Can Desalination and Clean Energy Combined Help to Alleviate Global Water Scarcity?

CAN DESALINATION AND CLEAN ENERGY COMBINED HELP

TO ALLEVIATE GLOBAL WATER SCARCITY?1

Aditya Sood and Vladimir Smakhtin2

ABSTRACT: The major present hindrance in using desalination to help alleviate global water scarcity is the costof this technology, which, in turn is due to energy cost involved. This study examines historical trends in desali-nation and breaks up the cost of desalination into energy based and nonenergy based. It then develops thelearning curves (relationship between cumulative production and market price) for desalination. Assuming thatthe photovoltaic (PV) technology will be the dominant form of energy used in the desalination process, the exist-ing PV learning curve and desalination learning curve are combined to explore the viability of large-scale adop-tion of desalination in the future. The world has been divided into seven regions and it is assumed that waterdemand from desalinated water will be met only within the 100-km coastal belt. It is shown that, in most of theregions, other than sub-Saharan Africa, Central America, and South Asia (where water tariffs are low), thedesalination (without considering energy) becomes viable by 2040. For PV technology, less than 1 million MWper annum growth is required till 2050 to make it affordable. Globally, desalination with renewable energy canbecome a viable option to replace domestic and industrial water demand in the 100-km coastal belt by 2050.

(KEY TERMS: desalination; learning curve; renewable energy; water demand; photovoltaic.)

Sood, Aditya and Vladimir Smakhtin, 2014. Can Desalination and Clean Energy Combined Help to AlleviateGlobal Water Scarcity? Journal of the American Water Resources Association (JAWRA) 50(5): 1111-1123. DOI:10.1111/jawr.12174

INTRODUCTION

The issue of global water scarcity is continuouslydiscussed in science literature and top internationalpolicy gatherings. Water scarcity can be quantita-tively expressed in terms of various indices, includinguse-to-availability ratio, number of people competingfor the same resource in a given area, per capitawater availability, etc. Regardless of the quantitativemeasures used, there is an overall consensus thatwater scarcity is progressing and will continue toincrease due to population growth, increase indemand for food, and climate change (Seckler et al.,

1998; Falkenmark and Rockstrom, 2004; Molden,2007; Rockstrom et al., 2009). Smakhtin et al. (2004)developed a water scarcity indicator — that explicitly“reserved” water for environmental purposes — glob-ally, with a spatial resolution of 0.5°. Based on thatstudy, Figure 1 shows that most of the highly popu-lated areas are already water stressed, i.e., there isnot enough river flow that can meet estimated envi-ronmental demands while also satisfying the require-ments of other sectors, such as agriculture, industry,and domestic use. The competition for water betweenthese sectors continuously grows with increasingworld population, which is expected to cross 9 billionpeople by 2050.

1Paper No. JAWRA-13-0021-P of the Journal of the American Water Resources Association (JAWRA). Received January 28, 2013; acceptedDecember 13, 2013. © 2014 American Water Resources Association. Discussions are open until six months from print publication.

2Respectively, Researcher (Sood), Integrated Hydrological Modeling, International Water Management Institute (IWMI), 127, Sunil Mawa-tha, Pelawatte, Battaramulla, Sri Lanka; and Theme Leader (Smakhtin), Water Availability and Access, International Water ManagementInstitute (IWMI), 127, Sunil Mawatha, Pelawatte, Battaramulla, Sri Lanka (E-Mail/Sood: [email protected]).

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION JAWRA1111

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION

Vol. 50, No. 5 AMERICAN WATER RESOURCES ASSOCIATION October 2014

Water scarcity may be alleviated through moreactive tapping into larger or underutilized watersources such as rainwater or groundwater, interbasinwater transfers, river flow regulation, water produc-tivity improvement, water demand management,recycling, etc. Yet, conventional sources and mea-sures have their limits and, in many regions of theworld, as evident from Figure 1, there are hardly any“conventional” options left to improve water availabil-ity/supply. At the same time, the world has virtuallyunlimited potential sources of water, which is beyondthe “freshwater box.” Every hydrology textbookcontains the basic estimates of global water sources.Freshwater (inclusive of fresh groundwater, water inice caps and glaciers, and rivers and lakes) consti-tutes only 3% of this total. The rest is water in theocean. Most of human water supply currently comesfrom rivers (which themselves constitute a fraction ofa percent of the total global water sources). Most, ifnot all, present-day efforts to alleviate water scarcity,are focusing on this fraction. Yet, saline or brackishwater, no matter how unpopular at present, may andmost likely will play a significant role in future waterresources management, especially in the water-scarceregions (Barker, 2003; Uche et al., 2006). Desalination,

a process that derives freshwater from seawater orbrackish water, may in principle, make a revolutionin water supply globally.

Desalination technologies can be broadly classifiedinto two groups — thermal process-based and electro-mechanical process (or membrane)-based technologies(Mathioulakis et al., 2007). Thermal process technolo-gies use distillation; this involves a phase change ofwater. Electromechanical technologies rely on a semi-permeable membrane and do not involve a phasechange. Because of the high cost of membranes, ther-mal technology has been more economical to use forseawater desalination, and membrane technology ismore suitable for desalination of brackish water(Karagiannis and Soldatos, 2008). This is especiallytrue in the regions where the energy is relativelycheaper. This may change in the future due to therising cost of energy and cost reduction in membranetechnology. Another way to characterize desalinationis in terms of the type of energy used, i.e., those thatuse a conventional source of energy and those thatuse renewable energy sources (RES) (Karagiannisand Soldatos, 2008). A conventional source of energyis defined as energy derived from hydrocarbons suchas coal, oil, and natural gas, and RES is defined as

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FIGURE 1. Global Environmental Water Scarcity Map with Boundaries of Countries andMajor World Economic Regions (modified from Smakhtin et al., 2004).

JAWRA JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION1112

SOOD AND SMAKHTIN

energy derived from renewable sources such ashydropower, solar and wind energy, geothermal, etc.RES commonly used for desalination are solar, wind,and geothermal energy types.

Desalination technologies at present remain expen-sive, energy consuming and thus not competitive withconventional water supply. The costs of desalinatedwater provision have, however, dropped from 1995USD 9.0 to 1995 USD 1.0/m3 over the last 40 years(Zhou and Tol, 2004). The cost has fallen furthersince then and has been reported to be as low asUSD 0.5/m3 for large-scale production (IEA-ETSAPand IRENA, 2012). The lowest rates are documentedby Al-Karaghouli and Kazmerski (2013) for reverseosmosis (RO) processes that range from 0.45 to 0.66USD/m3 for capacity ranging from 100,000 to320,000 m3/day for seawater and from 0.26 to 0.54USD/m3 for large capacity (40,000 m3/day) brackishwater desalination plants.

Another virtually unlimited resource is solarenergy. It currently constitutes only 0.03% in the glo-bal energy balance, but has grown in a decade (from1998 to 2009) from 964 MW to 30,060 MW (Brown,2011). As of 2011, solar photovoltaic (PV) accounts for1.4% of the global installed electricity capacity andhas been growing at a rate of 43% annually from2000 to 2011 (Gelman, 2012). The cost of installedsolar (PV) systems in the United States (U.S.) hasdropped from 2008 USD 11.8/W in 1998 to 2008 USD8.3/W in 2007 (Wiser et al., 2009) and is falling rap-idly — as of 2012 it was as low as USD 2.2/W in Ger-many, although it could be higher in other lessefficient countries (IEA-ETSAP and IRENA, 2013).The cost is expected to fall to USD 1.7-2.4/W by 2020(IEA-ETSAP and IRENA, 2013). Energy cost is thesignificant element in the high cost of desalinatedwater (Elhassadi, 2008; Semiat, 2008). It may beanticipated that as demand for freshwater increases,the cost of available water will go up. On the otherhand, with the continuing improvements in technolo-gies for desalination and renewable energy, solarenergy, in particular, and government policy support,the cost of desalinated water will go down. A combi-nation of affordable renewable energy with cheaperdesalination technology will, therefore, have signifi-cant impact on the future of water supply in certainregions and sectors. The recent trends in the develop-ment of both desalination and solar power are pro-mising.

This study attempts to answer the following ques-tions: (1) will desalinated water become affordableover time due to the development of its own technol-ogy and clean energy in large volumes, and if yes —how soon; (2) where in the world it will become moreacceptable and widely used; and (3) what implicationswill this have on water resource management in the

future? Considering the cost involved, the desalinizedwater can be considered as a replacement primarilyfor domestic and industrial water use, as these sec-tors already pay to receive water. As the cost oftransporting the water can be high, there is a regio-nal feasibility limit for the use of desalinated water.

WATER DESALINATION AND RENEWABLEENERGY: RECENT TRENDS

Different standards are used by organizations todefine freshwater. Water with total dissolved solidsunder 500 mg/l (U.S. Environmental ProtectionAgency and U.S. Geological Survey) or under1,000 mg/l (World Health Organization) is consideredfreshwater (NAS, 2008). Water with salinity levelsover 35,000 mg/l is considered seawater (http://ga.water.usgs.gov/edu/saline.html — accessed in Novem-ber, 2012). Water with salinity levels between fresh-water and seawater is considered brackish water.Some organizations further classify saline water intomultiple classes (based on salt concentration) such asnonsaline (<500 mg/l), slightly saline (500-1,500 mg/l),moderately saline (1,500-7,000 mg/l), highly saline(7,000-15,000 mg/l), very highly saline (15,000-35,000 mg/l), and brine (>45,000 mg/l) (FAO-http://www.fao.org/docrep/t0667e/t0667e05.htm — accessedin November 2013).

Although there are many technologies that existfor desalination, three of these are used most widelyat present, and will likely dominate in the future too.These technologies are multistage flash (MSF) distil-lation, multieffect distillation (MED), and RO(Khawaji et al., 2008). MSF and MED are thermalbased, and RO is membrane based. As of 2002, MSFand RO accounted for 36.5 and 47.2%, respectively, oftotal global desalination capacity, with MSF dominat-ing the large-scale (over 5,000 m3/day) capacity andseawater desalination (Khawaji et al., 2008).

The 2010 global capacity of desalination was about25 km3 of water per year (GWI, 2010), out of whichabout 65% is from seawater and the balance is frombrackish water, wastewater, and river water with lowsalinity levels. This is expected to go up to 47 km3/yrby 2016 (GWI, 2010). Considering the freshwaterwithdrawals of over 3,900 km3 annually (World Bankdata, 2011, http://data.worldbank.org/indicator/ER.H2O.FWTL.K3 — accessed in January 2013), thisforms less than 0.6% of the total freshwater with-drawals. The current use of desalination is dominatedby the Middle East and North Africa (MENA) regionand some of the Organization for Economic Co-operationand Development (OECD) countries such as the U.S.,


CAN DESALINATION AND CLEAN ENERGY COMBINED HELP TO ALLEVIATE GLOBAL WATER SCARCITY?

Australia, and Spain (other notable exceptions areChina and India). Most of the desalination capacitywas developed in the last two decades (Figure 2).NAS (2008) reports that the desalination capacity in2006 was 0.032 km3 of water per day and representedonly 0.3% of total freshwater use.

The main constraining resource in the adoption ofdesalination technology is the availability and cost ofenergy in the process. To date, it has only been usedin countries where there is high water scarcity andenergy is relatively inexpensive, such as in the Mid-dle East, or in affluent nations such as in the U.S.The top three countries that use the technology areSaudi Arabia, the U.S., and the United Arab Emir-ates (Khawaji et al., 2008). Based on the energy sup-ply, the cost of desalination has been documented byKaragiannis and Soldatos (2008). According to theiranalysis, the cost of water desalination throughrenewable energy is still much higher than thatthrough conventional energy.

Energy cost plays a bigger role in thermal desali-nation than in membrane desalination. The energyconsumption for MSF is between 24 and 37 kWhe/m

3

(“e” in kWhe or KWe refers to electric power); forMED, it is between 18 and 30 kWhe/m

3; and for ROit is less than 3.7 kWhe/m

3 (Semiat, 2008). For MSF,the cost of energy accounts for 59% of the total cost,whereas for RO it accounts for 20% (Elhassadi, 2008).Other studies, such as NRC (2008) shows energy tobe 51 and 46% of the total cost for seawater MSF andMED, respectively, and 37% of the total cost forseawater RO. For RO systems, the industry is reach-ing the upper limit of improving technology to saveenergy (Semiat et al., 2010), and in the best case sce-nario, not more than an additional 15% of energy canbe saved (NAS, 2008). Thus, the future of cheaper

desalination processes is dependent on the enhancedfuture availability of RES, which will have to becomeaffordable themselves.

Now, due to much higher fossil fuel prices andenvironmental issues, conventional energy expansionis curtailed, and this trend is likely to continue dueto concerns of climate change and the need to developRES. The data on average global growth rates in var-ious energy sources in the period 2004-2009 suggestthat solar power growth (based on cumulativeinstalled capacity as a proxy) is the highest of all at55%, followed by wind (27%) and biofuels (23%)(based on volumetric production as a proxy) (Ochs,2010). For comparison, oil, natural gas, and coalenergy growth rates over the same period were 0.4,1.8, and 3.2%, respectively. Over the last decade, thePV production increased by over 130 times, whereasthe wind installed capacity increased by over 90times (Figure 3).

Currently, only 1% of desalinated water comesfrom renewable energy-based process (IEA-ETSAPand IRENA, 2013). In the renewable energy-baseddesalination, three energy sources are used, i.e.,solar, wind, and geothermal, but the type of energymore suited depends upon many factors such as loca-tion, plant size, water salinity, and region-specificavailability (Al-Karaghouli and Kazmerski, 2011). Ingeneral, solar thermal is more suited for MSF andMED process, whereas solar PV and wind is suitedfor RO and electrodialysis (ED) process. Geothermalcan be used in both, thermal and membrane technol-ogy. Out of the current production of renewableenergy-based desalination, PV is the predominantsource of energy, providing energy to about 43% ofexisting desalination facilities. About 62% of thecurrent renewable energy-based desalination is from

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FIGURE 3. Trends in Renewable Energy Sourcesin the Last Decade (Source: Gelman, 2012).


SOOD AND SMAKHTIN

RO process and the rest from MFS and MED (IEA-ETSAP and IRENA, 2013).

Although, PV-RO systems have the advantage ofbeing more versatile in size and portability, thefuture is in large-scale units, as PV technology getscheaper. Presently, because of the high cost of PV,most of the prototype PV-RO systems are small scale,with capacity ranging from 53 m3/day to less than1 m3/day and the cost of producing water rangingfrom USD 14.9/m3 to USD 3.6/m3 (Al-Karaghouliet al., 2009). The energy consumption of desalinationof brackish water is smaller than that for seawater.Consequently, the cost of desalinizing seawater is 3-5times higher than brackish water (Al-Karaghouliet al., 2010). There is a wide range of cost estimatesin the literature for desalination that uses solarenergy. Al-Karaghouli and Kazmerski (2011) reportthe cost of PV seawater RO to be from 4.2 to 33 USD/m3 (0.5 l/h and <1 m3/day capacity, respectively) andthe cost of PV brackish water RO to be 3.6-14.9 USD/m3 (1.5-0.25 m3/day capacity, respectively). Theauthors report cost of desalination by solar stills tobe as high as 23.8 USD/m3 (for simple stills withcapacity of 4 l/(m2 day)) to 9.95 USD/m3 (for multief-fect stills with capacity of 12 l/(m2 day)). IEA-ETSAPand IRENA (2013) report cost of desalination usingsolar stills to be between 1.3 and 6.5 USD/m3 (forcapacity of <0.1 m3/day) and that using solar mem-brane distillation to be between 10.4 and 19.5 USD/m3 (for capacity from 0.15 to 10 m3/day). According tothe same study, the range of cost of desalination withPV-RO combination range from 6.5 to 9.1 USD/m3 forbrackish water to 11.7 to 15.6 USD/m3 for seawater(capacity of <100 m3/day). Many of these productionunits are in the research and development (R&D)stage (IEA-ETSAP and IRENA, 2013).

It may be anticipated that solar power (PV) canbecome the major source of energy in the future and,if harnessed effectively, may make the large-scaleadoption of desalination technology feasible. Withinvestment in R&D and provision of subsidies, theprices of renewable energy can be brought down (Bre-yer et al., 2010). Similarly, due to improvement oftechnology and economics of scale, the desalinationprocess is becoming less expensive.

TECHNOLOGY LEARNING CURVES

The pathway of technological developmentdepends on multiple factors, including public fundinvestment in the initial stages, R&D investments,and market demands. One of the ways to look at theimpact of these factors in technology (or product)

development is to build learning curves (or experi-ence curves) and extrapolate them into the future.Learning curves can be expressed in the form ofmathematical equations and used in modeling futurescenarios (Argote and Epple, 1990; IEA, 2000; vander Zwaana and Rabl, 2003; Neij, 2008).

A learning curve is a relationship between cumula-tive production of a commodity and its price in themarket. In theory, the relationship should be withthe cost. However, it is not easy to get the costs ofcommodities, and studies have shown that in a stablemarket the costs and prices move in parallel (Argoteand Epple, 1990). The concept of learning curve isbased on the premises that, in a competitive market,with experience, the adoption of newer technologyand increased sales, the cost (and hence the prices) ofcommodities go down. This relationship betweencumulative production and prices is a straight line ona double-logarithmic chart (Figure 4). This impliesthat there is a consistent reduction in the price ofany commodity as the cumulative production of thiscommodity increases. Each product or technology hasits own unique learning curve, which is characterizedby the progress ratio (PR). PR is defined as a changein price (i.e., price it reduces to, of the original price,e.g., PR of 0.8 implies that the price will drop to 0.8of the original price) due to doubling of cumulativeproduction. Lower PR (or higher learning rate [LR])means that a technology or a commodity “learns” fas-ter from the experience. LR is defined as (100 � PR),when PR is defined as a percentage. Thus, PR is usedto compare different technologies in terms of theirlong-term cost and adoption rates. The point where alearning curve meets the incumbent technology costline is called a break-even point. The area under the

Cost ofTechnology

Break-EvenPoint

Cost of IncumbentTechnology

Learning Investment

In [Cumulative Installed Capacity]

In[U

nit C

ost]

Cumulative Investment Cost ofIncumbent Technology

FIGURE 4. Representation of Learning Curveand Investment (adapted from IEA, 2008).



learning curve and the cost curve of incumbent tech-nology represents the investment required to bringthe newer technology to the break-even point. Thelearning curve is represented by the following equa-tion:

lnðCtÞ ¼ lnðC0Þ þ b � lnðntÞ ð1Þ

where Ct is expected cost at nt cumulative productionlevel; C0 is known cost of a product at initial phase(i.e., nt = 1) and has same unit as Ct; and b is slopeparameter obtained by regression.

Inclusion of the future of desalination tech-nology and renewable energy into global modelscan be achieved by representing desalination interms of experience curves with well-defined PRsand the break-even points for different regions ofthe world.

SCENARIO DEVELOPMENT

The focus of this study is on medium- and large-scale desalination units that run with renewableenergy, so that they can cater to larger waterdemands in different economic zones and can haveimpact on water budgets at the global level. Forscenario analysis, the world has been divided intoseven groups: sub-Saharan Africa (AFR), MENA,Eastern Europe and Central Asia (ECA), SouthAsia (SAS), East Asia and the Pacific (EAP), LatinAmerica and the Caribbean (LAC), and OECD(Figure 1).

Considering that there are cost limitations intransporting water, a global scenario is developedwhere the domestic and industrial water demand(based on population) is considered within a 100-kmbelt along the coast. Globally, about 33% of theworld’s population lives within 100 km of the coast,with sub-Saharan Africa having the lowest percent-age of 18% followed by ECA (17%), SAS (24%),MENA (37%), and EAP (38%). The highest is inOECD countries, with 50% of people living in thecoastal belt and 45% in the LAC region (authors’analysis).

To develop the scenario, first, the water demand indomestic and industrial sectors along the 100-kmcoastal zone is projected till 2050. Second, based onhistoric trends, the tariffs on future water supply areprojected. The scenario is developed to analyzewhether future desalination can be cost-effective tocater to the domestic and industrial demands alongthe 100-km coastal belt.

Projecting Future Water Demand

Figure 5 shows the increase in demand for domesticand industrial water, if the future projections for popula-tion and gross domestic product (GDP) are included inthe analysis. The domestic water demand is calculatedon 2000 base year data and projected up to 2050 by con-sidering population and income growth in the equationdeveloped by the International Food Policy ResearchInstitute (IFPRI) (Rosegrant and IMPACT Develop-ment Team, 2012) as follows:

gDDM ¼ gPOPþ gd � gINC ð2Þ

where gDDM is growth rate of municipal waterdemand (%); gPOP is population growth (%), gINC isper capita income growth (%); and gd is the elasticityterm of domestic water demand.

The industrial water demand is calculated herebased on the relationship between GDP per capita,water demand intensity and a time variable wasdeveloped using historic water demand figures(Rosegrant and IMPACT Development Team, 2012).Water demand in each of the industrial sectors —namely, manufacturing, energy, and agro-industry —is represented by the following equation:

DDI ¼ itcp: ðINCaiÞ:ðWPbiÞ: ðeci:TÞ ð3Þ

where DDI is the industrial depletive demand (km3);itcp is the intercept for the base year; INC is the percapita income (USD/capita); aι is the income elasticityfor industrial water demand; WP is the water price;bι is the industrial water price elasticity; cι is thetime trend coefficient industrial water demand; andT is the year from the base year.

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FIGURE 5. Regional Domestic and IndustrialWater Demand Projections.


SOOD AND SMAKHTIN

Table 1 shows the global coastal water demand,derived proportionally based on the coastal popula-tion. The coastal demand for domestic and industrialwater is likely to rise from the current level of 300 to1,290 km3 by 2050. The highest projected industrialand domestic water demand is in OECD and EAP —two of these regions account for 78% of global domes-tic and industrial water demand.

Projecting Future Price of Water

The tariffs charged for domestic water use varyconsiderably from region to region. Global WaterIntelligence (GWI) collects tariff data for over 180 cit-ies around the globe (http://www.globalwaterintel.com/tariff-survey/ — accessed in December 2012).The water tariff ranges from as low as 2012 USD0.14/m3 in India (average of 17 cities) to as high as2012 USD 4.32/m3 in Denmark (average of two cit-ies). A relatively strong relationship exists betweencountry per capita GDP and water tariffs (Figure 6).

The relationship between water tariff and per cap-ita GDP is better explained as linear for countrieswith lower per capita GDP, i.e., countries with GDPbelow USD 25,000 per capita (Figure 7). The linearrelationship, in this case, has an R2 value of 0.76 ascompared to 0.48 when trying to explain the relation-ship as a log for all the countries.

Table 2 shows water tariffs as calculated based onthe relationship developed above (linear below USD25,000 and then nonlinear) with per capita GDP (datacollected from IFPRI; Nelson et al., 2010). Looking atthe average rates, the lowest tariff rates are in SouthAsia, where it is likely to move from USD 0.083 toUSD 0.28 by 2050. The highest rates are in OECDcountries, where it will move from USD 1.99 to USD2.76 by 2050. There will certainly be a variation intariffs based on local conditions and policies, but thisgeneralization will suffice for the global study. There

is some cost involved in transporting water over longdistances. Analysis carried out by Zhou and Tol (2004)shows that for a 100-km horizontal distance, the costof transporting water is USD 0.05-0.06/m3 of water.The last column in Table 2 shows the tariff of water ifwater transport cost of USD 0.06/m3 is reduced fromthe calculated water tariffs.

SCENARIO ANALYSIS

Desalination Potential

Can the desalination meet the goal of providingwater at the projected water tariff rates? Based on

TABLE 1. Regional Domestic and Industrial Water Demand (km3)from 2010 to 2050 along the 100-km Coastal Belt.

Region 2010 2020 2030 2040 2050

AFR 3 6 9 16 27EAP 45 85 140 237 404ECA 7 11 15 22 30LAC 13 21 30 44 62MENA 4 7 10 15 21OECD 214 269 353 465 600SAS 13 24 42 77 143

Note: AFR, Sub-Saharan Africa; EAP, East Asia and the Pacific;ECA, Eastern Europe and Central Asia; LAC, Latin America andthe Caribbean; MENA, Middle East and North Africa; OECD,Organization for Economic Co-operation and Development; SAS,South Asia.

IndiaChina

Mexico

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Poland

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Portugal

South Korea

Spain

Italy

United Kingdom

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JapanUnited States

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Australia

y = 0.825ln(x) - 6.6R² = 0.48

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FIGURE 6. Relationship between Water Tariffs andPer Capita Income for Different Countries.

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FIGURE 7. Relationship between Water Tariff and Per CapitaGross Domestic Product (GDP) for Countries with Lower

Per Capita GDP, i.e., USD 25,000/Capita.



the methodology developed by Zhou and Tol (2004),the desalination cost was calculated for desalinationplants in different regions. The initial capital cost forthe desalination plants was amortized on the annualbasis. The total cost was split into 40% capital costand 60% operating cost. The total investment costwas amortized using 8% discount rate (same as usedby Zhou and Tol, 2004) and considering 25 years asthe design life of plants.

Based on the data from GWI (www.desaldata.com),the regional costs over the time period were calcu-lated and are shown in Figure 8. The graph shows asharp drop in cost of desalination between the mid-1960s and 1978. For this scenario analysis, the costtrends from 1975 were considered.

The cost of desalination can be broadly divided intotwo categories: energy related and nonenergy related.On average, energy contributes to 45% of the opera-tive expenditure in case of thermal-based technologyand 30% of the operative cost in the case of RO tech-nology. If only the electricity cost is considered, itcomes to about 32% of the total operative expendi-ture. The previous trends show a reduction in theproportion of energy cost in desalination. Based onthe last five years of data from GWI, the expenditureon total nonthermal energy, i.e., electricity-basedenergy, as a percentage of total cost, is shown inFigure 9. The energy cost has been normalized forthe changing cost of energy (based on the fluctuatingprice of crude oil in the international market). Thehighest percentage is in ECA region, where total

energy forms about 56% of the cost of desalination,and the lowest cost is in the OECD region, where itforms 25% of the cost. The average cost in 2011 was32.2%. Hence, there is scope for improvement inenergy efficiency at least to OECD standards, andthen further improvements due to advances in tech-nology.

Based on historic trends over the last five years,the reduction in energy cost as a fraction of total costof desalination is decreasing at an average of 4.5%per year, with the lowest being in OECD countries(at about 2.8%). Assuming the future trends followthe existing trend, the future electricity-based energycost as a percentage of total cost of desalinationwould follow the trend shown in Figure 10.

Developing Learning Curves

To predict the future of desalination technologywith renewable energy, learning curves of both theenergy component and the nonenergy component,which includes technological and operationalimprovements, were examined. Both these costs arecontrolled by separate learning curves. Assumingthat all future energy needs of the desalination pro-cess can be met by renewable energy, such as solarenergy through PV technology, the cost of futureenergy is controlled by learning curves of PV. The PVtechnology has been well studied and learning curveshave already been developed (IEA, 2000; Breyeret al., 2010). Their analysis has found that, for dataavailable from the mid-1970s to 2010, the PR of PVtechnology is 0.807 or the corresponding LR of PV is0.193 (or 19.3%). This means that the cost of energy

TABLE 2. Calculated Minimum, Maximum, and AverageWater Tariffs at Regional Level for 2010 and 2050.

All values are in 2010 USD/m3.

Region Year Min Max Avg

After RemovingTransport Cost

(USD 0.06/m3/100 km)

AFR 2010 0.038 0.458 0.099 0.0392050 0.055 1.904 0.342 0.282

EAP 2010 0.052 2.002 0.470 0.4102050 0.112 2.998 1.759 1.699

ECA 2010 0.079 0.751 0.278 0.2182050 0.229 1.953 1.063 1.003

LAC 2010 0.166 0.925 0.428 0.3682050 0.453 2.070 1.429 1.369

MENA 2010 0.144 1.607 0.440 0.3802050 0.357 2.544 1.357 1.297

OECD 2010 1.655 2.389 1.994 1.9342050 2.304 3.049 2.757 2.697

SAS 2010 0.051 0.117 0.083 0.0232050 0.092 0.564 0.280 0.220

Note: AFR, Sub-Saharan Africa; EAP, East Asia and the Pacific;ECA, Eastern Europe and Central Asia; LAC, Latin America andthe Caribbean; MENA, Middle East and North Africa; OECD,Organization for Economic Co-operation and Development; SAS,South Asia.

0

2

4

6

8

10

12

14

16

1940 1950 1960 1970 1980 1990 2000 2010 2020

Co

st (

2010

USD

/m3 )

Years

AFR EAP ECA LAC MENA OECD SAS

FIGURE 8. Historic Data on Cost Reduction in Desalination(authors’ calculations based on data from www.desaldata.com).


SOOD AND SMAKHTIN

generation by PV will reduce to 80.7% of the originalprice per doubling of the cumulative production ofPV.

The learning curves for desalination technologyhave not been developed before. Although the regio-nal cumulative production and the costs were avail-able, it was decided to develop a single globallearning curve, because (1) in this age of globaliza-tion, technology develops globally; (2) global data helpin averaging out extreme results; and (3) only globallearning curves exist for PV technology. The learningcurve for desalination was developed by taking outthe cost of energy from the total cost of desalinationand plotting the log of this cost against the log ofcumulative production capacity of desalination, andthis is shown in Figure 11. The PR value for desali-nation technology is 0.71, which translates into LR of

29%. This implies that, for every doubling of cumula-tive production of desalination, the cost of desalina-tion, without considering energy cost, falls to 71% ofits original cost.

Predicting the Future Viability

To predict the viability of meeting future waterdemand by desalination, a “back-calculating” approachwas taken. First, as discussed before, the averagewater tariffs were calculated for different regions(Table 3). These were based on changes in per capitaGDP and the historic relationship between water tar-iffs and per capita GDP. The water tariffs weredivided between the cost that is related to electricity-related energy and the cost that is non-electric energyrelated. The proportion of cost that is related to energy

y = -0.007ln(x) + 0.3621

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2007 2008 2009 2010 2011 2012

Years

AFR EAP ECA LAC MENA OECD SAS AVERAGE Log. (AVERAGE)

FIGURE 9. Trends of Expenditure in Energy in the Desalination Process at Regional Level (Source: www.desaldata.com). AFR,Sub-Saharan Africa; EAP, East Asia and the Pacific; ECA, Eastern Europe and Central Asia; LAC, Latin America and the Caribbean;

MENA, Middle East and North Africa; OECD, Organization for Economic Co-operation and Development; SAS, South Asia.

0.25

0.3

0.35

0.4

0.45

0.5

2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055

Years

FIGURE 10. Prediction of Future Energy from ElectricityExpenditure Composition as a Percentage of the Total

Cost (based on data from www.desaldata.com).

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

14 14.5 15 15.5 16 16.5 17 17.5 18

ln(C

ost/

m3 )

3/DAY)

FIGURE 11. Learning Curves for DesalinationTechnology for Global Data.



was also calculated based on historic trends. Thesecosts were considered to be the viable costs, i.e., if thecost of the desalination process leads to the provisionof water for industrial and domestic water demand, itcan then be considered as a viable solution.

Using the experience curves developed for PV tech-nology, desalination, and Equation (1), the analysiswas carried out to calculate the number of “doubling”of production that is required to bring the cost ofdesalination down to these “viable” levels.

For the PV technology, the initial cost was takenwhen the cumulative production was 1 MW (Breyeret al., 2010). Considering the current cumulativecapacity of 35,000 MW, this relates to about 15 dou-blings of cumulative production, which has alreadytaken place up till 2010. To meet the affordable costcriteria for energy in the desalination process, moredoubling of PV energy production is required. Theenergy use per unit of water produced varies from1.8 kWh/m3 for MED to 4 kWh/m3 for MSF, and4-5 kWh/m3 for RO processes (Khawaji et al., 2008).Due to future improvement in technologies, these val-ues can be further reduced to 2 kWh/m3 (Khawajiet al., 2008). For this analysis, the initial energy con-sumption of 4.5 kWh/m3 was considered, which waslinearly reduced to 3 kWh/m3 by 2050. For desalina-tion technology, the initial cost was taken from 1975,when the technology stabilized (from Figure 2 it canbe seen that, in 1975, the cumulative capacity ofdesalination was about 3 million m3/day, which rep-resents just over 2% of the current capacity; and fromthe trends in the desalination cost in Figure 8, it canbe seen that the cost drops sharply between 1965 and1975 before stabilizing). Table 4 shows the number oftimes the cumulative production of water from desali-nation needs to double to meet the criteria for afford-able desalination.

For the OECD countries, the desalination (withoutthe energy component) can already meet the viablestandards. For other regions, if we consider 2040 ashorizon, other than sub-Saharan Africa, Latin Amer-ica, and South Asia, demand for desalination can bemet with the current technology, whereas till 2020,only 1-4 doubling is required.

Table 5 shows the actual annual global productionrequired for PV in “million MW” and desalinationcapacity in “million m3/day.” The assumption madehere is that the growth in both the industries will beat uniform rate annually. These values have beencalculated using 2010 as a base year. For example,to provide affordable water to the industrial anddomestic market in the Latin America region by2030, the global PV production has to increase at arate of 8 million MW/yr and the global desalinationcapacity has to increase by about 3.4 million m3/dayannually.

TABLE

3.Projected

AverageTariffsof

Dom

esticWater;

Portion

ofElectricEnergyCostandNon

electric

EnergyCost,If

AlltheDem

and

IsMet

byDesalination

(allthetariffsandcostsare

2010USD

foracu

bic

meter

[m3]of

water).

Regions

Projected

WaterTariffs

Electric

Energyto

Tota

lCost

Ratio

Electric

EnergyCost

Nonelectric

EnergyCost

2010

2020

2030

2040

2050

2010

2020

2030

2040

2050

2010

2020

2030

2040

2050

2010

2020

2030

2040

2050

AFR

0.039

0.100

0.161

0.221

0.282

0.326

0.316

0.313

0.310

0.309

0.013

0.032

0.050

0.069

0.087

0.026

0.068

0.110

0.153

0.195

EAP

0.410

0.732

1.055

1.377

1.699

0.341

0.331

0.327

0.324

0.323

0.140

0.242

0.345

0.447

0.548

0.270

0.490

0.710

0.930

1.151

ECA

0.218

0.414

0.611

0.807

1.003

0.592

0.575

0.568

0.564

0.561

0.129

0.238

0.347

0.455

0.563

0.089

0.176

0.263

0.352

0.440

LAC

0.368

0.618

0.869

1.119

1.369

0.411

0.399

0.394

0.391

0.389

0.151

0.247

0.342

0.438

0.533

0.217

0.372

0.526

0.681

0.836

MENA

0.380

0.609

0.839

1.068

1.297

0.320

0.311

0.307

0.305

0.303

0.122

0.189

0.258

0.326

0.393

0.258

0.420

0.581

0.742

0.904

OECD

1.934

2.125

2.316

2.506

2.697

0.267

0.260

0.257

0.255

0.253

0.517

0.552

0.594

0.638

0.683

1.417

1.573

1.721

1.868

2.014

SAS

0.023

0.072

0.122

0.171

0.220

0.337

0.327

0.323

0.321

0.319

0.008

0.024

0.039

0.055

0.070

0.015

0.049

0.082

0.116

0.150

Note:

AFR,Sub-SaharanAfrica;EAP,East

AsiaandthePacific;

ECA,EasternEuropeandCen

tralAsia;LAC,LatinAmericaandtheCaribbea

n;MENA,Middle

East

andNorth

Africa;OECD,Organization

forEconom

icCo-op

eration

andDev

elop

men

t;SAS,Sou

thAsia.


SOOD AND SMAKHTIN

The current analysis is based on the premise thatfuture trends will be similar to the past ones. Asthere are many factors that can affect the future tra-jectory of technology development and it is difficult toaccount for them in such type of analysis, a sensitivityanalysis (SA) of the doubling was carried out. For theSA, the values of PR for PV and desalination werechanged by �5% of the original value calculated andthe water tariff was allowed to fluctuate by 5%. Therange of the number of doubling required is shown inthe parentheses in Table 4 and the correspondingrange of new annual global production required isshown in Table 5. As can be seen, the productionrequired for meeting the cost criteria is very sensitiveto the PR values, especially during the early decades.This is understandable since doubling of a large num-ber leads to a much larger number (as in exponentialgrowth). Even considering the upper limits of thenumbers, regions of the world, other than AFR andSAS, can still meet the future water demand till2050. This implies that the current pace of invest-ment in these technologies needs to continue orimprove to make desalination with renewable energya viable option by 2050.

DISCUSSION AND CONCLUSIONS

The future planning of water resources manage-ment needs “out-of-the-box” solutions to solve theissue of looming water scarcity. As the traditionalsources of freshwater run out in many regions, sea-water or brackish water will have to fill in the gapsin water demand vs. supply. Desalination technologyat market scale has existed for decades, but itremained constrained to a few countries mainlybecause of its high cost. However, as with any othertechnology, it becomes cheaper with time as its

experience in the industry and market share grows.Also, in the case of water, as water scarcity grows,the cost of water and the willingness of people to payfor it will also increase. This study examined the fea-sibility of replacing freshwater supply for the domes-tic and industrial sectors with desalinated waterwithin the 100-km coastal zone globally. It is likelythat both sectors will be willing and able to pay forthe cost of freshwater. This will not only reduce com-petition with the agricultural sector, but would alsoprovide more water to meet environmental waterrequirements. A big part of the desalination cost isthe energy cost. This study considered desalinationcombined with renewable energy. As this involvestwo emerging technologies, i.e., PV technology anddesalination itself, the analysis for this research wasalso broken up into two parts — analysis of costrelated to energy, and cost not related to energy. Thefirst is being “controlled” by the PV technologicallearning curve, and the second — by the desalinationtechnology learning curve.

If energy cost is not a constraint, the desalinationtechnology will reach the stage where it can providewater for the domestic and industrial sectors with 1-8(or 0-10, if PR is allowed to vary by �5%) “doubling”of its production capacity in most of the countries by2020. Except in the region of sub-Saharan Africa,Eastern Europe and Central Asia, and South Asia, by2030 desalination technology (without energy con-straint) is a viable option. In sub-Saharan Africa andSouth Asia, the cost paid by water users is muchlower than in the other regions. By 2050, even inthese regions, desalination can be affordable afterabout 4 � 2 “doublings” of its production capacity,respectively. This should be taken in the context that,since 1975, approximately 7.5 and 10 “doublings”have occurred in cumulative desalination productionin sub-Saharan Africa and South Asia, respectively.From the energy perspective, in all regions other thansub-Saharan Africa and South Asia, a doubling of

TABLE 4. Number of Times the Cumulative Production of PV and Desalination Needs to Double to Meet the Criteria for AffordableDesalination by Using PV Technology. The range shown in the parentheses is the values for �5% of the PR values calculated.

PV Desalination

Region 2020 2030 2040 2050 2020 2030 2040 2050

AFR 24 (16-35) 21 (14-32) 19 (12-29) 18 (11-27) 7 (5-9) 5 (4-7) 4 (3-6) 4 (2-5)EAP 14 (8-23) 12 (7-20) 10 (5-18) 9 (4-16) 1 (0-2)ECA 14 (9-23) 12 (7-20) 10 (5-18) 9 (4-16) 4 (2-5) 3 (1-4) 2 (1-3) 1 (0-2)LAC 14 (8-23) 12 (7-20) 11 (5-18) 9 (4-16) 2 (0-3) 1 (0-2)MENA 15 (9-24) 14 (8-22) 12 (7-20) 11 (5-18) 1 (0-2) <1 (0 to <1) —OECD 10 (5-18) 10 (5-17) 9 (4-16) 8 (3-14)SAS 25 (17-37) 22 (15-33) 20 (13-30) 19 (12-28) 8 (6-10) 6 (4-8) 5 (3-7) 4 (3-6)

Note: AFR, Sub-Saharan Africa; EAP, East Asia and the Pacific; ECA, Eastern Europe and Central Asia; LAC, Latin America and the Carib-bean; MENA, Middle East and North Africa; OECD, Organization for Economic Co-operation and Development; SAS, South Asia; PV, photo-voltaic; PR, progress ratio.



9-12 times (or 4-20, if PR is allowed to vary by �5%)is required by 2040 to bring the prices down to thelevels that are affordable to meet the projected watertariffs. For the other two regions, 19 (12-29 with SA)and 20 (13-30 with SA) “doublings” are required forsub-Saharan Africa and South Asia, respectively, forthe same time frame. In perspective, PV technologyhas shown 15 “doublings” between 1976 and 2010(Breyer et al., 2010). In terms of the absolute num-bers, the global PV production has to grow by lessthan 1 million MW/yr to meet the demand in all theregions except in sub-Saharan Africa and South Asia,but it is highly sensitive to changes in PR value. Simi-larly, except for sub-Saharan Africa, Eastern Europeand Central Asia, and South Asia desalination (with-out energy constraints) can meet the water demandaffordably. For other regions, to bring the cost of desa-lination down, the global capacity of desalinationneeds to increase at a rate of 31.8 (10-95 with SA)(sub-Saharan Africa), 3.7 (0-11 with SA) (EasternEurope and Central Asia), and 56.3 (18-180 with SA)(South Asia) million m3/day annually.

How fast the future growth in production takesplace will depend on the investment (both public andprivate) made in this sector, and also on the policies/incentives given by the governments in different coun-tries to support and encourage these technologies.Since 1970, the global capacity of desalination hasincreased at a rate of about 3 million m3/day annuallyand PV production at roughly 1,000 MW annually,most of the growth taking place in the last two dec-ades. The analysis in this study shows that the futureof desalination to meet the increasing water demandslooks promising. Considering that the nonenergy costof desalination can be met with much fewer doublingof technology, whereas energy-related cost willrequire more doubling, and looking at historic trends,it may be feasible to provide affordable water to mostof the world’s coastal population before the time frameconsidered in this study. Exact predictions are diffi-cult to make as there are many other players (such asR&D investments, interest groups, political will,water-use efficiency) that would influence the futuredevelopment of desalination technology.

The cost of environmental impact of desalinationhas not been considered in this analysis. The envi-ronmental impact can be critical in deciding thefeasibility of a desalination plant. Some of the envi-ronmental issues related to desalination are impacton aquatic organisms due to seawater intake; impacton marine water salinity, dissolved oxygen, high chlo-rine and metal concentration, and temperature dueto disposal of desalination affluent; greenhouse gasesemissions due to high energy use (Dawoud and AlMulla, 2012). The latter will not be an issue withrenewable energy-based desalination but other issues

TABLE

5.AnnualGlobal“N

ew”ProductionReq

uired

from

PV

andDesalination

toMee

ttheCriteriaforAffordable

Desalination

.Therangein

parentheses

show

sthevalues

for�5

%of

thePR

values

calculated.

PV

(million

MW)

Desa

lination

Capacity(m

illion

m3/day)

Region

2020

2030

2040

2050

2020

2030

2040

2050

AFR

50,851(248-117,794,259)

4,170(29-5,666,933)

718(6-654,167)

171(2-111,058)

1,155(316-4,684)

214(64-749)

72(23-230)

32(10-95)

EAP

70(1-23,255)

8(0-1,780)

2(0-258)

<1(0-50)

10(0-33)

(0-3)

ECA

74(1-24,903)

8(0-1,730)

2(0-238)

<1(0-45)

159(50-489)

32(9-91)

10(2-29)

4(0-11)

LAC

66(1-21,545)

8(0-1,830)

2(0-281)

<1(0-56)

26(5-74)

3(0-13)

(0-3)

—MENA

155(3-65,103)

21(0-6,024)

5(0-969)

1(0-201)

18(2-53)

2(0-9)

(0-2)

OECD

5(0-741)

1(0-182)

1(0-58)

<1(0-20)

SAS

129,657(527-395,859,126)

9,218(55-15,830,347)

1,491(12-1,685,650)

343(3-273,508)

2,301(583-10,420)

393(112-1,503)

129(39-443)

56(18-180)

Note:

AFR,Sub-SaharanAfrica;EAP,East

AsiaandthePacific;

ECA,EasternEuropeandCen

tralAsia;LAC,LatinAmericaandtheCaribbea

n;MENA,Middle

East

andNorth

Africa;OECD,Organization

forEconom

icCo-op

eration

andDev

elop

men

t;SAS,Sou

thAsia;PV,photov

oltaic;PR,progress

ratio.


SOOD AND SMAKHTIN

will still be there and need to be considered for sitespecific conditions.

ACKNOWLEDGMENTS

The authors acknowledge the CGIAR Research Program on Cli-mate Change, Agriculture and Food Security (CCAFS) and Water,Land and Ecosystem (WLE) for providing funds to carry out thisresearch study. Most of the analysis was carried out using dataprovided by GWI through their website (http://DesalData.com).

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Can Desalination and Clean Energy Combined Help to Alleviate Global Water Scarcity?