Prof. Abdennaceur Karoui

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Last Updated: Thursday, 08 November 2018 23:48

Solar Desalination Alternative that Today Could Supplement and Tomorrow Would Substitute On-Going Desalination Mega-Projects in the Gulf Region

The Gulf States, in the MENA region, are putting tremendous efforts to provide their citizens with fresh water, which is produced by desalination of sea water. This is long overdue, since many scientists in the seventies have been calling for MENA governments to act upon the insufficiency of fresh water. They have suggested technologies to solve the problem. Among these were scientists from Tunisia, who formed a research and development embryo at the IRST, that later have produced significant R&D work in the area of solar desalination.

The current development in the Gulf States is indeed very promising. It is hoped that the effort will be sustained and, ultimately, will rely on technologies powered by energy sources other than oil and gas.

Sea Water Desalination project in Qatar (Pictures extracted from video in Ref. 1).

Recently, I was asked by a colleague from abroad to give my opinion about the giant water desalination project in Qatar, where large pipelines and reservoirs are now being constructed to support desalination plants on their coast. The interested party wrote: “… In a major milestone, the Qatar General Electricity and Water Corporation is constructing what would become the largest man-made water reservoir in the world”. News articles and videos titled “Project of Gigantic Fresh Water Reservoirs in Qatar” show indeed a gigantic undertaking [1]. The project seems to have progressed well enough, to a non-return point.

Context of the Project
This mega-scale industrial project is for transporting water from centralized water production plants to huge storage central tanks. It shows the large magnitude of the water enterprise in that small and, fortunately, gas-rich country. The project is truly impressive in all its dimensions and will render great services for that part of the world. One would wish to see it duplicated in many other arid regions, where people need badly fresh water for survival. However, the reality looks more complicated than the project shiny faces presented by the news. A first oblivious question comes to mind: have the planners already considered turning off everything after the oil and gas will run-out? My colleague answered, that's impossible! 

Seriously, for the post-oil and gas era one wonders if the planners thought about alternative technologies for not discontinuing their future economic and societal progresses? It is hope so, though it was not mentioned, and personally, I doubt it. Since information is limited to what was reported by the local news outlets [1], which did not describe the technology, I could only think, on my own, what could possibly be a long term solution for fresh water in that region? Then I realized that any long term solution could be complicated by the country demography, visibly on the rise, and that tends to concentrate in cities. Moreover, the population has transitioned from mostly Bedouins and Nomads with their proved living traditions adapted to their climate, to cosmopolitan-centered population that adopted a totally new lifestyle and living in cities, which need humongous quantities of running fresh water, and other utility and services.

Questioning the Technological, Economic, and Societal Values of the Chosen Desalination Solutions

Although this project is immense, clearly, it is far from enough for eradicating the fresh water problem, though it is certainly going to largely benefit the country, soon.

First and foremost, the project does not seem to use technology adapted to the country climate, but overwhelmingly the old oil and gas based technologies. The main factors that led to such oblivious choices are obvious. First, conventional desalination methods are preferred by industry for IP reasons and for practically mastering the technology. Second, industrial projects are designed to be oil based, full scale because they are simpler to design, to implement and to operate, than alternative technology pathways. Third, centralization makes more profit. Fourth, industry cares less about the overall energy-efficiency and sustainability, as long as it produces the commodity using available technologies and resources. Fifth, industry wants centralization of production, for a better grip on the entire project and for the control of the commodity it produces. That’s understandable from the business view point, but not from the consumer side, as good citizens who care about their personal development and their environment. Sixth, no one (the market and the decision makers) forces companies to find new technologies. Sixth, the government pays, so who cares, as simple as that. Other strong reasons do exist, but are irrelevant to this discussion.

However, the employed desalination techniques are largely inefficient and use processes that are extremely energy-intensive, thus they do not promise long-term running water, Not at all!

The more I think about these, the more I become stun. In the mist of my confusion, another question came to my mind: has the local government taken any measure to let the consumer know that the fresh water production is extremely costly and the water must be handled with great care, and they should not forget the basic survival rules that used to be embedded in the country traditions. In my opinion, the project should have an exhortative approach and appeal to the consumer sensitivity to resource limitation. But bringing the totality of produced fresh water to cities conveys none of these. In contrary, it encourages more consumption and does not carry incentives to prevent misuse and waste. Maybe the company thinks that “as long as the government pays, it works for everybody”; if so, then that’s flat wrong, as it is not at all sustainable.  Despite that, the government could still re-teach its population the basic rules of water conservation through a variety of means.  I hope that they thought about that crucial aspect, and not be lured by the planned water abundance! In my opinion, even if it is a difficult choice, consumers must share part of the cost. The purpose is not to alleviate the exorbitant cost, it is only to keep the mind of the consumers focused on the need for conservation.

The water is essentially sent to the cities, where most of the expatriate populations are concentrated, and where tourism is well developed. So, the project focuses on drinking water for these cities, and seems not going to give some to farming and livestock. Moreover, the project has an industry finger-print and is operated by multinationals, rather than home-grown, population-centered, and looking at real needs and usefulness for future development of their citizens.

Clearly the entire project, alone, is not going to be a long term answer to fresh water problem in the country, when considering that the source is sea water (SW) the technology is conventional desalination, and the energy is from a short leaving source.  Large scale centralized desalination relies on 1) huge amount of energy to bring to the production plants, and 2) use of large number of membrane based systems (if reverse osmosis is used), or giant heaters (if flash-distiller desalinating systems are used) [2]. The desalination requires large machinery and maintenance, in addition to management problems.

The humongous energy need makes it a short living project. The question is: what will be the alternative for powering these massive units after gas and oil will run out? It would be a devastating disaster for the country, after 2 or 3 decades of economic and societal development, once fresh water production shuts down.

Some Efficient Solar Desalination Technologies

In this section, for illustration purpose of the solar desalination relevance, two technologies are presented. The literature largely reports on sophisticated designs of these categories, as well as many other solar desalination technologies.

Suggested Durable Solutions

By realizing that the country has 75mm rainfall per year, which provides 0.75 million cubic meter of fresh water per year, one can think of a significant, sustainable and easy solution for fresh water. Put that in the bigger picture and the sustainability context, one can suggest that the country will do well in the long term, if it will:

1. build and maintain water ways and many small reservoirs distributed over the territory to collect rain water.
2. support private and governmental sectors for collecting fresh water from the rain. The government can subsidize or pay for the construction of thousands of local reservoirs (for homes, villages, large buildings in cities, roads in cities, highways, airports…)
3. develop decentralized systems for desalination of brackish water (BW) by solar energy, whether single small units or batteries of desalinators. Several technologies exist and can be largely improved for instance, research can be done to improve simple desalination flat panels, association of batteries of flat panels, more sophisticated geometries, advanced absorbers,... coupling several renewable energy sources,…
4. develop decentralized solar energy SW desalination that uses small solar concentrator units, for example using cylindro-parabolic troughs [4],[5]. Again, many technologies exist and can be largely improved.
5. develop solar energy based filtration of used water by thermal distillation, just like in 4). The technologies can be optimized to match the type of used water and to provide enough throughput. Also other solutions do exist for water re-use.
6. leave the above described mega-project (which desalinates SW, and runs on gas) to provide fresh water to cities only. Meanwhile plan on substituting the energy source with a renewable energy source, to preserve these growing cities, or at least the essential parts of these cities.

There are more actions that will assure a longer term fresh water solution as well as a continuous improvement of the technologies; among these one can list:

1. Maintain a strong education program on water conservation,
2. Offer incentives that drive the consumers into adopting conservation and water re-use.

3. Promote R&D desalination programs that allow the scientific community to start thinking seriously about solutions for fresh water that are truly transformative, do not rely in the long run on oil and gas, and that are adapted to the regional context.
4. Involve industry in desalination pilot projects. Such projects will help industry scale-up sustainable solutions and distribute them country-wide.

Discussion of the Suggested Solutions

The presented solutions are not only usable in the Gulf region, but most of them, if not all, can be deployed in many other regions of the world, such as the Sahel, North Africa,…

collected all over the city, airports,..., and channeled in waterways to artificial lakes. The governing bodies (home owner associations, landlords, city, county,…) strive to maintain the water collection infrastructure clean. Once our subdivision got fined, because the homeowner association did not plant grass to cover the water ways in order to prevent ground erosion and transport of dirt to the water reservoir. Likewise, in the MENA region, people used to have rainwater reservoirs built underneath or close to their houses. Some towns have even large reservoirs owned by the population together with the city governing authority; the infrastructure used to be well maintained and cleaned annually during the dry season. So, the methods of collecting rainwater have been around for thousands of years. So let’s not lose them and let’s not substitute them by large plants, these are not sustainable. Many of such technologies blur the situation, as they present intense solutions that appear “wrongly” easier and practical. It will be too late to recover from the dangerous reality in which people are driven in, once they hit the reality. I am not against new technologies, in contrary I am a technologist, but in quest of sustainable ones that present realistic and robust solutions. One must not be fascinated by centralization of renewable energy and production of desalinated water in oil and gas powered large plants. These are wrong choices; they are not only costly but they are very inefficient, environmentally unfriendly (produce a lot of brine, gas emission,…), luring people in excessive consumption, eliminate contribution of individuals to sustainability, destabilize the regional balance,...

One must not forget that the country is blessed with two renewable energy sources, Solar and Wind, which can largely contribute to water desalination and other applications. They offer durable solutions and so many other societal benefits. In fact, components 2) to 6) will work nicely by just using solar energy (considering the huge potential the country has) for drinking water, in which case probably there would be no need for using other sources of energy for desalination. However, Wind Farms could be added if there is a need for boosting fresh water production for agriculture, and other energy needs, as a back-up. When needed [6],[7],[8], Wind Farms off the country shores, which are long enough, could be efficient enough.

Component 3) can be augmented by, possibly importing BW, from Basra region (482 Km distance). This source of BW, currently wasted in the golf, could be enough for producing fresh water, and may not have limitation over time.

Components 3) to 5) utilize technology that is not extremely high tech, and uses more common materials, thus it is a robust solution and can be easily scaled-up.

Component 5) is well suited for purifying biologically and chemically contaminated used water. Unlike other techniques, the solar energy based distillation, where small solar concentrators are utilized, excludes contaminants from diffusing into the separated fresh water phase. Recycling all used water produced by manufacturing plants, chemical manufacturers, hospitals, hotels, homes,... is a necessity that cannot be delayed. That applies to many countries, if not to all. In countries that have high solar energy potential, this particular application will directly benefit from it. They will be able to freely decontaminate water. The machinery is simple, robust, and is not vulnerable to the contaminants. This technology not only provides fresh water, but also solves environmental problems. It will certainly prevent contamination of sea shores and rivers by deadly chemicals.

Component 6) is being done. It will soon face a determining decision with regard to the type of energy that powers the desalination units. As stated above, the huge infrastructure will not be maintained once the gas and oil run out, unless alternative energy sources are utilized early enough to allow for technology transition. While it is logical to start with the now abundant gas and oil, only renewable energy sources will guarantee the future of this fresh water generators and collectors. Thus gas and oil must be substituted with renewable energy sources, in a second phase, in order to save these cities. These cities are strongly water dependent, more than any other cities. This point is mentioned to remind the reader the importance of fresh water in the region, but will not be discussed further, as it is out of the scope of the desalination theme discussed here.

Together the above set of solutions will enable true and lasting development for the country, we can refer to the overall approach as “water-desalination mix”, or  “fresh water mix”. While the sixth component is vital now, it can be guaranteed a longer lifetime, by moving it away (in the near future) from gas & oil with appropriate desalination technologies. Contrary to this, the mega-project will just create a momentarily prosperous economy and a large dynamics in the country with high risk of being ephemeral. A short living grand euphoria is not worth it at all, but a long term assured advancement is all what is needed.

Conclusion

The suggested five first components of a “sustainable desalination program” are sustainable, while the sixth will survive if alternative energy source substitutes the currently used gas and oil. The “water-desalination mix” approach will promote the development across the entire country, not only around the mega-cities located on the country shores. Not developing and adopting a true long term solution is hazardous. Thus, it is necessary to add to the current much respected effort, the development of appropriate infrastructure and technologies that are really adapted to the country and that guarantee a longer term development. As a matter of facts, decentralized desalination is excellent for fixing citizens to the land, especially people living in the countryside. The involvement of individuals in fresh water production, and more importantly its conservation and responsible usage, would be ensure a more sustainable development. Also decentralized desalination means: use of renewable energy, quick ROI, durable solutions, and positive societal impact. Production of sufficient quantity of fresh water can prompt more farming and can create wetlands that will sustain vegetation and wildlife. In closing, one must say, that solar energy based desalination involves individuals and makes them more responsible citizens and more productive.

A. Karoui

July 9, 2018

References:

[1] Project of the Gigantic Fresh Water Reservoirs in Qatar

http://www.qatar-tribune.com/news-details/id/85993

https://medium.com/dohanews/worlds-largest-water-reservoirs-nearing-completion-in-qatar-b1a1ee775361

https://dms.licdn.com/playback/C4D05AQEKf2NxyIGzaQ/3e3fc328b1834c4a9a127f1dc3f46f7e/feedshare-mp4_3300-captions-thumbnails/1507940147251-drlcss?e=1532887200&v=beta&t=KpYUpSh4juyXjDhoGgJGpnjfOPnJGQKrX3duzyrDVNo

[2] No references available as of yet.

[3] Sandra Postel, Solar Desalination Could be a Game Changer for California Farms.  Sandra Postel is director of the Global Water Policy Project, Freshwater Fellow of the National Geographic Society, co-founder of Change the Course, the national freshwater conservation and restoration campaign being piloted in the Colorado River Basin.

https://blog.nationalgeographic.org/2015/07/20/solar-desalination-could-be-a-game-changer-for-california-farms/

[4] Jean-Louis Boy-Marcotte, Jean-Louis Lamirand, Philippe A. H. Marchal, Richard J. A. M. Grossin, Solar energy collector system with cylindro-parabolic mirror, patent, US4149523A  Date: 1976-06-03.

Cylindro-parabolical solar energy collector US4515148A, Priority date: 1985-05-07.

Current Assignee: Bertin Technologies SA, Original Assignee: Bertin Technologies SA.

[5] A. Powell, Parabolic trough solar reflector, US06587137    (1984-03-07) and   US4611575A (1986-09-16) Original Assignee: Powell Roger.

[6] Because of the variation and availability of renewable energy sources coupling high power wind mills with solar based system could be a complicated the matter in the case of desalination. Integration of wind mills with a solar based desalination system must be well optimized. If water consumption and energy production are stabilized, a dedicated solar-wind system that powers a mid-size desalination system could be operated 24/7, smoothly, and with the least adversity. I strongly believe that is the optimal scale for successful solar-wind based desalination. Quantitative studies could give optimal figures, where technology, economic, and demographic parameters are incorporated in the optimization.

[7] It is well known that wind mill mechanical parts are delicate, and they undergo the usual wear and tear at the level of the turbine. But, what is less known is, in that region the wear and tear are accelerated by the effects of extreme heat. In addition, the entire machine is exposed to corrosion by sea water (for offshore wind farms), as well as sand riffles from the mainland. Compared to wind mills in the UK or Norway shores, they need additional and sustained maintenance during operation. Design precautions must be taken for the turbine, the blades, and the pole. A wind turbine on a tall post have an increased damage probability by the frequent tempests in that region of the world. Therefore, it is important that the technology is designed to permit quickly securing the turbine in its rest position, and must allow to bring it back to work position, all in an agile and easy manner. So the wind mill size here matters a lot.

[8] It is necessary for these wind mills not to have machine dead time.  As back-up generator, a wind mill could be damaged if its load varies intermittently (or abruptly) over a large load range. Furthermore, a windmill operated under no-load condition in high speed wind can self-destruct.  Therefore, situations where wind mills are oversized, prematurely installed, where the mill could be operated without (or with low) load, or have a mismatched source-load,… must be avoided.