Desalination around the world- how other countries are making fresh water from the ocean

[hunter]

3. It takes a lot of energy to desalinate seawater.

3 kWh/m3 in modern plants.

Burning fossil fuels to desalinate seawater is insane, and that's what most of these plants are doing. Even the "wind-powered" plants of Australia, are primarily coal powered, except by accounting, since electricity on the grid is electricity on the grid. One can't really say wind has "replaced" coal until coal consumption within the network is actually declining... Otherwise it's like saying you are quitting smoking by starting to chew nicotine gum, even as you smoke more cigarettes.

The equipment and maintenance cost of strictly solar flash-distillation projects are ferocious. Hot seawater is wickedly corrosive and fouling. Most older flash/distillation plants (fossil, nuclear, even a few solar experiments) have been replaced by reverse osmosis plants.

Forward osmosis looks promising in combination with thermal plants and might be a good fit with various types of thermal solar collection because the seawater side of the circuit in this type of plant remains cool.

But even with clean energy sources the water from desalinization is still very expensive and the intakes and outlets of the desalinization plant damage the existing aquatic environment. It's not simply that organisms caught in the intakes are killed and the saltier water disposed of, it's that many chemicals are used in the process to prevent fouling, etc., and these end up in the waste stream.

Whatever we do, we always return to the same problem. There are too many humans, and there are too many humans living in environments that would be very uncomfortable or deadly without imported water and air conditioning.