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Clean Power solar desalination California

Published on July 20th, 2015 | by Tina Casey


Buzz Gets Bigger Over Tiny California Solar Desalination Plant

July 20th, 2015 by  

What a difference a month makes. Back in June, the California Farm Bureau Federation reported that local officials were still a bit iffy over the prospects for scaling up a relatively small, demonstration-scale solar desalination plant for the water-starved San Joaquin Valley. We have no idea what changed their minds, but just last week the desalination plant’s developer, WaterFX, announced plans for bouncing the project up to a commercial-scale facility capable of producing 1.6 billion gallons of fresh water per year.

solar desalination California

Solar Desalination: That Was Then…

Commercial solar desalination could make a huge difference in California’s ability to maintain a viable agriculture sector under drought conditions. Conventional desalination involves huge amounts of energy, and solar energy provides a low-cost, sustainable way to reclaim otherwise unusable water.

In 2014, we took note when WaterFX cranked up its HydroRevolution solar desalination demonstration facility. The project, built for the Panoche Water and Drainage District, actually kills two birds with one stone. In addition to solar desalination, it involves a cost-effective system for reclaiming the huge quantities of salt generated by conventional desalination systems.

Fast forward to June 2015, and we find a mention of the plant in the Ag Alert, the weekly bulletin of the aforementioned California Farm Bureau Federation.

As described by Ag Alert assistant editor Kate Campbell, the solar desalination demonstration has its roots in an agreement by the region’s agriculture industry to reduce the discharge of salts and other pollutants, which seep through a complex tile drainage system into the San Joaquin River.


With the state of California in an ongoing drought, the water reclamation aspect of the project has given it new urgency.

In her article dated June 24, Campbell cites an official from Panoche, who seems to be pretty convinced that the WaterFX project, among others, will remain in the pilot phase for the next few years.

…This Is Now

So much for continuing the pilot phase for several years. Barely three weeks later, in a press release dated July 15, WaterFX announced that the solar desalination facility would make the jump from pilot to full commercialization, and the Panoche Drainage District had this to say:

Given the trend of highly uncertain inputs from the Delta, we need to develop a reliable supply of water in the Central Valley. This is a sustainable solution that can provide a substantial amount of additional water. After seeing the results from the demonstration plant by WaterFX™, we’re eager to get the HydroRevolutionSM plant online quickly and optimistic about seeing others replicate what we’re doing here…

Including its solar collectors, the expanded plant will be built on a 35-acre site, with the potential to scale up to 70 acres. WaterFX notes that the footprint compares favorably to the region’s conventional irrigation drainage management system, which encompasses about 6,000 acres.

How It Works

In conventional desalination systems, salty brine is forced through a membrane at high pressure, which accounts for the high energy use. In contrast, the WaterFX solar desalination system works on evaporation. It’s the same basic principle behind open-air lagoons, but the WaterFX process is much faster and integrates a system for capturing the evaporated water rather than letting it drift into the atmosphere.

The secret sauce is a modular unit that WaterFX calls Aqua4, which acts like an “engineered aquifer.”

WaterFX claims that the Aqua4 combination of solar energy and advanced absorption, enables it to evaporate and distill water 30 times more efficiently than natural evaporation.

Aqua4 is composed of off-the-shelf components, including a 400-kilowatt trough-shaped solar collector, which is used to heat mineral oil. The oil is then piped to a heat pump to ramp up efficiency, and the heat goes on to operate the distiller.

With an integrated thermal energy storage system, Aqua4 can operate continuously, whether or not the sun is shining.

As for the problem of brine disposal, the efficiency of the system enables it to produce relatively small quantities of highly concentrated brine, which is a much more efficient platform for resource recovery than large quantities of diluted brine.

WaterFX expects that gypsum, calcium compounds, magnesium salts, selenium, nitrates, and boron are among the recoverable substances from reclaimed brine.

Onwards & Upwards For Solar Desalination

Aside from recovering drainage water from agricultural sites, California is also eyeballing the vast potential of solar-powered seawater recovery. The state’s Carlsbad solar-enabled desalination plant, now under construction, will be the largest of its kind in the western hemisphere.

For the record, Saudi Arabia is building the largest solar desalination plant in the world, including a special filtering component to address the jellyfish issue.

An emerging technology I’m keeping an eye on is a fuel cell–based desalination system that partly offsets its energy consumption by generating electricity from wastewater.

Another interesting solar desalination project is Sahara Forest, which aims to use solar energy as part of an integrated desalination system for inland desert agriculture.

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Image: HydroRevolution system, via WaterFX.

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About the Author

specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

  • eveee

    A great discussion, but aren’t we missing the obvious? The Central Valley is much worse off during drought due to unsustainable farming practices.
    Lack of water to flush out boron, etc? Thats because particularly the southern part, the Carizzo plain, is a semi arid desert.
    As pointed out, conditions and problems are similar to those in Israel.
    Are they growing almonds there, too?

    • Larmion

      They are grown in Israel. In fact, the wild ancestor of the almond still grows there, and the first domesticated almond trees were grown in the Levant (Israel, Lebanon and neighbors). I believe almonds are refered to in Genesis as ‘the best of fruits’, though my Bible knowledge is patchy 🙂

      Almonds were brought to California because parts of the state enjoy the mild Mediteranean climate that almonds need. You know, warm with a wet winter. What those pioneering farmers and agronomists hadn’t counted on, was that some silly farmers would start growing dense groves of almonds in reclaimed desert (where there is no such thing as a wet winter…)

      California is huge. Parts of it are perfectly well suited to almond cultivation. Just not the ones where most of crop is grown today…

      • eveee

        Thanks Larmion. You have the proper background to explain this with nuance.

  • Wayne Williamson

    awesome…desal should be available when ever needed….

  • Steven Geiger

    This plant makes no sense at all. As others have pointed out, RO is already cheaper. Furthermore, RO can run 24/7 to gain full efficiencies and without spending additional capex on storage like this plant needs. This plant can only work ~8 hours a day/30% capacity factor.

    In fact, RO offers Ca. an elegant and extremely cheap storage solution for excess energy: you dump excess wind, solar or even nighttime baseload into RO and water is your storage medium.

    RO also allows for small and medium-sized installations to avoid pumping lots of water around.

  • This is great. My comment is just some quibbles. Nothing major. I’m a bit confused on the technology. It seems like it’s the integrated process their selling. A process scheme with four distinct units of operation: 1)solar thermal, 2) Evaporation/crystallization, 3)Heat pump for recovery, and 4) thermal storage. Where does the engineered aquifer come in? Beside the founder of Water FX having a background in hydrogeology and hydrology.

    Let’s say there isn’t global warming and burning any type of fossil fuel to generate heat is OK. The water treatment of desalination unit of operation is simply evaporation/crystallization. This doesn’t compete with reverse osmosis very well. Solids management is tricky when everything has to be as cheap as possible. So Tina and several spunky cleantechnica frequent commenters could start up a competing technology.

    Another quibble 65,000 gallons per day is pretty much nothing for agriculture. That is 45 gallons per minute. A garden hose with good city pressure is about 10 gallons per minute. So they got some scale up to do. Which is normal for a startup. Scale up takes someone like the giant French sewage handling concern Veolia to come around and swoop WaterFX up.

    Nonetheless, this is what process engineering is all about. Pulling together technology and tried and true operating units to make an something effective, implementable and economically competitive as scheme to sell. I’d be interested in learning what WaterFX special sauce is. There’s a lot of prior art and patents in water treatment, as well as energy and steam generation. It’s kind of hard to patent common processes – but doable with a good IP lawyer.

  • JamesWimberley

    The water is condensate from evaporation, presumably completely demineralized. Normal levels of minerals would have to be added for typical agricultural and domestic uses.

    • Bob_Wallace

      If they are planning to extract minerals from the brine output then the needed stuff could be added back in.

    • Aku Ankka

      For domestic use, perhaps (“taste” is affected by trace amounts of minerals), but is this really true for agriculture? I assumed most nutrients come via fertilization, and not much is from diluted minerals from water itself?

      • Larmion

        It’s vital. Salinity that’s unusually high or low rapidly kills plants not specifically evolved or bred for those conditions.

        The reason is not nutrition, as you rightly say. It’s osmotic pressure. Plants extract water (and dissolved nutrients) from the soil based on the osmotic gradiënt between root cells and the soil. Evaporation in the leaves then creates another gradiënt between root and surrounding air that pulls the water from root all the way to the tip of the shoot.

        Plants finely regulate their osmotic potential by regulated the amount of dissolved ‘compatible solutes’ (harmless charged molecules like proline) and various other mechanisms. That adjustment only works within fairly narrow limits though. Too little salt and the plant cell literally floods and rips open, too much and it shrivels and dries like a salted snail.

        Watering a plant with desalinated will briefly and locally (and over a long time permanently and over the entire field) create a hyposaline zone. The plants dies. Oops.

        But why are we making such a problem out of this? Desalination leaves you with a big fat pile of brine. Simply shovel some of it back in.

        • Aku Ankka

          Ah ok. Thank you for explanation!

          I did not doubt problems high salinity (which is why one can not drink seawater to avoid dehydration). But I did not think that reverse would be problematic, considering how low salinity fresh water has.
          But now I know. 🙂

          This is why I like discussions here: you learn new things, asking, answering, discussing.

    • Marion Meads

      Unfortunately, many of these minerals causes a lot of salt problems in the California Central Valley. We have mostly alkaline sodic soils with toxic to plant levels of boron, sodium and selenium. These all developed from continued irrigation, fertilizer applications, and lack of good drainage system. Lack of water for drainage to remove the excess salts, as the water evaporates without drainage, salt accumulation happens everywhere. Same problem in Iraq and other Mediterranean type of arid climate. Waters free of minerals would be extremely welcome in the California Valley.

      If you insist, the only beneficial minerals thing that you would add would be calcium and phosphates.

      • Bob_Wallace

        Any chance phosphates and calcium could be economically extracted from the brine?

        • Larmion

          Calcium: maybe. It’s there in great amounts, though seperating calcium from the potassium, magnesium and sodium also present is tricky. For plant purposes, it’s not bad to have all four though.

          Phosphate: nope, since it’s present only in trace amounts. Phosporus is a limiting nutrient to marine life.

      • Joseph Dubeau

        The Salton Sea comes to mind.

    • Jacob

      For agriculture you could mix a bit of domestic sewer water to get the impurities.

      But I do not know if the detergents that I flush down the toilet are bad for farming.

      • Larmion

        Standard detergents break down fairly rapidly, either in water treatment plants or in the field itself through bacterial action. Special detergents like those for really nasty grease stains or ones used in labs can be much more recalcitrant, but you really shouldn’t be flushing them down the sink anyway…

        I can’t think of stuff in properly treated sewage that would harm plants. Some chemicals in water, mainly drug residues, could upset soil bacteria though. It’s something that hasn’t been studied much, afaik.

    • Marion Meads

      Here’s the current problem of California Agriculture with too much minerals in the well water:


  • Jason hm

    Conventional reverse osmosis plants could act like energy sinks in arid regions with surplus wind or solar. I know better membrane components such as integrating graphene and other micro fabricated materials can dramatically improve inefficiencies. I’m in favor of the shotgun approach to emerging tech but eventually a process of winnowing occurs and I think improved reverse osmosis plus renewable energy will beat out direct thermal solar desalination.

    • Bob_Wallace

      Desal plants could serve as part time loads which would make ‘overbuilding’ wind and solar more economic. But only if the capex and fixed opex of those plants are low.

      Each year the plant has to pay its “mortgage” and fixed costs (property taxes, etc.). The cost of water = total annual costs / total gallons produced. Cut the total gallons produced by 50% and the cost per gallon doubles.

      Plus, ‘almost free’ electricity will go away as thermal plants close and subsidies dry up. Additionally EVs and storage will be waiting to suck up the least expensive supply.

      • Mike Dill

        I disagree about the ‘almost free’ electricity in your argument. I believe that we will need to overbuild the renewables portion of the grid similarly to what we currently have with fossil fuels. In the USA we have about 2 to 3 times the ‘normal’ load available, but it is not mused due to the fuel costs.

        Wholesale electricity from renewables (wind) is already being curtailed in California. Providing a dynamic and defined intermittent load for that ‘free’ electricity should make economic sense.

        Yes, batteries and other forms of storage will suck up a lot of the excess generation. I will wait and see if that load ends up larger than the possible supply, as it is not there now.

        • Bob_Wallace

          The reason that electricity prices drop so low at times now is due to thermal plants being so hard to turn on and off. Coal plants take hours, nuclear reactors take days.

          Wind and solar have operating costs of about 1 c/kWh. If they opted for the PTC and are in the first ten years of operation they can sell for 0 c/kWh and still make a penny. (2.3 cent subsidy – 1 cent opex)

          In order to avoid shutting down and then losing hours or days of income coal and nuclear plants must underbid wind and solar if the grid is oversupplied.

          Coal is going away. Nuclear will almost certainly die off over the next couple of decades (unless there is some breakthrough that drops the price of nuclear by 75+%).

          Subsidies will almost certainly be gone in less than 15 years. (Farms that get subsidies in the next couple of years will have used them up ten years later.)

          Now the base price, opex, for wind and solar will be 1 c/kWh. Why would the operator produce power and sell it for no profit? It will take 2 or 3 cents to get farms to flip the switch. The options for utilities will be much more expensive gas plants.

          • Mike Dill

            Bob, I agree with most of your numbers. The base price for solar will be about 1 c/kwh. The only question is selling the excess at that price or pushing the electrons into the ground (curtailed). I will bet on them selling it.

          • Bob_Wallace

            If I owned a solar farm I would not throw the switch unless I made some profit.

            I’m funny that way….

          • JonathanMaddox

            People seem to think curtailment of wind and solar power is difficult or expensive. Nothing could be further from the truth.

  • Marion Meads

    There is even better technology than this one now. Combine the model of Israel’s megadesalination plant along with the ultraefficient RO membrane porous graphene cheaply made from graphene that requires 1% of the typical RO membrane energy and we would have solved all the freshwater problems of the world! That 1% energy can be supplied by fewer solar panels.

    We can use the latest large scale desalination technology from Israel and the Oak Ridge National Laboratory’s cheap and efficient RO Membrane (uses 99% less energy than the standard RO membranes) and produce water at the cost of about $300 per acre-ft. Currently, most California cities buy their water at $800-$1,800 per acre ft from farmers. We would also need to build a large brine pipeline that will deliver the saltier brine into the far depths of the ocean so as not to affect the littoral zones and minimize damage to their marine ecosystems. We can also pipe some of the brine into the salt mines or salt flats and we can mine them for lithium, precious metals and other minerals. California Agriculture would thrive while not sacrificing its rivers for endangered species and the fishing industry which has declined from $12 B/year on its peak to just $2B/year when waters were siphoned off to the ever increasing almond orchards. We could have both industry thrive

    Currently Israel’s megadesalination plant sells water at 58 cents per 1,000 liters, equivalent to $715.42 per acre-ft.

    And combined with the sun-powered cheapest most efficient RO membrane, the evaporation method would be far too costlier. The newest RO membrane could bring down the cost of water to less than $300/acre ft. One of the world’s top ten innovation, and it can be improved by using the latest graphene membrane made from methane.


    Perforene was also developed by Lockheed-Martin with the same principle as the porous graphene of National Oak Ridge Laboratory, and the same, with 99% less energy than traditional RO membranes:

    • Bob_Wallace

      ” We would also need to build a large brine pipeline that will deliver the saltier brine into the far depths of the ocean so as not to affect the littoral zones and minimize damage to their marine ecosystems.”

      Might it be possible to dilute the brine stream and then feed out the diluted brine over a large number of nozzles into an area closer to shore that has a reliable current?

      I don’t have a feel for how concentrated the brine is. Is it 10x more ‘salty’, 100x, …?

      • Bob_Wallace

        Another question. You talk about $300 per acre-foot water. Would that be an affordable price for agriculture? For alfalfa as well as artichokes on drip lines?

        • Larmion

          I’m not sure about American farm margins. In Europe, that’s more than bearable for high margin horticulture (think greenhouses), but punitively expensive for arable farms.

          Of course, ‘affordable’ is a very changeable term. If water becomes expensive, farmers can raise prices accordingly. At least, they can if the crop is not a widely traded commodity (artichokes aren’t, for example).

          • Marion Meads

            In 2012, my water bill was about $350 per acre ft for my organic farm. In 2014, the price jumped to $1,100 per acre ft, and so I switched over to lower quality well water rather than supplied by the Friant Dam. I have solar power to pump water, so while not entirely free, as I have to amortized the solar powered pumping system, it is cheaper than the upcoming $1,500 per acre ft price tag coming next year. What worries me is that my neighbors have been heavily pumping groundwater and that would be very unsustainable.

            If politicians spends money on bullet trains instead of megadesalination plants, that bullet train would be a journey through nowhere but the dust bowl of the US. California is the food bowl of the world, at least when it comes to Almonds. We would lose our important Agricultural identity if we don’t have water. We have plenty of sunshine, and now we all have the ingredients to make the technology happen. We need will power on the super massive desalination project that will ever be taken to save California’s Agriculture and the US.

          • Bob_Wallace

            The important question is probably the cost of water if the California drought ends. Predictions are currently running along the lines of a wet winter due to a strong El Nino forming.

            If the ‘normal’ price of water is $350 and plants like this one can produce for $300 then private money should build them. A $50 profit would be sweet. And during a returning drought profits could soar.

          • Marion Meads

            El Nino recurs arryhtmitically with a period of 5-12 years. Plus, based on tree rings and other geologic studies, thousand year drought for California has happened several times in the past, and we are long overdue for one. The past five decades have been above the geological “normal”.

          • Bob_Wallace

            Yes, but we’ve also screwed with the climate. Things won’t necessarily proceed as usual in the future.

        • Babam

          That’s affordable considering that farmers are typically offered $800-$1500 per acre ft of water that they can sacrifice for the cities. About $700 per acre foot price is the break point of farming becoming more expensive than normal.

          • Larmion

            But is that price the real value of the water or a generous hidden subsidy designed to persuade farmers to give up their water willingly? The US, and the rich world in general, has a long history of this kind of backdoor subsidy.

        • eveee

          As I recall, that is way more expensive than Central Valley currently uses. It would force them to grow crops like it was more like the desert it is, but the drought is doing that anyway.
          Forget desalination. They need to grow crops that use less water. Then we can see where we are on desalination.

          • Bob_Wallace

            The Central Valley was not a desert. There was actually a lot of water in the Valley, a lot of wetlands, before stuff was shoved around for agriculture.

          • eveee

            The southern part of the San Joaquin. Bakersfield averages 6.5 inches annual rainfall. Palm Springs averages 5.8 inches.



            Farther north is not as bad, but its still not exactly Oregon.

          • Bob_Wallace

            Part of the Central Valley, the Sacramento River Valley, receives 20 inches of rain on average. The southernmost part of the Valley is semi-arid.
            Oregon has a desert.

          • eveee

            Yes. We have to be carful here. There are vast differences in aridity in each of those areas. Towards Sacramento its rainier. Precip gets through from the Coast thru the Delta. Bakersfield is not so lucky. The further South toward the Grapevine, the drier it gets. And its pretty much winter rains, so its mostly dry the rest of the year.
            There is a shocking change in precipitation in Oregon going across the Cascades away from Portland, too.

          • jeffhre

            Palm Springs?

          • eveee

            Yes Palms springs is described as virtually rain free, but like all of California receives precip in the winter months, almost none any other month. And the amounts are quite low. Palm Springs is across the Tehachapi and then across the San Bernardinos from Bakersfield. Both are pretty dry.

          • jeffhre

            All true. Let me rephrase that. Crops in Palm Springs?

          • eveee

            Almost. Bakersfield. And there are signs there off the road complaining about not getting enough water. In a semi arid desert like setting. ..
            because they are entitled to it…

          • eveee

            FYI, I do know what you mean about the agriculture thing making it worse, tho. Totally screwed up the ecosystem. And draining Lake Owen for LA didn’t help much either.

      • Larmion

        Seawater in the open sea is about 3.5% salts by weight, dropping to about 2% near estuaries. Saturated brine is 26% salts by weight.

        Littoral ecosystems are exquisitely sensitive to salinity. Many bivalves and other small animals die if local salt levels increase by as little as a few percent. Diluting before discharge is thus not really feasible, unless you are willing to accept a (small-ish) dead zone around the plant.

        Simply piping it deeper into the sea, where organisms tend to be more robust and mixing is much faster, isn’t that costly. And well worth it, given the importance of bivalves to marine ecosystems.

    • Jacob

      Lockheed-Martin is vaporware. They made some claims about a small nuclear reactor also.

      The Israeli RO desal plant is great and hopefully the TDS count of the water is very low.

      The energy required to purify water is at least 2kWh/1000L. So about 22c/kL is as cheap as it gets.

      Solve freshwater problems of the world?

      A huge chunk of the world’s poor live far away from the sea. It would take a huge amount of energy to pump water from the coast to where they live.

      Better to collect rainwater and build reservoirs inland.

      • Marion Meads

        You’re wrong on both counts.

        Lockheed Martin has product ready for licensing. And so does the National Oak Ridge Laboratory. About these porous graphene tech.

        60% of the entire world population are within 400 km of coastline, and 44% directly on the coastal areas.

        We are talking about California here, and if we can build pipelines from Canada to the Gulf of Mexico, building a water pipeline next to the ocean would be a fraction of the cost.

        • Jacob

          You did say “world”.

          The cheapest RO desal plant today as you know is the one in Israel that sells water for U$0.58/kL.

          Building an oil pipeline from Canada to the Gulf of Mexico is viable because oil is much more costly than water. 1000x as costly.

          What do you mean by “water pipeline next to the ocean”.

  • ttman

    This seems like a perfect use of an intermittent source of electricity. It doesn’t need storage because it doesn’t need to be producing fresh water at night.

    • Bob_Wallace

      It’s not using electricity as its main energy source. It’s a thermal solar plant. Some electricity used for pumping, system operations.

      And the collectors can run at night if thermal storage is added.

      What is missing in this article is a cost comparison with other desal approaches.

    • BlackTalon53 .

      Unfortunately it doesn’t work that way. In order to be able to be economical these kinds of installations need to be huge, and they need to be run 24/7.

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