Aqua Solaris – an optimized small scale desalination systemwith 40 litres output per square meter based upon solar-

thermal distillation

Jan de Koninga, Stefan Thiesenb*aZonne Water, Roosstraat 64, NL-3333 SM Zwijndrecht, The Netherlands

bMindQuest, Werner Strasse 203, 59379 Selm, Germany email: thiesen@uni-muenster.de

Received 14 March 2005; accepted 31 March 2005

Abstract

Classical small scale solar distillers (flat collector solar stills) have been in use especially in remote tropical

locations for more than a century, but they only utilize a fraction of the available solar energy flux per area. Our

aim was to develop a system that optimizes the energy efficiency and approaches the physical limit of freshwater

output as close as possible. The construction takes into consideration the general principles of thermodynamics.

The evaporation and (cooled) condensation chambers were separated, the evaporation chamber and surface

increasing material were expanded into the third dimension (a collector cubicle instead of flat collector),

additional mirrors are applied to increase the solar energy input and for wind protection, and the necessary

electronic microcontroller that controls the airflow rhythm was empirically optimized by a long series of test

runs and measurements. A prototype on the Island of Bonaire currently produces 40 l of freshwater per square

meter surface area at an ambient temperature of 30�C for an estimated life cycle of 20 years. The applications

are broad. Each unit can supply a large family with freshwater at low costs, and the water source can be

anything from sea water to water polluted with heavy metals and mineral poisons (e.g. arsenic polluted wells in

Bangladesh). The concept builds upon readily available low-cost standard materials and parts and can help to

alleviate numerous social and environmental problems, including local dependence on bottled water import, the

related garbage build-up on islands and adjacent coral reefs, water borne diseases as well as desertification,

deforestation and even unemployment. In addition to scientific and technical details various project proposals,

participatory approaches with local end-users and business models are presented.

Presented at the Conference on Desalination and the Environment, Santa Margherita, Italy, 22–26 May 2005.

European Desalination Society.

0011-9164/05/$– See front matter � 2005 Elsevier B.V. All rights reserved

*Corresponding author.

Desalination 182 (2005) 503–509

doi:10.1016/j.desal.2005.03.026

1. Background

The general situation regarding distributionand availability of safe drinking water in devel-oping- and even in developed-countries is wellknown, and the situation is likely to worsen inthe future as a result of population pressure,intensive agriculture and climate change, whichare a part of the multi factorial scenario thatleads to overuse of land and water resources. Inaddition numerous regions of the world are notinhabited or can only be inhabited by smallpopulations due to very limited freshwaterresources. Desalination generally is a widespread solution, but currently most systemsare capital and energy intensive steam distilla-tion and reverse osmosis facilities or small andreliable but relatively unproductive solar stills.However, in face of the world wide peaking oftotal oil production, the importance of solarenergy also in this sector cannot be overvalued.Increasing fuel prices will result in dramaticallyrising costs for freshwater produced from facil-ities based upon fossil fuels and also inincreased prices for bottled drinking waterimports around the world. ‘Especially in thefield of drinking water and food supply itmust be assured that also the costs for meetingthese basic needs necessary for survival doesnot exceed the financial abilities of also thepoorest members of the population’ [1].

Drinking water related problems especiallyin the tropics and sub-tropics include but arenot limited to:� Water borne diseases through microbial andparasite contamination.

� Water borne diseases through mineral con-tamination (arsenic in wells, residues frommines etc.).

� Deforestation & desertification (additionalwood as fuel for water sterilization).

� Additional garbage accumulation (plasticbottles/containers – a pressing problem onsmall islands).

� Decrease of carbon sinks and additionalCO2 release (see above, the latter also dueto long distance mass-transportation ofimported water).

� Steady capital drain from already impover-ished populations (continuous bottledwater import).The above and other factors are responsi-

ble for hundreds of thousands of deaths eachyear and lead to immense suffering and grow-ing dependencies of local populations on paidoutside supply that is beyond their control.

2. The technological goal

The classic solar still is a means to ease thesituation, but in many settings it is of limiteduse due its low yield of approximately onecubic meter of product water per year andsquare meter collector area for tropical loca-tions [2]. Our goal was to develop an opti-mized solar still with substantially increasedyield without sacrificing the benefits of theclassical solar still: reliability, utilization ofoften locally available low cost material andease of use. The vision was to develop a simpleto use, modular system that can be scaled asneeded and operate with little maintenance inremote locations for a long period of time.

The approach was a purely empiricalwhole-system-approach, almost entirely basedupon field- and laboratory experimentationand optimization. The following factors wereconsidered:� Optimal use of the available solar energy.� Concentration of solar energy by means ofadditional side mirrors (which, dependingon location, also act as wind shields).

� Expansion of the main collector into thethird dimension (a cube instead of a flatcollector).

� Dramatic expansion of the evaporation sur-face inside the collector cube using all-nat-ural materials.

504 J. de Koning, S. Thiesen / Desalination 182 (2005) 503–509

� Separation of evaporation and condensingchambers (two stage system, see Figs. 1and 2).

� The ideal gas law and thermodynamics.� Basic astronomy.� Utilization of excess process waste heat forpre-heating the input water.

� Utilization of locally available wind/soil/sha-dow/water as thermal sink to cool the con-denser chamber.

The only compromise where modernequipment and moving parts had to be intro-duced came in the form of a simple solarpowered controllable ventilator, which is anextremely durable low cost and mass pro-duced part as found in standard electronicequipment such as personal computers, anda simple, low cost microcontroller. Thesecomponents would have been consideredhigh technology only a generation ago, butfactually they now are penny products.

Having no support from scientific institu-tions and only private funds available, it wasnot possible to conduct thorough theoreticalmodelling and planning. Instead an ad-hocapproach was applied.

Once set up, the system was modified andoptimized along the way. In the beginning,additional collectors were used (still seen inthe form of the two rectangular structures onFig. 1), but this approach later was aban-doned in favour of the more effective- andsimpler- waste heat recycling, which furtherreduced complexity and costs.

During the developmental phase, Hygrotec[3] humidity, temperature and condensationpoint sensors were deployed in the differentparts of the systems, to determine the internaltemperature and humidity parameters in dif-ferent air flow situations. The system wascontinuously modified, and the airflow con-trol optimized by experiment. The loggeddata were then compared to the systems out-put to determine the optimal flow control, aclever feedback mechanism forming the baseof the microcontroller’s software – one of themain elements of the Aqua Solaris system.

All in all 15 different patented intercon-nected elements that enhance each other’sperformance contribute to the systemsproductivity.

The amount of energy that is necessary toevaporate 1 l of water under norm conditionsis just under 2260 kJ/kg. In a tropical

Fig. 1. Evaporator and surrounding mirrors (work-

ing laboratory demonstration version).

Fig. 2. Cooled condenser (working laboratory demon-

stration version).

J. de Koning, S. Thiesen / Desalination 182 (2005) 503–509 505

location like Bonaire, (Fig. 3), the sun deli-vers a total energy of approximate 28,000 KJper square meter surface area and day, whichwould then allow for a total evaporation anddistillation of ca. 12 l of water. The AquaSolaris prototype (Figs. 4, 5) however in itscurrent optimized version reliably produces40 l of product water, day in day out, andthe final industrial design will not cover morethan one square meter of surface area. Thesystem can be fed via sophisticated electronicfeeding or entirely manually.

3. Economics and practical issues

Ultimately the value of a solar desalina-tion system depends on its ability to functionunder real world conditions. These includephysical and geographical conditions as wellas social and economic realities. It must below cost, easy to use, durable and it must beaccepted by the population.

Our current estimate is that in its most basicversion Aqua Solaris can be produced at lessthan 200 Euro per unit, including all compo-nents, and it has an estimated life cycle of 20

years. Allowing for some production variationthis still results in the production of 14,000 l ofhighest quality drinking water per year – evenafter only one year, this would mean 1.4 ct perlitre – about 1/10th of the price of importedbottled water even in the cheapest cases. Anexample from the Island of Ebaye in theRepublic of the Marshall Islands showed thatduring water shortages and power down of thelocal water treatment plant prices according to

Fig. 3. Schematic representation of the Bonaire Pro-

totype; the wall protects the system from the cooling

trade winds, which at the same time are utilized to

enhance the condensation process.

Fig. 4. Real world look of the working prototype

producing 40 l freshwater per day; the industrial

design will include all components in one compact

cubicle.

Fig. 5. Possible industrial design scheme and relation

of the unit to the sun.

506 J. de Koning, S. Thiesen / Desalination 182 (2005) 503–509

some local reports went up to US$ 3 per gallonof potable water, which then had to beimported via the US military base on neigh-bouring Kwajalein Atoll [4]. This seems to bean extreme case, but the laws of supply anddemand are merciless. With one billion peopleon Earth having less than $1 available per day,even much lower water prices can pose a lifethreatening risk [5].

If the estimated total lifetime of the systemis taken into consideration, in a subsistencesetting the price per cubic meter of freshwaterwill be at or below the tap water costs inWestern Europe.

The system is particularly well suited as adecentralized solution for families, meetingthe immediate drinking water demand of tento twelve people per day. In addition it isfeasible to build a variety of small businessschemes around the system. It could be pos-sible to finance two or three systems as partof a micro credit scheme and start a smallscale water delivery service. With a revenueof only five cents per litre a realistic totalrevenue of 700 Euro annually could beachieved, an amount substantially above theper capita GDP of many developing coun-tries. Since the system is modular in natureand technically there is no limit as to thenumber of units that can be combined, villageor community water farms also are a possibi-lity, even in challenging environments. Thesystem already has proven its durability dur-ing Hurricane seasons on Bonaire. Suchwater farms could be operated commerciallyor as a service to community members. Thelatter could work particularly well in smalltraditional and well organized communities.

For development projects involving newtechnology a participatory approach is abso-lutely essential. The new technology cannotsimply be inflicted on a given community,since it may severely disrupt the social fabricin unforeseen ways.

An example has been reported about awater facility in Africa. Anthony Maslin,founder of the Australian solar companySES/SOLCO reported: ‘I heard about asolar pump installed in Africa, which keptbreaking down. After some investigation, itwas found that it was the women of the vil-lage sabotaging the pump – the very samepeople they were trying to ‘help’. No onehad bothered to ask any questions, and theend result was that they had taken away thewomen’s only social outing of the day – andthe only chance to get away from the men!’Such is not an isolated incident, therefore anydevelopment ‘aid’ must not only include butbuilt upon participation of the localpopulation.

SOLCO has initiated a business model inthe Maldive Islands which could also form arole model for Zonnewater/Aqua Solaris orsimilar ventures. Not the systems (in the caseof SOLCO photovoltaic powered reverseosmosis systems) are sold, but the water,and the entire business from maintaining thesystems over marketing and distribution ofthe locally produced water is in the hands ofthe local population, hence creating jobs andincome where it is needed most and at thesame time benefiting the environment [6].

Although the technological approach ofSOLCO is very well suited for the productionof larger water volumes, we are convinced,that families in developing countries can ben-efit even more from the Aqua Solaris con-cept, which also has been given the by-name‘Family Well’. In addition to allowing waterproduction at lower costs than with reverseosmosis, the main parts of the system aresimple and in many cases locally available.Although a ready made professional indus-trial design is under preparation, we plan tolaunch a licensing scheme, that will allowmost components of the systems to be pro-duced locally, which will help to create more

J. de Koning, S. Thiesen / Desalination 182 (2005) 503–509 507

regional income. Other than the low costmicrocontroller, a small solar cell for the fanand the fan itself there are no productsinvolved that cannot be made available inmost countries. Even if they are not available,the raw material, e.g. standard piping and flatglass etc., could be delivered and assembledlocally. Approaches like SOLCOs Solar Flowand Aqua Solaris are not competing butshould be considered as supplementing eachother to meet varying needs in varying loca-tions and social settings and on differentdimensions.

Another aspect is a division of the mar-kets. High tech versions of Aqua Solaris arein the planning for consumer level markets inthe first worlds. Applications are diverse andrange from fully automated ‘pool refillers’ toportable drinking water production foryachts. The division of the market into ahigh price high tech and a low price segmentwill make it possible to support the produc-tion and marketing in developing countrieswith funds obtained through marketing inthe higher price segment. It must also betaken into account that water shortage isnot only a problem of developing countries.Australia, for example, is one of the countriesthat is hit hardest and faces severe mid-termwater supply difficulties.

4. Vision

It is our vision to contribute to the better-ment of the environment and the human con-dition. Solar thermal water desalination andpurification has a positive impact on a largenumber of health and environmental pro-blems. A severe oil crisis is just beyond thehorizon, and when it comes, it will get everworse because the global oil supply eventuallywill not keep up with ever growing demand.Fuel costs will skyrocket, and especiallyremote communities in developing countries

and on isolated islands which often rely ondiesel power for both electricity productionand water treatment, will be hit hard. Besidesthe recent technological advances in the field,this background is the main reason why solarenergy will rapidly become competitive.Within ten years of time there simply will beno other alternatives in many situations. Ifnecessary, it is possible to live without elec-tricity, but not without safe drinking water.In our view Aqua Solaris is a solution to oneof the most pressing problems of some of thepoorest people on Earth. The benefits ofindustrial mass production could be fully uti-lized, and a remote dream might be to seelong and previously uninhabited desert coast-lines with row after row of Aqua Solaris sys-tems silently doing their work of slowlygreening the desert, e.g. in North-WesternAustralia, Namibia or Peru.

In combination with other new develop-ments, such as halophytic agriculture thatmakes use of edible salt loving plants, entirenew branches of economy could blossomwithin practically self sufficient communities.It is a dream, but not an impossible one.

In addition to water purification there aretwo additional spin off applications whichalso are patented: the production of highestquality sea salt and an economic way ofindustrial waste water treatment based uponthe all-natural fibres of the surface expanderin the evaporation chamber.

At this time we are in the planning phaseof a first larger pilot project. Suitable loca-tions in India are under survey, where thetechnology of solar thermal desalinationalready is relatively well accepted. We areconvinced that as soon as the industrialdesign is ready for mass production and alarger pilot project is under way, the AquaSolaris concept can rapidly spread aroundthe globe. To achieve this we are still look-ing for investment and industrial partners

508 J. de Koning, S. Thiesen / Desalination 182 (2005) 503–509

who share our vision of a humane, environ-mentally friendly and sustainable businessstyle.

5. The authors

Jan de Koning, founder of Zonnewater,worked as a manager at DuPont Chemicalsnear Rotterdam for 25 years before optingfor an early retirement scheme. He thenused his private funds to almost single-hand-edly develop the Aqua Solaris system anddeploy a field prototype on the Island ofBonaire. His vision is to develop a new ethi-cal business model that takes into accounthuman values and environmental aspects.

Dr Stefan Thiesen is a multi disciplinaryscientist working as a freelance science writerand consultant as well as activist. In additionto his Ph.D. in Astronomy (Munster, Ger-many, and Hawaii) and MA in Geography(University of London) he also holds a BS

from the University of the State of New Yorkand post graduate qualifications in watermanagement and energy consulting from theFraunhofer Institute. He is author of severalbooks and numerous articles.

References

[1] Uberlebensfrage Wasser – Eine Ressource wird

knapp, Entwicklungspolitik Materialien Nr. 94,

Bundesministerium fur Wirtschaftliche Zusam-

menarbeit, Bonn, 1995.

[2] Solar Distillation, Technical Brief, The Schuma-

cher Centre for Technology Development, Rugby,

UK, 2002.

[3] Company Information, Hygrotec, www.hygrotec.de

[4] Ebaye Water Problems, Yokwe Online, Majuro,

Marshall Islands, 2004.

[5] Aktionsprogramm 2015 – Armut bekampfen,

gemeinsam handeln, Bundesministerium fur

Wirtschaftliche Zusammenarbeit, Bonn, 2003.

[6] SOLCO Company Information, Perth, 2004.

J. de Koning, S. Thiesen / Desalination 182 (2005) 503–509 509