Published on February 28th, 2014 | by Tina Casey


New Math: Solar Power + Salt Water = Sahara Forest

February 28th, 2014 by  

The folks over at Sahara Forest Project have just alerted the Twitterverse that their new pilot facility in Qatar is good to go, and since we’ve been following that project since 2008 we’ll jump at the chance to update you on its progress from high concept to working hardware.

The idea behind Sahara Forest dovetails with the solutions we saw on a recent technology tour of Israel (sponsored by the organization Kinetis), namely, when you have several problems going on at once, mash them up together and see what happens.

In this case we’re talking about too much salt, too much sun, and not enough soil and water for farming. Israel found the key to the solution in brackish aquifer water, and Sahara Forest has come up with its own twist.

Sahara Forest Project

Sahara Forest concept courtesy of Sahara Forest Project.

The Sahara Forest Project

When Sahara Forest first came across CleanTechnica’s radar in 2008, we weighed in slightly over to the skeptical side, given the cost of solar power compared to other desert farming practices:

Of course, deserts can also produce lush vegetation using permaculture farming practices that are much cheaper to implement. But if countries are willing to invest in the Sahara Forest Project, more power to them—literally.

When we dropped in again in 2012 the idea of large scale solar powered greenhouses was beginning to gel, and right around this time last year we noticed that things were really starting to take off at the Qatar pilot plant:

Aside from the technology itself, one thing that stands out about the project is the speed with which it happened. Once all the agreements were signed, construction began early last year and was completed within a year.

The basic idea behind Sahara Forest is that solar power could be used to evaporate seawater for a freshwater source, and seawater could also pull double duty as a coolant for the greenhouses.

So far Sahara Forest has reported that its Qatar greenhouses are competitive with European yields, while using half the water of conventional greenhouses in the region.

Another key strategy is to use evaporative hedges to cool outdoor growing zones, and that has also proven effective. Together, both the indoor and outdoor cooling strategies enable the facility’s concentrated solar power plant to operate without cooling towers.

You can get many more details, including results from the algae operation, from the Qatar Pilot Plant Report.

The Qatar Sahara Forest Pilot Plant

Since last year, Sahara Forest and its partners have achieved their goals on the way to officially rolling out the facility to the public, and in particular to United Nations climate delegates.

The main hurdle was running the Qatar pilot plant through its paces during extreme summertime conditions.

With that under its belt, Sahara Forest is confident that the facility is fully functional and demonstrates the potential for ramping up to commercial scale while also contributing to a knowledge base for future enhancements. In addition to the farming operation itself, the Qatar plant also hosts R&D facilities for desert agriculture with a focus on algae and halophyte (salt loving plants) cultivation, alongside its seawater-cooled greenhouses and solar power plants.

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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+.

  • Jay Dillon

    Have you looked at the Passarell Process for desalinating seawater? It seemed to me that it was an energy efficient and cost effective option for medium and large installations.

  • yayayapjdgjw

    Imagine what we can do with this technology! it will be awesome for the future of Africa and the Sahara! being able to do lots with the land restoring vegetation making food money and jobs and cooling down the environment this will help restore the sahara back to what it was originally a forest which considering how large this soon to be forest is we may be able to feed the world for many generations to come. before the worlds population starts to age and fall naturally anyway.

  • Alex

    This is not going to work at the level and scale needed. This is false hope. The only way to restore grasslands is through Holistic Management.

  • sault

    I remember seein a similar story about planting huge numbers of Jatropha curcas trees along the coastlines of these desert areas and using desalinated seawater just to get them established. These plants make a great deal of biodiesel in their seeds and would sequester a large amount of CO2 while also locally cooling the climate. Kind of a pipe-dream, but Sahara Forest might just be able to prove that these re-greening efforts might be possible.

  • Kyle Field

    Extremely exciting – both for food production and desalination. Thanks for sharing 🙂

  • Adam Devereaux

    Why not combine IBM’s solar concentrated power technology that produces fresh water and try and create an expanding re-greening of marginal desert land? I misunderstood the title- I was expecting an attempt to create an actual Forrest in the Sahara similar to the farm led re-greening efforts in Africa.

    It’s amazing what really could happen with the technology we already have if politics and will aligned with potential. Imaging solar powered farms re-greening marginal lands that experienced desertification due to prior human activity. The impact this would have on global warming would be not insignificant as well. Though before we go that route stopping destruction of existing rainforest would probably be a good idea.

    • Omega Centauri

      “The impact this would have on global warming would be not insignificant as well.”
      That happens to be true, but the effect is to further warming not reduce it. The extra sunlight absorbed and the extra moisture in the atmosphere which traps heat more than balance out the effect of the sequestered CO2. There may be plenty of other reasons for doing this, but climate change mitigation is not one of them.

      • Adam Devereaux

        I’m not so sure that is true, most models I’ve seen show the carbon sequestration as a net gain. NERC’s work with Forest encroachment in Arctic tundra not withstanding. But that is a different matter and a very different ecosystem from a desert landscape with virtually no stored carbon in the soil.

        • Omega Centauri

          I don’t have any numbers. But consider this, the desert regions are high insolation, and generally light colored ground. Dust as an aerosol is a cooling factor. So you are absorbing an extra maybe twenty percent of sunlight for a small amount of sequestration. Then you increase the atmosphere’s moisture content, which is an increase in the greenhouse effect.

          I would be surprised if the desert warming effect isn’t quite a bit larger than the warming effect of arctic/subarctic trees.

          You are talking geo-engineering, and trying to play off one effect versus another.

          • sault

            You are mistaken. Plant cover cools the surrounding area a great deal. Remember, bare sand or rock can get extremely hot in the sun, just like the “urban heat island effect” causes cities to be several degrees hotter than nearby rural areas. In addition, bare sand / rock can store heat for many hours into the night, raising the temperature for hours. Plants generally track air temperatures and have much less thermal mass to heat up in the first place. The enhanced cooling of plant cover will also negate much of the warming effect of higher humidity levels since the amount of water that air can hold is strongly dependent on its temperature. Keep in mind, that higher humidity levels can also lead to more cloud formation downwind, negating even more of the enhanced warming from the H2O.

          • Omega Centauri

            No you are missing the emergy budget. Plants evaporate water, which converts sensible heat o latent heat. When it condenses -as clouds or dew, it gives the heat back. In the meantime it acts as a greenhous gas. Then you have the fact there is more heat, because moe of the sunlight was absorbed in the first place. The cooling is local, the warmer effects are spread much further -often hundreds of miles away -but they are real.

          • eject

            A rather large amount of energy is needed to evaporate water. Furthermore higher water contents in the atmosphere greatly increase the heat capacity. This means that the atmosphere can take a lot more energy for every increase in temperature.
            All those places have been forest before and they should be returned to that state.

          • Omega Centauri

            Climate is about the balance between incoming and outgoing energy. Heat capacity doesn’t affect the equilibrium temperature.

            Much of North American north of 40-45N was icecap for most of the Pleistocene, should we be trying to restore it to that state?

        • Surf

          Plant cool and area by evaporation and reflection. Plants preferentially reflect green and yellow light.. they only use red and blue light to grow. Plants reflect about 1/3 of the visible spectrum and much of that is reflected back into space. the heat that is gained dispite the reflection is disipated by evaporating water. The soil under the plant then stays cool allowing night time temperatures to fall faster.

          • loudnessjr

            We can’t stop the iceberg from melting now, it’s too late. So how we counter the rising sea level then? ‘Watering the dessert’. Millions of acres of land in the middle east, sahara and african countries can use desaltinized sea water to stop hunger, grow plants and animals. Solar power is the only economical energy to provide the power needed to desaltinized sea water. There’s no scientific research saying that by growing plants at the dessert can cause global warming. It just paranoia.

          • Bob_Wallace

            You might want to calculate the number of gallons in the top inch of the world’s oceans.

            If you want to lower sea level by that amount you’re going to have to pump out, desalinate, and distribute those gallons over a very few days, continuously. That water is going to be used for watering plants, they will transpire water which will then turn into water vapor, and then rain. The water you put on the desert stays there only a short time.

            The glaciers and land ice we are now melting was stored water. It was out of the rain/evaporation cycle.

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