The solution to "desalination is too expensive" is ALSO not to only use your desalination facility some of the time, and also when the price of energy is highest.
Solar is cheaper per watt in many parts of the world, assuming you don't care when you get those watts. You can build more solar capacity than what's needed during daylight hours in which case you can't sell the energy due to there being too much of it, so high price of energy becomes irrelevant.
(or: you can't build a large number of solar power plants without affecting the market price of electricity)
Ah, so now your plan to reduce the cost of desalinization is to build so many solar power plants that you literally have more energy than you can possibly sell during the highest demand parts of the day. Well, that sounds like a good cost reduction technique.
