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The article states --

"Desalination used to be an expensive energy hog, but the kind of advanced technologies being employed at Sorek have been a game changer. Water produced by desalination costs just a third of what it did in the 1990s. Sorek can produce a thousand liters of drinking water for 58 cents. Israeli households pay about US$30 a month for their water — similar to households in most U.S. cities, and far less than Las Vegas (US$47) or Los Angeles (US$58)."

But I saw nothing about where the energy comes from, the type of source, the scale. I'd like to compare this with local proposals, etc.

One of the biggest DeSal issues is cost of conversion and source, proximity of source, etc. play a huge factor.




The energy comes from the grid. The nice thing about the grid is that it lets you abstract out power, kinda like bandwidth on the Internet. Do you care which data center a new app lives in?

But if we must, I suspect the supply side (of electricity) I suspect most new supplies in Israel are solar PV located in the Negev, since peak demand there correlates with sun.

And what sort of local proposals are you imagining as alternatives to desalination?


It looks like almost all 'grid' power in Israel comes from hydrocarbon sources, with the largest part being coal, followed closely by natural gas, and distantly by diesel.[1]

[1] https://en.wikipedia.org/wiki/Energy_in_Israel


So cost of local energy generation is a big part of it. "The Grid" here in CA, is highly variable in cost depending on where you live.

In the Monterey Bay Area, one proposal by a local oceanographer/hydro geologist was at Moss Landing where there is a power plant and could provide (with pumping/piping, etc) for both Monterey and Santa Cruz county.

Santa Cruz, being ... polite ... unable to play well with others, was pushing their own thing which would disrupt a good part of the town, had no local power generation, and would require extra pumps, storage, and what not all over town. Something in the $100s of millions for a county of < 250k. The regional approach makes way more sense, but local politics and all.


Israel's grid is presently fed by coal and gas:

https://www.iea.org/sankey/#?c=Israel&s=Balance


How do those costs compare with something in Northern or Central CA, with the same coal/ng source?


The breakthrough here (and I've only skimmed the article) is in 1) reverse osmosis 2) without organics-clogging of filters. That is, basically, keeping pond scum from fouling your molecular-differentiating filter system, which is what it takes to split water from salt.

That and various energy efficiency improvements.

Much of this comes down to questions of "what are the energy costs" and "how much energy can we supply".

I'm not a huge fan of desal generally, especially where it's reliant on fossil-fuel energy. On the other hand, it actually plays into another area I've had some interest in -- seawater-based Fischer-Tropsh fuel synthesis (SFTFS). That's the task of taking seawater, separating carbon from it (mostly in the form of dissolved carbonate and bicarbonate -- the dissolved CO2 fraction is small), and electrolysis to split out hydrogen.

That problem divides into a few parts:

1. Electrolysis of hydrogen. Essentially a solved problem at large scales. Example: nuclear powered submarines replenish their oxygen supply through electrolysis (I'm not sure what they do with the hydrogen resulting). Since water is 89% oxygen by weight, the amount of water you need to process here is small. There's an energy cost (more below).

2. Removing carbonate & bicarbonate from seawater. Here the fraction is far smaller -- a few fractions of a percent by weight. The reason you're looking at seawater is because energetically it's far easier than getting CO2 from air. And yes, seawater is also necessary. The probme here is getting enough water -- you've got to process tremendous volumes.

3. Synthesising hydrocarbons from this (that's the Fischer-Tropsh bit). Fairly well established, and exothermic to boot, so it doesn't cost energy.

4. Energy input. You only get out about 60% of what you put in to split out hydrogen. That normally isn't a very good bargain except for a few useful things about hydrocarbons, below.

The upshot is that desal and SFTFS have a few things in common: taking in gobs of water, purifying that so you don't gum up the works, and applying fairly hefty amounts of energy to it.

What desal offers is a proving ground for developing that seawater handling capability, at scale, and in particular the filtration parts. It would also be possible to combine the processing (though there might be other reasons for not doing so). In theory, you'd ingest seawater, electrolise some of it for hydrogen, capture the carbonate/bicarbonate (which aren't of interest for tapwater), feed your C & H to the FT synthesis process, and continue with the remainder of the water to your desal system.

Why bother making hydrocarbons? Because they're damned useful. Renewable energy has advantages, but it doesn't store or transport well. Synthesized hydrocarbons would be precise (and in fact, more precise) analogs of methane, petrol, kerosene (a/k/a jet fuel), and deisel. For some applications, including standby generation, gas heat, some industrial processes, and powered air and marine transport, they're about the only real viable option. I suspect they may continue to see use in private / passenger transport as well, and possibly rail (electrification is an option, but has challenges). There are industrial processes which also utilise gas and oil feedstocks, notably Haber-Bosh nitrogen fixation (though alternate processes might emerge).

Even if we end up with a small fraction of total energy coming from hydrocarbons (marine and air would be ~12% of the present total), the process could prove quite useful.

Large-scale desal could be a proving ground for related technologies.




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