[warcher]

Batteries have proven extremely resistant to the scaling of solar panels. I would love to be wrong about this, but overwhelmingly people with an agenda just kind of hand-wave past grid scale energy storage problems that we have generations of evidence against being easily or cheaply solvable.

The thing about this plan that I love though, is that who cares if the desal plant runs at night? Desalination can take all of the power you can feed it and then some, and if it shuts off after sundown, who cares? Stop filling your freshwater reservoir until morning, at which point you just run flat out all over again.

[adrianmonk]

It does matter, though. Suppose you need X amount of fresh water output per month. And suppose that for Y dollars, you can build a plant that supplies X if it runs 24 hours per day.

If, instead, you can only run your plant 8 hours per day instead of 24, then you need to build a plant three times as big, which costs 3Y dollars.

This is where batteries (or other energy storage) may become useful. If you can build them for less than 2Y dollars, then you can build the whole system for cheaper.

[amluto]

My question is: should it actually cost 3Y? Sure, if you take an off-the-shelf design and triple it, it will cost around three times as much.

But there should be at least some efficiencies that can be gained. For example, energy conversion is not cheap. Rather than building solar inverters that produce 480VAC and using 480VAC pumps or pump drives, what if the pumps ran on DC?

Or, for more fanciness, what if the pump drives were themselves the MPPTs? Have the solar panels arranged so they produce a sufficient voltage for the motor drive bus even at minimum output, and make the drivers smart enough to run the right number of pumps at the right power and to do so while tracking the maximum power point? That’s a lot of power electronics that could be avoided.

Also, if a plant is willing to store a day’s worth of seawater and brine, then the intake and discharge systems only need to be sized for maximum daily average flow, not peak sunshine flow.

[warcher]

What I'm saying is that the freshwater reservoir is a totally free grid scale battery for a desal plant. No need to save it, just make fresh water while the sun shines and drink it whenever.

[adrianmonk]

Energy storage would serve two purposes:

(1) Ensure you always have fresh water available since you're continuously producing it.

(2) Reduce the size of desalination plant you must build by allowing you to run it 24x7.

You're right that you can just store the fresh water, so batteries aren't needed for #1. But the article is talking about how to achieve #2.

[warcher]

Yeah, I'm just saying-- a big desalination plant is a solved problem. Grid scale energy storage has been ten years off for almost as long as nuclear fusion. The original author just hand waves their way through what would be the biggest energy breakthrough in a hundred years to save a couple bucks running a desalination plant.