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Sunday, October 22, 2017

Solar powered boreholes

Power Options Limited is a leading supplier of solar water pumping systems.

Solar technology is very well suited to pumping water. A typical system includes one or more solar panels, an efficient 12 volt DC pump, a controller (with float switches), and a linear current booster. We stock all these.

As long as it's daytime and the float switches show that the water source is not empty and the cistern in the house is not overflowing, the pump will run.  The linear current booster allows the pump to run even if it's cloudy out.

Reasons for using Solar Water Pumping?

If you need to supply water beyond the reach of power lines, then solar power can solve the problem. Photovoltaic powered pumps provide a welcome alternative to fuel-burning engines, windmills, and hand pumps. They produce best during sunny weather, when the need for water is greatest.

Among the equipment we stock and use to set up solar powered water pumping systems are;

Solar Panels - Photovoltaic (PV) panels produce in cold or hot weather. Solar water pumps are specially designed to utilize DC electric power from photovoltaic panels.

Low volume pumps - Low volume pumps use positive displacement (volumetric) mechanisms which seal water in cavities and force it upward. Lift capacity is maintained even while pumping slowly. These mechanisms include diaphragm, vane and piston pumps.

Centrifugal Pumps - Centrifugal pumps are used where higher volumes are required.

Surface Pumps - A surface pump is one that is mounted at ground level.

Submersible pumps - A submersible pump is one that is lowered into the water. Most deep wells use submersible pumps.

Pump controllers - A pump controller (current booster) is an electronic device used with most solar pumps. It acts like an automatic transmission, helping the pump to start and not to stall in weak sunlight.

Solar trackers - A solar tracker may be used to tilt the PV array as the sun moves across the sky. This increases daily energy gain by as much as 55%. With more hours of peak sun, a smaller pump and power system may be used, thus reducing overall cost. Tracking works best in clear sunny weather. It is less effective in cloudy weather.

Storage equipment - Storage is important. Three to ten days’ storage may be required, depending on climate and water usage. Most systems use water storage rather than batteries, for simplicity and economy.

Float switches - A float switch can turn the pump off when the water tank fills, to prevent overflow.

 Advantages of Solar Pumps

 Compared with windmills, solar pumps are less expensive, and much easier to install and maintain. They provide a more consistent supply of water. They can be installed in valleys and wooded areas where wind exposure is poor. A PV array may be placed some distance away from the pump itself, even several hundred feet (100 m) away.

Applications

  • Commercial or Domestic Water: Solar pumps are used for private homes, water venders, villages, medical clinics, etc.
  • Irrigation: Solar pumps are used on small farms, orchards, vineyards and gardens. It is most economical to pump PV array-direct (without battery), store water in a tank, and distribute it by gravity flow. Where pressurizing is required, storage batteries stabilize the voltage for consistent flow and distribution, and may eliminate the need for a storage tank.
  •  Livestock Watering: Among our clients ranchers are enthusiastic solar pump users. Their water sources are scattered over vast rangeland where power lines are few, and costs of transport and maintenance are high. Some ranchers use solar pumps to distribute water through several miles of pipelines.

Other clients have had us supply them with portable systems, moving them from one water source to another.

 A water pump can be powered by its own Photovoltaic array, or by a main system that powers lights and appliances. We sometimes use an elevated storage tank, or a second pump called a booster pump to provide water pressure. Or, the main battery system can provide storage instead of a tank. Rain catchment can supplement solar pumping when sunshine is scarce.

 When designing a system, we view the whole picture and consider all the resources.

There are no limits to how large solar pumps can be built. But, they tend to be most competitive in small installations where combustion engines are least economical. The smallest solar pumps can lift water from depths exceeding 200 Feet (65 m) at 1.5 gallons (5.7 liters) per minute. In a 10-hour sunny day it can lift 900 gallons (3400 liters).

Slow solar pumping lets us utilize low yield water sources. It also reduces the cost of long pipelines, since small sized pipe may be used. The length of piping has little bearing on the energy required to pump, so water can be pushed over great distances as low cost. Small solar pumps may be installed without heavy equipment.

The most effective way to minimize the cost of solar pumping is to minimize water demand through conservation. Water efficiency is a primary consideration in solar pumping economics.

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