprecedented.
- ncmncm 4y ago
  A long, leaky pipe achieves the same thing without the tanks.
  - robonerd 4y ago
    There is public opposition to building desalination plants in part because a lot of people don't like that solution. For starters, it just sounds bad; it sounds like a company brushing aside pollution concerns by saying they'll spread it out where you can't see it. That characterization isn't fair; but fair or not, poor public perception still stalls land development. More significantly, it requires more infrastructure under the water where it will be difficult to inspect and repair. Furthermore there is a financial incentive for plants to neglect these pipes. Suppose there is a break in the pipe that discharges concentrated brine straight into the ocean. Slowing or ceasing production until the pipe could be repaired would be very expensive to the plant operator. On the other hand if they ignore the problem, they wouldn't have to slow production and it would cost them nothing (unless they got caught.)