I’m not a water or energy expert, but I have occasionally paid attention to the California ISO’s insightful – while perhaps somewhat dry – blog. This is the grid operator that coined the term “duck curve” to describe the abundance of solar energy available on the grid during the daylight hours, above what energy is being demanded during those hours.
So yes, there is indeed an abundance of solar power during the daytime, for much of the year in California. But the question then moves to: where is this power available?
For reference, the California ISO manages the state-wide grid, but not all of California is tied to the grid. Some regions like the Sacramento and Los Angeles areas have their own systems which are tied in, but those interconnections are not sufficient to import all the necessary electricity into those regions; local generation is still required.
To access the bulk of this abundant power would likely require high-voltage transmission lines, which PG&E (the state’s largest generator and transmission operator) operates, as well as some other lines owned by other entities. By and large, building a new line is a 10+ year endeavor, but plenty of these lines meet up at strategic locations around the state, especially near major energy markets (SF Bay, LA, San Diego) and major energy consumers (San Joaquin River Delta pumping station, the pumping station near the Grapevine south of Bakersfield).
But water desalination isn’t just a regular energy consumer. A desalination plant requires access to salt water and to a freshwater river or basin to discharge. That drastically limits options to coastal locations, or long-distance piping of salt water to the plant.
The latter is difficult because of the corrosion that salt water causes; it would be nearly unsustainable to maintain a pipe for distances beyond maybe 100 km, and that’s pushing it. The coastal option would require land – which is expensive – and has implications for just being near the sea. But setting aside the regulatory/zoning issues, we still have another problem: how to pump water upstream.
Necessarily, the sea is where freshwater rivers drain to. So a desalination plant by the ocean would have to send freshwater back up stream. This would increase the energy costs from exorbitant to astronomical, and at that point, we could have found a different use for the excess solar, like storing it in hydrogen or batteries for later consumption.
But as a last thought experiment, suppose we put the plant right in the middle of the San Joaquin River Delta, where the SF Bay’s salt water meets the Sacramento River’s freshwater. This area is already water-depreased, due to diversions of water to agriculture, leading to the endangerment of federally protected species. Pumping freshwater into here could raise the supply, but that water might be too clean: marine life requires the right mix of water to minerals, and desalinated water doesn’t tend to have the latter.
So it would still be a bad option there, even though power, salt water, and freshwater access are present. Anywhere else in the state is missing at least one of those three criteria.
I think these are valid arguments but I also think you’ve dismissed one key point by simply saying it’s too expensive. That is, pumping fresh water back upstream. If you were to properly consider the problem the actual cost would be determined by cost per distance traveled and you essentially decide the distance by which ever you are budgeted for. If it’s not feasible to pump back to a usable hydroelelectric dam, pump it up into tower reservoirs.
I never specified that California would be the best place to implement this process. Hopefully, as solar becomes more widely adopted, these areas could be decided by idea conditions. Also, subsequent solar grids could be tied in to pump the water even further upstream, as solar adoption becomes more popular.
I suppose the question is, what does a bucket of water cost if it comes from the groundwater or the next mountains/lake and what does it cost if it comes from a multi-million desalination facility… I mean even if the energy is free (which it’s not) the whole plant has to be built, staffed and maintained. And having an expensive factory sit around idle during the night and peak power and just operational from 10am to 3pm isn’t economical and makes the water that comes out of it even more expensive. And regular water is cheap. Even after being carried around by trucks in the worst case.
If it’s too expensive compared to normal water, no-one is going to buy it. And the millions of dollars invested in the desalination plant won’t get a return. And then it’s just throwing money out of the window. It could be cheaper to just discard the exess energy than invest millions into something that doesn’t sell. And then you could throw good money after bad and try to subsidize the effort. But I don’t think it’s viable unless it’s a desert or some other geological factors rule out other water sources.
In other words, green technology is not feasible from an economic standpoint. Did you factor in the effects of global warming or the cost of depleting known waterways/systems?
I mean you also have to factor in the carbon footprint of the concrete that goes into the desalination facory. And producing solar panels also isn’t light on the planet. It’s going to be a complicated equation. But large factories like desalination plants plus the energy also don’t come without consequence for the planet. Even more so if they’re underutilized. I’m not sure if that counts as “green” anymore. The technology is probably neither feasible from an economic standpoint, nor from an ecological one.
By your estimation.
Sure. I’m not a professor for water treatment. But I haven’t heard any of them advocate for this, so there might be a reason to it. And with the constraint, it has to be powered just by excess solar energy, I’m pretty sure I’m right. That might change if you find cheap regenerative energy that runs the plant 24/7 and there are other geological factors that make alternative water sources less attractive. But there is no way it’ll work like this. And I mean we use lots of water everyday. Not just in the house, but also for farming and whatnot. You’re going to need a massive amount of energy to have a noticeable impact and save other water sources. And solar doesn’t have a particularly good carbon footprint. There are lots of reasons why my estimation might be closer to the truth. (For current technology, of course.) The desalinated water will come with a carbon footprint and a price. And both of them might not be favorable.