Technical Assessment For Solar Powered Pumps Final For Public With Logos (Final)
Technical Assessment For Solar Powered Pumps Final For Public With Logos (Final)
Technical Assessment For Solar Powered Pumps Final For Public With Logos (Final)
BACKGROUND
Following the Syrian Crisis, the majority of refugees are being hosted in communities that
are among the poorest in the country, including the North of Lebanon and the Bekaa. These
communities suffer from poor water services due to lack of adequate infrastructure and have
limited means to expand local sources of livelihood including agriculture.
Given the opportunities available to use renewable energy for water pumping for both water
distribution networks and for the extraction of water for irrigation, an assessment of the
viability of solar pumps needs to be assessed.
Review the types of PV systems that could be used to run the pump taking into
consideration the efficiency and cost. Suppliers and Dealers of such systems should
be identified and consulted.
Distinguish the appropriate type, model, and number of solar panels needed for
different uses, with particular focus on pumping capacity for potable water
distribution networks and agriculture, to always ensure the highest performance and
efficiency.
Identify all required electronic device (the controller unit) which matches the PV
power needed to regulate the operation, starting and stopping the pump.
Describe and highlight on the efficiency of such PV system especially in bad weather
and in low light conditions such as cloud cover and storm.
Outline the general maintenance needed for such system, including financial and
technical resource requirements
ACKNOWLEDGMENTS
Throughout the preparation of this document, appreciated support and valuable information
have been provided by professionals and experienced individuals in the sector.
This report is prepared by Nader Hajj Shehadeh who is an energy specialist with experience
in Energy Efficiency and Renewable Energy since 2005. He currently works as an independent
energy consultant in Lebanon and the GCC, and heads a professional business and energy
Disclaimer
The findings, interpretations and conclusions expressed in this report are those of the
authors and do not necessarily represent those of the United Nations Development
Programme or the donor. The project partners do not guarantee the accuracy of the
data included in this report. The boundaries, colours, denominations, and other
information shown on maps and images in this work do not imply any judgment on the
part of the project partners concerning the legal status of any territory or the
endorsement or acceptance of such boundaries. The project partners do not assume
responsibility of any kind for the use that may be made of the information contained in
this report.
$ US Dollar
A Ampere
AC Alternating Current
API American Petroleum Institute
BOQ Bill of Quantities
Capex Capital Expense
CEDRO Community Energy Efficiency & Renewable Energy Demonstration Project for Lebanon
DC Direct Current
DOE Department of Energy
G gravity
gal Gallon
gpm gallons per minute
ha Hectare
hp horsepower
hr Hour
J Joules
kg Kilogram
km Kilometer
kW KiloWatt
kWh KiloWatt-hour
LCB Linear Current Booster
LCEC Lebanese Center for Energy Conservation
MDG Millennium Development Goals
min Minute
MPPT Maximum Power Point Tracking
NEEREA National Energy Efficiency and Renewable Energy Action
Opex Operating Expense
pc Piece
PDP Positive Displacement Pump
PSH Peak Sun Hour
PV Photovoltaics
PVGIS Photovoltaic Geographical Information System
TDH Total Dynamic Head
UN United Nations
UNDP United Nations Development Programme
UNHCR United Nations High Commissioner for Refugees
US United States
V Volt
W Watt
ρ Density
TABLE OF CONTENTS
Background ______________________________________________________________________________________ i
Introduction ____________________________________________________________________________________ 1
Why Solar pumping? __________________________________________________________________________ 1
Basic Definitions ______________________________________________________________________________ 3
References _____________________________________________________________________________________ 59
LIST OF TABLES
LIST OF FIGURES
INTRODUCTION
Water is a basic necessity of life. Be it for drinking, irrigation, livestock, or domestic use, there
is nothing of such a crucial importance to human health and well-being. This puts water as one
of the major issues in the UN’s Millennium Development Goals (MDG). Seven out of the eight
MDGs rely on the water and sanitation target to be achieved, namely eradicating extreme
poverty and hunger; achieving universal primary education; promoting gender equality and
empowering women; reducing child mortality; improving maternal health; combating HIV,
AIDS, malaria and other diseases; and ensuring environmental sustainability.
Potable water is usually moved from sources at lower levels such as rivers, ponds, wells, and
other ground sources to higher levels for irrigation, domestic use, and other needs. Whether
being moved vertically from deep to surface levels, or horizontally from one location to another,
water requires energy as a major component linked to water availability and consumption.
Pulling up a rope with a bucket at its end, manually pushing a hand-pump to bring up water to
surface levels, putting domestic animals to move in a loop to do the job, and connecting an
electrically-driven water pump to move water around are all means of energy applications used
to supply water to communities and individuals. The rope and bucket is history now; the hand-
pump is way impractical; cattle of these days are too lazy for water pumping; leaving us with
electrically-driven pumping systems as the most reliable and practical solution. While most
pumping systems rely on the electric utility’s power for its affordability and reliability to a
certain extent, it remains more feasible for some applications located in remote and non-
electrified regions to have their own independent power supply. This is achieved through the
use of independent diesel generators or other renewable energy technologies such as wind and
solar power.
Available abundantly and free, offering a financially feasible and technically practical solution,
solar water pumping is becoming very common in agricultural applications to be regarded as
an emerging solution providing water to disadvantaged and unfortunate communities.
Using sophisticated yet well-established technologies, solar energy empowers a water pump
that moves water from wells, ponds, and other water sources to ground levels and to end use
locations. Thus, as long as the sun is shining, water is being pumped and moved around either
to a water storage location or directly to consumers. This avoids the hassle of batteries for
power storage that makes solar PV applications disfavored in many cases.
Solar pumping is considered a more economically feasible solution due to the lower operating
expenses (Opex) related to fuel supply and maintenance costs and reduced carbon footprint as
compared to diesel generators. Tens of thousands of solar water pumps are in operation all
over the world, meeting consumption needs especially in regions beyond power lines and
producing best during sunny seasons when the demand on water reaches its peak.
Basic Definitions
Alternating Current An electric current that reverses its direction at regularly recurring
intervals. Commonly used in most household appliances.
Centrifugal Pump A type of pump that uses an impeller to spin water and push it out
by centrifugal force.
Diaphragm Pump A type of pump in which water is drawn in and forced out of one or
more chambers, by a flexible diaphragm.
Direct Current An electric current flowing in one direction only and substantially
constant in value.
Flowrate The amount of fluid that flows in a given time, normally expressed
in units of cubic meters per hour or gallons per minute in the US.
Foot Valve A check valve that prevents water from flowing back down the pipe.
It is placed in the water source below a surface pump.
Friction Loss The loss of pressure due to flow of water in pipe due to distance
covered, fittings, and other factors.
Linear Current An electronic device that conditions the voltage and current of a PV
Booster array to match the needs of a DC-powered pump, especially a
positive displacement pump. It allows the pump to start and run
under low sun conditions without stalling. It is also called a pump
controller.
Peak sun hours The equivalent number of hours available in a certain location per
day when the intensity is enough to produce 1 kW of energy. Usually
in the range of an annual average of 3 to 7 hours per day.
Solar Insolation The amount of sunlight falling on a specific area for a given period
of time. Also known as solar irradiance and given in kWh/m 2 /day.
Suction Lift The vertical distance from the surface of the water in the source, to
a pump located above surface pump located above.
Surface Pump A pump that is not located on ground level to suck out water from
lower level sources.
Dynamic Head The summation of vertical lift and friction loss in piping.
Watt Peak The maximum capacity of the PV panel(s), also known as the rated
power of the panel. It is the maximum amount that can be produced
under standard test conditions.
Distribution of water through networks and in piping channels is driven by a properly designed
pumping system that uses an electrically or mechanically driven pump to do the job. The pump
is mainly used for dewatering purpose to reduce downtime from large rain events and to
continuously transfer water from one point to another.
There are two major types of water pumps currently available in the market; the first is the
centrifugal pump, which uses a rotating impeller to move water into the pump and pressurize
the discharge flow. Centrifugal pumps are able to pump fluids with various specifications
regardless of the viscosity levels, but are specialized with thin liquids and high flow rates.
Centrifugal pumps are used in buildings and fire protection for water supply. Also used in wells
and boost applications for water supply and pressure boost.
The second is positive displacement pump (rotary pump) that delivers a fixed amount of flow
through the use of a flexible diagram undergoing mechanical contraction and expansion. This
kind of pump is perfect for high viscosity fluids, and specialized for low flow and high pressure
combination. The fact that positive displacement pumps remove air from the lines and
eliminate the need to bleed the air makes them very efficient.
Wherever the electric grid is available, it is mainly used as the primary source of power. For
remote applications, onsite diesel generators have been used for a long period of time to
power irrigation and water distribution pumps in un-electrified regions. Renewable energy
started to become more and more of a feasible solution especially with the increasing
insecurity of electricity supply and the unstable fuel prices, offering farmers and rural
residents environmentally friendly power sources to pump water. Technologies utilizing
solar energy for electrically powering the water pump are becoming more common, offering
competitive advantages over traditional fuel-driven generators.
Hand Pumps
This is probably the most ancient and trivial method for water
pumping. All it needs is a human pumping water by hand, able to
transfer water from an underground source to surface level.
Advancements have been made over time to construct a similar foot
pump or a bicycle pump, applying the same concept but can be run
by kids instead.
watercharity.org
Animal-driven Pumps
Donkeys, cows, camels, and sometimes sheep are used to pump water
for irrigation and domestic use. The animals are connected to a water
wheel and planned to keep walking in a tight circle to turn an axle
which in turn powers the waterwheel. This way water is pumped into
ground level and made available for use mainly for irrigation worldwidefood.org
applications.
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Wind Pumps
Traditional wind mills have been used for centuries, pumping water
directly from underground sources to end use which is mainly irrigation.
The wind turbine is coupled directly to a water pump, so as long as the
wind blows, there is water being pumped and made ready for use. It
consists of a wind turbine, a pump, and a piping system. georgeadamson.org
Solar Pumps
Solar pumps are the most feasible non-fossil-based technology for water
pumping. It is even more feasible than the traditional wind mills due to
their ability to pump water as long as the sun is there. It consists of solar
panels, a pump controller, a DC pump, or an AC pump with an inverter.
Some pumps use a linear current booster (LCB) that allows having an Engineeringforchange.org
extra current to start up the pump through voltage modification. This allows the pump to
start and run even on cloudy days.
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How it Works
Solar pumps utilize the photovoltaic effect to produce free electricity used for water
pumping. Photons of light hit a collection of solar cell, exciting electrons into a higher state
of energy, making them act as charge carriers an electric current. This is how Photovoltaic
(PV) cells produce electricity.
The photovoltaic effect was first observed in 1839 by Alexadre-Edmond Becquerel, and is
now used to produce electricity from one of the most dominant renewable energy resource.
The method is simple! DC electricity is produced in a set of silicon solar cells gathered in
modules and put together into arrays. Connected to a pump that can be either surface or
submersible. Surface pumps are mounted at ground level its inlet linked to the well and its
outlet to the water delivery point, while submersible pumps are completely lowered into the
water (best applicability for deep wells). Both DC and AC pumps can be used; in the case of
AC, an inverter is needed to convert DC to AC. The operation of the pump is controlled by a
pump controller that assess the voltage output of the panels.
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Storage can be done by the use of elevated water tanks or storage ponds where water is
stored until it is demanded and delivered to end-users, or through the use of batteries that
store electricity and save it until there is demand for water. The first is apparently more
feasible and less maintenance-demanding as compared to battery storage systems.
Some solar pumping applications use tracking systems to maximize power production and
increase daily gain, through single axis or dual axis tracking solar collectors. This is applied
in case of high volume demand but requires large water storage volumes.
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Why Go Solar?
Solar energy has been widely utilized for its positive impact on the environment and its
ability to replace oil-based electricity generators. Yet, there is more into solar energy when
it comes to water pumping, making it a more feasible and technically reliable solution for
agricultural and domestic applications.
There are many reasons to consider solar pumping as an alternative to conventional fuel-
based techniques. Table 3 shows the main advantages of solar water pumping over other
technologies
Category Advantage
Maintenance Low maintenance requirements
Running Cost Almost no running cost
Independence No fuel dependence
Operation Unattended operation
Pollution Zero pollution (no emissions, no spills, no waste)
Production Produce best during sunny weather, when water is needed most
Noise No noise produced
Lifetime Long lifetime (more than twice that of conventional technologies)
Flexibility Easily relocated, moved, or expanded
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Applications
Solar water pumping is primarily used in irrigation applications in remote areas and rural
regions where these applications are mainly demanded. Yet, solar water pumping is also
used for a variety of other applications such as domestic water supply, livestock watering,
and irrigation.
A lot of decentralized applications use batteries for electricity storage as they tend to use the
solar panels for their own domestic electricity consumption, which requires storage for
consumption during off-sun hours.
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Solar pumping is most suitable with application requiring low flow and pressure, which
keeps open channels and drip irrigation as the most suitable methods when coupled with
solar PV pumping.
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System Design
A good solar pumping system is the one properly designed and sized to fit the job
requirements. Various designs exist for a variety of applications, requiring research and
technical design to avoid system insufficient performance or unnecessary cost incurrence.
Unlike traditional utility or private generator powered systems, where large pumps are
normally installed to pump water in large volumes whenever power is available, solar PV
pumping requires more austerity as system components are really expensive and efforts
need to be done to bring system set up cost to a minimum.
During the design phase, system designers need to decide on whether the system is to be on-
grid or off-grid, with storage or without it and whether storage is in batteries or in elevated
water tanks. They need to decide on the type of pump being used and whether the
application requires a submersible or a surface pump, using AC or DC power. These all are
factors that affect the system performance and feasibility of the proposed solution.
On-Grid vs Off-grid
Typical PV systems are grid-connected, allowing feeding produced electricity into the utility
mains and thus using it as a storage volume. The concept behind on-grid systems is to reduce
the additional expenses of batteries and avoid lost excess energy that is being produced but
unused due to low demand.
In solar pumping applications, when the grid is available, some systems are hooked into the
grid allowing for a two-way exchange of power, working as such:
(1) When solar energy is available, and there is demand for water, water is directly
pumped to end use using solar power
(2) When solar energy is available, and there is demand for water but not consuming all
the electricity produced, excess electricity is fed into the grid
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(3) When solar energy is available, and there is demand for water but requiring more
power than what is produced by the solar PV system, extra electricity provided from
the grid
(4) When solar energy is available, and there is no demand for water, electricity is fed
into the grid
(5) When solar energy is not available, and there is demand for water, water is directly
pumped to end use using grid power
For applications where the utility grid is not available, mainly remote and not electrified
regions, the PV system is installed as a stand-alone system, sometimes connected to a private
generator and sometimes just left as a stand-alone unit.
The private generator plays the roles (1), (3), and (5) of the grid mentioned above. It
provides electricity when needed unless there is a storage system in place. This storage
system allows to store electricity or water to offer availability during night times and winter
seasons.
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Water storage is very practical when the system is properly sized. During sunny days, the
system provides enough water more than the daily requirements, since pumping is free, this
water can be stored in water tanks that should be sized to ensure sufficient storage volume
depending on climatic conditions and water consumption patterns. This is also called the
direct drive system design.
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Pump Type
Submersible vs Surface
There are two major types of pumps used in water pumping, the selection process depends
on the type of water source, the flow requirements, and the site conditions.
Surface pumps are used in shallow wells ad surface water sources such as streams and
ponds. It can only pump water from around 7 meters below ground level with the ability to
push far uphill but with a limited total dynamic head of 14 meters. Yet, to maintain pump
efficiency and increase system reliability it is recommended to keep the suction lift to a
minimum.
(1) Delivery pump: Moves water from a location to another, at both high or low pressure
(2) Pressure pump: Pressurize small water systems in homes and small buildings
(3) Booster pump: Maintain pressure or flow for towns and communities
Surface pumps are less costly than submersible pumps, and offered at larger variety, but
submersible pumps are mainly used for deeper wells although they are also suitable for
surface applications.
A submersible pump is usually positioned inside the underground well, normally located
more than 7 meters below ground level. Some pumps can go as deep as 450 meters below
ground level, with high durability characteristics and ability to tolerate water with relatively
high levels of salinity. Recent technologies are developing floating submersible pumps where
the pump is positing in a floating unit on the top of the water.
There are two major categories of submersible pump, the most common is centrifugal used
for low head and high water volume and the other is positive displacement including helical
rotor pumps and diaphragm pumps used for high head and low volume.
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Head Flowrate
Pump Type Remarks
(m) (m3/day)
Centrifugal 0 to 80 6 to 20 Similar to conventional pump
Figure 8: Major types of water pumps that can be used with solar energy [ 3]
AC vs DC
PV produces electricity in DC form, thus giving DC pumps an advantage over AC pumps due
to the avoidance of additional costs for the use of an inverter and the reduced efficiency
caused. But DC pumps are only suitable for small applications where the required flow is
relatively low.
Layout Design
Structure
Solar panels can be ground-mounted, roof-mounted, or post-mounted depending on the site
conditions. Metallic structures are normally used to hold the panels, these structures are
designed to withstand high winds and stormy weather.
The structure itself needs to be properly coated and protected against environmental factors
such as rain, humidity, and other conditions.
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Orientation
In order to maximize the performance of solar panels, it is essential to install them facing
true south, with an acceptable tolerance of 15 degrees towards east or west that doesn’t
significantly affect the performance. For applications needing solar energy in the morning
more than it does in the afternoon, a shift towards the east is practical to receive the solar
rays as early as possible.
In some situations there could be some shade caused by trees or other obstacles at one of
the sides, which requires shifting the panels slighting to the opposite sides to avoid shading
as much as possible.
Tilt
The panel can get the best out of the solar radiation when its surface receives the solar rays
at a perpendicular angle, allowing for a maximum solar ray density per unit area. But since
the sun path varies from day to another, being at higher levels during the summer and lower
in relation to the horizon.
energy.gov
According to the sun path and the latitude of Lebanon, the best tilt angle has been shown to
be around 55 degrees in winter and 15 degrees in summer, with 35 being an average value.
Rule of thumb says that the tilt angle needs to be almost as much as the latitude of the
location with a 5 degrees tolerance.
The optimal solution would be changing the tilt angle on daily basis to match the solar
radiation angle, but since this is not a practical solution, the application decides on the tilt
angle. In applications demanding maximum production in winter for example, there is a
tendency to go above average to guarantee best performance in higher demand seasons.
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For solar water pumping, water demand is at its highest during summer season, thus solar
panels are best when tilted at an angle of 30 or 25 degrees relative to horizontal ground level.
Sun Tracking
Although not very practical for solar water pumping applications, it is worth mentioning that
some applications do require sun tracking. This is done either by daily tracking, or seasonal
tracking, and sometimes both together known as dual tracking as shown in Figure 3 earlier.
Tracking systems can increase the output by as much as 35%, but also incur additional costs
and require more maintenance over the lifetime of the system.
Pump Location
The pump should be located in an enclosed room called a pump pit or a pump house. Surface
pumps are not water proof and need to be kept away from water and protected from
environmental conditions to prolong their lifetime and reduce maintenance requirements. If
a submersible pump is used, the pump will be inserted in the borehole, but should not be too
close to the bottom of the borehole or else it will stuck in dirt and lead to pump damage.
Distance between the pump and the PV panels should be kept to a minimum to reduce
voltage drop in the cables. Increased distance causes harmonics and would require a
harmonics filter to avoid damages to the pump and the inverter/controller.
Other Considerations
In order to make solar PV pumping a viable solution, several considerations need to be made
especially in the case of irrigation. These considerations make PV water pumping a
competitive and practical solution as compared to conventional diesel and grid-tied systems.
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(2) It is recommended that the plot size for solar irrigation doesn’t exceed 4 ha.
(3) High rates of system utilization are recommended to achieve economic viability,
making permanent crops and continuous crop rotation in arid climates the best
option for solar irrigation
System Components
A typical system consists of four major components that together make up a solar water
pumping unit capable of providing large capacities of water during summer and winter
times. The major components are the PV panels, the solar pump, the controller, and the
storage volume. Some systems use batteries as a storage volume while others use water
tanks.
There are other minor components that are also used such as the mounting structure, wiring,
piping, float switch and others.
PV Panels
The photovoltaic panel is the energy collector that receives solar radiations and converts
them to electrical energy. This conversion process loses as much as 80% of the energy thus
leaving us with an efficiency of 20% at best cases.
PV panels are considered the most important and effective items in the PV system, making
up almost 80% of the overall system cost (assuming no battery storage needed). How many
modules and how much collection area is a topic that will be studied under the system sizing
section.
PV panels produce DC electricity, they are interconnected together in series and parallel to
achieve the desired voltage and current.
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Solar Pump
The choice of pump type, size, and capacity depends on the application and its requirements.
In principle, submersible pumps are used in wells deeper than 7 meters and surface are used
for shallow wells.
Regardless of that, DC motors are widely applied in small applications with capacity not
exceeding 3 kW, mainly applicable for small water demand such as gardening, landscaping,
small volume livestock watering, etc. DC pumps are more efficient and more practical as they
do not require an additional component to convert current to Ac for instance. This reduces
costs and avoids additional efficiency drops.
Ac pumps are used for larger applications with capacities exceeding 3 kW, requiring an
inverter to change the current that the solar panels produce (DC) to a current that is suitable
for the pump (AC).
Latest 3-phase pumps use a variable frequency AC motor and a three-phase AC pump
controller that enables them to be powered directly by DC power produced by the solar
modules.
Controller
The controller plays a vital role in the system performance due to its ability to regulate the
power production to match that produced by the panels with that required by the pump. It
also plays a critical role in protecting the system by turning it off when the voltage is at
inappropriate level, meaning too low or too high compared to the operating voltage range of
the pump. This voltage protection role helps extend the lifetime of the pump and reduce
maintenance requirements.
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Storage Volume
The sun is not always there, and even when it is there the flow rate doesn’t always meet the
daily water demand. This requires the use of a storage volume that can benefit from the solar
energy available all day long and store it either in electrical energy form in batteries or as
potential energy form in storage tanks.
Batteries are only used when there is no possibility to have a water storage volume or when
the volume is not sufficient. They increase the set up invoice by almost double and require
frequent maintenance and replacement at least every 4 years. This makes water storage a
more practical and efficient solution.
The storage volume and capacity requirements depends on the application and the pattern
of water demand, but in principle the tank is sized with a capacity that is 3 times the daily
demand on average . In some applications storage volume can go to a capacity of 10 times
the daily water demand.
Other components
Other components include the support structure that provides stability to mounted solar
panels, electrical interconnections including cables, junction boxes, connectors and switches,
earthing kit for safety in case of lightning or short circuit, and plumbing requirements from
pipes and fittings required to connect the pump come as part of the installation.
In addition, a harmonics filter might be required to avoid inverter and pump damage.
Whether a filter is required or not should be mentioned in the inverter datasheet.
Sizing Methods
Oversizing would incur unnecessary costs, and undersizing would lead to insufficient
performance. This is why each component needs to be properly designed and sized to meet
the specific requirements of the project. It is the only way to guarantee reliability and system
durability, and achieve the desired performance.
The steps that need to be followed in the sizing process of a new water pumping system
powered by solar are presented in Table 7.
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Table 7: Steps and their outputs in the sizing process of a solar pumping system
(a) The depth of the well (A) decides on whether a surface pump can be used or not. For
wells deeper than 7 meters below ground level, it is demanded to use a submersible
pump instead even though it costs more.
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(b) The water level (C) decides on the position of the submersible pump. Clearance needs
to be kept between the bottom of the borehole and the pump.
(c) Delivery capacity (Tested delivery capacity) measures the capacity of water source to
provide water in a sustainable manner. Withdrawing more than the tested delivery
capacity leads the borehole to become a dry well as the discharge rate exceeds the
water resource replacement rate.
(a) Water demand is the major factor affecting the size of the pumping system. It is
calculated as a daily consumption rate and in some times as an hourly rate in case the
consumption pattern requires that.
Table 8 shows the average values used as international benchmarks for the daily
consumption rate in various applications such as residential, livestock, and irrigation.
Table 8: Daily consumption rate average values for different applications [4 ][6 ][7]
(b) The storage capacity is the volume of water that need to be stored to ensure sufficient
and continuous supply of water to end users. Storage tanks usually range in capacity
between a storage of 2 to 10 days depending on the location and the usage patterns.
For example, if the daily demand is 2,000 liters the storage volume should be at least
6,000 liters, and could go up to 20,000 liters in some applications.
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In order to ensure sufficient storage, the pumping system needs to be sized with
additional water volume demand of between 10% and 40% based on the application.
The total head is the distance between the storage delivery points to the submerged depth
of the pump in addition head losses through the piping system. It is the summation of
elevation head, major losses head, and minor losses head.
(a) The static head (D) is the height between ground level and the storage volume. It
should be kept to a minimum to reduce the lift requirements of the pump, but needs
also to take into consideration the suitability of the storage location. Every meter of
height accounts for one meter of dynamic head.
(b) In order to compute the dynamic head, an approximate value is used measuring the
distance covered by pipes from ground level to the storage volume in the horizontal
direction. For a perfectly horizontal path only 5% of the covered distance is accounted
for, meaning that if the pipe runs for 100 meters in the horizontal direction with no
inclination, 5 meters are added to the dynamic head. In case of inclination, the height
difference should be accounted for in the storage height value.
Example:
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It is recommended to use a safety factor of 20% going up to 30% if the water condition is
unstable. For this purpose, it is imperative to keep the pump head higher than the total head
calculated by at least 20%.
(a) Lebanon is blessed with good solar radiation levels, varying from a yearly average of
1,700 kWh/m2 in the least irradiated regions to 2,500 kWh/m2 in those regions with
best solar irradiance. Irradiance reaches highest levels during the months of May,
June, July, and August, peaking in July at more than 300 kWh/m2 per month.
Figure 13: Solar irradiance data for the city Zahle in Bekaa [4]
(b) Peak sun hours (PSH) indicates the average equivalent hours of full sun energy
received per day, this varies based on the location and the tilt angle, with 1 PSH equals
to 1 kWh/m2/day.
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The flow rate can be calculated from the water demand and the peak sun hours per day.
Calculated in m3 per hour, the flow rate is the result of the demand in cubic meters divided
by the peak sun hours in hours.
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The pump power required can be computed in one of two main methods. The first method
is using the pump sizing chart provided by the pump manufacturer and requiring two
variables only that are the total head (3) and the flowrate (5).
Flow rate and TDH are plotted on the sizing chart as shown in Figure 14 in red and green
respectively, with the blue curves being pump performance curves. The point of intersection
between flow and TDH is the point of reference. The selected pump needs to have its curve
encompassing the reference point, preferably the closet one to guarantee best efficiency.
Other type of pump performance charts are also common and will be used in the rest of this
document, which allows matching the pump flow with the pump head curve and match it
with the required peak power. Example curves for positive displacement and centrifugal
pumps are shown in Figure 15 and Figure 16.
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The second method uses a formula that calculates pump power from the total head (3) and
the flowrate (5), water density, and gravity. It is not recommended to use this method as it
sometimes return inaccurate data. It is better to refer to official datasheets published by
manufacturer to avoid being too theoretical in the sizing process.
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G = 9.8 m/s2
The efficiency factor is normally take 80%, and the inverter efficiency taken around 85%.
The inverter efficiency is only applied if there is a need to convert from DC to AC and an
inverter is being used.
The final stage is deciding on the solar array connections and how to make the
interconnections in order to achieve the desired voltage and current.
Connecting the panels in series adds up the voltages of the panels while keeping the current
fixed. While parallel connections add up the current while keeping the voltage fixed.
Table 10 shows the effect of parallel and series connections on the voltage and current of PV
modules. Each module is assumed to have a voltage of 40V and current of 3A.
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None 40 3
Series 120 3
Parallel 40 6
Cost
Solar pumping is most practical and financially feasible when the power line is more than 1
km away from the pump location. The investment that would be made to have a solar-
powered water pump makes more sense than that made to extend power lines.
On average, extending the power lines costs somewhere between 18 and 36 USD per meter,
in Lebanon there is no official data published by EDL as each case is studied on its own. But
there is no doubt that the numbers wouldn’t be any lower than 18 USD per meter of lines.
The cost of a solar PV pump depends on the requirements and the site conditions. The
availability of the pump also plays a major role and the security levels in the area do have an
influence on the investment value.
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International benchmarks are available from previous experiences in the developing world,
especially in India. Data published by Energypedia showed an average investment rate of
$5.93 USD per Wp for a 1 kWp PV drinking water supply system and $11.85 for a ready-to-
operate system including pumping system, logistics, set-up, reservoir, construction, water
distribution. This rate drops as the capacity increases to reach $4.63 and $7.59 respectively
as shown in Figure 17. Nowadays, these rates are expected to have dropped by at least 20%
due to the latest advancements in PV cells technologies and the drop in prices.
A comparative chart for diesel water pumping and PV water pumping is presented in Figure
18 where methods are compared in terms of m4 delivered, with m4 equals volume in cubic
meters multiplied by the total dynamic head in meters.
Figure 17: Investment cost of PV pumping systems for drinking water supply [1 1]
In Lebanon, A typical 10 kW solar pumping system for domestic water use delivering 13,000
liters per day would cost around 20,000 USD, assuming that the pump is already available,
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making an average of $2 per Watt. Smaller systems tend to have a higher USD per watt rate
but normally not exceeding $4 per watt.
Table 11 shows the cost range of major components of a solar pumping system and presents
the case of a typical 10 kW pumping system, and Table 12 shows the price variation as
compared to the size range considering economies of scale.
Economic Analysis
Solar pumping makes more sense in applications not demanding very high water supply, so
the solar powered pump can operate slowly based on the solar radiation availability. When
compared to conventional diesel generator pumps, it appears that solar pumping pays back
the investment in an average of 2 years.
According to a study performed by Emcon Consulting Group for the UNDP in Namibia, aiming
at assessing solar pumping as compared to diesel pumping, a medium size solar pumping
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system with a head of 80 meters and flowrate of 12 m 3/day would break even in 2 years with
diesel at an average price of $0.86 per liter and 2.6 years with diesel at $0.57 per liter. The
results of the assessment is shown in Figure 19.
For other flowrate and head values, Table 13 shows the breakeven for different values,
highlighting in yellow the cases where solar pumping would make sense. The blocks in grey
identify cases where there is no alternative pump to be used for solar pumping, in such a
case diesel still needs to be used or the solar PV system will be designed to provide electricity
to the existing AC pump.
Table 13: Years to breakeven – when solar becomes cheaper than the diesel option [1 2]
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System Performance
The output of the solar pump varies by season, all depending on the solar insolation level
and the power of the pump. A simplified way to estimate the water pumped volume is
presented based on the formulas used in the sizing process but going in reverse.
Also
Conclusion:
With the solar insolation varying by month, the water volume pumped will also vary based
on those values.
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Sizing
With a water depth being less than 7 meters, a surface pump will be used.
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With a THD of 16 meters (52.5 ft) and a flow of 0.69 m 3/h (3 gpm), using the pump sizing
chart for positive displacement pumps, the water pump and its relative power is identified
The pump operating voltage and technical specification are determined from the datasheets.
Assuming that the minimum operating voltage of the pump is 60V.
In order to supply the power of 200 W, two panels will be used each with a power rating of
117 W at 35.5 V and 3.3 A. the panels will be connected in series to reach the 60V voltage requirement
of the pump.
The final designed system now utilizes 234 Watt solar panels at 71 V and 3.3A.
Cost Estimation
Table 14: Cost estimation for example 1
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Performance
2.04 PSH
= ×
m3/h h/day
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Given data:
- Cattle: 150 milking cows Month PSH Month PSH
- Well depth: 16 meters January 4.213 July 8.096
- TDH: 50 m February 5.049 August 7.986
- Location: Bekaa March 6.017 September 7.645
- Tilt angle: 30° April 6.721 October 6.479
- PSH (20°): 6 hrs/day May 7.623 November 5.082
- PV Panel: 117 W; 35.5 V; 3.3 A June 8.173 December 3.982
-
Sizing
With a water depth being more than 7 meters, a submersible pump will be used.
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Using the second method for pump power calculation, with a THD of 50 meters (164 ft) and
a flow of 2.21 m3/h (9.73 gpm), and using the pump sizing chart for positive displacement
pumps, the water pump and its relative power can be identified.
The pump operating voltage and technical specification are determined from the datasheets.
Assuming that the minimum operating voltage of the pump is 60V.
In order to supply the power of 700 W, six panels will be used each with a power rating of
117 W at 35.5 V and 3.3 A. The panels will be connected in series and parallels (2 groups of three
panels each) to reach the 60V voltage requirement of the pump.
The final designed system now utilizes 702 Watt solar panels at 106.5 V and 6.6A.
Cost Estimation
Table 16: Cost estimation for example 1
Inverter Watt - -
Other material Watt 702 $0.09 $63
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Performance
1.96 PSH
= ×
m3/h h/day
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In the case of battery usage for energy storage, which is not a very good idea, maintenance
and battery replacement would be required every four years on average. There are some
modern batteries that can live up to 8 years but are still considered expensive and would
require very delicate preventive maintenance that might not be present in typical solar PV
pumping applications (mainly in rural and remote regions).
For the other components, the PV modules are considered sturdy and strong enough to
withstand harsh environmental conditions coming with a warranty of 10 years, an expected
lifetime of more than 25 years, and normally an efficiency maintenance guarantee that
ensures efficiency drop doesn’t exceed 20% over the period of 25 years.
The pump normally lives for more than 8 years and can reach 14 years if well maintained.
Usually it is sold with a 2 year-warranty and spare part availability.
Other than that, only occasional inspection and regular maintenance is required, at no cost,
to make sure the system is doing fine and avoid losses due to dust or other residues sticking
to the panel. It is essential to properly operate and maintain the pumping system to achieve
high efficiency and reliable operations.
Operation Guidelines
o The pump should be switched off when not in operation
o The pump should never run dry. This is a concern only for surface pumps. It is critical
to make sure the suction is primed before turning on the pump
o The pump should be properly mounted and fixed on the base-plate to withstand
vibrations and avoid unwanted noise that could also reduce the lifetime of the pump
o The pump should be used daily for at least 15 minutes to avoid problems
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o Pump should be covered adequately for weather protection. In a pump pit with
adequate air venting system (passive or active)
o The surface pump should be kept away from water at all times
o The pump should not be switched on and off too often. There should be at least 15
seconds between a switch off and a switch on
o Sharp bends should be avoided in the pipe lines to avoid unnecessary pressure drops
o In case of thunders and strong wind, panels should be kept in the zero-tilt position
(applicable only for tracking systems)
o The cover of the main junction box should not be left open
Regular Maintenance
Monthly
o Panel Cleaning: Clean the panels regularly to avoid particles, feces, leaves, and other
residues from blocking the sun. Panels can be cleaned with a plain piece of cloth with
the use of some water when available.
o Panel Inspection: Inspect the PV panels to make sure there are no cracks or damages
Biannual
o Shadow Prevention: Check the panels for any shadow and perform necessary
trimming of trees if necessary.
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Annual
o Valves Inspection: Check and clean the foot-valve.
o Electrical Components Check: Check switches, fuse, wiring, junction box and
connections.
Biennial
o Pump Inspection: For surface pumps, carbon brushes need to be checked and replaced
every two years.
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The largest renewable energy market in Lebanon is the solar water heaters market. A market
that has been developing tremendously since the beginning of this century to be ranked
among the most developed markets in the world by the International Energy Agency. The
solar PV market is not as developed; it only started during the past couple of years after the
Ministry of Energy and Water through the LCEC launched a green loan financing mechanism
with the Central Bank of Lebanon. This financing option, called NEEREA, offers individuals
or institutions interested in implementing a green initiative to benefit from long term loans
with very low interest rates.
As NEEREA developed, the market started growing with several companies adding solar PV
solutions to their scope of work and many others being established to offer this service. Yet,
there is not much done in the solar pumping sector, and most installations performed are
either in the residential or institutional fields being offered as an alternative power supply
source to back-up generators.
Table 18 presents the major socioeconomic factors that play a major role in identifying the
potential for solar pumping in Lebanon.
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Factor Situation
Availability of solar Lebanon has a total of at least 3,000 sun hours per year, with an annual
radiation average solar insolation of more than 2,200 kWh/m 2, and a daily global
sunny period of more than 4.8 kWh/m2.
Suitability with Water for agricultural use is needed most during the summer season. This
agricultural needs is the period where the solar insolation peaks making solar pumping a
very practical solution
Having a wider look at the market, there are several barriers that are hindering the
development of solar pumping in Lebanon that need to be resolved. This includes market-
related, technology-related, and regulatory barriers.
Table 19: Major barriers and potential solutons for solar pumping in Lebanon
Barrier Solution
Technology No standardization & quality control Enforce standards and follow up on quality
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CASE STUDIES
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Contractor
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Contractor
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Contractor
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Contractor
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Service provided*
Company Name Website
D S I M
Acemco www.acemco.com.lb
Albina www.albinagroup.com
ASACO www.asacogtc.com
Dawtec www.dawtec.com
Earth Technologies www.earthtechnologies.com.lb
Ecosys - Midware www.itgholding.com
EEG www.eegroup.info
Elements Sun & Wind www.elementssw.com
Green Arms www.greenarms.co.uk
Green Essence www.greenessencelebanon.com
Panoramic Solar www.panoramic.ws
SIG www.saleminternationalgroup.com
Solar Wind ME www.solarwindme.com
Solar World www.solarworld.com.lb
Solarnet www.solarnet-online.com
Yelloblue www.yelloblue.com
REFERENCES
[1] ScoutHub, LLC. (2014). Pump Applications. Retrieved December 17, 2014, from
http://www.pumpscout.com/all-pump-applications/
[2] Bhavnagri, K. (2010, January 21). Solar Trackers. Retrieved January 3, 2015, from
http://www.solarchoice.net.au/blog/solar-trackers/
[3] Solar-Powered Water Pumping Systems for Livestock Watering. Agriculture and Agri-
Food Canada.
[4] Gleick, P. (1996). Basic Water Requirements for Human Activities: Meeting Basic Needs.
Water International, 21, 83-92.
[6] Jenkins, T. (December 2014). Designing Solar Water Pumping Systems for Livestock.
Cooperative Extension Service - Engineering New Mexico Resource Network.
[7] Morales, T., & Busch, J. (2010). Design of Small Photovoltaic (PV) Solar-Powered Water
Pump Systems (Technical Note No. 28). Portland, Oregon: Natural Resources
Conservation Service.
[11] Photovoltaic (PV) Pumping. (2014, October 6). Retrieved January 8, 2015, from
https://energypedia.info/wiki/Photovoltaic_(PV)_Pumping
[12] Emcon. (2006). Feasibility Assessment for the Replacement of Diesel Water Pumps with
Solar Water Pumps. Windhoek, Namibia: UNDP.
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