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.
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.
It usually makes more sense to pump water to a nearby reservoir uphill. That water can be released back through turbines when solar production is lower - pumped hydro are basically giant batteries. So not so much pumping it back upstream, but a similar idea, just without expensive desalination.
Not a saltwater coast, but the Ludington plant on Lake Michigan is a good example of this: https://en.wikipedia.org/wiki/Ludington_Pumped_Storage_Power_Plant
I think they’re more asking about getting usable water than energy storage
Why not both?
gotta do something with the brine
We are talking about humanity here, we will pump the brine into tapped out oil and gas holes and end up salting the aquifers.
Brine can be transported to different parts of the ocean? It’s a massive bodie of water. Widespread adoption would have to be massive as well to see significant increases in molar concentration.
Salinity doesn’t really work like that. You can’t just dump a bunch of brine and expect it to just mix with the rest of the seawater. A lot of that depends on temperature, currents, etc. You might just end up forming a brine lake in the ocean if the brine just so happens to end up at the bottom without ever mixing. Not to mention brine isn’t always just concentrated salt and water. It can include byproducts from desalination.
Reference:
People have made the argument for dumping nuclear waste in the ocean. I believe adding brine to existing brine resivours won’t be too much of a hassle.
Are there any brine reservoir in the ocean? That doesn’t seem to be a thing. It either mixes properly with the ocean if proper mechanisms are set or it just ends up sinking to the bottom of the ocean and killing everything there.
There’s storage inland, but that also has its own problems.
Nuclear waste in the ocean follows a similar idea (although larger in scope). You can’t just dump it and be done. You have to create a plan to slowly release it (over decades) to (hopefully) not adversely affect life
Sure there are. They’re in the lost river, where the juvenile ghost leviathans live. Just go down to the bottom of the blood trench and you’ll get there.
where exactly? what do you want to kill and pollute? what area deserves it?
Land acquisition cost and not in my backyard’ers. At least here in Southern California. There is no chance that a loosely regulated and toxic high salinity waste water plant would get past public and environmental scrutiny. The only really viable areas are the last local refuges for many.
Like from Mexico to Santa Barbara, the camp Pendleton Marine Corps base is one of the only viable spots. The decommissioned nuclear power plant would be one of the mostly likely spots to build such a facility, but that is surrounded by a state park and some of the most prised undeveloped local surf real estate. Many municipal and commercial projects have vied for that land, but there is fierce local opposition from a wealthy and very politically well connected public.
There has been occasional talk about opening up the Pacific side of the 5 freeway to public development as this is some of the federal government’s most valuable real estate. Even if this happened, that would become one of the most elite places to live in the country.
Few people know this, but the Southern California coast around Orange County and North of San Diego is a spot of rare deep ocean upwelling. There is a micro climate here within a couple miles of the coast that is regulated by the ocean upwelling maintaining temperatures. It is always cooler in the summer and warmer in the winter here and almost always between 50°F and 80°F even when a few miles away it can be 40°F-100°F. This is one of the main reasons why real estate in these areas is so high.
- chemical batteries are cheaper
- we don’t really need the water that badly
- desalination needs somewhere to dump the brine
- it costs tens of millions to billions to build a pump and pipe large enough to pump a meaningful amount of water uphill into reservoir
- an investment in desalination needs to be run continuously to make sense financially
Is there a state with excess energy that can’t be sold or used in a better way?
Locally, yes. Solar (and wind) energy isn’t uniform in timing or location, so when there’s too much of it relative to consumption, there needs to be a profitable way to use it rather than just dumping it into resistive heating or letting the panels wear out faster at open circuit. Desalination is a pretty good idea since places with high solar resources also tend to be poorer in water resources. The challenge is the capital costs of desalination plants and competition with existing water sources - water rights are a giant ratfuck by themselves. I think it’ll make sense to build desalination plants that can absorb excess energy generation, but if there’s even political will for it, they’ll take a lot of time to build up
You could also have a power grid and distribute the excess electricity to the next state where it’s cloudy. Or do other things with it. Or build the AI datacenters there, that Google etc are currently planning to power with small nuclear reactors… I believe desalination is a very wasteful option compared to other things.
Transporting large quantities of electricity isn’t easy, you have to have large enough interconnects to handle the energy you’re moving around.
Entire Europe is connected. Sure we’re still missing quite some cables to get the regeneratives to where they’re needed. And I suppose this doesn’t cover the UK. But it’s no problem to move around quite some energy across parts of a continent.
IIRC, California overproduces electricity during sunny summer days due to solar, but solar production drops in the evenings right when demand is peaking due to people getting home from work and cooking dinner and whatnot. There are better applications for that energy than desalination though - battery storage right now, and maybe running electrolyzers for green hydrogen production someday in the future.
Do we have numbers on how much electricity actually gets discarded (in a year)? Sure, we don’t use that much during the day. But I bet companies are happy electricity is cheaper during daytime when we work. And we can cut down on natural gas during the day. And use it for air condidioning specifically when it’s warm anyways. I wonder how much excess is actually left after all of that.
The only state this would be viable in is California. As the state won’t invest in desalinization to provide water for coastal areas, I doubt it will desalinate and pump the water up.
Any question like this can always be answered by asking yourself, who would profit from this?
