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SolarTown Learning

The Basics of Solar Water Pumps

12-23-2009
Category: Solar Water Pumps

Solar Water Pumps Provide Clean Reliable Energy in Remote Areas

Solar water pumps are a great resource to power a pump in any geographic location. Solar pump applications make economic sense because they provide clean reliable power in remote areas, saving fuel and power line costs. Solar power water pumps are easy to install, since you do not need a battery or battery charging equipment. When the sun is shining, the system is pumping, when the sun is not shining, the system is off.Solar water pumps

Battery systems can be integrated into the system, but the addition of a storage tank and a larger pump will allow storage of excess water overnight and during cloudy conditions. Solar modules can be mounted almost anywhere, but should face south (for North America) and be positioned in unobstructed light for maximum output.

Most farm and ranch applications should have the solar modules and pump controller mounted on a raised pole to stay above snow drifts and potential damage from animals. Basic pump systems only require a few components- the pump controller, and the solar modules. Here we will take a closer look at their roles and how to choose the right parts for you.

Controllers are Integral Part of the Solar Water Pump System

Solar charging controllers are key in maximizing pump performance and energy input. Although it is possible to connect the pump directly to the output terminals of the solar module, a controller provides much better pump performance, a start/stop control, and it maximizes the life of the pump. It prevents the pump from trying to operate when there is not enough voltage, and it has stalled. Pumps have a minimum current draw required to run. If this is not met, the solar water pump will stall and no pumping will occur.

During less than ideal solar periods, output of the solar module can be below the amp draw required for the pump to begin pumping. A solar pump controller will convert any excess voltage of the solar array to more output current, allowing the pump to operate during ‘stall' periods. If the pump was hooked directly to the panel it would not operate during these times.

Solar Water Pumps Flow and Lift

Solar water pumps are designed to provide a flow of water (GPM) for a given pressure or lift (head). Pump "head" is measured in feet, and represents the total lift the pump can raise water from a low point to a high point. Sometimes head is expressed as (PSI), and 1ft of head=0.433PSI.

In order to determine the head requirements of you pump, you need to determine your site requirements. As an example, I want to fill a tank on top of a small hill. The water level in this tank will be 5 feet high above ground level, and the hill top is 50-feet higher than the well. The well is 100ft deep and the pump will be positioned 80ft down. The water line is 30ft below the surface, and we anticipate the "drawn down" or level the water falls once pumping starts, to be 20ft.

You do not need to calculate the head from the location of the pump or the bottom of the well, but from the draw down point or the well water surface. Therefore, I have 55ft of elevation above ground and 50ft below ground (30ft to water table +20ft of draw down) for total of 105ft or 45.4PSI of head to fill the hilltop water tank. It's that easy.

Solar Water Pump Specifications

Most solar water pump specifications are listed in a table providing the flow rate information at specific heads. Generally speaking, as the head increases the flow rate declines. Therefore it is important to size your pump based on your flow rate and head requirements.

For instance if you do not have a high flow rate requirement, you will need a less powerful pump and solar panel, saving money. Selecting the right solar array for you pump is based on your pumping requirements and location. Although it varies by location to location, the average year round daylight in the US is 4.5 hours. Knowing how long you can expect the solar pump to run daily, allows you to calculate the size of the pump to meet your needs. Once you have determined your flow rate and head needs, pump specifications will indicate their power requirements.

Most low flow solar pumps are 12V but there are commercial pumps with higher voltages that operate at 24V or 48V. You will want to size your solar array larger than the pump requirements in order to account for efficiency loss and to keep your pump operating at maximum power. Depending on the pump you choose, you may need more than one panel to increase voltage. SolarTown's staff will be happy to help you correctly size your solar modules.

Pipe Sizing for Solar Water Pumps

It is important to protect your pump intake from sediment and debris that can clog components and cause the motor to breakdown. Pipe sizing is integral in a pump system. Low flow pump systems do not maintain enough water velocity to prevent sediment build-up, and based on total piping distance, pipe thickness may vary to prevent flow rate decrease due to friction loss and eventual choking off water flow. However, pipe thickness also adds to your head requirement. For every 100ft of 1/2in PVC pipe used in a system, the head require increases by 1ft for a 1gpm system. Thus it is important to consider pipe size to maximize flow rates and consider how much piping will be required to when calculating pump sizes.

SolarTown Can Help Select Your Solar Water Pump

With the basic information provided above you should now have an understanding of the general requirements behind a pump system. Their relatively simple design makes them easy to install and cost effective, making solar water pumps a clean reliable cost effective solution to meet all of your water pumping, storage, and irrigation needs. Now that you have the basics you can begin to understand how to design your own solar water pump system. Of course, SolarTown is glad to help. Our team is here to offer its expert advice to help you determine the right solar pump, panels, and accessories to suit your needs.


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