Sounds like it would be cheaper to build desalination plants on the coast, and pipe the water in. Iran certainly has the technology and brainpower to do that.
They share the same gas field with Qatar, who does all their desalination with all the excess gas production they can’t sell.
Qatar has no surface freshwater or groundwater. So all of their water is desalinated. It’s often still quite salty to the taste though - the last few ppms would be an exorbitant cost to remove.
However, Qatar has 3 million people. Iran has 92 million people - 9 million in Tehran alone. So their half of that gas field in the Gulf contributes far less energy per capita.
And even if the energy is free (unlimited natural gas, fusion, magic, whatever) desalination is still fairly expensive. I think only about 50% of the cost is energy, the other half is CapEx, operations, and replacing the membranes as they get used up.
I have read about experimental desalination techniques that do a better job, and use less energy, but I haven't heard much about that, lately.
I'd think that this kind of research would be a priority. It won't be long, before we start having water wars (like olden times, but with nastier weapons).
The low hanging fruit have been long picked. Reverse osmosis is within 50% of the thermodynamic limit.
If you have gigawatts of low grade waste heat (Iran does, in theory), you can run multistage flash distillers of the waste heat, and those have more than an order of magnitude separation to the thermodynamic limit (they also have lower CAPEX, lower maintenance and lower water pre-treatment requirements than reverse osmosis).
I wasn't talking about what they were discussing (desalination for farming). I was talking about moving an entire city, as opposed to getting enough water to deal with just that city.
Actually it says the desalinated water is too expensive even for farming, it’s only used for heavy industries, so it’s certainly not a solution for the domestic supply of 9 million people.
And don’t confuse moving the capital city with actually relocating Tehran. Tehran’s not going anywhere. What they’re proposing is building a new capital city, but it’ll be the rich and the political and religious elite who move there. The millions of poor and powerless living in Tehran will get left behind. Some will be able to migrate south, but many won’t.
