1. No category

April 2015
Exchange Issue 15
Solar - Driven Water Pumping:
An Untapped Resource for Lebanon
Guest Author: Mr. Nader Hajj Shehadeh
Energy Consultant, Lebanon
[email protected]
1 Introduction
Why Solar Pumping?
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. Millions of cubic meters
are pumped every day all over the world for rural
applications, with electricity and onsite generators
being utilized as the primary sources of power.
Renewable energy started to become more and
more of a feasible solution in the recent years
given the combination of high energy prices and
lowering costs of renewables, especially solar
PV technologies, providing farmers and rural
residents with environmentally friendly power
sources to pump water with clear competitive
advantages
over
traditional
fuel-driven
generators.
Available abundantly, solar energy offers a potentially
financially feasible and technically practical solution,
with solar water pumping becoming very common in
agricultural applications using sophisticated yet wellestablished technologies to empower water pumps
that move 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.
When compared to other water pumping methods
that have been and are more commonly utilized,
such as diesel-powered, wind-powered, humanpowered and animal-powered sources, solar
pumping has its advantages as demonstrated in
Table 1.
Solar water pumping is becoming a more common
application in rural areas, primarily used in irrigation
and domestic water supply for private homes, camps,
villages, rural medical centers and other facilities .
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Table 1: Advantages and Disadvantages of various energy sources for water pumping
Farms, orchards, vineyards, and domestic gardens
are using solar pumps for irrigation and cattle
watering purposes, with best results and most clear
feasibility in application requiring low flow and
pressure, making open channels and drip irrigation
the most suitable methods when coupled with solar
PV pumping.
How does it Work?
The method is simple. Direct current (DC) electricity
is produced in a set of silicon solar cells, connected
to a pump that can be located either on the 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 alternating current (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 assesses
the voltage output of the panels (see Figure 1).
Storage can be done by the use of elevated water
Figure 1: Typical off-grid surface and submersible solar pumping system sketch
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tanks or storage ponds where water is stored until it
is 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 more feasible and
requires less maintenance compared to battery
storage systems.
A typical system consists of four major components
that 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.
The PV panels are considered the most important
and effective items in the pumping system, making
up almost 70% of the overall system cost (assuming
no battery storage needed). Panels produce DC
electricity, they are interconnected together in series
and parallel to achieve the desired voltage and
current.
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 pumps installed on the surface are used
for shallow wells. DC motors are widely applied in
small applications with capacity not exceeding 3 kW
[Jekins 2014)] , 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. 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.
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 an 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.
Figure 2: Typical solar pumping system for irrigation, livestock and domestic water supply
Sizing the Solar Water Pump
There are different factors that affect the applicability
of the solar pump and the system’s optimal capacity.
The sizing process normally requires the following
data:
1)
Water source inspection to evaluate the
water depth, water level, and delivery capacity and,
accordingly, decide on the type of pump and water
capacity available
Water demand on site is based on the application
and the number of cattle, acres of irrigated area, and/
or number of residents to supply water to. There are
some benchmarks used, for example a milking cow
consumes 95 liters per day, while a horse consumes
76, and a hectare of rice consumes 100 liters, etc…
[Jekins (2014), Gleick (1996), Morales et al (2010)]
2)
Total head including dynamic and static head
in order to evaluate the friction loss
3) Solar resources online including solar
radiation and sun peak hours per day in order to
design the PV arrays
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4)
Required flow rate based on the water
consumption profile on site
Based on this data, the pump is sized and the solar
PV system is designed accordingly. Some solar pump
manufactures offer simplified graphs allowing the
sizing of the complete system through the knowledge
of the basic flow and head requirements (see Figure
3).
Figure 3: Example solar pump sizing diagram (Mono Pumps Limited, 2007)
Financial Performance
Solar pumping is most practical and financially
feasible when the national grid 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 [CEMC (2014), Home Power (2014)], but in
Lebanon there is no official data published by EDL
on these costs.
International benchmarks are available from previous
experiences in developing countries, especially
India. According to a study performed and published
on Energypedia.com, the average investment for a
1 kWp solar water pumping system is around $5.93
USD per Wp excluding pumping system, logistics,
set-up, reservoir, construction, and water distribution
costs. A ready-to-operate system, including pumping
system, logistics, set-up, reservoir, construction, and
water distribution costs is $11.85 per Wp.
The study goes beyond 1kWp and assesses larger
systems of capacities of 2kWp and 4 kWp, to find out
that the rate drops to $4.63 per Wp for basic 4kWp
system, and $7.59 for a 4kWp ready-to-use system,
as shown in Figure 5.
Figure 5: Investment cost of PV pumps systems for drinking water supply (Energypedia, 2015)
A comparative chart for diesel water pumping and PV
water pumping is presented in 6 where methods are
compared in terms of m4 delivered, with m4 equals
volume in cubic meters multiplied by the total dynamic
head in meters.
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Figure 6: Water pumping cost of diesel compared to PV per m4 (Energypedia, 2015)
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, 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.
When compared to conventional diesel generator
pumps, it appears that solar pumping pays back the
investment in an average of 2 years. Results have
shown that a medium size solar pumping system with
a head of 80 meters and flowrate of 12 m3/day would
break even in two years with diesel at an average
price of $0.86 per liter and 2.6 years with diesel at
$0.57 per liter, as shown in Figure 7.
Figure 7: Diesel versus solar water pumping breakeven point for different diesel price
For other flowrate and head values, Table 2 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.
For example, a water pump with a flow rate
requirement of 8 cubic meters per day and a head of
80 meters would break even in 1.3 years (16 months),
and a system with 25 cubic meters and 40 meters
head would break even in 2.6 years (32 months)
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Table 2: Years to breakeven - when solar becomes cheaper than the diesel option )Emcon, 2006)
Solar Pumping for Lebanon
Solar Resource
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, as shown in Figure 8.
Figure 8: Solar irradiance data for the city of Zahle in the Bekaa (SolarMEDAtlas)
Potential and Opportunities
Solar water pumping has a huge potential in the
agricultural sector in Lebanon, where large amounts
of water is demanded especially during summer
seasons. Yet, it is not very common among farmers
and people involved in the agricultural sector.
There are no more than 15 projects implemented in
Lebanon, with more than 80% of them initiated by the
technology provider rather than the farmer himself.
This is an indication of how much there is a lack of
awareness among users, and there is a need for
more efforts and incentives to make it a viable and
applicable solution.
According to the latest statistical review performed by
the ministry of agriculture, there are around 175,000
farmers in Lebanon working in various agricultural
activities. The total agricultural land is somewhere
between 215 and 277 thousand hectares (215,000
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ha reported by ministry of agriculture in 2011, and
277,000 ha reported by the ministry of information in
2010). 25% of this land requires watering according
to the ministry of agriculture, making around 54,000
hectares.
The water demand in the agricultural sector is 877
million cubic meters per annum, requiring a pumping
power of 260 MWp of solar PV to power pumps,
assuming an average total head of 100 meters. If
pumped using diesel pumps, these systems consume
an annual diesel capacity of 26 million liters, costing
$13M at an average diesel price of $0.5.
At an average investment rate of $2 per Wp,
switching all irrigation pumps to PV requires an
overall investment of $53M, leading thus to a payback
period of 4 years.
With the utilization of proper financing mechanisms,
solar pumping can become more and more
financially attractive to farmers and individuals living
in rural regions, where the purchasing power is low
and it is rarely possible to invest large amounts of
money in solutions like solar pumping. This is where
NEEREA comes in handy, offering farmers funding
opportunities that require no upfront investments,
with low interest loans paid over a long period of time.
The overall irrigation demand would avoid the
consumption of around 26 thousand tons of diesel
per year, thus avoiding greenhouse gas emissions of
around 68 thousand tons of carbon dioxide equivalent
per year.
Conclusion & Recommendations
To date, Lebanon is not an oil-producing country,
remaining highly dependent on foreign resources of
fuel for electricity production. This gives renewable
energy and especially solar an added value and
presents it as a reliable solution contributing to
increasing energy security in the country and
reducing energy demand.
The solar water heaters market is the biggest
renewable energy market, being followed by the PV
that 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.
Although there is not much solar pumping projects
in operation, there is a significant potential for the
development of this sector in Lebanon, especially
with the frequent fluctuation of fossil fuel price and
the growth of water demand in rural regions where
various agricultural activities are abundant.
Table 3 presents the main barriers hindering the
development of solar pumping in Lebanon that
need to be resolved. This includes market-related,
technology-related, and regulatory barriers.
Table 3: Major barriers and potential solutions for solar pumping in Lebanon
Having a proper financing mechanism in place, and
raising awareness among farmers and end users are
definitely game changers. This would push the solar
pumping market forward and create an attractive
market place for investors and technology providers.
With a payback period ranging from a few months to
few years, there is no doubt sola pumping is capable
of being the next big thing.
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References
CEMC (2012). Line Extension Charges. Retrieved
from
http://www.cemc.org/line-extension-charges.
asp, Cumberland Electric Membership Corporation
Emcon. (2006). Feasibility Assessment for the
Replacement of Diesel Water Pumps with Solar
Water Pumps. Windhoek, Namibia: UNDP.
Energypedia (2014, October 6). Photovoltaic (PV)
Pumping. Retrieved January 8, 2015, from https://
energypedia.info/wiki/Photovoltaic_(PV)_Pumping
Gleick, P. (1996). Basic Water Requirements for
Human Activities: Meeting Basic Needs. Water
International, 21, 83-92.
Home Power (2014), Line Extension Fees
Copyright © UNDP/CEDRO - 2015
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 (UNDP).
The Consultant does not guarantee the accuracy
of the data included in this report. The boundaries,
colors, denominations, and other information shown
on maps and images in this work do not imply any
judgment on the part of the Consultant or UNDP
concerning the legal status of any territory or the
endorsement or acceptance of such boundaries.
The United Nations Development Programme and
the Consultant assume no responsibility of any kind
for the use that may be made of the information
contained in this report.”
Jenkins, T. (December 2014). Designing Solar
Water Pumping Systems for Livestock. Cooperative
Extension Service - Engineering New Mexico
Resource Network.
Mono Pumps Limited (2007). Solar Powered Water
Pumping. Literature Reference: ART 29/4.
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.
Ministry of Environment (2010). State and Trends
of the Lebanese Environment. Chapter 3: Water
Resources.
[email protected]