1.
How does the sun power a pump?
2. Where do solar pumping systems work?
3. Will they work in winter?
4. Will a system save me money vs. the alternatives (Petrol
/ Diesel Generators, Mains Electric)?
5. Where and how are the panels located?
6. How do Solar Tracking Systems work?
7. Can batteries be used in water pumping systems?
8. Does the system have to be earthed?
9. How difficult is it to install a solar pump system?
10. Does it have to be fixed or can I move it around?
1. How does the sun power a pump?
Solar PV (photovoltaic) panels are large flat rectangles, typically somewhere
between the size of a radiator and the size of a door, made up of individual
solar energy collectors called solar cells covered with a protective sheet of
glass. Just like the cells in a battery, the cells in a solar panel are designed
to generate electricity; but where a battery's cells make electricity from chemicals,
a solar panel's cells generate power by capturing sunlight instead. The sun's
energy, or photons, cause electrons in the solar cells to move rapidly and it
is this movement that becomes electricity. Each cell generates a few volts of
electricity and the combined solar modules panel combines the energy they produce
to make a bigger electric voltage and current. The product of this voltage and
current results in the power rating (watts) of each solar panel. Providing sufficient
power (Volts x Current) is generated by the panel the pump motor will turn and
pump water. The important thing to note is that, in order to generate electricity
solar panels need sun 'light' not 'heat', so on a cold sunny day they will operate
perfectly well.
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2.
Where and when do solar pumping systems work?
Designed correctly, solar pumping systems work anywhere where there is sufficient
sunlight (technically called irradiance) and the intensity of light varies greatly
throughout the day. They don't work at night! Morning and afternoon sunlight
is less intense because it is entering the earth's atmosphere at a high angle
and passing through a greater cross section of atmosphere, which reflects and
absorbs a portion of the light.
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3. Will they work in winter?
Yes they will, although the sun's energy is weaker (because the sun is lower in
the sky relative to the panel surface) and water output will be lower than summer
output. Fortunately, most needs for water correspond with the sunniest seasons
of the year - spring, summer and autumn but if the same amount of water is needed
in winter then the system can be designed to meet the winter demand; in this scenario
the system will be running less often in summer otherwise it will pump far more
water than is required.
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4. Will a system save me money vs. the alternatives (Petrol / Diesel
Generators, Mains Electric)?
As water sources are often sited where grid power cannot be economically provided
and generator refueling and maintenance costs are becoming far too prohibitive,
the economy and reliability of solar electric power make it an excellent choice
for remote water pumping. As a result, more and more livestock and crop producers
are enthusiastic solar pump users. Solar pumping systems in remote locations
will more often than not be cost effective compared to generators, even with
5 times the initial capital cost. Low end generators, which are initially inexpensive,
require consistent maintenance and have a design life of approximately 1,500
hours. Small to medium sized solar pumping systems often initially cost less
than a durable slow speed engine driven generator. Most larger pump systems
initially cost more than generator systems, but tend to be far more economical
in the long run and significantly less hassle! If getting electricity to your
water source is hugely expensive, solar is an excellent economic choice. This
fact is reinforced by the staggering costs of extending power lines and the
escalating price of diesel fuel. A solar pump minimises future costs and uncertainties;
the fuel is free. Moving parts are reduced to one, an extremely reliable pump
motor, providing near-zero maintenance costs.
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5. Where and how are the panels located?
Solar modules should be located in a sunny spot, facing south (or north if you
are south of the equator), where no shading occurs. Even shadows from a tree branch,
tall grass, or fence posts can substantially reduce power output. If they are
not high enough off the ground then passing animals, people or machinery can cause
a reduction in performance as the pump cannot be re-started for 20 minutes (a
protection measure to avoid the pump motor overheating due to 'cycling'). If nothing
can regularly pass in front of a panel then it must be at least well clear of
growing crops and grass. For these reasons we typically mount the solar modules
on a pole, or twin poles for larger systems. Panels can be installed on ground
mounts but must be above any obstacles as outlined above. The solar array can
be placed away from the water source if shading is a problem and cable size can
be increased to compensate for longer cable runs and the associated voltage drop.
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6.
How do Solar Tracking Systems work?
Optimal solar panel performance is achieved if the sun is kept at 90 degrees to
the panel. Although less expensive and tolerate higher wind loading, Fixed Mount
structures result in an element of the sun's energy being lost as it arcs across
the southern sky. Tracking mount structures monitor the sun's position in the
sky and orientate the panels to maintain the 90 degree angle to the sun all day
long. This provides more power to the pump over a longer period of the day, producing
20% to 40% more water each day. Although more expensive, Trackers offer a great
advantage when pumping water. Positive single axis trackers are known for their
excellent reliability and service life. They take very little power from the system
as they operate (4 watts). Positive trackers come with a 3 year warranty and are
highly recommended in all locations. The heavy duty actuator is operated by some
very simple electronics that measure the length of the previous day by measuring
the time that the panels are producing any voltage. This time span is then split
into 6 equal periods and the array is moved from east to west in 15 degree intervals.
At night the array is moved to the horizontal position to minimize wind loading.
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7. Can batteries be used in water pumping systems?
While batteries may seem like a good idea, they are expensive (a battery bank
can double the cost of the system) and have a number of disadvantages in pumping
systems. They reduce the efficiency of the overall system because you do get get
back all the energy you store in a battery and they require periodic replacement.
Batteries also require additional maintenance and under and over-charge protection
circuitry which adds to the cost and complexity of a given system. For these reasons,
only about five percent of solar pumping systems employ a battery bank and are
generally used in household situations that require water pressure at night for
showering, bathrooms etc.
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8. Does the system have to be earthed?
What about lightning? Earthing is required
and the Pump installation manual covers this in some detail, suffice to say that
the system needs to be earthed to either a steel well head or Earth Rod kit (supplied).
Surges induced by lightning are one of the most common causes of electronic controller
failures in solar water pumps. Damaging surges can be induced from lightning that
strikes a long distance from the system, or even between clouds. The risk of damage
is greatly reduced if the installation instructions are closely followed.
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9. How difficult is it to install a solar pump system?
It isn't difficult at all; we have designed our systems for straightforward installation;
we do all of the complex wiring before shipping to you. Installation simply consists
of building the concrete footings (full instructions are supplied) and bolting
together the pole mount and panels, installing the earthing and connecting 6 to
8 wires from the pump, low water sensor and float switch (optional) into the junction
box. The controller and junction box come bolted to the pole mount post and are
pre-wired. A full step by step, illustrated installation manual is supplied and
telephone back-up is available.
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10. Does it have to be fixed or can I move it around?
Ground mounted solar pumping systems are more easily portable, whereas larger
systems and pole mounts can be moved but require more effort. By mounting the
solar system on a suitable trailer (ensuring it is fully earthed after moving
to the new position) a system can be moved from borehole to borehole, river to
river etc. This increases the economic return by maximising the use of a system
through the seasons and/or using it to correspond with the rotation of grazing
areas, irrigation areas etc.
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