ELI5 Why we can’t use giant domes to create large scale water desalination.


See, the idea would be to use a huge glass dome to catch evaporated water over the ocean. And a trough around the sides of the dome would funnel into a pipe to take the water to be further treated. The problem for me is that this idea seems so obvious that there has to be a reason why it’s not already happening.

To specify, I meant using a series of small domes just off shore. Let’s say 50 ft. diameter and you just build a lot of them like a solar panel grid.

In: Engineering

The main reason I suppose is that we already do that. It’s the atmosphere and it cant be beat in scale. Second reason I suppose is it’s cost prohibitive.

There are much, much cheaper ways to desalinate water than to build a titanic glass dome over the sea.

You’re effectively proposing using solar power to evaporate water so you can desalinate it.

Evaporative desalination requires an obscene amount of energy because water is so good at absorbing energy and takes a lot of energy to go from liquid to gas.

It is far far more efficient to use reverse osmosis to desalinate water, it requires about 1/10th the energy as evaporating the water. You’d be far better off building a large quantity of solar panels and a big distillation plant than building a giant dome over a portion of the ocean.

In practice way too expensive. If you have ever seen a picture of an oil rig, it gives you an idea of how strong waves and weather can be on the ocean. Now imagine building a structure many many times that size. This would be so expensive to build. Now also consider how much energy you’d need to pump the water you collect any distance. Any energy savings you get by using the sun to evaporate the water would almost certainly be negated by the energy needed for pumping.

If we were desperate (and didn’t bother too much with conservation), it would probably be far far cheaper and simpler to build huge dams in the mountains to collect rainfall & snowmelt (essentially what you’re proposing minus the clouds and rain) and then let gravity feed the fresh water to where its needed through aqueducts, canals or pipes. And as a byproduct maybe also get a lot of cheap renewable electrical power.