THE POTENTIAL FOR WIND-POWERED
DESALINATION IN WATER-SCARCE COUNTRIES
Master of Arts in Law and Diplomacy Thesis
Submitted by Edward Spang
7 February 2006
© 2006 Edward Spang
http://fletcher.tufts.edu
Abstract
This paper explores the global potential for integrating wind power and
desalination technologies to increase water supplies. Desalination processes allow for
the conversion of abundant salt water to relatively scarce freshwater and therefore
represent great potential for water scarcity alleviation. A major limitation of desalination
is its high energy requirements, and therefore it is useful to explore how renewable
energy sources (such as wind) can be linked into desalination systems for sustainable
freshwater production into the future. Desalination and wind technologies are
summarized in this paper, including growth trends, costs, and emerging technological
advancements. GIS is then used to generate a map of global wind-powered desalination
potential “hotspots”, to give a rough idea where the integration of these technologies
might be the most applicable. The analysis generated a short list of countries that have
the greatest potential for leveraging gains from wind-powered desalination plants,
including: Barbados, Cape Verde, Egypt, Haiti, Libya, Madagascar, Mauritania,
Morocco, Saudi Arabia, South Africa and Yemen. While there are significant limitations
to the data used for this paper, it is hoped that the results of this analysis will generate
discussions and further research on the implementation of wind-powered desalination in
the identified countries, as well as other regions of the globe.
i
Table of Contents
INTRODUCTION
1
WATER RESOURCES OVERVIEW
2
GLOBAL SUPPLY
WATER AND SUSTAINABLE DEVELOPMENT
2
3
DESALINATION
6
TECHNOLOGY BACKGROUND
INTRODUCTION
THERMAL DISTILLATION
MEMBRANE TECHNOLOGIES
COMPARISON OF TECHNOLOGIES
GROWTH AND DISTRIBUTION
GROWTH
DISTRIBUTION
COSTS
EMERGING TECHNOLOGY
6
6
8
8
9
12
12
15
16
19
WIND POWER
21
INTRODUCTION
TECHNOLOGY BACKGROUND
GROWTH AND DISTRIBUTION
GROWTH
DISTRIBUTION
COSTS
EMERGING TECHNOLOGY
21
22
25
25
25
27
29
DESALINATION & RENEWABLE ENERGY
31
OVERVIEW
WIND ENERGY AND REVERSE OSMOSIS
EMERGING TECHNOLOGY AND OPPORTUNITIES
31
34
38
MAPPING GLOBAL POTENTIAL FOR INTEGRATED WIND & DESALINATION
TECHNOLOGY
42
INTRODUCTION
GIS DATA
POLITICAL BOUNDARIES
COASTLINES
42
43
43
43
ii
GLOBAL WIND POWER POTENTIAL
WATER SCARCITY
WATER POVERTY INDEX
GIS METHODOLOGY
ACCESS TO THE COAST
LOW-COST WIND POWER POTENTIAL
INSUFFICIENT WATER SUPPLY (1) – WATER SCARCE COUNTRIES
INSUFFICIENT WATER SUPPLY (2) – WATER POVERTY INDEX
GIS RESULTS
RESULTS SUMMARY
A BRIEF CASE STUDY: THE POTENTIAL FOR HAITI
ANALYSIS
43
44
45
46
46
47
48
49
49
49
50
51
CONCLUSION
55
BIBLIOGRAPHY
57
iii
Introduction
"If we could ever competitively, at a cheap rate, get freshwater from salt water,
that would be in the long-range interest of humanity and would dwarf any other
scientific accomplishments" - President John F. Kennedy, April, 19611
Water is life – a critical substance for the survival of all living organisms on the
Earth. For humans, the services provided by fresh water expand beyond physiological
necessity to include other essential uses: hygiene, sanitation, agriculture, energy,
industry, navigation and recreation. As the human population continues to grow
exponentially, we encounter greater scarcities of water around the world. According to
the United Nations Environment Programme (UNEP):
Two hundred scientists in 50 countries have identified water shortage as one of
the two most worrying problems for the new millennium (the other was climate
change).2
Unprecedented commitment on a global scale to innovate new water technologies and
management systems will be required to 1) preserve the quality of our current supplies, 2)
reduce the demand for water through gains in efficiency, and 3) increase the overall
quantity of freshwater available.
This paper specifically seeks to address the third intervention described above, by
exploring the global potential for integrating wind power and desalination technologies to
increase water supplies. Desalination processes allow for the conversion of abundant salt
water to relatively scarce freshwater and therefore represent great potential for water
scarcity alleviation. A major limitation of desalination is its high energy requirements,
1
2
Gleick 2001
United Nations Environment Programme (UNEP) 2003, http://www.unep.org/wed/2003/keyfacts.htm
1
and therefore it is useful to explore how renewable energy sources (such as wind) can be
linked into desalination systems for sustainable freshwater production into the future.
Both desalination and wind technologies are summarized in this paper, including
growth trends, costs, and emerging technological advancements. These brief descriptions
provide snapshots of the current status of these technologies and their markets, as both
independent and integrated technologies. GIS is then used to generate a map of global
wind-powered desalination potential “hotspots”, to give a rough idea where the
integration of these technologies might be the most applicable.
Water Resources Overview
Global Supply
“Water, water, everywhere, nor any drop to drink”3
Only 2.5% of the total amount of water on the planet is freshwater, of which 74%
is frozen in ice caps and glaciers, 25.7% is underground or in soils, and only 0.3% is
available as surface freshwater.4 Of this available freshwater, it is estimated that humans
withdraw 54% of this water, and water that we are not directly using we are increasingly
polluting as a result of continued economic development and population growth5. As a
result, 40% of the world population is struggling with serious water shortages, with the
majority of this burden falling on people who live in remote rural areas and rapidly
expanding urban areas.6
3
Coleridge, Rhyme of the Ancient Mariner.
UNEP 2003
5
Postel 1996
6
UNEP 2003
4
2
As the global populations and economies steadily expand, the global demand for
freshwater resources will continue to grow. Since 1950, global water use has tripled and
in the next 20 years, it is estimated that humans will require 40% more water than is
currently being used.7 Meanwhile, the existing supply of natural water resources is
declining as a result of increasing water pollution (90% of wastewater in developing
countries is released directly into rivers and streams without treatment) and
overexploitation of groundwater sources (groundwater currently supplies 50% of
drinking water, 40% of industrial water and 20% of agricultural water globally.)8 Finally,
climate change may disrupt current rainfall patterns and regional water cycles around the
globe. These combined pressures suggest increased water scarcity in the future, and a
growing need for a proactive response in the spheres of water policy and management.
Reducing water scarcity can take two forms: augmenting supply or reducing
demand. Historically, the supply side solutions have been pursued with greater vigor, and
although this paper specifically addresses yet another supply-side solution, the author
would like to emphasize the importance of exploring water conservation and demand
management initiatives in conjunction with supply-side interventions.
Water and Sustainable Development
The link between water and sustainable development represents a nexus for
development interventions. Water is intricately related to health, human dignity, gender
empowerment, agricultural production, industrial expansion, transport and environmental
protection. It is estimated that 470 million people (the majority of whom live in
7
8
UNEP 2003
Ibid.
3
developing countries) currently live in water stressed countries and this number will
increase to three billion by 2025.9
At the most basic level of development access to safe water is critical for survival.
In fact, 80% of illnesses and deaths in developing countries are caused by water-borne
diseases, which represent a massive burden on both the ill and those who care for sick
family members (usually women).10 Finally, in areas where water sources are far from
the home, women and children generally shoulder the task of hauling water to the house.
This daily task can often becomes a major obstacle for children to receive adequate
schooling and for women to pursue income-generating opportunities.
The first global attempt to improve access to safe water was the UN-declared
Drinking Water and Supply Decade from 1981-1990. While efforts under this program
expanded services to 816 million people, the population growth that took place over the
same decade meant that there was only a 3% net increase in service.11 The global effort
towards improving water supply was renewed in 2000 as part of the UN Millennium
Development Goals (MDGs) and access to improved sanitation was added to the MDGs
at the Johannesburg Summit in 2002.12 The final version of Target 10 for water and
sanitation under Goal 7 (Ensure Environmental Sustainability) of the MDGs reads as
follows, “Halve, by 2015, the proportion of people without sustainable access to safe
drinking water and basic sanitation.”13
9
UNEP 2003
Ibid.
11
WHO/UNICEF 2000, p7
12
UN 2002
13
Lenton and Wright 2004
10
4
Of the approximately 6 billion people on the planet, 83% (or 5.2 Billion) have
access to safe water, leaving 1.1 billion people struggling to access safe water on a daily
basis.14 The WHO/UNICEF Joint Monitoring Program (JMP) defines “safe water” as
water that comes from an “improved source” as listed in Table 1 below:
Table 1. Improved and Unimproved Sources of Drinking Water15
Improved Sources
Unimproved Sources
Household connection
Unprotected well
Public standpipe
Unprotected spring
Borehole
Rivers or ponds
Protected dug well
Vendor-provided water
Protected spring
Bottled water*
Rainwater collection
Tanker truck water
*Bottled water is not considered improved due to limitations in the potential quantity, not quality, of the water.
As the primary agency responsible for monitoring global progress towards the
Millenium Development Goals (MDGs) in Water and Sanitation, the WHO/UNICEF
JMP has the difficult task of aggregating a massive amount of data from around the world
into a limited set of indicators to represent “access to safe water.” While this monitoring
effort is critical for mapping the progress of nations towards the MDGs, it is less useful
as a snapshot understanding of global access to safe water. For example, a house that is
connected to a water pipe will be regarded as having “access to safe water” even thought
the quality of the water might be poor or the service intermittent. Considering the
potential for this kind of misrepresentation, it is likely that the WHO/UNICEF JMP
numbers might be overestimating the numbers of people with “access to safe water,” and
therefore, the problem may be even more pervasive than the statistics suggest.
Regardless of how the problem is measured, the massive scale of the problem is
evident. The real challenge is to increase the water services available to the
14
15
WHO/UNICEF, 2004
Ibid.
5
approximately one billion people currently without adequate access. Real progress in the
realm of water provision will require the coordinated efforts of governments, foreign aid
donors, NGOs, local institutions and target communities. For these groups to
communicate and plan effectively, they will need to have knowledge of a range of
potential solutions for addressing water shortage. This paper explores the role of
desalination technology as one of these potential solutions.
Desalination
Technology Background
Introduction
The process of generating fresh water from seawater, or desalination, has been in
operation for over 50 years.16 The impetus for the development of this technology is clear
as saltwater makes up 97.5% of water resources on the planet, representing an effectively
limitless source of freshwater in the context of desalination.17 In addition, 40% of the
world’s population lives within 60 km (37.3 miles) of the coast18 suggesting that the
benefits of desalination have the potential to reach a large target population.
However, it is important to state that desalination should not be viewed as the
panacea for the world’s water problems. The utility of desalination is generally
recognized as being limited by its costs, energy requirements and geography. Therefore,
desalination processes should be viewed as a supplement to existing water supplies, and
should only be implemented in conjunction with pollution prevention and demand
16
Wagnick 1998 by Semiat 2000
UNEP 2003
18
UNEP 2003
17
6
management programs to protect and improve the efficiency of use of current water
supplies.
Many desalination technologies currently exist and are in operation at various
scales around the globe, allowing human populations and industries to grow and thrive in
previously inhospitable locations. Two basic technologies are utilized to remove the salts
from ocean water: thermal distillation and membrane separation. See Figure 1 below for a
categorization of desalination technologies. This section addresses only those
technologies identified by the large red boxes, as these are the most widely adopted
desalination technologies. Eventually, the potential of using indirect solar through a wind
energy converter will be discussed.
Figure 1. Categories of Desalination Processes19
19
Oldach 2001
7
Thermal Distillation
Thermal distillation technologies in their various forms all depend on the same
concept: converting saltwater to steam and then condensing and collecting the freshwater
distillate. Thermal distillation units began to be installed in the 1960s at a commercial
scale, or up to 8,000 cubic meters per day.20 The three basic technologies for thermal
distillation include: Multi-Stage Flash (MSF) Distillation, Multi-Effect Distillation and
Vapor Compression.
All three of these distillation technologies are based on converting salt water to
steam in a series of chambers of progressively reduced pressure. The reduced pressure
allows the saltwater to boil at lower temperatures, thereby requiring less thermal energy
input. MSF and MED processes tend to be on a larger scale than VC, although VC units
are sometimes used in combination with the other processes. For schematic drawings of
these three types of thermal distillation, see Appendix I.
Membrane Technologies
Membrane technologies rely on the basic process of using selective membranes to
separate salts from water molecules. Membrane technologies began to be commercially
viable in the 1970s, and include two basic processes: Reverse Osmosis (RO) and
Electrodialysis (ED). See Figure 2 below for a basic illustration of how these two
technologies use membranes to separate salt from water.
20
Buros 2000
8
Figure 2. Selective Membrane Processes: Electrodialysis and Reverse Osmosis21
Both processes require energy inputs to overcome the existing osmotic pressure
between fresh water and saltwater. ED technology is usually limited to brackish feed
water, while RO technologies can be used with brackish waters (BWRO) or seawater
(SWRO). Electrodialysis (ED) was developed about 10 years before RO and uses electric
currents to draw salts through a selective membrane, leaving behind a freshwater effluent.
Reverse Osmosis (RO) relies on forcing salt water against membranes (usually made of
cellulose acetate or aromatic polyamide) at high pressure, so that water molecules can
pass through membranes and the salts are left behind as a briny concentrate.22 For
schematic representations of these two types of membrane technologies see Appendix II.
Comparison of Technologies
The selection of an appropriate desalination technology depends on a range of
variables, including: type of feed water, energy source, quality of freshwater output and
plant size. Table 2 below compares the major technologies based on these variables.
21
22
USAID by Buros 2000
Oldach 2001
9
Table 2. Characteristics of the Major Desalination Processes23
Feed Water
Energy
Process
Type
Source
Multi-Stage Flash
Distillation (MSF)
Seawater
Steam
Multiple-Effect
Distillation (MED)
Seawater
Steam
Vapor Compression
(VC)
Seawater
Electricity
Sea Water Reverse
Osmosis (SWRO)
Seawater
Electricity
Brackish Water Reverse
Osmosis (BWRO)
Brackish
Electricity
Electrodialysis (ED)
Brackish
Electricity
Note: *with energy recovery **without energy recovery
Typical Max
Plant Capacities
(m3/day)
Typical Energy
Requirements
(kWhel/m3)
~10
5,000-60,000
10-14.5
~10
5,000-20,000
6-9
~10
2,400
~350-500
128,000
7-15
4-6*
7-13**
~350-500
~350-500
98,000
45,000
.5-2.5
.7-2.5
Product Water
Quality (ppm
TDS)
As shown in Table 2 above, all processes work well with seawater except ED,
which is limited to treating brackish waters. RO is capable of treating either seawater or
brackish waters. Using RO, brackish waters require significantly less energy to process
and allow for a higher recovery rate than seawater (25-40% recovery for SWRO and 6585% recovery for BWRO)24, so operational costs for SWRO systems tend to be 3 to 5
times greater than BWRO systems.25
Energy sources vary across the technologies, with MSF and MED technologies
relying upon thermal energy and VC, RO and ED processes requiring electricity. The use
of steam for thermal distillation processes allow for the efficient integration of these
technologies with power plants or other industrial processes that produce waste heat.
Alternatively, the electrical input for VC, RO and ED technologies make theses processes
more suitable for integration with electrical generators, including renewable sources such
as wind turbines and solar photovoltaics.
23
Adapted from Loupasis 2002
Oldach 2001
25
Loupasis 2002
24
10
The different processes do not produce the same quality of water. Distillation
processes produce higher quality freshwater, with total dissolved solids averaging about
10 parts per million of total dissolved solids (ppm TDS) in comparison to membrane
processes which produce freshwater with approximately 350-500 ppm TDS (see Table 2
above). The WHO standards for potable water allow for a maximum value of 1500 ppm
TDS.26 So even though the freshwater produced by membrane processes is of lower
quality than distilled water, it is still well below WHO maximum standard for TDS. Some
RO plants include a secondary treatment process to further improve water quality and
remove the taste of salt residue, but this process is not required for health reasons.
Finally, Table 2 shows the typical maximum production capacities for each
desalination technology. SWRO plants demonstrate the greatest maximum capacity with
128,000 cubic meters per day (m3/d) followed by BWRO (98,000 m3/d), MSF (60,000
m3/d), ED (45,000 m3/d), MED (20,000 m3/d), and lowest capacity represented by VC
(2,400 m3/d). It is important to note that these numbers represent typical maximum
capacities, and do not represent actual production limits of each technology. Additionally,
while RO is capable of high capacity production, it is also well suited for small and even
micro-installations (such as individual sailboats at 0.1 m3/d). The RO systems are
modular, so membranes and pumps can be successively added to increase the capacity of
RO installations.
Figure 3 below shows results from a 1998 inventory of desalination plants,
illustrating that MSF technology is the most widely adopted process around the world at
(44% of desalination technology) with RO technology close behind (42%).
26
Ibid.
11
Figure 3. Distribution of Global Desalination Operations by Technology27
This distribution suggests that of the currently available technologies, MSF and RO have
historically been the most preferred technologies for desalination. As the current
technologies continue to be refined and new technologies are developed, it is likely that
this distribution will change in relation to the relative costs of the technologies.
Growth and Distribution
Growth
The installation of desalination technology has grown steadily around the world.
Figure 4 below shows that capacity has increased from essentially 0 to over 22.5 million
cubic meters per day (~6,500 million gallons per day) between 1965 and 1998.
27
IDA 1998 by Buros 2000
12
Figure 4. Total Installed Capacity of Desalting Facilities28
As global demand for freshwater increases and global supplies decrease (as a
result of pollution, saltwater intrusion and groundwater overexploitation), it seems that
this growth trend in the desalination market will continue well into the future.
Additionally, advances in desalination technology and increasingly competitive
production costs will likely add to the potential for future growth.
Among the various technologies for desalination, Reverse Osmosis (RO) seems to
be growing at the fastest rate (approximately 12% annual increase or 200% overall
increase between 1988 and 1997) as evidenced by Figure 5 below. The rapid growth
potentially signifies technological advancements and reduced energy requirements that
have lowered the cost of RO relative to the other methods for desalination (see section on
Costs below.)
28
IDA 1998 by Buros 2000
13
Figure 5. Distribution of Desalination Capacity by Type of Technology29
Membrane-based desalination plants generally require less time for construction
than thermal plants. Large MSF installations can take between three to five years, while
large RO plants can be constructed in 18 to 24 months.30 Meanwhile, small-scale RO
operations can be installed in four to five weeks.31 The rapid construction of small RO
plants is especially interesting for development and relief efforts, where freshwater
supplies must be delivered to needy populations (such as displaced refugee) on relatively
short notice.
Appendix III shows a table comparing RO technology to MSF and MED
distillation technologies. According to this source, RO technology has a comparative
advantage to the other methods relating to: total energy requirements, low capital costs,
and high potential for further improvement. As discussed earlier, the modularity of RO
29
IDA 1998 by Buros 2000
Loupasis 2002
31
Loupasis 2002
30
14
system designs allows for this technology to be applied flexibly to match the demand
requirements for various sites. For these reasons, in addition to the appropriateness of
linking RO to wind power (discussed later), RO technology will be the focus of this
paper. For a more detailed comparison of desalination technologies, see Appendix IV.
Distribution
The International Desalination Agency publishes an inventory of all existing
desalination plants with pertinent information relating to location, type of process used,
feed water characteristics, cost of production, quality of water produced, type of energy
input and other pertinent variables. However, due to financial constraints, this author
could not afford to purchase the data set, so the distribution information below is an
incomplete set of installations around the world. Table 3 below shows desalination
installations in seven countries. Of these countries, Saudi Arabia has 48.8% of the total
installed capacity and the US has the second greatest capacity at 26.8%. It is also
important to note that 48.5% of the capacity in these countries is covered by MSF
technology, followed by RO technology at 39.8%.
Table 3. Installed Desalination Plants Capacity (in thousands of m3/d)32
Country
Saudi Arabia
USA
Kuwait
Libya
Spain
Italy
Algeria
Total
Percent (%)
32
MSF
2700
50
350
400
56
200
60
3816
48.5
MED
50
50
0.6
VC
50
130
40
75
30
325
4.1
Adapted from Loupasis 2002
15
RO
1000
1600
50
130
230
40
80
3130
39.8
ED
94
280
67
45
50
16
552
7.0
Total
3844
2110
400
597
371
365
186
7873
100
%
48.8
26.8
5.1
7.6
4.7
4.6
2.4
100
Table 4 below shows the composition of the current water supply in a set of ten
water scarce countries. As evidenced by the data, Kuwait and Qatar are 100% dependent
on desalination for municipal and domestic water supply. Additionally, the water scarce
countries of Barbados, Jordan and Yemen are 100% dependent on groundwater sources,
suggesting a future need for desalination plants to replace the supplies from depleted
aquifers.
Table 4. Current of Municipal, Domestic, Water Supply in Water Scarce
Countries33
Costs
It is difficult to compare the costs of desalination installations at an aggregated
level because the actual costs depend on a range of variables specific to each site. The
type of feed water, desalination technology, production capacity, water quality standards,
local construction costs (materials and labor), and energy costs all strongly influence the
final cost. However, energy requirements necessary to separate salt from water tends to
be the greatest contributor to costs, whether through thermal processes or high-pressure
membrane separation. According to Table 2 (pg. 9) RO technologies with energy
recovery systems require the least amount of energy to process seawater (at 4-6 kilowatt
33
FAO Aquastat 1997 by Bremere, et. al., 2001
16
hours per cubic meter, kWh/m3,) compared to all other technologies. Even without
energy recovery systems, RO remains competitive with the other technologies in terms of
energy usage. Finally, if brackish water is included as a potential input, then the energy
requirements for RO drop significantly and are basically equivalent to using ED
treatment for brackish water (0.5-2.5 kWh/m3).
See Appendix V for more detailed cost comparisons between the different
desalination technologies. The data show that the costs of RO systems ranging from
approximately 0.90 cents per gallon (US$2.37/m3) for a plant with capacity of .03 million
gallons per day (mgd) to 0.21 cents/gallon (US$0.55/m3) for a 30 mgd capacity system.
RO remains the cheaper option at both low and high production capacities in comparison
to the other technologies. However, it is important to restate that desalination cost data is
extremely site specific, so the comparison of costs across the different technologies is not
as straightforward as it may appear in the Appendix V table.
Figure 6 below shows the cost composition for a standard SWRO installation.
While energy clearly represents a significant portion of the total cost (26%), the greatest
cost influence actually arises from the fixed costs (mostly capital costs at 31%).
However, it is important to note that RO technology has the lowest fixed capital costs in
comparison to MSF and MED technologies (see Appendix III). Regardless of this fact,
the importance of fixed capital costs to the overall cost composition once again
demonstrates the importance of economic parameters, such as the interest rate and
discount rate, to determining overall installation costs.
17
Figure 6. Cost Composition for a Typical34 Seawater RO Plant35
The development of cheaper and more effective membranes, improved energy
efficiency systems, and other technological advancements has allowed the cost of SWRO
to decline significantly. Figure 7 below illustrates the dramatic reduction in costs (66%
reduction) across a set of actual SWRO installations around the world.
Figure 7. Cost Evolution of the SWRO Process36
34
Based on SWRO plant Sabha A, Israel.
Ebensperger and Isley 2005
36
Ibid p15.
*Projected estimate
35
18
Costs might be further reduced through the implementation of subsidies
specifically for desalination projects. The subsidies can be viewed as investments in
research or as a catalyst to help bring the sector to scale so that further cost savings can
be realized. In the US, the “2004 Desalination Energy Assistance Act” was implemented
to provide incentive payments to selected desalination installations to reduce the actual
electricity costs.37 Finally, local costs for desalination installations in developing
countries might be further reduced through development assistance programs and NGO
projects.
Emerging Technology38
Reverse osmosis technologies have continuously improved over the years,
resulting in the fastest growth of this desalination technology relative to all the others (see
Figure 5 on p. 14). RO systems can be made more efficient by advancements in various
components of the process, including: pump design, energy recovery, membrane
thickness, the chemical sensitivity of membrane materials, and pretreatment.
High-pressure pumps drive the RO process by forcing the seawater against the
selective membranes at a pressure sufficient to overcome osmotic pressure, thereby
allowing the freshwater to separate from the salty feed water. These pumps represent the
majority of energy required for the RO process, so the development of more energy
efficient pumps would save maintenance by producing more fresh water per unit of
energy.
37
Ebensperger and Isley 2005
This paper focuses specifically on RO desalination, so while there have been technological advances in
all types of desalination technologies, this section only addresses technological advances relating to RO.
38
19
Similarly, the recovery of energy from the pressurized brine concentrate saves
energy costs and increases efficiency. In a typical RO plant 40% of the feed water is
converted to freshwater, leaving 60% of the pressurized water as effluent.39 In other
words, the leftover salty water is still pressurized and the energy of this pressurized
wastewater can be recaptured within the system. Some advances have already been made
in this area through the installation of energy recovery turbines and piston systems in RO
plants. See Appendix IIB for a schematic drawing of an RO plant with an energy
recovery turbine as compared to a plant without this technology in Appendix IIA.
The quantity of freshwater produced by pushing salt water through a membrane is
inversely related the thickness of the selective membrane.40 Therefore, thinner
membranes allow for a more efficient production of freshwater. While current membrane
“skins” are already quite thin, ranging from 50-300 nanometers (nm) thick, any
advancement in creating even thinner membranes will increase the economic efficiency
of the system.41
As mentioned previously, most RO membranes are made of either cellulose
acetate (CA) or aromatic polyamide (PA). While these membrane materials function
similarly as selective membranes, they both have particular chemical sensitivities that
threaten the longevity of the membranes. The quality of CA membranes are compromised
when exposed to pH levels outside the range of 3.5 to 6.5, while PA membranes
deteriorate as a result of exposure to chlorine.42 Therefore, if new membranes are
39
Oldach 2001
Ibid.
41
Ibid.
42
Ibid.
40
20
developed that have greater resilience to variable chemical conditions, it will reduce costs
by increasing the longevity of RO membranes.
Membranes are also sensitive to other chemical factors, temperature, pressure and
biological agents.43 To prevent membrane fouling or rupture, feed water is generally
pretreated, which can include adjusting pH and various filtration processes. Costs can be
reduced and efficiency of freshwater production increased by any advances in
pretreatment technologies or the development of membranes that require less intensive
pretreatment processes.
Wind Power
Introduction
The operating principle behind wind generators is the conversion of the kinetic
energy of wind into electricity. The blades of a wind turbine capture this kinetic energy
from wind to spin a rotor that can be used to generate electricity. The power of the wind
(P) is determined by three variables: the density of air (, in kilograms per cubic meter),
the area of the windmill blades (A, in square meters), and the wind velocity (V, in meters
per second). The relationship between wind power and these variables is given in the
following formula:
As evidenced by this formula, wind speed has the greatest influence on
determining potential wind power (wind power determined by the wind speed cubed doubling the wind speed increases potential wind power by a factor of eight.)
43
Oldach 2001
21
Considering wind speeds (and directions) can be highly variable on differing time scales,
designing wind generators that can withstand periodic gusts of high velocity winds is a
critical aspect for the feasibility of wind power systems. Additionally, intermittent winds
mean variable power production based on exogenous factors, which is a general criticism
of the potential for expanding wind power generation.
Furthermore, it is important to note that while the formula above does provide a
value for wind power, this is not the value of the wind power captured by the wind
generator because the blades do not stop the wind completely (a necessary result of
complete conversion of kinetic energy to electricity.) In 1919, Albert Betz, a German
physicist, calculated the maximum wind power conversion potential of wind turbines to
be 59.3%, known as the Betz limit.44 However, a recent study has shown that the Betz
limit may have been an overestimation because Betz neglected to incorporate the
curvature of fluid streams (such as air currents) into his calculations. This same study
suggests that the practical conversion rate at maximum efficiency is closer to 30% for
typical, horizontal-axis wind turbines.45
Technology Background
Humans have harnessed the power of wind for production purposes for thousands
of years. The earliest evidence showing the use of wind-powered mills in China around
3000 BC and wind-powered water pumps in Babylon around 1600 BC.46 Large-scale use
in Europe began in the 12th century for milling and irrigation, and in the case of the
44
Gorban et. al. 2001
Ibid.
46
Oldach 2001
45
22
Netherlands, for massive drainage of land areas below sea level.47 Despite the broad
application and development of this technology over thousands of years, it largely
dropped out of favor during industrialization as fickle winds were replaced with more
reliable fossil fuels.
In the 1970s, American engineers experimented with large, lightweight wind
turbine designs, but their attempts generally failed as the machines were commonly
destroyed by heavy winds.48 In the mid-80s, Danish wind companies (such as Vestas
Wind Systems) began to build heavier, more rugged models that have become the global
standard for turbine designs. 49 A typical modern turbine has three blades on a horizontal
axis, spanning 77 meters in diameter and capable of producing 1500 kW.50 Further
technological advances have included computer systems that automatically adjust blade
position and speed to produce electricity as efficiently as possible and also protect the
turbine during high winds.51
As mentioned above, the majority of modern wind turbines operate on a
horizontal axis, but vertical-axis turbines can also be used. An advantage of vertical-axis
turbines is that they do not have to be manually or digitally oriented towards the wind,
but rather can utilize wind from any direction without adjustments. Additionally, some
studies suggest that vertical-axis turbines have the potential to more efficiently convert
wind power into electrical energy (35% conversion rate as opposed to 30% maximum for
47
Oldach 2001
Fairley 2002
49
Ibid.
50
Archer and Jacobson 2005
51
Ibid.
48
23
horizontal–axis turbines).52 See Figure 8 below for a representation of both horizontal
and vertical axis wind turbine designs.
Figure 8. Schematic Representation of Horizontal and Vertical Axis Wind
Turbines53
Site selection plays a critical role in the viability of wind power production. The
importance of wind speed was discussed as a critical determinant of wind power potential
in a region. Not only does the local wind velocity need to be high, but it also needs to be
somewhat consistent for a wind generator to be economically efficient. Therefore, having
wind speed measurements throughout the year for many years is important data necessary
for determining the viability of a wind power site.
In addition to consistent, high velocity winds, proper sites need to be relatively
free of obstructions, such as: large buildings, forests, rocky cliffs, etc. A large obstruction
can create a 200-300m “wake” that can reduce wind speeds at a downwind turbine by up
52
53
Gorban et. al. 2001
AWEA 2005, www.awea.org/faq/basiccf.html
24
to 10%.54 Consequently, the potential for offshore wind farms becomes obvious as the
coastal shelves provide a massive resource of relatively uninterrupted wind space.
Growth and Distribution
Growth
Despite some of the difficulties associated with wind power mentioned above the
global wind capacity has increased steadily over the decade. Figure 9 below shows that
capacity increased from approximately 5,000 megawatts (MW) in 1995 to nearly 50,000
MW in 2004. This tenfold increase in ten years represents an annual growth rate of
approximately 26%. From 2003 to 2004, total capacity increased by approximately 8,000
MW.
Figure 9. World Wind Capacity55
Distribution
The use of wind power is not evenly distributed around the world. In fact, nearly
three quarters (72%) of all installed wind power capacity is in Europe as shown in Figure
10 below.
54
55
Oldach 2001
AWEA 2004
25
Figure 10. Regional Distribution – Installed Wind Power Capacity in 2004 (in %)56
Appendix VI provides more detailed information about the global distribution of wind
power, including data on how many MW of wind power were added in each region in
2004. Note that India and China, which collectively represent a significant proportion of
the developing world, seem to be aggressively installing wind power systems. China
added 197 MW in 2004 for a 35% increase over previous capacity and India added 875
MW in 2004 for 41% increase over previous capacity.
The uneven global distribution of wind power availability is partially determined
by the availability of sufficient wind sources, but more importantly, it seems that the
political and economic landscapes of the region influence the adoption of the technology.
For example, the countries in Europe have made a stronger political commitment to
environmental agreements as evidenced by participation in the Kyoto Protocol, whereas
the North American region (and more specifically the U.S.) have erred on the side of
56
adapted from GWEC in AWEA 2004
26
protecting the economy over the environment by relying on conventional fuels for power
production.
It is also important to note that the relatively undeveloped regions of the Pacific,
Latin America & the Caribbean, and Africa have the lowest installed capacities for wind
power generation, totaling only 6% of world capacity. It seems logical that the greater
initial capital costs of wind power might be a barrier for adoption of this technology in
less developed countries. Of course, these regions also have less total energy available
per capita than the developed countries. This suggests that there is great potential to
expand wind power in these countries, not only as a supplement energy structure, but also
as a primary source for areas that are currently without any access to an electricity
network.
Costs
The cost effectiveness of wind generators is primarily influenced by the wind
resource availability of a proposed site and the economic parameters that influence
capital costs.57 As mentioned above, available wind power depends mainly on the local
wind speed – more electricity can be produced in areas with consistent, high-velocity
winds. Wind generators tend to have high initial capital costs, but low operating costs
because of the lack of fuel costs. Therefore, the economic parameters related to the cost
of capital and interest/discount rates are significant variables in the cost calculations.
Costs less than US $0.05 per kWh have been achieved for some grid-connected
wind generators, and costs of approximately $0.03 per kWh are projected for a wind
57
Oldach 2001
27
installation in Scotland in a region that has consistent, high-speed winds.58 Neither of
these cost estimates includes the cost of power storage, which would significantly
increase the estimates.
These costs continue to decrease as advancements are made in the design
technology and the sector continues to grow and gain from economies of scale. By one
estimate, manufacturers of heavy-duty wind turbines have reduced costs fourfold since
1980.59
Appendix VII provides cost estimates of wind power and other renewable energy
sources as compared to nuclear energy and fossil fuels. Onshore wind systems cost about
3 to 5 cents per kilowatt hour (kWh) and offshore wind systems are double the cost at 6
to 10 cents/kWh. However, these costs are projected to drop by 2020 to approximately 2
to 3 cents/kWh. Fossil fuel costs are estimated at 2 to 4 cents/kWh for natural gas and 3
to 5 cents/kwh for coal. It is likely these costs are underestimated considering the costs of
fossil fuels rose dramatically in the last year (the price of a barrel of oil hit an all-time
high of $70.85 in August 2005).
Furthermore, these estimates for fossil fuels most likely do not include externality
costs associated with fossil fuel dependent systems, which may include the health costs
from particulate air pollution and costs associated with greenhouse gas emissions and
climate change. Additionally, countries without oil reserves are forced to import oil,
thereby spending valuable foreign exchange for ongoing energy costs. With an
operational wind sector, it is possible for a country to not only reduce dependence on
foreign oil, but also export wind-generated electricity to neighboring countries.
58
59
Oldach 2001
Fairley 2002
28
Considering the burden of costs for wind power fall primarily in the early capital
costs, one-time capital-related subsidies might be an effective policy mechanism for
governments attempting to reduce their carbon emissions. Specifically, under the Kyoto
Protocol there are opportunities for development assistance in developing countries for
renewable energies under the Clean Development Mechanism (CDM), described below:
Under the CDM, an industrialised country with a GHG [Greenhouse Gas]
reduction target (an Annex B country) can invest in a project in a developing
country without a target (non-Annex B), and claim credit for the emissions that
the project achieves. For example, an industrialised country may invest in a wind
power project in a developing country that replaces electricity that would
otherwise have been produced from coal. The industrialised country can then
claim credit for the emissions that have been avoided, and use these credits to
meet its own target. For industrialised countries, this greatly reduces the cost of
meeting the reduction commitments that they agreed to under the Kyoto
Protocol.60
If national government subsidies were to be successfully implemented, then the costs of
installing wind power are further reduced in relation to fossil fuel energy production.
Furthermore, according to the Worldwatch Institute, nearly half a billion dollars of
development assistance is transferred annually to developing countries for renewable
energy programs (with $151 million delivered specifically for wind programs in 2003).61
With this scale of support, there is clearly great potential for wind power in the context of
global development.
Emerging Technology
Wind energy technologies continue to advance and new prototypes may
contribute to reduced costs of wind energy production. Strategies for improving
60
61
CDM Watch 2005, www.cdmwatch.org/about-cdm.php
REN21 2005
29
performance include making the turbine blades lighter, further developing vertical access
technologies and improving power storage systems.
A company in Washington State, Wind Turbine, designed a wind generator with
blades that are approximately 40% lighter than standard turbine blades and it is estimated
that these lighter blades could reduce capital costs by up to 20-25%.62 Lighter wind blade
designs have historically failed in strong winds. The Wind Turbine design team sought to
avoid potential damage by making to adjustments to the conventional wind generator
design. First, they placed the blades on hinges to allow flexibility for reduced drag during
high winds.63 Second, the blades face downwind, rather than upwind, so they have room
to flex backwards without striking the turbine tower and they are able to adjust
automatically to changing wind directions.64 Further prototypes for lighter turbine design
include the use of only two blades per turbine, rather than the conventional three blades.
As mentioned previously, wind generators with vertical axis turbines (see Figure
8 on pg. 23) might be able to convert wind energy into electrical energy at a greater
efficiency than horizontal axis turbines (35% conversion potential for vertical axis
systems as compared 30% for horizontal axis systems).65 An increase in 5% of energy
production would significantly reduce the investment cost per kWh.
A drawback to wind energy production is the variable electrical production rates
based on changing wind speeds. For wind power to become a more viable option on a
global scale, better power storage systems will need to be developed to create a more
consistent supply of wind energy. The development of advanced batteries will allow for
62
Fairley 2002
Ibid.
64
Ibid.
65
Gorban, et. al. 2001
63
30
efficient power storage in the future, but these technologies have not yet matured and
require further development.
Desalination & Renewable Energy
Overview
The coupling of wind energy and desalination systems holds great promise for
increasing water supplies in water scarce regions. An effective integration of these
technologies will allow countries to address water shortage problems with a domestic
energy source that does not produce air pollution or contribute to the global problem of
climate change. Meanwhile the costs of desalination and renewable energy systems are
steadily decreasing, while fuel prices are rising and fuel supplies are decreasing. 66
Finally, the desalination units powered by renewable energy systems are uniquely suited
to provide water and electricity in remote areas where water and electricity infrastructure
is currently lacking.
The study of the potential interface between desalination and renewable energy
technologies has increased significantly in the last five years. Considering that the energy
requirements for desalination continues to be a highly influential factor in system costs,
the integration of renewable energy systems with desalination seems to be a natural and
strategic coupling of technologies.
Renewable energies can power desalination plants through three types of energy
media: thermal (heat), physical (shaft) and electrical. Figure 11 below shows the types of
desalination technologies most appropriate for the various sources of renewable energy.
66
Tzen 2005
31
The red box outlines the integration of wind power and desalination systems, which is the
focus of this paper.
Figure 11. Desalination Technologies Available for Renewable Energy Sources67
PV = Photovoltaic Solar, RO = Reverse Osmosis, ED = Electrodialysis, MVC = Mechanical Vapor Compression, MED
= Muti-Effect Distillation, Multi-Stage Flash Distillation, TVC = Thermal Vapor Compression
Considering the costs and effectiveness of both desalination and wind energy
technologies are highly site specific, when these technologies are integrated the site
location becomes even more critical for a successful installation. The quote below
summarizes the variables that influence a renewable energy-based desalination plant:
The viability of any RES [Renewable Energy Systems] desalination combination
will mainly depend on:
• the renewable energy potential at the particular site and the form of useful
energy which is available after conversion from renewable sources, be it
thermal, mechanical, electrical.
• the required production capacity from the desalination plant; this capacity
somehow determines the size of the energy collection subsystem.
• the availability of maintenance and experienced personnel for plant operation
at the particular site.
• the total system cost.68
Table 5 below shows the relationship between various energy inputs and criteria
for desalination technologies. This analysis suggests that while wind is well suited for
desalination process requiring electrical power, wind energy can be problematic as an
energy source because it is highly location dependent and has intermittent power output.
67
68
Adapted from Tzen 2005
Loupasis 2002, p21
32
Table 5. Evaluation of renewable energy technologies69
Note: 3 = excellent compliance with criterion; 2 = good compliance with criterion; 1 = poor compliance
with criterion.
However, Table 5 seems to overestimate the problem of wind predictability. While wind
is intermittent, it is somewhat predictable as long as there is sufficient historical wind
data. Given thirty years of wind speed data, it is reasonable to assume an average annual
wind velocity, and therefore calculate potential annual energy output.
As a result of these many influential criteria for determining the best combination
of renewable energy (RES) and desalination technologies, there is a broad range of
existing installations of RES desalination facilities. As evidenced by Figure 12 below,
wind-powered RO systems make up approximately 19% of total RES desalination
facilities, second only to photovoltaic-powered RO units (32%).
69
Oldach 2001
33
Figure 12. Distribution of Renewable-Powered Desalination Technologies70
Wind Energy and Reverse Osmosis
An important consideration for wind-powered desalination project design is
whether to have an autonomous (off-grid) or grid-connected system. This decision will be
heavily based on the local context, such that sites close to larger population centers can
use grid energy as a backup to the renewable energy source. Alternatively, remote
communities might not have any substantial electrical infrastructure, so a standalone
system would be better suited for this type of environment.
An advantage of grid connection is that the desalination system can continue to
operate in low winds, and can provide a more dependable supply of energy in general.
Additionally, the system could be set up so that any residual wind energy not used for
desalination can be sold back to the grid, thereby lowering operational costs by
generating operational revenue.
70
Adapted from Tzen
34
For autonomous wind-powered desalination, a power storage or backup generator
may be required to continue operations in periods of reduced wind. This additional
system is required because wind power varies with available winds, but most current
desalination systems are currently designed to operate with consistent energy input.71 An
affordable and effective power storage system would be more desirable than a backup
generator because residual wind energy could be conserved and used rather than
introducing a system that requires fuel sources.
In some cases, fossil fuel systems have been avoided by coupling wind energy
with photovoltaic (PV) systems as an energy backup, but PV systems are also subject
variable energy output.72 In other words, in periods of low wind and low solar energy
availability (nighttime) the desalination system would lack sufficient energy input.
However, as mentioned in the Emerging Technologies section below, there are currently
designs that allow for variable energy input for desalination operation, thereby precluding
the need for back-up generators and energy storage.
Regardless of the difficulties associated with intermittent power production, it
seems that wind-power desalination represents a promising coupling of innovative
technologies (see quote below).
However, the prospects of this combination [wind-powered desalination] are high
mainly due to the low cost of wind energy. The operational experience from early
demonstration units is expected to contribute to improved designs and a large
number commercial systems are expected to appear in the market place soon.73
71
Loupasis 2002
Tzen 2005
73
Loupasis 2002, p26
72
35
In fact, the intermittent nature of wind energy is uniquely suited for water-based
applications (such as desalination and pumping) because the water can be processed and
stored in periods of high winds and the water stored in reserve can be used during periods
of low winds. Effectively, the water storage system acts as a battery, but with an
efficiency of nearly 100%.
An additional study explores the relationship between renewable energy systems
and desalination plants based on plant capacities. Table 6 below suggests that windpowered RO installations are recommended for small (1-50 m3/d) and medium (50-250
m3/d) capacities, but for larger capacities wind-powered vapor compression (VC) systems
are recommended.
Table 6. Recommended Renewable Energy–Desalination Combinations74
These results are somewhat puzzling given that VC units were identified as
having significantly lower maximum production capacities (2,400 m3/d) than RO
74
Oldach 2001
36
systems (128,000 m3/d).75 Table 6 above classifies anything greater than 250 m3/d as
“large”, so VC technologies can be considered as having a “large” capacity in this
analysis. This suggests that the intermittent availability of wind production imposes a
greater limit on RO units than VC units, and this makes sense considering that
membranes are designed to work at a specific, optimal capacity.76
However, given the flexible, modular structure of both technologies (membranes
can be added to increase desalination capacity and turbines can be added to increase
power capacity), it seems that there might be a greater potential for large-scale windpowered facilities than Table 6 suggests, especially in the context of any technological
advances that address the intermittent availability of wind speed.
An interesting synergy exists between the technologies in relation to coastal
geographies. Clearly desalination plants processing seawater gain from being situated
close to the water, both for easy access to feed water as well as easier disposal of the
briny concentrate. While wind systems certainly gain from relatively consistent coastal
winds, the real advantage comes from the recent development of offshore wind
technologies. As mentioned previously, wind energy can be significantly reduced by the
presence of large obstructions near a site. Offshore technologies allow the turbines to be
located miles offshore, thereby reducing dramatically the presence of any potential wind
dampening obstructions. A project in Denmark completed in 2002, involved the
75
76
See Table 2 p. 10
Oldach, 2001
37
installation of 80 wind turbines (160 MW total)77 between 14 and 20 km offshore and
able to power approximately 150,000 Danish households.78
Emerging Technology and Opportunities
The disconnect between the variable power production of wind and the need for
consistent energy input for most desalination systems was mentioned earlier. This
relationship is important to address to improve the efficiency of wind-powered RO units.
If RO units could be designed to respond effectively to variable energy input, then the
need for backup energy storage or generators could be replaced by water storage systems
at a significantly reduced cost. In other words, the desalination units would operate at
variable capacities based on the available wind. During times of high wind, excess water
could be stored in a tank for use when winds fail. Therefore, the water storage system
effectively becomes an energy storage system (a battery) and access to water becomes
more consistent, no longer relying on the immediate availability of winds.
In fact, a company based in Germany, ENERCON GmbH, has addressed this
specific limitation of RO technology. As a company focused primarily on wind energy
products, ENERCON’s operations have expanded to include desalination technologies.
They have developed an RO technology that involves a piston system used for energy
recovery that also enables variable levels of energy input. See Figure 13 below for a brief
description and a graph illustrating ENERCON’s “flexible operation range” desalination
technology (note: the y-axis units should be cubic meters per day, m3/d).
77
78
REN21 2005
Fairley 2002
38
Figure 13. ENERCON: Flexibility in Power Supply79
This technological development for energy recovery and flexible energy input
allows for cost savings and an easy integration with a wind generator. Additional
developments by ENERCON include readymade modular RO installations that
substantially reduce initial capital costs, automated operation for reduced labor costs,
pretreatment systems that do not require input chemicals and remote monitoring. The
collection of these technological innovations has the potential to dramatically improve
the integration of wind power and RO technologies if it is able to perform as well as the
company claims.
In addition, in the context of international development, the ENERCON modular
concept and automated operation create potential for these units to be installed quickly in
79
ENERCON 2005, www.enercon.de
39
remote and underdeveloped coastal areas (see Table 7 below). If coupled with wind
power, the installation of these units could represent long-term investments in
development in areas previously burdened by scarce water supplies. See Appendix VIII
for an entire brochure on ENERCON’s desalination program.
Table 7. ENERCON Modular Installation Options80
Technological advancements aside, it is also important to examine institutional
developments for the support of RES desalination systems. Institutions can expedite the
adoption of innovative technologies through efforts in research and development,
knowledge sharing, political pressure and seed funding. In relation to RES desalination
programs, two institutions have surfaced since 2003: ADIRA and ADU-RES.
Project ADIRA (Autonomous Desalination system concepts for seawater and
brackish water In Rural Areas with renewable energy - Potential, Technology, Field
Experience, Socio-technical and Socio-economic impacts) was formed in conjunction
80
ENERCON 2005
40
with MEDAWARE81 and co-funded by the European Commission.82 Led by FraunhoferISE of Germany and in collaboration with Turkey, Spain, Greece, Jordan, Egypt,
Morocco and Cyprus, the intention of the five-year project (August 2003 – August 2007)
is to install a series of small autonomous desalination units in the partner countries using
existing technology. While final reports on the project are not yet available, the project
demonstrates significant commitment by the partner countries and the European
Commission to RES desalination technology.
The Coordination Action for Autonomous Desalination Units based on
Renewable Energy Systems (ADU-RES), a consortium of 8 Mediterranean countries and
various desalination and renewable energy institutes and enterprises, was also formed
through a contract with the European Commission.83 In just over two years of duration
(April 2004 – October 2006), the project has four primary goals: Further Development of
R&D, Cost Analysis, Formulation of Policy Initiatives, and Political Dialogue and
Dissemination.84 This project represents another promising effort towards elevating
knowledge of RES desalination units. However, it is important to note that both
organizations are heavily based in the Mediterranean region, and there seems to be little
discussion for the potential of these technologies in the developing countries. See
Appendix IX for the flyer from an ADU-RES-sponsored 2005 conference in Tunisia.
81
MEDAWARE - Development of tools and guidelines for the promotion of the sustainable urban
wastewater treatment and reuse in the agricultural production in the Mediterranean countries
82
Project ADIRA 2005, www.adira.info
83
Project ADU-RES 2005, www.adu-res.org
84
ADU-RES 2005
41
Mapping Global Potential for Integrated Wind &
Desalination Technology
Introduction
As mentioned above, the use of both wind power and desalination technologies
are growing in absolute terms, as well as geographically. Meanwhile, the cost of
implementing both of these technologies is decreasing.
Additionally, the global
population continues to grow, creating increased demand for both energy and water
resources. Assuming all of these trends continue, it is likely that the integration of these
two technologies will become an attractive option for increasing regional water supplies
by producing freshwater from seawater.
However, the potential for these technologies is not evenly spread across the
globe. Regions that are not located close to the coast will not have an easily available
supply of seawater for conversion to freshwater (the conversion of brackish groundwater
in interior regions is beyond the scope of this paper.) Furthermore, the availability of
powerful winds is clearly necessary for a wind power station to be economically
effective. Finally, countries that already have sufficient per capita water supplies will not
require alternative technologies for further supply augmentation.
Potential “hotspots” for the implementation of wind-powered desalination can be
determined by identifying regions that meet all the restrictions mentioned above: access
to the coast, sufficient wind power and scarce water supply. Geographic Information
Systems (GIS) is the ideal tool for identifying these wind-powered desalination (WPD)
hotspots because it allows the user to perform analyses based on spatial reference data.
The GIS methodology for performing this type of analysis is outlined below.
42
GIS Data
GIS analysis involves the integration of data as georeferenced map layers to
determine spatial trends in the data. In this study, there are four critical map layers
required to determine WPD hotspots:
1.
2.
3.
4.
A map of the political boundaries of all countries in the world.
A map of all the coastlines in the world.
A map of global wind power potential.
A map indicating countries with insufficient water supply.
Political Boundaries
The political boundaries map simply shows the borders of all countries of the
world. The data for this map layer comes from the GIS software company, (ESRI) as part
of the basic MapInfo software package.85 This map serves as the base map to which all
other data is georeferenced, so that there is a common spatial coordinate system across all
data sets. Each data set will is overlaid or applied to this map for the final spatial analysis.
Coastlines
The coastline map also comes from the data set included with the ESRI MapInfo
software.86 This map shows all the coastlines of the world, including both continental and
island coasts.
Global Wind Power Potential
A team of researchers at Stanford University collected surface wind speed data
from 7,753 surface wind measurement stations located around the world and calculated
the estimated wind speed at 80 meters altitude at the same locations.87 The researchers
85
ESRI 2005
Ibid.
87
Archer and Jacobson 2005
86
43
adjusted the wind speed estimates specifically to 80 meters to get a more accurate
understanding of global wind power potential because this is the hub height of a typical,
77-meter diameter, 1500 kilowatt wind turbine.88 (See Figure 8 on pg. 24 for a diagram of
a horizontal–axis wind turbine.)
The global wind power potential map shows the location of these 7,753 surface
wind measurement stations and includes the wind speed calculations for 80 meters of
altitude. While this map does not show the wind power potential for every location
around the world, it does provide some indication of the wind power potential for certain
regions of the globe.
Water Scarcity
In 1997, Population Action International (an international NGO) published a
report on global water scarcity for the years 1955, 1995, and 2025.89 They calculated
natural water scarcity by dividing the quantity of available fresh water by the national
population to determine per capita water availability. Countries that have per capita water
availability less than 1,000 cubic meters are considered “water scarce”, while nations that
have less than 1,700 cubic meters of water available per capita are considered “water
stressed.” See Table 8 below that identifies water scarce nations in the past, present and
future.
88
89
Ibid
Gardner-Outlaw and Engelman 1997
44
Table 8. Countries Experiencing Water Scarcity in 1955, 1990 and 2025 (projected),
Based on Availability of Less than 1,000 cubic meters of Renewable Water Per
Person Per Year90
Countries added to
Countries added to
scarcity category by scarcity category by
Countries added to
2025 under all UN
2025 only if they
Water-scare
scarcity category by
population growth
follow UN medium
countries in 1955
1990
projections
or high projections*
Malta
Qatar
Libya
Cyprus
Djibouti
Saudi Arabia
Oman
Zimbabwe
Barbados
United Arab Emirates Morocco
Tanzania
Singapore
Yemen
Egypt
Peru
Bahrain
Israel
Comoros
Kuwait
Tunisia
South Africa
Jordan
Cape Verde
Syria
Kenya
Iran
Burundi
Ethiopia
Algeria
Haiti
Rwanda
Malawi
Somalia
*Cyprus will have more than 1,000 cubic meters of renewable fresh water annually per person in 2025 if it
follows either the UN low or medium population growth projection. Zimbabwe, Tanzania and Peru can
avoid falling below 1,000 cubic meters per capita only if they follow the UN low projection.
Water Poverty Index
An alternative to the water scarcity index described above, the Water Poverty
Index (WPI) can be used to determine countries with insufficient distribution of water
supplies. As mentioned above, water scarcity is not necessarily caused by natural scarcity
alone. While a country might have abundant available freshwater at the national level,
their may be regional areas or marginalized populations that experience water scarcity.
The Water Poverty Index (WPI) is a metric used to link “physical estimates of water
availability with socioeconomic variables that reflect poverty.”91 The WPI is an aggregate
indicator (values range from 0 to 100 with low numbers representing poor access to
90
91
National Council for Science and the Environment 2005 (http://www.cnie.org/pop/pai/water-14.html)
Sullivan 2002
45
water) constructed from five indicators representing proxy values for: resources, access,
capacity, use and environment. The potential value for creating a WPI is captured in the
quote below:
The development of a Water Poverty Index is intended to help this process of
identifying those areas and communities where water is most needed, enabling a
more equitable distribution of water to be achieved.92
Unfortunately, the WPI is still in the process of development, and many countries
of the world have not been assigned a WPI value. Therefore the data set used in this
analysis is incomplete, but useful for a comparative analysis of countries with unmet
demand for water resources.
GIS Methodology
As mentioned above, the spatial analysis for this paper involves isolating WPD
hotspots by applying a set of spatial and attribute restrictions to all the regions of the
world. These restrictions included: access to the coast, sufficient available wind power
and insufficient water supply. These restrictions can be applied to the data set one after
another until the hotspot regions with the desired characteristics are revealed.
Access to the Coast
As mentioned above, the wind power potential data set does not include
measurements for all regions of the world. Therefore, we will only be able to analyze
wind power potential for the regions where we do have measurements. However, we
need to further restrict the data set to wind power measurement locations that are close to
the coast to ensure sufficient and easy access to a supply of salt water. To achieve this
92
Sullivan 2002
46
end, the coastline data set and the global wind power potential data sets will need to be
integrated for a simple spatial selection calculation.
The first step of the analysis was to choose an appropriate limit for the distance a
wind power site could be from the coast. It is assumed that the wind power station and
the desalination unit will be sited at the same location so that the efficiencies of energy
transfer can be realized. Therefore the location of the wind power unit is limited by the
geographic restrictions of the desalination plant. Seawater desalination plants are more
efficient when located close the coast for two reasons: input sea water needs to pumped
from the ocean into the plant and output disposal brine needs to pumped back out to the
ocean (disposing of output brine on land carries greater actual and environmental costs).
For the purposes of this study, potential sites for wind-powered desalination were
limited to within 25 kilometers of the coast. This restriction was applied to the spatial
data by selecting all the wind power sites that fell within a 25 kilometer buffer area
around the coastline data layer. This simple calculation allows for the creation of a new
map that shows only the potential wind sites that are close (within 25 km) to the ocean.
Low-Cost Wind Power Potential
Wind speed, and subsequently potential for wind power production, is not evenly
spread around the world. Wind turbines can only be cost effective in areas where there is
sufficient wind speed to produce significant electrical or physical (shaft) power. It is
understood that wind speeds of Class 3 and above (greater than 6.9 meters per second,
m/s) at 80 meters of altitude are sufficient for the low-cost production of wind power.93
93
Archer and Jacobson 2005
47
Therefore, the next restriction will be to remove potential wind sites that have wind speed
estimations of less than 7 m/s.
This indicator of the global wind power potential data layer is not determined
spatially, so a simple selection by data attribute can remove all data points with wind
speed measurements less than 7 m/s. This operation can be accomplished using the data
attribute table in MapInfo, so that data points can be selected to create a new map that
will show only the wind measurement sites within 25 km of the coast and demonstrating
wind speeds greater than or equal to 7 m/s.
Insufficient Water Supply (1) – Water Scarce Countries
The final restriction is to identify the remaining potential wind sites that are
located in countries with insufficient water supplies. This final restriction is based on the
spatial relationships between the “sufficient global wind power close to the coast” data
layer and the “water scarce countries” data layer. All countries identified as water scarce,
both presently and in the future (2025 calculations), are included in this data layer to
create a more robust understanding of where these technologies might be appropriately
utilized now and in the future.
This particular spatial selection will identify the final set of wind measurement
sites that can be classified as WPD hotspots. A new map is created representing all the
wind potential sites that are within 25 km of the coast, show wind speed estimations
greater than or equal to 7 m/s at 80 m, and are located within countries that are currently
water scarce or show potential for water scarcity in 2025. A final spatial selection can be
used to identify the water scarce countries that contain WPD hotspots and shows where
48
the hotspots are within each country. Appendix X is the map of “Wind-Powered
Desalination Potential in Water-Scarce Countries.”
Insufficient Water Supply (2) – Water Poverty Index
In addition to selecting the final hotspots using the Water Scarcity index, I also
used the Water Poverty Index to generate an alternate set of hotspots as a comparative
study. As outlined in the previous section, the set of wind stations with measurements
greater than 7 m/s and within 25 km of the coast was further restricted by identifying only
those stations that fell within the bottom third of the WPI (values ranging from 35-50.)
The results of this alternative measure of insufficient water supply on selecting sites for
wind-powered desalination in Appendix XI, “Wind-Powered Desalination Potential in
Countries with WPI less than 50.”
GIS Results
Results Summary
Through the use of GIS, I was able to apply a set of spatial and attribute
restrictions on the global data set of wind power potential to identify potential sites or
hotspots for wind-powered desalination, shown in Appendices X and XI. Using two
different sets of data as proxies for insufficient water supplies at the national level, I was
able to identify two sets of results for countries with potential for wind-powered
desalination, shown in Table 9 below:
49
Table 9. Countries Identified as Containing Hotspots for Wind-powered
Desalination
Countries
Water Scarce Data
Water Poverty Index Data
Barbados
X
Cape Verde
X
X
Egypt
X
Haiti
X
X
Libya
X
Madagascar
X
Mauritania
X
Morocco
X
X
Saudi Arabia
X
South Africa
X
Yemen
X
X
*Countries in bold to show that they contain WPDP hotspots using either data set to signify insufficient
water supply.
A Brief Case Study: The Potential for Haiti
Haiti is a water scarce country and it also happens to be the poorest country in the
Western Hemisphere.94 In 2003, approximately 74% of energy consumed in Haiti came
from combined renewable and waste sources95, largely represented by fuelwood
combustion.96 As a result of this dependence on fuelwood, much of the land in Haiti has
become deforested, which has further exacerbated water quality problems as increased
quantities of eroded sediments runoff into the rivers.97
While the situation in Haiti is certainly dire, the country does have an untapped
reserve of energy in the form of strong winds. If this wind energy could be effectively
harnessed, then its current water shortage could be at least partially alleviated through
desalination. Meanwhile the production of electricity from wind could stimulate
development while simultaneously reducing the previous household dependence on
94
CIA 2005
IEA Energy Statistics 2003
96
Earthtrends 1999
97
CIA 2005
95
50
fuelwoods, which could subsequently reducing the rate of deforestation. While this is
certainly an optimistic view of the power of integrated renewable energy-desalination
systems, it is an important alternative to explore for countries (such as Haiti) that might
be overlooking important resources that are available for their development.
Analysis
The resultsgiven in Table 9 (pg. 50) present a useful understanding of where
wind-powered desalination might be an effective technology for increased water
technology. On first glance it seems that the countries that contain hotspots using either
the Water Scarcity or WPI measures (Cape Verde, Haiti, Morocco and Yemen) might
represent more robust opportunities for WPD installation. However, this was not the
objective behind using both Water Scarcity and WPI as indicators, but rather it was to
determine hotspots using two imperfect proxies for insufficient water supply. It is more
interesting to view the results as a set of countries that might want to incorporate WPD
technologies into their national water planning strategies and policies.
As discussed earlier in the paper, the installation of both of these technologies
requires a detailed understanding of the potential sites. However, the data sets utilized for
GIS sets are not sufficiently detailed for any actual site planning for this technology.
Even on a relatively broad scale the data is limited by a variety of characteristics,
including aggregated national level data, wind potential point data, type of water scarcity
data, lack of brackish water data, lack of production capacity estimates and lack of
knowledge about existing WPD facilities.
51
Regional Data – Water Supply
For a more realistic analysis of hotspots for WPD, it would be necessary to use
spatial data sets that have more detailed regional information. For example the data sets
used to represent insufficient water supply are national level aggregates that do not take
into account regional variations in access to water. For instance, the Northeast region of
Brazil has scarce water resources, but the overall country is not considered water scarce
because at the national level there is more than 1000 m3 per capita. This limitation in the
data set becomes particularly evident since there has already been an application of WPD
in NE Brazil and studies have been published to expand the use of this technology in the
region.98
Point Data – Wind Potential
Furthermore, the data for global wind power potential is limited to the locations of
existing wind measurement stations. If this data could be interpolated to represent a
continuous surface of data, it might be possible that wind potential exists in more water
scarce countries than were identified in this limited analysis. For example, high wind
power was identified in the interior of Tanzania, however the coastal measurements
showed only medium potential. A continuous surface of wind data may have allowed for
the identification of hotspots within 25 km of the coast that lay between the medium
potential coastal sites and the high potential interior sites.
Water Scarcity vs. WPI
Of the two data sets used as proxies for determining insufficient water supply, the
Water Scarcity data set is a more appropriate measurement for this analysis. The indicator
98
Corvalho and Riffel 2003
52
for determining water scarcity is strictly a measure of total water resources available
divided by the population. Therefore an increase in water supply through wind-powered
desalination plant would directly influence this indicator regardless of all other variables
except population.
Conversely, the Water Poverty Index is based on the aggregation of five
indicators, only one of which is based on absolute supply of water. Therefore, an increase
in supply from a wind-powered desalination unit might have only a marginal impact in
improving this indicator. Additionally, the WPI indicators is still being refined and a
value has not been assigned to all the countries of world, so that the analysis using WPI
in this paper is an incomplete estimate of WPD hotspots in the world.
While the Water Poverty Index potentially provides a more holistic assessment of
access to water within a country, the issues of access to water relating to access, capacity,
use and environment are beyond the scope of the intervention addressed in this paper. Of
course, if a country moves towards implementing WPD technology, the success of the
implementation will depend on the successful integration of the project into a National
Water Plan that addresses issues such as equity, poverty, appropriate use and
environmental protection.
Finally, it would be useful to incorporate data from the International Desalination
Association (IDA) inventory of existing desalination facilities as an additional indicator
of water scarce regions. After all, if desalination plants have already been constructed in a
particular location, it is likely that there is insufficient water supply. For instance, many
of the Pacific Island nations (and many small island regions in general) rely on
desalination technology to augment the natural water supply, because it is cheaper than
53
transporting water to these remote areas. However, since none of these regions are
identified as Water Scarce and many of these regions were not assigned WPI values,
none of these nations were identified as having potential WPD hotspots.
Seawater vs. Brackish Water
This analysis focused only on the use of seawater for potential desalination feed
water. Another analysis could include data relating to brackish water supplies, and
subsequently inland wind sources, since the desalination facilities would no longer be
limited to the coast.
Scale of Production
This analysis does not address the distinction between large- and small-scale
potential for WPD. Clearly different scales WPD production will be appropriate
depending on a hotspot’s proximity to population centers of different magnitudes. In
certain circumstances, micro-scale WPD might be appropriate for small, isolated
communities on the coast or small islands, while industrial-scale WPD will be required to
meet the needs of large cities.
Current WPD Locations
An additional limitation of this study includes a survey of the existing
implementation of WPD. Appendix XII shows places where the author was able to find
evidence of existing or planned WPD projects. (A complete inventory of worldwide
desalination plants was carried out in 2004 by the International Desalination Association
(IDA), but the author was unable to access this data for financial reasons.)
54
As evidenced by Appendix XII, there is no overlap between countries identified
as WPD hotspots in this GIS analysis and existing WPD production. It is likely that the
gap arises from greater access to financial and institutional resources in the countries with
current WPD projects, as compared to the hotspot countries identified in this paper’s
analysis. In fact, this gap may represent great potential for technological exchange from
the industrialized North to the developing South relating specifically to water resource
management and development.
Conclusion
This paper begins with a quote from President John F. Kennedy that is as salient
in 2006 as it was over forty years ago in 1961. Indeed, the ability to cheaply produce
freshwater from seawater is a powerful tool to improve the lives of millions of people
around the world who are in dire need of safe and accessible water supplies. However,
this technology should not be viewed in the present context as a band-aid that can solve
the world’s water shortage. Rather, it needs to be viewed as an ongoing and long-term
technological supplement to appropriate management of existing water resources.
Since desalination is an energy intensive process, the widespread application of
desalination technology for increasing regional water supplies is intricately linked to
global energy issues. As such, the current and long-term potential for desalination is
significantly limited by the availability of cheap energy. While renewable energy sources
are not currently considered “cheap”, their costs are decreasing steadily, especially in the
context of increasing fuel prices and growing awareness of the environmental
externalities of traditional fossil fuel combustion (air pollution and climate change).
55
Therefore, the realization of JFK’s vision of cheap freshwater produced from the
oceans may in fact be driven by wind turbines, solar panels and other emerging
renewable energy technologies. The successful development of these technologies will be
especially important for developing countries that are currently experiencing water
scarcity and do not have access (geographically or economically) to sufficient
conventional energy resources to implement desalination systems (the case of Haiti).
This last point was the purpose of the GIS analysis for this paper – to identify
countries that have existing water shortages, access to the coast and wind energy
potential. This analysis generated a short list of countries that have the greatest potential
for leveraging gains from wind-powered desalination plants. While there are significant
limitations to the data used for this paper, it is hoped that the results of this analysis will
generate discussions and further research on the implementation of wind-powered
desalination in the identified countries, as well as other regions of the globe.
While it is interesting to look at the potential for these technologies on the global
scale, in many ways, it seems the most useful research will come from national and
regional level studies that seek to answer the same question: what is the potential for
renewable energy-powered desalination in alleviating water stress in the region? It is at
this level where the issues of regional water management, local population sizes, existing
infrastructure, available funds, and physical site characteristics can be more accurately
incorporated into analyses for specific water policy and development program
recommendations. After all, the sooner these technologies are transferred from ideas on
paper to projects in the field, the sooner that target populations can start to benefit from
improved access to water.
56
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Appendix I.
Thermal Distillation Desalination Technologies: Schematic Representations
Appendix IA. Schematic Representation of Multi-Stage Flash Desalination (MSF)
Plant99
Appendix IB. Alternate Representation of MSF Plant100
99
Semiat 2000
USAID by Buros 2000
100
60
Appendix IC. Schematic Presentation of Horizontal Tubes Multi-Effect Distillation
(MED) Plant101
Appendix ID. Alternative Representation of MED Plant102
101
102
Semiat 2000
USAID by Buros 2000
61
Appendix IE. Schematic Representation of Vapor Compression (VC) System103
Appendix IF. Schematic Presentation of a Horizontal Tube, Vapor Compression
Desalination Unit104
103
104
USAID by Buros 2000
Semiat 2000
62
Appendix II.
Selective Membrane Desalination Technologies: Schematic Representations
Appendix IIA. Diagram of Basic Reverse Osmosis (RO) Plant105
Appendix IIB. Diagram of RO Desalination Plant w/ Energy Recovery106
105
106
USAID by Buros 2000
Semiat 2000
63
Appendix IIC. Hollow Fiber Membrane107
107
Buros 2000
64
Appendix IIE. Diagram of Electro-dialysis (ED) System108
Appendix IIF. Alternate Diagram of ED System109
108
109
USAID by Buros 2000
Ibid.
65
Appendix III.
Summary Comparison of RO, MSF and MED Desalination Technologies110
110
Al-Mutaz 2000
66
Appendix IV.
Detailed Comparison of Desalination Technologies111
Appendix IVA. Evaluation of Distillation Processes
Note: 3 = excellent compliance with criterion; 2 = good compliance with criterion; 1 = poor compliance
with criterion.
111
Oldach 2001
67
Appendix IVB. Evaluation of Other Desalination Processes
Note: 3 = excellent compliance with criterion; 2 = good compliance with criterion; 1 = poor compliance
with criterion.
68
Appendix V.
Unit Product Costs for Conventional and Novel Desalination Processes by Capacity,
Plants Operating in 2001112
112
Ettouney 2002 by Ebensperger and Isley 2005
69
Appendix VI.113
113
AWEA 2004
70
Appendix VII.
Costs of Renewable Energy Compared with Fossil Fuels and Nuclear Power114
114
ICCEPT 2002 by REN21 2005
71
Appendix XII.
Country
Australia
France
Germany
Greece
Greece
Israel
Middle East
Locations of Existing and Planned WPD Projects
City/State
Year
Notes
Perth
2005
Planned115
Cost: AU$387 million
(US$287.39 million)
Wind Capacity: 80 MW (48 turbines)
Desalination Capacity: 45 Gigaliters/yr
Lastours
2002
Existing116
Wind Capacity: 5kW
Desalination Energy Consumption: 20kWh/m3
Northern
2005
Planned117
Region
Desalination Technology: Mechanical Vapor
Compression (MVC)
Wind Power: 75% shaft, 25% electrical
Lavrio
2001
Existing118
Capacity: 0.13 m3/hr, (3.12 m3/day)
Desalination Technology: RO
Feed water: seawater
Power Supply: 900 W (wind), 3.96 kWp
(Photovoltaic solar)
Battery Capacity: 1800 Ah/100h
Unit Water Cost: 23 /m3 (US$27.53/m3)
Patras
2002
Out of Commission119 (lack of wind)
Wind Capacity: 35 kW
Desalination Capacity: 1) 5m3/d 2) 22m3/d
Maagan
1999
Existing120
Capacity: 0.125 m3/hr, (3 m3/day)
Feed water: brackish
Power Supply: 600 W (wind), 3.5 kWp (PV)
Battery Capacity: 1500 Ah
Unit Water Cost: 7.53 / m3 (US$9.01/m3)
NA
2002
Existing121
Wind Capacity: 11 kW
Desalination Capacity: 25m3/d
Desalination Technology: RO w/ energy recovery
115
Kneebone 2005
Loupasis 2002
117
Innovation Relay Centre (IRC) – Northern Germany 2005
118
Tzen 2005
119
Loupasis 2002
120
Tzen 2005
121
Loupasis 2002
116
80
Country
Puerto Rico
Sardinia
City/State
NA
NA
Year
1998
2002
Spain
Gran Canaria
2002
Spain
Pozo
Izquierdo,
Gran Canaria
2004
Spain
Tenerife
2002
UK
Loughborough 2003
USA
USA
USA
Hull, MA
Lubbock, TX
Oahu, HI
122
123
124
125
126
127
128
129
130
2005
2005
2002
Desalination Energy Consumption: 11kWh/m3
Notes
Existing122
Planned123
Wind Capacity: 15 kW
Existing124
Wind Capacity: two 230 kW turbines
Desalination Technology: Reverse Osmosis (RO),
Electrodialysis (ED) and Distillation
Existing125
Capacity: 0.8 m3/h (19.2 m3/day)
Feed water: seawater
Nominal power: 15 kW
Battery Capacity: 190 Ah
Unit Water Cost: 3-5 /m3
(US$3.59-5.99/m3)
Planned126
Wind Capacity: 200 kW
Desalination Capacity: 200 m3/d
Project: PRODESAL
Local Wind Speed: 7.5 m/s
Existing127
Capacity: 0.5 m3/h (12 m3/day)
Feed water: seawater
Nominal power: 2.5 kW
Battery Capacity: no battery
Unit Water Cost: 1.78 /m3 (US$2.13/m3)
Planned128
Planned129
Existing130
Desalination Capacity: 4000L/d (4m3/d)
Local Wind Speed: 8.5 m/s
Point Reyes Light 1998
Loupasis 2002
Ibid.
Tzen 2005
Loupasis 2002
Tzen 2005
Johnson 2005
Texas State Energy Conservation Organization (SECO) 2005
Liu, Migita and Park 2002
81
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E-mail: [email protected] · www.enercon.de
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(RO). In this process pressurised seawater flows over a membrane. The structure of the membrane retains
the dissolved salts – water is able to permeate. The result is pure drinking water.
After passing the membrane, a three-piston system recycles the energy of the remaining seawater pressure
with virtually no loss.
endangered areas
Thus desalination and energy recovery occur in a continuous complementary process, forming a cycle.
very dry areas
dry areas
semi-dry areas
THE ENERCON COMPANY
As drinking water becomes ever more precious, seawater desalination and water purification are becoming
more important. Even in regions where drinking water supplies are now adequate, it won’t be long before
drinking
water
Piston 1
Piston 2
Piston 3
RO-module
brine
new solutions are needed to secure them.
As the leading manufacturer of wind power turbines, ENERCON sees a major challenge to accelerate supply
using regenerative solutions. Hence, besides the development, manufacture and optimisation of wind power
plants, ENERCON’s product portfolio includes research into and implementation of drinking water production
systems.
ENERCON has been active in drinking water production since the mid-1990s. The modular and energy-efficient
desalination systems developed by ENERCON have reached series maturity and represent a sustainable
concept for the world’s drinking water and energy supply.
seawater
intake
BASIC FUNCTIONALITY OF ENERCON’S SEAWATER DESALINATION PLANT
Feedwater
Intake
Filtration
Reverse Osmosis
Membranes (RO)
FLEXIBILITY IN POWER SUPPLY
Drinking Water
(0 bar)
ENERCON plants have no fixed operating point. The water
production can range between max. 12.5% and 100% of
the nominal capacity by adjusting the piston speed according
m > /d
500
to demand. This has two main advantages: Firstly, operation
is possible with a fluctuating energy supply, and secondly,
output can be adjusted flexibly to water demand without
shutting down the plant.
400
300
200
Only about 25% of the energy in the reverse osmosis process
UV
Desinfection
Feedwater
(Seawater: ~ 56bar)
(Brackish water: ~28bar)
Brine
(Seawater: ~ 54bar)
(Brackish water: ~26bar)
is used to produce drinking water, so without a recovery
method, about 75% would go to waste. ENERCON’s energy
recovery system comprises a low-pressure pump (max. 20
bar) and a three-piston system, which raises the pressure
100
0
0
400
800
1200
1600 2000
kW/d
up to 70 bar and simultaneously re-uses the remaining
energy. There is no need for a second (high-pressure) pump.
So this system consumes very little power and works
extremely energy efficient.
ENERCON Desalination Plants
with a flexible operation range
Conventional Desalination Plant
with a fixed operation point
Pump
(20bar)
ENERCON Energy
Recovery System
Brine
(0 bar)
MODULAR CONTAINER DESIGN
ENERCON’s seawater desalination plant is modular, comprising various containers. Each 20-foot container
contains a separate part of the plant. This design enables easy worldwide transport and set-up logistics and
also guarantees optimal protection of the plant from climatic influences.
1. Power and control container
The feedwater flows through filters and an UV-disinfection system to the ENERCON Energy Recovery System.
The pump pressure of 20bar is transferred to ~ 56bar/seawater or ~28bar/brackish water and flows to the
RO-membranes. At the RO-membranes, feedwater separates into drinking water and brine. Drinking water
leaves the system and brine, still under pressure, flows back to the energy recovery system to support the
process.
2. Desalination/RO container
3. Water storage container
4. Pretreatment container
1
2
3
4
APPLICATIONS
DIRECT CONNECTION OF ENERCON’S SEAWATER DESALINATION PLANT TO THE PUBLIC GRID
Connecting the ENERCON seawater desalination plant directly to a stable grid poses no problem. The sea
water is extracted from the open sea with a suction pipe or through a well and fed to the plant.
ENERCON’S SEAWATER DESALINATION PLANT IN COMBINATION WITH AN ENERCON WIND ENERGY
CONVERTER AND LINKED TO THE PUBLIC GRID
The seawater desalination plant’s primary power supply is generated by an ENERCON wind turbine. Costal
locations present excellent conditions for wind power, especially on islands. During strong winds, the surplus
energy can be fed directly into the public grid. When there is insufficient wind the desalination plant can be
powered from the grid.
CHARACTERISTICS OF ENERCON’S SEAWATER DESALINATION SYSTEM
ENERCON’S SEAWATER DESALINATION PLANT AS A STAND-ALONE GRID SYSTEM
Very low energy consumption: The ENERCON recovery system saves 30% energy
No need for chemicals: Physical control processes eliminate the need for chemicals
Energy-efficient output adjustment: Without reducing efficiency, water production can be
adjusted to demand and energy availability within a range of 12.5 % to 100%
ENERCON has developed a stand-alone grid system to guarantee a continuous, stable supply of energy and
water to consumers in remote areas far away from the public grid. The seawater desalination plant’s primary
power supply is generated by an ENERCON wind energy converter. In combination with other system
components, such as a synchronous machine, flywheel, battery and diesel generator, the system supplies
and stores energy and water precisely according to demand. ENERCON’s energy management system ensures
ideal utilisation of the wind and water supply, while guaranteeing exceptionally high quality of the island grid.
Based on the power and output variability, ENERCON seawater desalination plants can also
be applied in weak power grid areas or as stand-alone systems
DIFFERENT OPTIONS
Fully automatic operation, including re-start after a power failure, cleansing cycles, control
depending on energy and feedwater availability
TYPE
TYPE
OF WATER
CAPACITY
IN m3/DAY
NUMBER OF
RO UNITS
NUMBER OF
20’’ CONTAINERS
PUMPS PER
RO UNIT
EDS SW 300
Seawater
175 - 350
1
4
1
EDS SW 600
Seawater
175 - 700
2
4
1
EDS SW 900
Seawater
175 - 1050
3
5
1
EDS SW 1200
Seawater
175 - 1400
4
5
1
EDS BW 600
Brackish
350 - 700
1
4
1
EDS BW 1200
Brackish
350 - 1400
2
4
1
EDS BW 1800
Brackish
350 - 2100
3
5
1
EDS BW 2400
Brackish
350 - 2800
4
5
1
Low operating costs; due to very low power consumption per m3 of drinking water produced
Low noise emission
Remote plant monitoring with ENERCON’s SCADA system: Monitoring regardless of location
enables online viewing of all operating data. The data can be generated in tabulated or
graphic form, statistical assessments can be calculated, etc.
No 24 hour personnel necessary
Combination with renewable energy systems, such as wind turbines
Desalination Units powered by
Renewable Energy Systems
Opportunities and Challenges
26 September 2005
Hotel Savana, Hammamet, Tunisia
Organised in the framework of the project ADU-RES
and supported by the EC under the 6th Framework Programme
Participation free of charge - registration required
For registration and more information contact:
Chaibi M.Thameur: +216 - 71 709 033/719 630
[email protected]
Michael Papapetrou: + 49-89-72012 792
[email protected]
English – French interpretation will be available
www.adu-res.org
Programme of the Seminar
09:30
Introduction
09:50
10:10
Project ADU-RES
Water supply Water Supply situation in the
rural areas of Tunisia
situation in
Tunisia
On-Site situation in Central
Tunisia
Questions and discussion
Coffee break
Description and performance of
Pilot
Installations the pilot plant in Sfax, Tunisia
Using geothermal and solar
energy for autonomous water
desalination
Spanish Cooperation project in
Southern Tunisia: PV-RO
desalination unit in the village of
Ksar Ghilène
Successful plants worldwide
Questions and discussion
Lunch break
Improvements in energy
Research
efficiency
and
Development Development of an autonomous
solar rankine cycle system for
RO desalination
Solar desalination for water
supply in Southern Tunisia
Questions and discussion
Coffee break
Solar thermal desalination for
Market
rural applications
available
technologies The Solco PV-RO system
The ENERCON Wind - RO
System
Questions and discussion
Conclusions and next steps
Closing
session
End
10:30
10:50
11:00
11:30
11:50
12:10
12:30
12:50
13:00
14:00
14:20
14:40
15:00
15:10
15:30
15:50
16:10
16:30
16:40
17:00
Welcome
Mohamed Nejib Rejeb,
INRGREF
Christian Epp, WIP
Taoufic Brahem, DGGR
Abedeljellil Afli, CRDA
Kairawan
Aref Maalej, ENIS Sfax
Karim Bourouni, ENIT
Thameur Chaibi, INRGREF
Penelope Ramirez, ITC
Eftihia Tzen, CRES
MurrayThomson,
Loughborough University
Dimitris Manolakos, AUA
Hammami Naceur, ANME
Stefan Thiesen,
ZONNEWATER
Duncan Stone, SOLCO
Frank Hensel, ENERCON
Panel Discussion
Organised jointly by:
INRGREF