Realization and Study of Desalination Prototype Assisted

by Solar Energy

A. Hamine, B. Faiz, H. Idrissi Azami, El. Ouacha

Laboratory of Metrology and Information Processing, Faculty of Sciences,

Ibn Zohr University, Agadir, Morocco.

Keywords: Solar desalination, solar energy application, desalination prototype, water treatment technologies.

Abstract: Southern Morocco is considered a water-scarce area, with many cities having limited access to water. Water

quality is an additional stress affecting the available water supply. In these semi-arid to arid regions of our country, there is

a significant saline load in groundwater. The treatment of these water sources at potable levels requires desalination. The

desalinization of water by solar energy seems to be the most appropriate technical means to solve the global problem of the

shortage of fresh water in the arid and sub-Saharan zones. This technique will provide a new source of irrigation and supply,

particularly in those countries far from the ocean and experiencing significant water stress. This work presents the

preliminary results of an autonomous prototype of desalination assisted by solar energy. This article aims to realize and study

an autonomous prototype of small-scale desalination and subsequently the feasibility and development of another prototype

of large-scale solar desalination. Finally, the preliminary results obtained by this prototype are encouraging and will allow

us to consider a large-scale prototype that can be compared to technologies based on other sources of energy, from a point

of view, cost range, expected and actual production of supply water.

1 INTRODUCTION

Access to drinking water is one of the major issues of

the coming decades. Research on desalination

technologies with high energy efficiency must

therefore be particularly active.

This paper presents a autonomous prototype

desalination simultaneously producing desalinated

water and concentrated brine that can be used to

produce Lithium for the drums. The electrical

energy is provided by photovoltaic panels, which

gives our system a permanent autonomy for the

possibility of implant

ation in isolated site.

The development of an economically viable

autonomous water desalination system using solar

energy to produce distilled water and irrigation water

for such areas is central to this study. Large areas of

southern Morocco depend strongly on drilling water

or wells. In many rural and agricultural areas, access

to well water has a constraint is that the water has a

high salt concentration.

However, many rural areas in southern Morocco that

don’t have reliable access to drinking water are

located in geographical areas where annual levels of

solar radiation are high and groundwater saline is

available. Current saltwater treatment technologies

consume a lot of energy. Solar distillation is one of

the technologies that does not require electricity for

the production of desalinated water. This article aims

to realize and study an autonomous prototype of

small-scale desalination and subsequently the

development of another prototype of large-scale solar

desalination, thereafter, to study the feasibility and

profitability of the substitution of the fuel energy used

in desalination plants by renewable energy.

2 DESALINATION PROCESS

The conventional desalination process requires large

amounts of energy, either in the form of waste heat or

in the form of grid electricity. Conventional

electricity sources in the network are not available in

many rural areas in these areas. However, many

communities in southern Morocco that do not have

reliable access to drinking water are located in

geographical areas where annual levels of solar

radiation are high and groundwater saline is available.

Hamine, A., Faiz, B., Idrissi Azami, H. and Ouacha, E.

Realization and Study of Desalination Prototype Assisted by Solar Energy.

DOI: 10.5220/0009770803010306

In Proceedings of the 1st International Conference of Computer Science and Renewable Energies (ICCSRE 2018), pages 301-306

ISBN: 978-989-758-431-2

301

The development and optimization of solar

distillation designs had to meet the objectives of our

study, from viewpoints, durability and performance

while providing sufficient volumes of unpolluted

water.

3 WATER POTENTIAL IN

SOUTHERN MOROCCO

The Sahara Basin has the lowest mobilized renewable

resources, with a total of 19 Mm³ (25Mm³ taking into

account unconventional resources). Renewable

resources are mainly groundwater (68%). (

Agoussine,

2003).

The water potential of the Sahara Basin is well below

the scarcity threshold with 161 m³ per inhabitant per

year.

3.1 Surface Waters

The average annual surface waters amounts from 50

to 60 Mm³ per year, an average of 115 m³ per

inhabitant, a level well below the national average of

604 m³ per inhabitant. The mobilized surface waters

are entirely resources regularized by the dams and

amount to 2 Mm³, (

Agoussine, 2004).

3.2 Groundwater

The most important aquifers in the Sahara basin are

the Foum El Oued water table, the deep Paleogene

aquifer and the deep Lower Cretaceous aquifer.

The deep water table of the lower Cretaceous is the

most important in the basin by its extension. Its

geology and power have allowed the constitution of a

considerable underground water reserve at the basin

level. The deposit consisting of whitish sands and red

sandy clays has large variations in depth, lithology,

productivity and quality. The underground potential

of this aquifer amounts to 13 Mm³,

(Jellali, 1995).

4 THE QUALITY OF WATER

RESOURCES

4.1 Surface Water and Drilling

The quality of the drilling water and boreholes are

generally average with a salinity that varies between

2 and 3g/L in the center of the basin. However, this

salinity is variable in the basin, the water is brackish

towards outcrops to the east (3 to 5g/L) and becomes

even more salty towards the west to reach high

salinities in the region of Akhfenir-Dcheira, Lamsid

(up to 30g/L), (

Agoussine, 2004).

4.2 Groundwater Quality

The deep water table of Paleogene covers an area of

50000 km². The productivity of boreholes that capture

the aquifer varies between 5 and 40 L/s, water quality

is acceptable in the south (2 to 3g/L) in the region of

Dakhla, Bir Gandouz and bad in the north (6 to 10

g/L),

(Jellali, 1995),(Agoussine, 2004).

Renewable water resources remain constant as

demand for water increases. In southern Morocco, a

large percentage of those without access to drinking

water live in rural and semi-arid areas. The scarcity

of water is, however, exacerbated by the poor water

quality of surface and groundwater resources.

Many southern communities that don’t have reliable

access to water are located in areas where

groundwater has a significant salt load, (Table 1).

These geographical areas have high levels of annual

solar radiation.

Table 1: Groundwater and brackish water potential in

southern Morocco, (Jellali, 1995).

Nappes

Potential in Mm

Tarfaya 10

Foum El Oued 4

Cretaceous inf and sup of

Sahara

Moyenne vally Daraa 60

TOTAL 87

5 DEGREE OF SALINITY

Salinity refers to the total of non-toxic inorganic

compounds dissolved in water, measured by total

dissolved solids (TDS) and electrical conductivity

(Ce). Electrical conductivity is measured in mS / cm

and is related to TDS. TDS is defined as all

compounds dissolved in water that carries an

electrical charge.

Salinity is mainly reflected by the atoms: Na, Ca, Mg,

, Cl and K. Humans tolerate moderate salinity

(SDT)<1g/L. At MDT levels above 3g/L, fatal

intestinal and kidney damage may occur. The high

salt content also has a negative aesthetic effect on

drinking water (bad taste).

Table 2: Degree of salinity in underground and brackish

water in southern Morocco, (Jellali, 1995).

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302

TABLECLOTHS SALINITY (g/L)

Tarfaya 3,5

Foum El Oued 3 á 8

Cretaceous inf and sup of the

sahara)

2 á 3

Moyen Vally Daraa 0,5 á 16

The treatment of salinity, groundwater and brackish

water at potable levels requires desalination. Two

main groups of desalination technologies exist:

thermal technologies and membrane technologies

reverse osmosis. The conventional desalination

process requires large amounts of energy, either in the

form of waste heat or in the form of grid electricity.

Conventional electricity sources in the network are

not available in many areas of southern Morocco.

6 POTENTIALITY IN TERMS OF

SUNSHINE RATE

Most of the southern regions of Morocco average

more than 6500 hours of sunshine a year, and average

solar radiation levels are between 4,7 and 5,5 kWh/m

in one day, (Ministry in charge of the environment,

1998).

Solar energy can be used to provide the energy

needed for a desalination process in the form of

thermal energy or electricity.

7 DEVELOPMENT OF THE

PROTOTYPE

Solar desalination systems require adaptation to local

conditions such as water demand, groundwater

quality, ambient conditions, and access to

maintenance equipment. The design had to be robust

to withstand outdoor use, with minimal supervision

and maintenance and a maximum volume of

desalinated water. Since the system is intended for

remote rural areas, only solar energy would be used

without any external electrical requirements for the

components.

The proposed prototype will be based on solar-

assisted desalination, this implies an increase in the

temperature in the groundwater due to the solar

energy absorbed in the solar panels and a subsequent

heat transfer to the groundwater in the evaporation

tank. In turn the heated water evaporates at the air-

water interface which increases the humidity of the

air, the humid air is cooled to condense in clean water,

in other words desalinated.

The design shown in this work is a new configuration

for a small-scale modular solar desalination system

adapted to local conditions in the southern regions of

Morocco. Energy autonomy is the main feature of this

prototype that uses desalination technology.

The pumping process powered by photovoltaic cells

and the distillation process powered by solar thermal

panels. To achieve these objectives, a solar

desalination technique has been developed. The

design therefore represents a new configuration for a

small scale modular solar desalination system

adapted to local conditions in the southern regions of

Morocco.

7.1 Presentation of the Prototype

The solar field will consist of approximately 10m2 of

flat solar photovoltaic panels producing 2KWc/day,

necessary to supply all the pumping processes and for

the compressor and two flat thermal solar panels to

heat the saline water. With a power of about 110Wc

per panel.

The solar panels were assembled in a north-facing

array tilted at 20 degrees to compensate for the

ecliptic's tilt. This will ensure that the solar radiation

input angle will be perpendicular in summer and will

be optimal on solar panels for most of the year to

ensure maximum radiation transfer into the system.

Figure 1.

Figure 1: Diagram of the prototype.

The design of the prototype is in the form of a

cylindrical tank volume 10l, with several funnels. The

saline pumped from the well enters the evaporation

tank at room temperature and will be heated by the

PV panel fluid flowing through the copper coils

inside the evaporation tank.

The heat exchanged at the saline water will heat the

water between 70 Ԩ and 88 Ԩ during the winter,

causing evaporation and the formation of steam.

Figure 2.

Realization and Study of Desalination Prototype Assisted by Solar Energy

303

Figure 2: Diagram of the assembly of the prototype.

This laboratory scale prototype (see figure 3).exploits

both heat and light emitted by the sun to produce an

average of 1,5l per 5 hours of fresh water in winter.

Figure 3: Real prototype.

7.2 Parameters Affecting the Prototype

Output

The productivity of this solar desalination prototype

will be affected by the ambient operating conditions.

These include ambient temperature, solar insolation,

wind speed and panel cooling temperature, well water

depth, solar panel orientation, and supply water

temperature.

8 MICROCLIMATE STUDY

METHODOLOGY

The solar desalination prototype is installed in winter

at the Guelmim High School of Outdoor Technology.

The experimental setup will include:

 The solar desalination prototype (evaporation

tank with funnels, condensation part, PV panels, 12V

circulation pumps);

 PT100 temperature probes for different

operating points of the prototype (evaporation tank,

condensation zone, photovoltaic panels, sun and

shade) with a data logger set to measurements at 1

minute intervals;

 A weather station that is available at school for

ambient measurements at a recording interval of 5

minutes.

The temperature profile as well as the ambient

conditions (sun and shade temperature, wind speed,

wind direction, wind chill temperature and

precipitation) were recorded for a typical winter study

month and took the average.

The data recorded by the weather station located at

the following GPS coordinates:

(29°00'07.1"N10°05'00.3"W)/(29.001981,-

10.083422) were downloaded during the month of

November and stored in Excel format, so that we can

identify them with well water desalinated by the

prototype. Conductivity and pH measurements were

also recorded all day for one month.

9 RESULTS AND DISCUSSION

Figure4, shows the average temperature

measurements of a winter month in ambient

conditions throughout the day. This curve shows that

the average solar temperature reaches a maximum of

32°C around 15:00.

The average cooling temperatures of the panels were

slightly higher than the temperature of the sun (sensor

exposed directly to solar radiation) before the first

half-days of midnight at 14:24 min and lower after

15:00.

Figure 4: The average per day during the temperature

measurements of the month of November.

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Figure 5 shows the average gust and wind velocity

measurements for a winter study month in ambient

conditions throughout the day. This curve shows that

the average wind speed is about 3.5Km/h/day. The

wind tornado profiles show fluctuations throughout

the day, this may influence the performance of the

panels and consequently the volumes of the distillates

obtained.

Figure 5: Velocity profile for 24 hours.(The average wind

speeds during the month of November).

Figure 6 represents the average temperature profiles

of a month of study, for different points of operation

of the prototype for a day, measured by PT100

temperature probes, at the levels of (solar panels,

sensor measures solar radiation, temperature shade,

evaporation tank, condensation tank).

Figure 6: Temperature profile measured at different points

of the prototype for 24 hours. (Average temperature of the

month of November).

There is a good correlation between the highest

average temperatures in the evaporation reservoir and

those of the average ambient temperatures measured

by the weather station.

The average temperatures in the evaporation tank

reach 60°C between 12h00 and 15h30 correspond to

the average ambient temperature between 20 and

30°C. It has also been noted that the average

temperature in the evaporation vessel is delayed

compared to the average temperature of the panels

until 09:30, after which it increases steadily up to a

maximum temperature around 70°C to 80°C, between

13:30 and 14:00.

The initial warm-up period (up to 09:00) is necessary

for the equilibrium conditions to be reached in the

solar panels before the circulation pumps are

automatically activated by a microcontroller.

The warm-up time required to heat the salt water is

relatively short with temperatures rising to 30°C in 15

minutes and 60°C in 120 minutes after activation of

the circulation pumps by the microcontroller.

We also note that when the circulation pumps stopped

around 15:30, the temperature of solar panels

decreases regularly which causes the significant drop

in temperature in the evaporation tank. Some

temperature drops observed in the evaporation vessel

correspond to an increase in wind speed and a

decrease in ambient temperature.

The initial volumes of distillate produced will also be

low since most of the heat required for evaporation is

taken from the water itself. To maintain the

temperature of the water, heat must be provided. In

order for the molecules of a liquid to evaporate, they

must be located near the surface and have sufficient

kinetic energy to overcome the intermolecular forces

in the liquid phase.

Only a small proportion of the molecules meet these

criteria, so that the rate of evaporation is limited.

Since the kinetic energy of a molecule is proportional

to its temperature, evaporation occurs more rapidly at

higher temperatures. As rapidly moving molecules

escape, the remaining molecules have lower average

kinetic energy and the temperature of the liquid

decreases. Energy is used to break bonds that hold

water molecules, which is why water evaporates

easily at the boiling point at 100°C, but evaporates

much more slowly at the freezing point.

Net evaporation occurs when the rate of evaporation

exceeds the rate of condensation. The average flow

rates of distillates vary between 3 ml/min and

6ml/min reached between 12:00 and 15:30, until

16:00, from 16:00 there is a sharp decline in the

production rate, figure 7.

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305

Figure 7: Maximum volume of distillate recovered between

10:00 and 16:00.

Although the following study is taken from well

water, average electrical conductivity (eCm) was

measured for a few days in November, the latter

decreasing daily from 0.33 mS/cm to 0.04 mS/cm

during the day, the best quality being produced at the

end of the afternoon. The PH also drops almost every

day between 11:00 and 15:30 from 8 to 6.4.

10 CONCLUSION

According to this preliminary study of the prototype

presented, it has been found that there is a good

correlation between the highest temperatures in the

evaporation tank and those of the ambient

temperatures measured by the meteorological station.

The initial volumes of distillate produced will be

small because most of the heat required for

evaporation is taken from the water itself. This

prototype produces an average of 1,5 liters/day of

desalinated water in winter, or 45 liters/month using

300 liters of salt water. Based on encouraging

preliminary results showing satisfactory drinking

water production ratios, there are many opportunities

to improve the efficiency of our prototype.

This future combination will allow us to increase the

volume of treated saltwater by studying a large-scale

prototype, the latter can be compared to technologies

based on other sources of energy, from the point of

view, range of expected costs and actual production

of supply water and this while minimizing the amount

of brine produced.

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Mr. JELLALI, "Development of water resources in

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