Why is desalination so difficult?
practical.engineering
Why is desalination so difficult?
1–10 of 644 posts
Re: Why is desalination so difficult?
#2Solar stills are one of those basic survival tools anyone living in an arid region near a salty body of water should understand how to rig. They’re dirt simple and as easy to build as a prison still with the added bonus of only requiring the sun as an external power source.
Similarly everyone should know how to rig a basic water purification system using gravel, sand, and charcoal in series.
Even just as applied science experiments to do with kids they’re worthwhile.
Edit: Water based solar power is generally an area I think that deserves more research. While photovoltaics have their advantages, water is cheap, clean, and reliable. Heating water with sun during the day and using it for household heating at night is the simple application that I’m most familiar with, but I wouldn’t be shocked if there’s some scale where an economically interesting Carnot cycle becomes possible.
Re: Why is desalination so difficult?
#3It's not difficult. It's just energetically uphill. Undoing entropy costs energy. Second Law of Thermodynamics.
Re: Why is desalination so difficult?
#4Solar stills are one of those basic survival tools anyone living in an arid region near a salty body of water should understand how to rig. They’re dirt simple and as easy to build as a prison still with the added bonus of only requiring the sun as an external power source. Similarly everyone should know how to rig a basic water purification system using gravel, sand, and charcoal in series. Even just as applied scie…
Water isn’t the most efficient way of doing that but the principle is sound. There are molten salt solar arrays that work similarly.
Re: Why is desalination so difficult?
#5It's not difficult. It's just energetically uphill. Undoing entropy costs energy. Second Law of Thermodynamics.
Separating two things isn't necessarily expensive. Think of coin sorters that just use gravity and different sized holes.
Re: Why is desalination so difficult?
#6I remember reading that it causes some problems related to fishing because the fish all migrate further out.
Re: Why is desalination so difficult?
#7Re: Why is desalination so difficult?
#8It's not difficult. It's just energetically uphill. Undoing entropy costs energy. Second Law of Thermodynamics.
Separating two things isn't necessarily expensive. Think of coin sorters that just use gravity and different sized holes.
You need to bring the coins uphill in the first place.
Re: Why is desalination so difficult?
#9Probably very dumb idea, but would it be feasible to just pump and sprinkle sea-water on hot, dry desert and let it naturally evaporate, and then collect it as fresh rainwater back? i.e. how much water would you need to evaporate to have a noticeable increase in rainfall?
Re: Why is desalination so difficult?
#10It's not difficult. It's just energetically uphill. Undoing entropy costs energy. Second Law of Thermodynamics.
It's not tricky, but it's a lot of work, which is a kind of difficulty.