Solco Sun Mill: FAQ

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FAQ

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Answers

How do solar pumps work?

A solar pump is essentially an electric pump attached to a standalone power supply. There are generally four parts:

A 'wet end', which is the mechanical device that moves the water. Sun Mill pumps utilise various types of wet ends. Some use a helical rotor that 'screws' the water from a low level to a high level. Others use a centrifugal rotor that acts the same way as a fan does to move air. The Sun Mill Original uses a piston and valve assembly.
An electric motor, which transforms electrical energy into rotary motion. The electric motor is often connected directly to the wet end. For submerged pumps, this means that the motor is of a special submersible type that is water proofed. The Sun Mill Original has an above-ground motor that is of simpler construction.
A control box, which determines how much current to draw from the solar panels at any instance, for any amount of available sunlight.
Solar panels, which transform light energy directly into electrical energy.

You can provide your own piping to route water from where it is to where you want it, or get a Sun Mill dealer to help you design your water delivery route.

What happens when it's cloudy?

When clouds pass in front of the sun, the intensity of light falling on the solar panels drops. The solar panel will not be able to produce as much current as during full sun. If a motor attempts to draw too much current from a solar panel the power delivered can be adversely affected. This is the reason for the control box - it senses the drop in light intensity caused by a cloud, and reduces the current the motor draws to keep the maximum amount of power flowing.

Under all but the heaviest of clouds, your pump will continue to function, only with a reduce flow rate. The Rapid and the Quicksilver use a helical rotor wet end that is particularly good at operating under cloud.

How reliable are solar pumps?

Solar pumps are the reliability gold standard for moving water. The design of a solar pump minimises moving parts. By minimising moving parts wear is localised to just a few components and breakdowns become very infrequent. This means that a solar pump, once set up correctly, can run for many years with minimal intervention required on your behalf. This is not to say that they require zero maintenance: it pays to periodically check your solar pump components for wear and replace them before a breakdown occurs.

Who can benefit from solar pumping?

Solar pumps can benefit anyone who regularly needs to move significant amounts of water, without having access to metropolitan or town scheme water. This may include homeowners on rural or semi-rural properties, farmers who need to water livestock and irrigate crops, or even small communities that may wish to raise their water supply to improve pressure. Sun Mill pumps see service in all of these scenarios, filling everything from home and hobby farm water tanks to entire communities in remote locations.

Who is behind Sun Mill?

Sun Mills were originally developed in Western Australia by Solar Energy Systems in the late 1990's. In 2001, Solar Energy Systems became Solco Ltd. and Sun Mill pumps became part of a larger family of solar products. In 2012 Solco continues to deliver water and power solutions across Australia and the world - see www.solco.com.au.

How much total dynamic head (TDH) can a Sun Mill pump to?

The different Sun Mill models have different capabilities. In general, there is a compromise between the head that is required to be overcome and the amount of water that can be pumped during a period of time. The Aqua is capable of pumping up to 70m (700kPa or 100psi). The Cascade is capable of pumping up to 35m (350kPa or 50psi). The Sun Mill Original is capable of pumping up to 60m (600kPa or 87psi). The Quicksilver and Jetstream are capable of pumping up to 120m (1200kPa or 175psi). Larger Rapid systems are capable of pumping up to 230m (600kPa or 330psi).

In practice, you are not limited by the amount of TDH you need to overcome. To pump higher heads, multiple Sun Mills can be daisy-chained together.

How much water can a Sun Mill pump?

The amount of water that a Sun Mill will pump depends on the pump model and the total dynamic head (TDH) that needs to be overcome. At 15m head, the smallest Sun Mill pumps around 2,600 litres per day. The largest Sun Mill can pump well over 100,000 litres per day at 15m head. The chart at left shows the capabilities of the Aqua, Cascade, Original Sun Mill and Quicksilver models. The Jetstream model is not shown, as its potential is essentially unlimited.

Do Sun Mills use batteries?

Some Sun Mill versions implement a sun-tracking system powered by an actuating arm. The arm is powered by a small 12 volt battery which is trickle-charged by the solar panels. Tracking system batteries tend to enjoy long life, as they are rarely discharged more than a few percent from maximum capacity.

Are Sun Mill pumps suitable for liquids other than water?

We do not recommend using a Sun Mill to pump liquids other than water. Corrosive liquids will degrade and eventually destroy your pump. Highly viscous liquids such as oil can foul the pumping mechanism and significantly reduce performance.

You may use a Sun Mill to pump brackish or dirty water, however be warned that you may reduce the pump's life by doing so. If you must pump water containing particulates, we recommend performing more frequent maintenance. All water pumps should have inlet filters fitted to keep moving parts free of foreign matter.

What kind of weather conditions can the Sun Mill stand?

Sun Mills are designed to operate out in the open, under intense sun or heavy rain, or in high winds for years on end. Any plastics used in the pump's components are UV stabilised.

It is advisable to remove the solar panels from your Sun Mill if you are expecting a cyclone or severe hail storm to pass through your area. Sun Mills are designed so that this is a simple and quick process, taking only a couple of minutes.

How much does a Sun Mill cost?

Prices for examples of the different Sun Mill models are available on our products page. The low volume Aqua starts at $2,215 ex GST. Jetstream models can range into six figures for high head, high flow configurations. Note that these costs are one-off, with very little ongoing costs involved. This compares favourably with diesel or petrol-powered pumps in the long term.

What kind of maintenance do Sun Mills need?

Maintenance schedules vary depending on the pump model. Submersible pumps will benefit from being removed from the bore and checked for wear on a six-monthly cycle. Piston pumps will benefit from a lubrication and wear check every three months.

Only the mechanical parts of a Sun Mill require maintenance. The solar panels and electronic components are maintenance-free: you can expect your solar panels to deliver power reliably for over 25 years without any form of maintenance being required.

How long will a Sun Mill last?

Different parts of your Sun Mill have different lifespans. The solar panels are designed to last for over 25 years before needing replacement. Electronic components will last at least 10 years. Mechanical parts will require regular replacement of bearings and bushings around every 5 years to maintain optimum operation. Nitrile seals should be replaced every 2 years to maintain optimal flows.

Do Sun Mills come with a warranty?

Sun Mills are sold with a 12 month warranty on parts and labour.

Where do I go to buy parts for my Sun Mill?

Sun Mill replacement parts are available from 202 dealers located across Australia and selected international locations. Click here to find the dealer nearest to you.

My Sun Mill isn't pumping as much as I expected. How can I get more water out of it?

In most instances, more water can be pumped by increasing the solar power installed - adding more solar panels. Whether your pump can be upgraded depends strongly on the model and the way it is configured. Often, adding an incompatible component to your pump can degrade performance instead of enhancing it. Locating the bottleneck in your pumping system is a job for experienced personnel - we strongly recommend that you contact your local dealer to discuss your needs before attempting to reconfigure your pump.

Can I have my Sun Mill turn off automatically?

Yes. An optional low-source switch can be attached to the Sun Mill to sense when your bore or dam runs dry, turning off the pump accordingly. Additionally, you may wish to include a tank-full switch that senses when the destination tank is full, again turning off the pump.

What is the difference between a fixed and a tracking array?

A sun-tracking solar array changes its angle in an east-west direction throughout the course of the day so that it faces directly at the sun at all times.

The amount of power produced by a solar module is affected by the angle that the light hits the surface. When light hits the solar cell surface at a low angle, it is more 'spread out', so that less light falls on the array's surface area. A tracker ensures that light always falls on the array at the best angle possible.

A fixed array does not adjust its angle dynamically. A fixed array may, however, be angled in a north-south direction towards the sun's winter or summer path through the sky and adjusted occasionally (2 or 4 times a year) to catch the sun better at these times.

Tracked arrays require fewer solar panels to output the same amount of energy over the course of the day compared to a fixed array. This reduces solar panel costs, however there are initial and ongoing costs associated with fitting and maintaining the tracking hardware.

What effect does adding a tracker to my array have?

Sun tracking arrays produce more power and thus more water. In bright sunlight a tracking array can provide around 40% more power over the course of the day. The difference is most notable in the morning and afternoon: the water pump will start pumping earlier, and pump more during the early and late hours.

Sun trackers are less effective in cloudy weather: the cloud diffuses the incoming sunlight, which hits the array from many angles at once instead of from a single bright spot in the sky.

About rebates

Am I eligible to receive a government rebate when I buy a Sun Mill?

The federal government encourages the use of renewable energy systems in areas off the main power grid and may provide a rebate for your Sun Mill. The rules surrounding the rebate program are detailed and will not apply to all solar pump installations. We urge you to visit http://www.environment.gov.au/settlements/renewable/rrpgp/ and read the rebate guidelines to determine whether you qualify.

The Aqua and Cascade products do not satisfy the rebate program requirements, which specify a minimum flow of 8,000L per day at a total dynamic head of 20m. Sun Mill Original, Rapid, Quicksilver and Jetstream systems may qualify, depending on other factors outlined in the guidelines.

Solco satisfies the supplier and designer requirements as listed in the guidelines. Your Solco dealer satisfies the installer requirements of the guidelines.

About Installation

Where can I install my solar array?

The sun powers your pump through the solar array. If your array falls under shade at any time the power it can produce will be markedly reduced. Shade on even a small part of the array will reduce power disproportionally and may cause the pump to stop working. For this reason, your array should be sited in an area that is guaranteed to receive sun for as much of the day as possible, all year round. Take note of the location of trees that may grow tall enough to shade the array in the future and move the array appropriately.

Try to find a location for the array near the pump motor, but note that the array does not need to be sited near the motor. The array can be located hundreds of metres away from the pump head, but electrical wiring will need to be sized carefully so that power is not lost in transit. The further your array is from the pump motor the higher gauge wire you will require, and the cost you incur will rise accordingly.

Does my solar array need to be on a pole?

Your solar array is mounted on a pole to reduce the accumulation of dust on its surface, and to raise it above growing vegetation. If the array tracks the sun, the pole is also required to provide a range of movement.

A thin film of dust on your solar array will not significantly affect its operation. Rain, especially on dry ground, kicks dust into the air in thick globules that will affect your solar array's performance if allowed to accumulate. The pole raises the array above this airborne dirt, representing a maintenance-free way of keeping your array clean.

Do I need to adjust my solar array with the seasons?

Whether you adjust your array seasonally depends on your water needs. Most arrays will be tilted in a north-south direction to provide the best flow for summer (this will be 10° from horizontal from low latitude up to about 33° latitude and will vary at higher latitudes), because that is when most people need water the most. This tilt angle does not provide the best flows in winter, however, and some applications require a more consistent year-round flow. There are a few different ways to manage seasonal sun-angle variation:

Maximise summer flow: tilt your array to the noon angle of the summer sun and leave it. This provides optimal water flow during the summer, but reduced performance during the winter.
Maximise consistency: tilt your array to the noon angle of the winter sun and leave it. This provides optimal water flow during the winter when the sunlight is weaker. Summer performance will be reduced. This combination of raising winter flow and reducing summer flow provides the most consistent water flow throughout the year.
Maximise year-round flow: adjust the angle of your array periodically. It is not necessary to adjust the array more than 4 times a year and for most purposes twice a year is adequate. Adjusting the array more often provides diminishing benefit. For twice per year adjustment move the array between the winter and the summer angle around the time of the autumn and spring equinoxes (the end of March, and the end of September). For four times per year adjustment move the array from summer to equinox angle around the end of February, from equinox to winter angle around the end of April, from winter back to equinox angle around the end of August and from equinox to summer angle around the end of October.
Compromise: tilt your array to equinox angle and leave it. The equinox angle is the same angle as your latitude.

Note: we have used "summer", "equinox" and "winter" angles here - the exact angle depends on your location.

Small array frames provide three pre-drilled bolt holes for selecting seasonal tilt. These holes are designed to be generally applicable, and are not optimised for specific locations. Large array frames provide a continuous-adjustment system that allows any angle to be selected.

Glossary

What is total dynamic head? Why is it important?

Total dynamic head (TDH) is a measure of how much force your pump needs to exert to move water. TDH is a combination of hydraulic head and friction loss.

Hydraulic head is the force required to lift water against gravity. Water in any section of pipe is weighed down by all the water above it. The further your water inlet is below your outlet, the more hydraulic head (measured in metres, kilopascals or pounds per square inch) needs to be overcome.

Friction loss refers to the fact that as water moves through a pipe, it has to slide along the walls of the pipe. Although water is slippery, there is still some friction to be overcome. The smaller the pipe diameter, the faster the water is moving. Therefore, more friction loss is experienced and the pump requires more power to operate effectively. The situation is complicated by turbulence in the water at high flow rates, and the presence of any elbows in your pipe system, where water must change direction quickly.

What is insolation?

Insolation is a measure of the intensity of sunlight, and this light intensity is converted directly into electric current by solar cells. The figure commonly quoted is that 1000 watts of light power fall on every square metre of ground. This is not the case for most locations at most times. Latitude, time of the year, time of the day, shade and cloud all have an effect on insolation levels in your location.

When you specify a TDH and flow level required for a solar pump, we use the Bureau of Meteorology's average insolation figures for your area to figure out how much solar power to include to meet your needs.

What is voltage?

Voltage is a measure of how much energy an electric current has.

Electricity is essentially a flow of electrons. You can think of it as a flow of water. When electrons have high energy they are said to have high voltage. High voltage electrons are able to travel more easily through a conductor such as a wire or the windings in a motor, producing larger currents and more power.

What is current?

Current is a measure of the rate of flow of electricity.

Electricity is essentially a flow of electrons. You can think of it as a flow of water. Current is a measure of how many electrons are travelling through a wire at any one time. Thinking of water, a low current is like a creek, where high current is like a river. Higher currents correspond to higher power in electrical devices.

What is power?

Power is a measure of the rate of energy conversion.

Electricity is essentially a flow of electrons. Every electron has energy, called the voltage. The amount of electrons flowing is called the current. The energy (voltage) in each electron added up for all the electrons in an electric current tells us how much energy the current has as a whole. Power is a measure of how much of this energy moves through a device every second.

A motor, for example, converts the energy in an electric current into rotary movement. The amount of energy it converts every second is the motor's power consumption.

What is a kilowatt-hour?

A kilowatt-hour is a unit of energy.

Power, or energy converted per second, is measured in watts. A kilowatt is 1000 watts, which is roughly the power consumption rate of devices like electric water heaters, fridges, microwaves and kettles. A kilowatt-hour refers to a 1000 watt device operating continuously for 1 hour.

A 500 watt solar pump will produce a kilowatt-hour of electrical energy every 2 hours or around 2.5 kilowatt-hours every day.

Energy is often measured in kilowatt-hours because it leads to convenient numbers. For example, we might just as easily measure energy in watt-seconds, but now the solar pump above is producing 9,000,000 watt-seconds of energy per day. Most people find it easier to think in smaller numbers.

If you are on scheme power your power bill will quote the average number of 'units' you use every day. These units are actually kilowatt-hours.

What is the difference between connecting panels in series and parallel?

There are two ways of connecting solar panels together: series and parallel.

When you connect solar panels in series, the positive cable from one panel is connected to the negative cable of another. The voltage of the two panels combined is the sum of the voltage from each panel, whereas the current is not affected.

When you connect solar panels in parallel, the positive cable from one panel is connected to the positive cable of another, and the negative cable is attached to the negative (you will need a couple of double-adapters, as the cable ends are keyed to only connect positive to negative). The two panels together can deliver the sum of the currents of each, though the voltage remains unaffected.

Thus, to increase the voltage of a solar array, you connect panels in series. To increase the current, you connect panels in parallel. Doing either increases the power delivered by the array, since power=voltage x current.

The voltage that a solar array is allowed to deliver is limited by safety concerns. As voltage increases, electricity becomes more dangerous. Thus, cables are often connected in series up to a maximum safe voltage, then to increase power, sets of panels already connected in series are connected in parallel to increase the current the array is able to deliver. Such arrangements are often referred to as 'strings'.

Care must be taking to match panels when they are being connected together. When panels with different current ratings are connected in series, the set will only be able to deliver the current of the lowest-rated panel, which not only wastes power, but may overload the limiting panel. If panels or sets of panels with different voltages are connected in parallel, a current will flow between them, potentially damaging one or the other.

FAQ

About Solar Pumps

About Sun Mill

About Rebates

About Installing

Glossary

Answers

About rebates

About Installation

Glossary