How feasible - economically and technologically, is it to get potable water through desalinating sea water using solar energy? I looked for previous threads about this, but could not find any.
Pretty feasible–here is an Amazonlink to one–but the real question is “enough potable water for what?”
Solar stills, as far as I know, are for survival/small boats at sea.
Oh, to be done at a large scale. How large a scale? Would be interesting to know.
Typical daily water consumption for 1000 American households --> 1,500,000 liters
Specific heat capacity of seat water is ~4000 J/kgK and lets’ heat it from 10C to 100C (sea water wont boil at 100 exactly but this is a BoE)
Total energy would be - 40001.5e690 -->540x10[sup]9[/sup]J over 8 hours of solar activity (you have to heat a days’ worth in 8 hours and then send it out). So you have power requirements of 18MW (540e9 J / 28800 seconds).
Lets say solar incidence at sea level is about 600W/m[sup]2[/sup] so that mean you need a solar collector of about 180m a side to heat a solar furnace.
I thought Israel used solar power for their desalinazation plants?
~VOW
The Wikipedia entry for desalination gives a list of places that use desalination. It seems like large-scale desalinization is expensive, and only relatively wealthy nations can afford it.
You’d need to also include the heat of vaporization.
But where it gets tricky is that you’d use the cold water coming in to condense and then cool the desalinized water going out. Much of the energy spent heating the water is recovered, used to preheat the cold sea water, so it reduces your energy requirement.
Right, and you’d use multiple effects and lower than ambient pressures in some stages to reduce evaporation costs. It still would be too expensive on a large scale.
True, but if I understand it right actual boiling systems tend to use reduced pressure to flash boil the water. And then you have to hold salinity concentrations constant so you’d need to preheat incoming water and I bet there’s a small horde of other energy consumers as well.
And that’s only for 1000 households. Maybe photovoltic powered reverse osmosis systems are more energy efficient despite conversion losses?
This is not my specialty, but I understand that distillation is a horribly energy intensive way to desal water. I’m pretty sure that nearly all commercial processes run reverse osmosis. This, however, is not heat driven. The OP may be interested in reading up on forward osmosis, where ammonia and carbon dioxide are dissolved in the “fresh” side of the membrane to reverse the typical osmotic gradient. The ammonium carbonate is removed with heat. There is at least one startup trying to sell this tech, but I’ve no idea if they’re making money.