Frequently asked questions (FAQ's)
Solar water pumping systems have now been around for over 20 years. Even after all these years there are still unanswered questions – no longer are the questions about how the technology works, but what the technology can do.
How long do solar pumps last?
Solar pumps are made of many components and these have a variety of lives. There are system that are now 10 years old.
Is a solar pump user serviceable?
They should be, and most are. However the bigger Brushless DC systems have complicated electronic controllers that cannot be serviced by anyone other than a trained technician.
What is the cost of maintenance?
Most solar pumps work for around 2,500 hours per year. This is equivalent to the life of a family car. Maintenance cost depends on the size and type of system – the range is between $ 200.00 to $ 1,000.00. It is always a good question to ask “What is the cost of maintenance?”
What are the best solar modules?
All solar modules are alike - they all deliver Watts of power. Some modules work better in high temperature, while others are smaller for the same rated power. All solar modules have a 20 year limited warranty, and all cost about the same price.
Is temperature de-ration important in solar modules?
Yes, but only for the maker of the system. Most solar modules lose performance in the heat of the day. Crystalline modules (older technology) are de-rated by up to 30% of their power. This means in hot conditions a 60Watt module only delivers 42 Watts.
How much sunshine is there per day?
This differs from month to month. The useable hours per day is rarely more than 7.8 hours – that is, the number of hours when the insolation value is 1000 watts per square Metre. 1000 Watts per Sq. Mtr. for one hour is called one Peak Sun Hour (PSH).
Do solar pumps work on cloudy days?
Yes, in fact some cloudy days will produce more water because the modules are cool. Generally, however performance will be reduced, often by about half.
What factors affect solar water pumps?
The critical factors are the volume, and the height to which the water is to be pumped. With regard to volume the seasonal demand is important. Can the system pump enough during the less sunny seasons?
How easy are solar pumps to install?
W.D.Moore & Co’s solar pumps are supplied completely assembled (and tested). This means that installation is just a matter of concreting a pole in the ground, sliding the array on top, and lowering the pump into the bore. The downhole equipment is also supplied pre-wired.
Why do people buy solar pumps?
Solar pump are simple, easy to maintain, cheap to run, safe, and mobile; but mainly because they are the latest technology. They also offer the opportunity to control the water flow.
Are solar pumps safe?
Generally the system voltage is less than 48 Volts DC. This is not a lethal voltage. However larger systems do use voltages up to 180 volts DC, and these must not be handled by anyone other than a qualified technician.
How much does a solar pump cost?
From $3,000 up to $35,000, depending on how much water is required, and how far the water is to be pumped.
When should a tracker be used?
Trackers add about a third more water per day, for the same number of modules; or less modules could be used if a lower output were required. The real benefit of a tracker is if the bore does not produce much water – then a tracker will permit a lower flow rate over more hours per day. The decision to use a tracker or not is most often dependant upon the flow required and the pumping depth, and is decision made by the system designer. If it less expensive to use a tracker then that’s when a tracker will be recommended. A simple rule is “if it system will work without a tracker, then don’t use one.”
What do Controllers do?
Controllers are essential for most solar pumping systems because they maximise the power from the modules going to the motor. Acting like a gearbox in a car, they vary the current to the motor in the same way a gearbox varies the revs to the wheels – in the morning and afternoon when the insolation (the amount of sunlight) is low they reduce the voltage and increase the current. The pump will work at a lower speed but water will still be pumped.
Why are positive displacement pumps used ?
Simply for efficiency. Posititive displacement pumps are more than three times more efficient than centrifugal pumps. This means less modules can be used.
Why not use batteries?
It is not that batteries are not used; it’s that their use is avoided. Batteries are inefficient and a waste of scarce power. The only time to use batteries is if the system needs to pump at night.
How far can solar pumps pump?
There is really no limit, except for the cost. If the pipeline is able to handle the head, a solar pump can be designed to do the job.
Can an AC power supply be used with a solar pumping system?
Yes, in some cases.
Is efficiency important?
The efficiency of the pump and motor are most important. For this reason most solar pumps are positive displacement type pumps. The efficiency of the solar modules is not important as module efficiency is only related to surface area – water pumping systems are usually in open paddocks. Why is area of any importance?