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?
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.
I wrote my comment in response to the question, and IMO, I did it justice by listing the various considerations that would arise, in the order which seemed most logical to me. At no point did I believe I was writing a design manual for how to approach such a project.
There are much smarter people than me with far more sector-specific knowledge to “properly consider the problem” but if you expected a feasibility study from me, then I’m sorry to disappoint. My answer, quite frankly, barely arises to a back-of-the-envelope level, the sort of answer that I could give if asked the same question in an elevator car.
I never specified that California would be the best place to implement this process.
While the word California didn’t show up in the question, it’s hard to imagine a “state on the coast” with “excess solar” where desalination would be remotely beneficial. 30 US States have coastlines, but the Great Lakes region and the Eastern Seaboard are already humid and wet, with rivers and tributaries that aren’t exactly in a drought condition. That leaves the three West Coast states, but Oregon and Washington are fairly well-supplied with water in the PNW. That kinda leaves California, unless we’re talking about Mexican states.
I’m not dissing on the concept of desalination. But the literature for existing desalination plant around the world showcases the numerous challenges beyond just the money. Places like Israel and Saudi Arabia have desalination plants out of necessity, but the operational difficulties are substantial. Regular clogging of inlet pipes by sealife is a regular occurrence, disposal of the brine/salt extracted is ecologically tricky, energy costs, and more. And then to throw pumped hydro into this project would make it a substantial undertaking, as dams of any significant volume are always serious endeavors.
At this point, I feel the question is approaching pie-in-the-sky levels of applicability, so I’m not sure what else I can say.
