Smart Grid and Renewable Energy, 2012, 3, 43-50
http://dx.doi.org/10.4236/sgre.2012.31006 Published Online February 2012 (http://www.SciRP.org/journal/sgre)
43
Optimization of Renewable Energy Power System for
Small Scale Brackish Reverse Osmosis Desalination Unit
and a Tourism Motel in Egypt
Faten Hosney Fahmy, Ninet Mohamed Ahmed, Hanaa Mohamed Farghally
Electronics Research Institute, Giza, Egypt.
Received December 4th, 2011; revised January 30th, 2012; accepted February 7th, 2012
ABSTRACT
The main objective of this work is to design an optimal—efficient economic power renewable energy system that feeds
the required electric load of a small scale brackish reverse osmosis desalination unit and a tourism motel located in
Hurghada, Egypt. Four renewable energy power systems are presented in this paper to select the most optimum one of
them. These suggested renewable energy systems are PV-wind hybrid system, stand-alone wind system, stand-alone
photovoltaic system and PV-wind-fuel cell hybrid system. The sizing, optimization and economic estimation of the
proposed systems were performed using HOMER software. HOMER solves the optimization problem to minimize the
global cost and provides the optimum wind turbine, PV, battery and fuel cell ratings. In addition, a comparison between
the four different suggested power system configurations is illustrated in details. PV-wind hybrid system realized the
lowest net present cost and levelized cost of energy. Also, this system was able to provide energy approximately all the
day. The battery state of charge varies between 83% and 99% and it was found that, the PV-wind hybrid system is more
suitable than the others for the selected site and the suggested electrical load.
Keywords: PV; Wind Turbine; Fuel Cell; Hybrid System; Net Present Cost; HOMER
1. Introduction
As the energy demands around the world increase, the
need to alternative energy sources is increased. In addi-
tion to, the rapid depletion of conventional energy (fossil
fuel) resources on a worldwide basis has necessitated an
urgent search for alternative energy sources to cater to
the present day demands. The clean green renewable
sources of energy are expected to play more significant
role in the global energy future. Also, with the increasing
concerns on air pollution and global warming, the clean
renewable energy sources that are environmentally
friendly, unexhausted e.g. solar energy, wind, hydrogen,
geothermal etc. have attracted energy sectors to generate
power on a large scale. Wind and solar energy technolo-
gies are the forerunners amongst various types of re-
newable sources [1,2]. The vast and continuous devel-
opment of the Red Sea zone has led to extensive and in-
creasing potable water demands to match the tourist, in-
dustrial and urban settlements. Given the worsening wa-
ter situation in Egypt due to the massive and increasing
demand by the agricultural sector, supplementary non-
conventional sources including desalination of sea and
brackish water, and reuse of waste water, represent very
important sources to ensure maximum water allocation
for its uses [3]. Also, water demand in a vastly growing
and developing Egyptian community was analyzed as
characterized by a rising standard of living, expansion of
industrialization in mining and petroleum sectors and the
vast expansion of tourist development [4]. There are dif-
ferent methods of seawater and brackish desalination
appropriate for Egyptian environment and recommended
the method of selection of the technology to be used in
each particular site where the possible energy sources are
screened. A small scale reverse osmosis (RO) desalina-
tion system powered by renewable energy sources pre-
sents an ideal solution to provide freshwater to small
communities isolated at remote areas [5]. In the last dec-
ade, desalination, especially by RO, has become one of
the principal safe sources of supply of potable water, and
even water for agricultural use, it is in the Mediterranean,
Africa, the Middle East, and so on, where the potable
water supply is a high priority problem. All this leads to
the need to identify new sources of supply such as the
desalination of brackish or sea water [6,7]. Coupling of
renewable energy and desalination systems holds great
promise for increasing water supplies in water scarce

Optimization of Renewable Energy Power System for Small Scale Brackish Reverse Osmosis Desalination Unit and
a Tourism Motel in Egypt
44
regions. An effective integration of these technologies
will allow Egypt to address water shortage problems with
a domestic energy source that does not produce air pollu-
tion or contribute to the global problem of climate
change. Meanwhile the costs of desalination and renew-
able energy systems are steadily decreasing [8], while
fuel prices are rising and fuel supplies are decreasing. In
addition, 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 [9-11]. As the energy
cost is one of the most important elements in determining
water costs where the water is produced from desalina-
tion plants. The aim of this work is to design an optimum
—efficient cost power renewable energy system for po-
wering brackish water reverse—osmosis desalination
system to deliver in the order of 5 m3 of fresh drinking
water per day required for feeding a tourism motel plus
electrical power for supplying the main equipments re-
quired for a motel with the electrical power demand. This
study is performed for the region in Hurghada in Egypt.
Four power system configurations using different energy
sources, namely, stand-alone photovoltaic system, stand-
alone wind system, PV-wind-fuel cell hybrid system and
PV-wind hybrid systems are studied in this paper. Also, a
comparative study between these different power sys-
tems configurations is introduced. These different sys-
tem configurations are simulated in HOMER environ-
ment for sizing optimization which minimizes the system
cost. Also, the simulation results are reported in this pa-
per.
2. Proposed Reverse Osmosis Desalination
Unit
Reverse Osmosis process is used chiefly for separating
the solvent (water) from aqueous salt solutions. As
shown in Figure 1, the brackish water, pumped from a
well to a storage tank, passes through the desalination
unit and exits in two branches, one as potable water that
is stored in special tank and another as brine water (ele-
vated salinity) that is directed to an evaporative pond.
The feed water enters the unit at a salinity value of
around 3400 ppm and exits as fresh water permeate at a
salinity of around 30 ppm. An external mixing process is
arranged at the exit to produce water for consumption at
a salinity level of around 300 ppm.
3. Load Data
The main goal of system sizing is to achieve the right
balance between daily needs of electrical energy con-
sumed by the loads and daily produced electrical energy
by the generator. The daily consumed electrical energy
by the loads has to be identified at the beginning of sys-
tem sizing, so as to calculate the daily needed electrical
energy and the total peak power of the generator. Also, it
is very important to determine the amount of water con-
sumed by 20 motel inhabitants and the amount of water
required for the daily operation of the motel which is
calculated to be around 5 m3/day. Therefore, the required
electrical load consists of the power needed for supplying
the small scale RO desalination unit and the electricity
required to operate the domestic electrical load of the
motel. According to Reverse Osmosis manufacturer [12,
13] power required to produce 5 m3 per day is 1.8 kW.
This means that, the daily energy required for desalina-
tion unit is approximately 45 kWh. The BWRO (brackish
water reverse osmosis) load is assumed to operate for 24
hours from 0:00 to 24:00. Also, the motel is populated by
approximately 20 inhabitants (15 guests and 5 workers)
and includes a kitchen, a small garden and a small swim-
ming pool. Table 1 shows the daily electrical load re-
quirement of RO unit and the motel total load of appli-
Figure 1. Block diagram of RO system.

Optimization of Renewable Energy Power System for Small Scale Brackish Reverse Osmosis Desalination Unit and
a Tourism Motel in Egypt
45
Table1. The daily electrical load requirement.
Appliance No. of unitsRated
power (W)
Operation
periods (h)
Reverse osmosis unit 1 1800 24
TV 1 80 11
Refrigerator 1 100 24
Energy saving lamp 2 40 15
Indoor lamp 18 20 15
Fan 18 100 14
Washing machine 1 1000 4
Blower 1 100 10
ances. Figures 2 and 3 shows the estimated daily load
power variation in summer and winter respectively for
a small scale RO desalination unit and a tourism motel
located in Hurghada in Egypt, with a full load of 8.5 kW
as shown in these figures.
4. Site Characteristics
Site selection is based on the following criteria [14]:
· Availability of brackish groundwater.
· Potential of solar radiation and wind speed.
· Electric grid and fresh water network are not avail-
able in the vicinity of the site.
· The social, economic and ecological situation of the
beneficiaries.
· The demand for fresh water.
Hurghada city is the chosen zone as the site under
consideration. It is located at 27˚17′N latitude, 33˚46′E
longitude, elevation 1m and Red sea climate district. The
city is characterized by an intensive solar radiation. Wind
is also an abundant resource. Two water wells are se-
lected to be the water supply for the reverse osmosis de-
Figure 2. Daily load data in winter.
Figure 3. Daily load data in summer.
salination unit. These wells are Abu Shegala and Umm
Huweitat wells. Each has a depth of 160 m and is located
near Hurghada city [15]. Since the performance of re-
newable energy power system is highly dependant on the
environmental conditions, a site-specific analysis is re-
quired to investigate the associated cost, component size
and overall economics.
5. Resources
The types of renewable energy sources available in the
coastal areas are those of the sun and the wind. Wind and
solar energy resources of Hurghada city are considered
for this study.
5.1. Solar Energy Source
The use of photovoltaic technology, especially in regions
without access to electrical energy from a central power
grid but good solar resources, can play a significant role
in meeting the power demand to run a water-desalination
plant. Red-Sea Coast is known as a rich area of solar
energy and high wind speed. The available solar resource
greatly influences both the configuration and the cost of a
hybrid system. Monthly average solar insolation data for
the selected remote area is shown in Figure 4. We notice
from this figure that, the highest values of the solar inso-
lation are during the summer months (May, Jun., Jul, and
Aug.) and the lowest values are during the winter months
(Nov, Dec. and Jan.). Solar radiation data for this region
was obtained from Egyptian Solar Radiation Atlas [15].
The annual average solar radiation for this area is 6.38
kWh/m2/d.
5.2. Wind Energy Source
Among the coastal areas, the zone of Hurghada is the
highest in wind energy applications. A monthly average
wind speed for Hurghada city was obtained from Egyp-
tian Solar Radiation Atlas. As it is cleared from Figure 5,
the most year months have wind speed values ranging
from 5.7 m/s to 7.8 m/s. The annual average wind speed
in Hurghada is found to be 6.93 m/s [15].
6. Systems Components
In addition to renewable energy sources (wind and solar),
various combinations of PV array, wind turbine, fuel cell,
electrolyzer, battery, and power inverter modules were
taken into account towards identifying an economic solu-
tion that would meet the required load [16].
6.1. Photovoltaic Panels
I
n this study, photovoltaic panels were specified with

Optimization of Renewable Energy Power System for Small Scale Brackish Reverse Osmosis Desalination Unit and
a Tourism Motel in Egypt
46
Figure 4. Averages solar radiation profile for hurghada city.
Figure 5. Averages wind speed Profile for Hurghada city.
capital and replacement costs of 8000 $ and 7000 $ re-
spectively, this cost includes shipping, tariffs, installation,
and dealer markups [16]. Some maintenance is typically
required for the batteries of a PV system. A derating fac-
tor of 80% was applied to the electric production from
each panel. This factor reduces the PV production by
20% to approximate the varying effects of temperature
and dust on the panels. The panels were modeled as fixed
and tilted south at an angle equal to the latitude of the
site.
6.2. Wind Turbine
In this analysis, Generic 3 kW model is considered [17,
18]. It has a rated capacity of 3 kW and provides 24 V dc

Optimization of Renewable Energy Power System for Small Scale Brackish Reverse Osmosis Desalination Unit and
a Tourism Motel in Egypt
47
as output. Cost of one unit is considered to be $1200
while replacement and maintenance costs are taken as
$800 and $75/year respectively [17]. The life time of the
turbine is estimated to be 20 years.
6.3. Fuel Cell
The fuel cell considered in this study has a capacity of 1
kW. Its initial cost is $3000 and its replacement is $2500.
Annual operation and maintenance cost is $175. The life
time of fuel cell is estimated to be 5 years [18,19].
6.4. Electrolyzer
Water electrolyzer consists of several cells connected in
series. Two electrodes of the elcrolyzer are separated by
an aqueous electrolyte or solid polymer electrolyte. Elec-
trical current through the electrolyzer enables the de-
composition of water into hydrogen and oxygen.
The capital cost of one kilowatt of the electrolyzer in-
cludes electrolyzer electronics is 2000 $. The replace-
ment cost of the electrolyzer is assumed to lower than the
capital cost because some components included in the
capital cost have longer life time than the stack itself.
The replacement cost is 1500 $. A durability of 20 years
was given within the scope of this simulation[19].
6.5. Hydrogen Tank
Hydrogen storage tanks are also included in the electro-
lyzer model. Cost of a tank with 1 kg capacity is assumed
to be $1300. The replacement and operational costs are
taken as $1200 and $15/year respectively [19].
6.6. Batteries
One of the major requirements for renewable energy
power systems is to ensure continuous power flow by
storing excess energy from the renewable sources. Tor-
gan L16P lead acid battery type was chosen because it is
a popular and inexpensive option. HOMER considered
the battery sizes from 0 - 20. The voltage regulated lead
acid battery is rate at 24V and has a capacity 360 Ah.
Initially cost for one battery is $275. The replacement
batteries will cost another $275. The operation and main-
tenance cost add further 3 $ with a minimum life time of
5 year [16].
6.7. Inverter
A reliable and efficient power electronic inverter is
needed to maintain flow of energy between the ac and dc
components. The inverter size of 1 kW is taken in this
model. Lifetime of the inverter is considered to be 15
years with an efficiency of 90%. It is one of the major
costs of the system. For a 1 kW inverter, the initial and
replacement costs for the inverter each is $700, with no
cost for operation and maintenance [16].
7. Basic Economical Modeling
The total Net Present Cost (NPC) of the power system is
the objective function to be minimized in the optimiza-
tion process. To calculate the NPC of the system we si-
mulate it throughout its lifetime, obtaining the energy
produced and consumed by the components, their own
lifetimes, the number of times in which the components
must be replaced, the operating and maintenance costs,
the fuel costs, etc.
The renewable energy system cost represented by the
net present cost (NPC) is expressed as:
1
&
M
Ti ii
i
CCICMOCRc

 
i
S (1)
where CT is the total system cost, This cost takes into
account the initial (capital) and all other costs required
for the system to operate properly over its life. m is the
number of used energy sources, five main parts are con-
sidered: PV array, wind turbine, battery bank, fuel cell
and the inverter. CI is the initial capital cost, CR is the
replacement cost, CM & O is the operation and mainte-
nance cost and CS is the salvage value at the end of the
project [20,21].
The constraints of the optimization problem are ex-
pressed as follows:



Subject to loadpower output
maxunserved load%Load



8. Simulation
We perform the simulation to obtain the optimum power
system configuration that meets the previously men-
tioned load profile. National Renewable Energy Labora-
tory (NREL)’s, Hybrid Optimization Model for Electric
Renewables (HOMER Version. 268Beta) has been used
as the sizing and optimization software tool. It contains a
number of energy component models and evaluates suit-
able technology options based on cost and availability of
resources [18,22,23]. Analysis with HOMER requires
information on resources, economic constraints, and con-
trol methods.
The four previously mentioned power system con-
figurations which are submitted to the technical and eco-
nomical analysis can be addressed as follow:
Power system 1: “PV-wind hybrid system”.
Power system 2: “stand-alone wind system”.
Power system 3: “stand-alone PV system”.
Power system 4: “PV-wind-fuel cell hybrid system”.

Optimization of Renewable Energy Power System for Small Scale Brackish Reverse Osmosis Desalination Unit and
a Tourism Motel in Egypt
48
9. Optimization Results
The simulation results of the four power system configu-
rations are displayed in Table 2. Power system 1, which
is the PV-wind-battery hybrid system offers the much
lower NPC and Levelized cost of energy (LCOE) with
PV and wind combined together. On the other hand,
power system 3 has higher Initial Capital Costs, NPC and
LCOE. While system 2 has the cheapest initial capital
cost while the NPC and LCOE are higher than power
system 1. This is due to considerable increase of re-
placement, O&M costs. It is cleared that the use of initial
capital cost as the primary decision criteria in remote
area power generation systems is misleading and inap-
propriate. Relying on LCOE, NPC as the key decision
parameters instead of using initial capital cost will result
in the better selection of remote energy technologies.
Also, the high PV-wind-fuel cell power system cost
over PV-buttery system is due to the high capital cost of
fuel cell system and electrolyser compared to the battery.
Economic competitiveness for hydrogen energy systems
is obtainable only with a significant reduction of capital
costs together with a strong decrease in energy prices.
According to the results of the optimization process the
optimal power system comprises a 5 kW PV array, a 6
kW wind turbine, a 10 kW inverter and 10 batteries.
Figure 6 shows the PV-wind-Battery hybrid system ar-
chitecture simulated in HOMER. The proposed system
gives us a total net present cost of $69,524. The cost of
energy is 0.321 $/kWh and the initial capital required is
$40,750.
As shown in Figures 7(a), (b) the load is supplied
with a hybrid system comprising of a PV array, wind
generator and battery storage. As cleared in Figure 7(a),
the PV/Wind hybrid system is able to provide energy
approximately all time of the day. It can be observed that,
the load could be met right through the day .The battery
state of charge varies between 83% and 99% as shown in
Figure 7(b).
Figure 6. HOMER implementation of the PV-wind-battery
hybrid system.
(a)
(b)
Figure 7. Hourly data for pow er system 1.
Table 2. Optimization sizing results.
tem Power system 1
PV-Wind-Battery system
Power system 2
Wind-Battery system
Power system 3
PV-Battery system
Power system 4
PV-Wind-Fuel cell system
Optimization sizing results
5 kw PV array
6 kW PV wind turbine
10 battery each 8.64 kw·h
10 kw inverter
12 kW wind turbine
20 battery each 8.64 kw·h
10 kw inverter
10 kw PV array
10 battery each 8.64 kw·h
10 kw inverter
100 kw PV array
120 kw wind turbine
14 kW fuel cell
80 kw electrelyzer
50 kg hydrogen tank
10 kw inverter
Capital cost ($) 40,750 36,500 51,250 799,800
O & M ($) 5,016 10,033 314 37,790
Replacement cost ($) 26,983 30,677 40,175 127,996
Net Present cost ($) (NPC) 69,524 74,652 87,956 903,281
Levelized cost of energy
(LCOE) ($/kwh) 0.321 0.356 0.414 4.305

Optimization of Renewable Energy Power System for Small Scale Brackish Reverse Osmosis Desalination Unit and
a Tourism Motel in Egypt
49
Figure 8 shows the hourly data for wind-battery sys-
tem. It can be observed that the load could be met right
through the day with excess energy. The battery state of
charge varies between 93% and 100%. The use of stand-
alone wind electricity generation systems is limited in
rural areas as wind resource is site dependent and de-
pends on the season. It does not produce usable energy
for a considerable portion of time during the year.
Figure 9 presents the same hourly data but for PV
stand alone system. A PV stand alone system may not
easily satisfy loads on 24-h basis as the variation of solar
electricity generation does not always match with the
time distribution of load demand. As shown the battery
state of charge varies from 30% to 44%. Figure 10 pre-
sents the hourly data for PV-wind-fuel cell hybrid system.
As shown in this figure, the system easily satisfies loads
on 24-hours basis.
10. Conclusion
In this paper, the design of an optimum–efficient cost
renewable energy system that meet a known electric load
of small scale brackish reverse osmosis desalination unit
and a tourism motel was developed. The computer pro-
gram (HOMER Pro.) solves the optimization problem to
minimize the objective function considering the different
constraints and provides the optimum wind, solar and
battery ratings. In addition, the comparison between the
four suggested different power system configurations
was illustrated with details. These systems are compared
(a)
(b)
Figure 8. Hourly data for pow er system 2.
(a)
(b)
Figure 9. Hourly data for pow er system 3.
(a)
(b)
Figure 10. Hourly data for power system 4.
with respect to the total net present cost (NPC) and lev-
elized cost of energy. The PV-wind- battery system, of-
fers the much lower NPC and LCOE. On the other hand,
PV-fuel cell wind hybrid system has higher initial capital
costs, NPC and LCOE. PV-wind-battery system confi-

Optimization of Renewable Energy Power System for Small Scale Brackish Reverse Osmosis Desalination Unit and
a Tourism Motel in Egypt
50
guration comprising of 5 kW PV array, a 6 kW wind
turbine and 10 batteries each has a capacity of 8.64 kWh
is the most economic solution under given resource and
load conditions. Also, the high PV-wind-fuel cell system
cost over PV-buttery system is due to the high capital
cost of fuel cell system and electrolyser compared to bat-
tery. Therefore, the major obstacle in using hydrogen as a
storage medium is the high cost associated with it.
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