Drm Clima2012 Fcul 1 2jun2012

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June 01, 2012,CLIMA 2012 - III National Congress on Climate Change - FCT UNL, Lisbon

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WIND ENERGYDRMTECHNOLOGY FOR

POTABLE WATER SUPPLY

A Cape Verde ExampleRita Sousa1, Maria Joo Martins2

1: University of Minho, [email protected]: Ecoviso, [email protected]

Abstract: In developing countries water and energy needs are a priority and an everyday concern.Typical methodologies respond to water and energy supply problems through independent solutions.In this paper we present an innovative technology called DRM, Dutch Rainmakerthat allows a com-

mon approach for both issues. DRM is a windmill technology that produces fresh water either from air,saline or brackish water using wind energy. It is a patented technology, a simple and robust systemwith low maintenance and infrastructural costs. Therefore it may be installed in areas with differingclimate conditions. DRM is, in its essence, a mitigation and adaptation technology, although here weconsider GHG emissions mitigation issues only.

Our study evaluates a plant to be installed in Cape Verde. It regards the production of fresh water fromsaline water, where water is directly harvested from salty water without using fossil fuel energy,namely diesel, usually necessary for generators in Cape Verdes islands. It has an expected average wa-ter production of 60m3/day/windmill. Results show the increase of local population with access to safewater; higher water consumption per capita; an increase in the penetration of renewable energy in thecountry, and consequently savings in CO2 emissions; and lower water costs for consumers are ex-pected.

KEYWORDS: Desalination, wind power, GHG emissions, Cape Verde.

I. IntroductionIn developing countries fresh water supply, inadequate quantity and quality, is currently a chal-lenge, mostly because of infrastructure limitationsand shortage of the water resource itself. A possi-ble solution to meet future consumption is pro-vided by seawater, since the oceans representapproximately 97% of the water on the globe. Onthe other hand, surface water appears to bemostly brackish water, also useful if treated(Showers, 2002). In consequence, the desalinationof brackish water and seawater presents itself asan immediate possibility to tackle the above re-ferred shortage.

Regarding desalination, various processes havebeen developed within evaporation and mem-brane separation methods. The difficulty with

their application is that all associated technologiesrequire a generous amount of energy to desalinizewater. This energy is usually electric power, in thecase of developing countries such as Cape Verdesometimes fuelled by diesel generators.

It is also of relevance to note that scientific studieson the water sector usually aim exclusively at is-sues regarding adaptation to climate change,mostly because of its immediate importance tohuman life (Muller, 2007). Nevertheless, as weshow in this paper, water supply also allows forGHG emissions mitigation actions, thus contribut-


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ing to adaptation-mitigation integration at policylevel, as it has been advocated as a better bal-anced solution (Klein et al., 2005; Mata andBudhooram, 2007; Swart and Raes, 2007).

In fact, regarding greenhouse gas emissions, thewater supply systems are responsible for direct(through fuel burning) and indirect (electricityuse) emissions, in water capture and water treat-ment stages.

Under this framework, the aim of this paper is topresent a new technology for the direct produc-tion of fresh water from seawater or brackishwater, or even from air, using wind power as analternative to electric power used in conventional

technologies, allowing for greenhouse gas emis-sions reductions, i.e. local mitigation measures.

In chapter 2 we describe Cape Verdes needs forfresh water, in chapter 3 we look at desalinationprocesses and in particular we describe the DRMtechnology and its advantages for small islandscommunities, in chapter 4 we report our examplein Cape Verde, including expected projects results.We conclude the analysis in chapter 5.

II.Cape Verde water supply availabilityand associated energy use

The Republic of Cape Verde is a ten-island coun-try, with an area of 4000km2. The Cape Verdeanlandscape is not particularly green because of itscharacteristics of almost no rainfall (average227mm/year). Global freshwater availability in

Cape Verde, strongly influenced by the climate, istherefore a problem. In this country we find achronic shortage of water (less than1m3/inhabitant/year). Urban development andconsequent growth of water needs worsen thesituation.

Although access to drinking water from severalsources has grown in the last years, there are stillmajor gaps regarding supplies from fountains,

national network and other sources. According tothe 2010 Census, only 30% of the population has

public water network connection (supplied byElectra, the national water company), 45% collectwater at water fountains and 25% from othersources (wells and water springs) (Chart 1). Wa-ter transport is carried out mainly by women and

children, on foot.

Chart 1 - Population with access to safe water and sanitation(Source: Association of Commerce, Industry and Tourism,Cape Verde).

A significant fraction of the population does notyet have access to regular supplies. The waternetwork provides only irregular supplies for ur-ban population and in rural areas the situation isworse due to scattered communities and difficultaccess to many of them (IMF, 2008).

In short, water supply and overall water resource

management have been a challenge in Cape Verde,in terms of supply availability and cost to families.

Taking into account the geographical and climaticcharacteristics of the Cape Verde islands and theconsequent lack of fresh water sources and rain, itis understandable that the country has becomeincreasingly dependent on seawater desalination.This process supplies 88% of water needs in CapeVerde (Chart 2).

Chart 2 - Cape Verde water sources, 2003-2007 (Source:National Agency for Economic Regulation, Cape Verde).

In 2008, 91.6% of Electras water supply camefrom desalination plants (table 1):


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Table 1 - Electra water production (m3) in 2008.

Process N. plantsTotal

production

Multi Effect Distillation 1 194 002

Reverse Osmosis 8 3 556 430Mechanical Vapour Com-pression 5 132 509

Total desalinated water 3 882 941

Total subterranean water 353 682

Desalination is an energy intensive activity andcan therefore be directly linked to the productionof electricity. In Cape Verde desalination is re-sponsible for the use of 10% of the electricalpower generated (IMF, 2008).

The use of alternative energy sources, like windand solar, comes now into view as a needed viablesolution. The Government has already stated theinterest in an integrated management of waterresources, including aspects regarding a greateruse of renewable energy to produce water Thegoal is to have 50% of water desalination pow-ered with renewable energy by 2020 (INGRH,

2007).

III. Desalination processesIII.A. Common desalination processes

Evaporation and membrane separation are themain methods on which conventional desalinationtechnologies are based. Others include crystalliza-tion, ion exchange, but their representation is

currently negligible (He and Yan, 2009). Evapora-tion methods include Multi Stage Flash (MSF),Multi Effect Distillation (MED), both used in com-bination with power plants, and Vapour Compres-sion Distillation, working on the principle of aheat pump. On the other hand, the most commonmembrane separation processes are Reverse Os-mosis (RO) and Electro-dialysis (ED) (Figure 1).MSF and RO are the leading processes around theworld with MSF representing 93% of evaporation

methods and RO 88% of membrane separation(He and Yan, 2009).

Figure 1 Most common desalination processes.

Cost-efficiency of all technologies using the abovereferred processes were analysed in several re-

search studies and, in general, evaporation proc-esses proved to be more energy intensive thanmembrane processes (Einav et al., 2003). In fact,considering that energy is an important input indesalination, RO has been recognized as the mostefficient process, and hence, has become the fa-vourite (Einav et al., 2003). Studies show that theproduction of 1m3 of water requires 3.5 to 4.5kWh in a RO typical plant (Einav et al., 2003).However, land use, impact on groundwater and on

the marine environment, including the composi-tion of discharge brines and noise pollution arealso aspects to be considered when evaluating theimpact of a desalination plant. Typically, RO plantshave higher discharge concentrations of salts, andare noisier than MSF plants (Einav et al., 2003).

Regarding the use of alternative energies in de-salination plants, solar, wind and nuclear havebecome more competitive in recent years (He andYan, 2009). Since solar evaporation plants or solarenergy powered RO systems require large imple-mentation areas, wind power is more adequate toislands, for it does not require much land. Studieshave demonstrated the technical feasibility of ROand mechanical VC wind-powered desalination(Forstmeier et al., 2007), and cost evaluation hasalso been assessed for RO plants (Garca-Rodrguez et al., 2001).

Next step technology in desalination involves awind powered flash evaporation process and is

Desalination

Processes

Evaporation

Multi Stage Flash(MSF)

Multi EffectDistillation (MED)

Vapour CompressionDistillation (VCD)

MembraneSeparation

Reverse Osmosis(RO)

Electro-Dialysis(ED)


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described in the following chapter. This technol-ogy was considered to be the best desalinationsolution over RO technologies given the condi-tions of the Cape Verdean municipality chosen.

III.B. DRM technologyDRM water-to-water specifications

The concept of DRM technology is a modificationof the traditional electricity generating windmill.

Figure 2 - DRM windmill for water treatment.

In this water-to-water technology, the generatedenergy in the wind turbine is used directly todrive a closed loop heat cycle which results inwater treatment by evaporation and condensation(Figure 3). Wind energy (1) is used to directlydrive a compressor (2) that compresses a coolant,in this case ammonia (NH3). The compressionresults in heat generation that is used for flashevaporation (5) of the saline or brackish water.After this, the compressed ammonia is expanded

(4) resulting in a temperature decrease. The wa-ter vapour generated in the evaporation stage cansubsequently be recovered by extracting heatusing the cooled ammonia (6). Since wind energyis directly used, it increases considerably theprocess efficiency when compared to otherswhere fuel is needed to previously power an en-gine.

Depending on the source, treated water will becomparable to demineralised water and may un-

dergo post-treatment processes so that it may beused as drinking water (water-to-water). The ex-

pected maximum yield is 80m3/day depending onlocal climatic conditions. In Table 1 we summarizethe DRM water-to-water technical specifications.

Figure 3 - Process and detail of the water-to-water DRMtechnology.

Table 2 - Technical specifications of a DRM windmill.

Value UnitInstalled power 100 kWWind speed (model) 13 m/sWind speed(minimum) 2,5 m/sProduction (average) 50 60 m3/dayProduction (maximum) 80 m3/daySpecific energy use (waterpumping)

2,15 kWh/m3

Rotor diameter 18 21 mArea swept by blades 40278 m2N. of blades 3 blades

Tower height 37 mTower weight 25 ton


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This technology may also be applied in an air-to-water process: since the technology is based on aheat cycle it also allows the recovery of waterfrom air by cooling it, resulting in moisture con-densation.

DRM Technology advantages for Cape Verde

purposes

As previously referred, other desalinization proc-esses are commonly used, as RO or MSF. However,their use of renewable energy sources is still verylimited. Wind-powered DRM solves the energyproblem of desalination without requiring a largeamount of wind. This is the most important ad-vantage of DRM technology. Other advantagesinclude: a reduced need for infrastructures; asimple, robust and low-maintenance system witha high lifespan (up to 20 years); reduced mainte-nance and operating costs; possibility of applica-tion in areas of diverse climatic characteristics. Infact, depending on the existing wind, one or twowater-to-water windmills have the capacity toprovide irrigation water to a community of 2000people.

Considering a desalination plant to be imple-mented on an island with small communities DRMtechnology has both environmental and economicadvantages when compared to RO. State of the artRO requires electric power, usually from networkor diesel generators, although latest develop-ments include experimental wind powered ROplants. DRM is a simple system that only works onwind. Regarding the process, RO requires a pre-

filtering and a frequent membrane substitution. Italso originates a concentrate containing high lev-els of chlorine, copper and antiscalants that mayhave impacts on the ecosystem when dischargedinto the aquatic environment, as mentionedabove. DRM does not require the use of antisca-lants nor generates a concentrate.

IV. Application of DRM water-to-water in Cape Verde

IV.A. Project phases, location and populationThis project aims to demonstrate the potential of

DRM technology application in Cape Verde,through the installation of 4 windmills for produc-tion of drinking water from seawater and brackishwater.

The rural area is a prime target for implementa-tion of the project because of its needs regardingbasic infrastructure and access to water. It is ex-pected that the 4 windmills provide safe water for6000 people.

The project will undergo seven actions, startingwith a validation study regarding the chosen loca-tion. Then on a second phase, all equipment andstructures will be implemented. Actions three,four and five will occur simultaneously and com-prise the operation and monitoring, and aware-ness raising and training activities. Finally, theproject will be transferred to local authorities(action six), and to conclude, a seventh action con-sists in consulting support after transfer.

This is a pioneering project to be replicated in thefuture in other municipalities and / or industrialunits.

IV.B. Expected results and indicatorsThere are two specific objectives of this project:the supply of drinking water using renewableenergy and the capacitation of the population and

technicians involved.Increased access to potable water for the localpopulation is the first expected result. The secondregards the energy used in collecting this water:increased supply of potable water using renew-able energy. The third result is stimulation onconsumption, representing an increase in m3 ofwater consumed per capita.

In places where access to potable water is limited,DRM will reduce the need for water collection atwater fountains, while at the same time reducing


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the need to build infrastructures for water supplyfrom already existing desalination plants. In CapeVerde the water consumption from fountains isabout 15L/person/day and from its national net-work of 35L/person/day. We consider that people

will have access to larger quantities of potablewater (3rd result) at an estimated 40L/person.This results in the supply of potable water to 6000people, with the installation of 4four windmills(1stand 3rd results).

We set up a comparison between the implementa-tion of 4 DRM windmills and the installation of anew RO desalination plant. The considered ruralpopulation has no access to the water network

and is dependent on water supply from fountainsor water tankers, provided by the municipality.For model purposes we compared the implemen-tation of these 4 towers to the best alternativewhich would be implementation of a new RO de-salination plant, as demonstrated in chapter 3.

Specific conventional energy consumption associ-ated to the DRM windmills is associated to waterpumping and amounts to 2.15kWh/m3. Recallingthat RO plants have an energy intensity of

4kWh/m3, then savings may amount to1.85kWh/m3 in a worst case scenario, where elec-tric power must be provided by the grid for waterpumping. Considering UNCTAD indications forAfrican electricity emission factors, Cape Verdespower sector emits 0.629kCO2eq/kWh. So, our1.85kWh/m3 savings may be translated into1.16kCO2eq/m3. In this situation, this four towerproject totalizes savings of 279kCO2eq/day, or102tCO2eq/year. Considering that wind is a re-

newable energy source with almost no emissionsin greenhouse gas accounting principles, we mayconsider further developments in DRM technol-ogy that will allow water pumping to be fuelled bythe tower energy itself. In this case, total savingswill amount to 4kWh/m3 regarding the electricityuse by a RO plant. In this case, savings would sum603kCO2eq/day, or 220tCO2eq/year. These valuesare associated with water consumption by 6000people.

Further analysis must take place in order to calcu-late emissions savings from the substitution ofwater tankers by DRM technology. We currentlyhave no data to perform this study, but knowingthat a diesel fueled vehicle/tanker emission factor

is higher than the electricity grid emission factor,carbon savings will exceed the values presentedabove.

A fourth result of this DRM project is an increasedpenetration of renewables in the country. Consid-ering that in average a 100kW wind tower pro-duces about 75000kWh of energy per year, de-pending on the wind and tower itself, this fourthresult is automatically fulfilled.

Finally, Cape Verde is considered to have veryhigh water prices, because of its scarcity. Electraprices are about 3-4$/m3 of water. Next stepanalysis will include water tariff calculus with thepurpose of reducing water costs for families. Thiswill be the project last result: a reduction in theprice of water.

V.ConclusionsIn this paper we present a pilot application ofDRM water-to-water, a new desalination technol-ogy, in a rural municipality in Cape Verde. Thistechnology operates on wind power, and becauseof this it is highly competitive with state-of-the artRO desalination processes, for small communities.In this water-to-water technology, the generatedenergy in the wind turbine is used directly todrive a closed loop heat cycle which results inwater treatment by evaporation and condensa-

tion. Since wind energy is directly used, it in-creases considerably the process efficiency whencompared to others where fuel is needed to previ-ously power an engine.

This project aims to demonstrate the potential ofDRM technology application in Cape Verdethrough the installation of 4 windmills to providesafe drinking water for 6000 people, using renew-able energy, and capacitating the population and

technicians involved. The increase of m3

water percapita consumption from 15 L/day/person to


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40L/day/person is also an expected result. Lastly,this project will save 102tCO2eq/year or even220tCO2eq/year if technology developments willallow the use of wind energy for water pumping.More studies are needed on emission of water

supply by auto-tanks, and on water tariff.

Although we recognize that this sector has a smallimpact on emissions when compared to trans-ports or residential sectors, we also consider wa-ter to be a crucial sector for human living, so allpossible mitigation measures in this sector shouldbe implemented. The use of renewable energy indesalination is therefore an important step forsustainable growth and development in small

islands developing countries.

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VI. ReferencesEinav R, Harussi K, Perry D, 2003, "The footprint of thedesalination processes on the environment"Desalination152 141-154

Forstmeier M, Mannerheim F, D'Amato F, Shah M, LiuY, Baldea M, Stella A, 2007, "Feasibility study on wind-powered desalination" Desalination203 463-470

Garca-Rodrguez L, Romero-Ternero V, Gmez-Camacho C, 2001, "Economic analysis of wind-powereddesalination" Desalination137 259-265

He T-x, Yan L-j, 2009, "Application of alternativeenergy integration technology in seawaterdesalination" Desalination249 104-108

IMF, 2008, "Cape Verde: Growth and PovertyReduction Strategy Paper II (200811) - Joint Staff

Advisory Note", in IMF Country Report (InternationalMonetary Fund, Washington, D.C.)

INGRH, 2007, "Diagnostico do Sector da gua eSaneamento", (Instituto Nacional de Gesto dosRecursos Hdricos)

Klein R J T, Schipper E L F, Dessai S, 2005, "Integratingmitigation and adaptation into climate anddevelopment policy: three research questions"Environmental Science & Policy8 579-588

Mata L, Budhooram J, 2007, "Complementaritybetween mitigation and adaptation: the water sector"

Mitigation and Adaptation Strategies for Global Change 12 799-807

Muller M, 2007, "Adapting to climate change: watermanagement for urban resilience" Environment andUrbanization19 99-113

Showers K B, 2002, "Water Scarcity and Urban Africa:An Overview of UrbanRural Water Linkages" WorldDevelopment30 621-648

Swart R, Raes F, 2007, "Making integration ofadaptation and mitigation work: mainstreaming intosustainable development policies?" Climate Policy 7

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