Results 1 to 16 of 16

Thread: Cool "new" technology

  1. #1
    Join Date
    Jun 2005
    Posts
    14,420

    Cool "new" technology

    There is a technology I wanted to ask about. It's something I've heard about, and it seems like a really cool idea, but as far as I know it hasn't really been implemented so there must be some downside, maybe production costs and maintenance? Anyway, I'd be interested in any feedback.

    This is something that I think would work fairly well in relatively sunny, dry places like California or Australia or Northern Africa.

    Basically, you build a pipe that pumps seawater into a farm of devices, which take the water and boil it using parabolic antennas that focus the sunlight onto pipes. The steam is then used to drive turbines, which create electricity, which can be used to pump the water but also, if there is excess, for consumption. And you get fresh water, and salt, which you can sell. So it seems a win-win solution. I guess there is a problem with maintaining the generation devices from salt damage. But what else?
    As above, so below

  2. #2
    Join Date
    Dec 2011
    Location
    Very near, yet so far away
    Posts
    397
    Quote Originally Posted by Jens View Post
    There is a technology I wanted to ask about. It's something I've heard about, and it seems like a really cool idea, but as far as I know it hasn't really been implemented so there must be some downside, maybe production costs and maintenance? Anyway, I'd be interested in any feedback.

    This is something that I think would work fairly well in relatively sunny, dry places like California or Australia or Northern Africa.

    Basically, you build a pipe that pumps seawater into a farm of devices, which take the water and boil it using parabolic antennas that focus the sunlight onto pipes. The steam is then used to drive turbines, which create electricity, which can be used to pump the water but also, if there is excess, for consumption. And you get fresh water, and salt, which you can sell. So it seems a win-win solution. I guess there is a problem with maintaining the generation devices from salt damage. But what else?
    I think the main problem would be actually boiling enough water to drive a turbine. Plus the salt would be left in the pipes and block them quite quickly.

  3. #3
    Join Date
    Mar 2004
    Posts
    19,227
    That doesn’t sound new. I think I read ideas like that decades ago. From some of the older stuff I remember reading, my understanding is that parabolic mirrors only work well in direct sunlight, so lose out on overcast days with diffuse sunlight. The mirrors also need to be kept reasonably clean, and there will be a lot of them. If you’re heating a pipe well above ambient, parasitic heat loss can leak a lot of the gain from the mirror, so they need to be insulated. Commonly this is done with putting the inner black pipe in an outer glass tube and maintaining at least a partial vacuum in the outer tube. This gets expensive.

    Phase change of water in the tube can cause damage and not only by boiling but at night there might be freezing. In this case, salt would also be an issue. Usually for higher temperatures they heat some other liquid with a high boiling point and low freezing point like an oil, and use a heat exchanger to heat water if that is the intended use. You also have to deal with leaks in a large system. On spinning turbines: Efficiency depends on temperature difference with ambient so it will be low if it is just over boiling. It needs to be really hot and that’s difficult.

    My guess is that these days reverse osmosis powered by PV panels located in an optimal location like a (hopefully) nearby dry desert might be more practical and less expensive. But that is still an expensive way to get fresh water.
    Last edited by Van Rijn; 2020-Sep-11 at 10:38 AM.

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." — Abraham Lincoln

    I say there is an invisible elf in my backyard. How do you prove that I am wrong?

    The Leif Ericson Cruiser

  4. #4
    Join Date
    Jun 2005
    Posts
    14,420
    Quote Originally Posted by Van Rijn View Post
    That doesn’t sound new.
    Yes, that’s why I put the scare quotes in the thread title. About the rest of the comments, thanks and I guess that’s why it hasn’t been implemented.


    Sent from my iPhone using Tapatalk
    As above, so below

  5. #5
    Join Date
    Apr 2007
    Location
    Nowhere (middle)
    Posts
    37,998
    Solar desalination is a growing field of research. If you want new: https://www.nature.com/articles/s41893-020-0590-x on a method of purifying salt water by sunlight using a metal-organic framework.

    As for using desalination as a power and water source at the same time, I think that's asking too much of a simple sunbeam. Boiling water is energy-intensive, you're just not going to get much power output without an impractically large collection area.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  6. #6
    Join Date
    Jul 2005
    Posts
    19,647
    Quote Originally Posted by Van Rijn View Post
    That doesn’t sound new. I think I read ideas like that decades ago.
    Yes, the concept was included in the original Von Braun space station and moonship concepts in the late '50s.
    Here's the parabolic solar heater in my own model of the lunar orbiter concept:
    moonship8.jpg
    And at right on the arm below the crew capsule in the lunar lander:
    von-braun-lander-8.jpg
    Good quality sunlight and fresh water, of course.

    Grant Hutchison

  7. #7
    Join Date
    Sep 2006
    Posts
    643
    Remove the turbines, because the return isn't worth it, and I'm pretty sure Saudi Arabia and the UAE are doing that already for fresh water. The salt is not an asset however, it's closer to toxic waste. They generally return it to the ocean but that raises the salinity near the discharge and causes problems.

  8. #8
    Join Date
    Apr 2007
    Location
    Nowhere (middle)
    Posts
    37,998
    Saline would have to be directed to drying pans to make salt... which also requires large surface areas. So you'd need to build it in open land not being used for anything else, which means you'd have to have large pumps and pipelines to send the potable water to populated areas. It all runs into money, more than you'd spend on conventional sources; effectively you'd be building a whole new infrastructure.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  9. #9
    Join Date
    Apr 2011
    Location
    Norfolk UK and some of me is in Northern France
    Posts
    9,223
    I recall reverse osmosis is preferred and is used extensively to get fresh water from brine. You need some pressure to drive it and there are several feasible ways depending on scale. For large scate, electricity from PV can drive a pump. For small scale a pressure from heated air or steam would be easy to do with a solar focus device. Boiling seems a waste but you could recover most of the heat as a preheating coil, if you have no membrane handy!
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  10. #10
    Join Date
    May 2003
    Posts
    6,166
    I just want to chime in that while Jens's idea (and everyone's comments) are mostly focusing on the desalinization part of the process, the other half of this, using mirrors to concentrate sunlight and then using the heat produced to drive a turbine for energy is something that's being actively done today (take a look here, for example).
    Conserve energy. Commute with the Hamiltonian.

  11. #11
    Join Date
    Apr 2007
    Location
    Nowhere (middle)
    Posts
    37,998
    Quote Originally Posted by Grey View Post
    I just want to chime in that while Jens's idea (and everyone's comments) are mostly focusing on the desalinization part of the process, the other half of this, using mirrors to concentrate sunlight and then using the heat produced to drive a turbine for energy is something that's being actively done today (take a look here, for example).
    I was under the impression that it was the combined nature of the OP proposal that made it "new". Neither solar boilers nor desalinization by themselves are new.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  12. #12
    Join Date
    Jun 2005
    Posts
    14,420
    Quote Originally Posted by Noclevername View Post
    I was under the impression that it was the combined nature of the OP proposal that made it "new". Neither solar boilers nor desalinization by themselves are new.
    Actually, I put the "new" in quotes in the title of the thread. And the reason I used the scare quotes is that actually, I had read something about the idea quite a long time ago, but never really heard any further development, so my intention in using the quotes was to mean, "it's not really new but only new in the sense that it hasn't materialized."
    As above, so below

  13. #13
    Join Date
    Mar 2004
    Posts
    19,227
    Quote Originally Posted by Grey View Post
    I just want to chime in that while Jens's idea (and everyone's comments) are mostly focusing on the desalinization part of the process, the other half of this, using mirrors to concentrate sunlight and then using the heat produced to drive a turbine for energy is something that's being actively done today (take a look here, for example).
    The solar thermal power towers are an example where the technology definitely works and has some advantages (it’s fairly straightforward to store heat for nighttime generation) but is more expensive than PV now is, so PV arrays are usually being built instead.

    By the way, I’m sure I’ve read about solar thermal concepts for power *and* desalination decades ago. Popular Science had articles on various solar power schemes almost every month back in the ‘70s and some of the ‘80s (as oil prices dropped back down it became a much less popular topic). I remember “greening the deserts” was an often mentioned topic.

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." — Abraham Lincoln

    I say there is an invisible elf in my backyard. How do you prove that I am wrong?

    The Leif Ericson Cruiser

  14. #14
    Join Date
    Mar 2004
    Posts
    19,227
    Quote Originally Posted by Jens View Post
    Actually, I put the "new" in quotes in the title of the thread. And the reason I used the scare quotes is that actually, I had read something about the idea quite a long time ago, but never really heard any further development, so my intention in using the quotes was to mean, "it's not really new but only new in the sense that it hasn't materialized."
    Yes, basically the issue with any solar power scheme is that it needs a lot of hardware over a large area, so the trick is to make it inexpensive to build and low maintenance. A lot of schemes that would work technically can be too expensive in practice. Desalination also is usually one of the most expensive ways to get water, so outside of desert climates where there are no other options, you usually don’t see it.

    That said, there has been a lot of improvement in reverse osmosis hardware. It is very common for private boats used on the ocean to have reverse osmosis equipment and has saved the lives of people that had equipment failures. It’s been used at large scale in Israel and other very dry countries.

    But cost is an issue. I remember an article a few years ago, when we in California were five years in to a severe drought and things would be getting desperate if it lasted another year. One city was thinking of building a desalination plant, but it would take a few years and would produce expensive water. They mentioned a similar situation in, I believe Australia, where a city had gone ahead under similar conditions and the next year after it was built, the rain came. The water was so expensive they mothballed the plant, so it went to waste. In our case, the next winter was indeed much wetter. We often get that: a few dry years followed by a very wet one.

    "The problem with quotes on the Internet is that it is hard to verify their authenticity." — Abraham Lincoln

    I say there is an invisible elf in my backyard. How do you prove that I am wrong?

    The Leif Ericson Cruiser

  15. #15
    Join Date
    Jun 2005
    Posts
    14,420
    Quote Originally Posted by Van Rijn View Post
    By the way, I’m sure I’ve read about solar thermal concepts for power *and* desalination decades ago. Popular Science had articles on various solar power schemes almost every month back in the ‘70s and some of the ‘80s (as oil prices dropped back down it became a much less popular topic). I remember “greening the deserts” was an often mentioned topic.
    Yes, I remember the same thing, though I'm not sure how long ago it was. I remember reading of the idea of having such plants in northern Africa, and then selling the generated electricity to the European market. So it was a kind of "killing two birds with one stone" idea.
    As above, so below

  16. #16
    Join Date
    Jun 2005
    Posts
    14,420
    Quote Originally Posted by Van Rijn View Post
    Yes, basically the issue with any solar power scheme is that it needs a lot of hardware over a large area, so the trick is to make it inexpensive to build and low maintenance. A lot of schemes that would work technically can be too expensive in practice. Desalination also is usually one of the most expensive ways to get water, so outside of desert climates where there are no other options, you usually don’t see it.
    Yeah, I guess it's a bit like the idea of mining gold and platinum from asteroids, where it seems very attractive until you consider the cost compared to other ways of getting minerals that are already being used.
    As above, so below

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •