• How It Works: Water Well Pump

    If you live in a town or city, you probably don't give much thought to how the

    water you use each day gets to your house. Even small villages often provide a network

    of supply pipes that transport water to each home in the neighborhood. All you need to

    know is how to open the tap at the sink.

    Move a few miles out of town and the picture can change. While the inner workings

    are still—thankfully—invisible, your water supply is independent from the

    neighbor's down the road. Each home has its own well from which to draw water. More

    than that, each home has its own electromechanical system for getting the water from the

    well to the house. At the heart of each system is a pump

    , and the most common types are jet pumps and submersible pumps.

    Well types

    In many areas of the country, finding potable water is as easy as getting out a

    shovel and digging a hole in the ground. Okay, maybe "easy" isn't the

    right word, but wherever the water table is only several feet below the surface of the

    ground, part of the battle may already be over. In such a shallow-well situation,

    lifting the water up to the house is going to be a little easier, if only because the

    distance you have to move it is modest.

    If your area doesn't have a high water table, or if it lacks a stable supply of

    potable water near the surface, you must dig deeper to achieve the same result. And

    because a deep well means that the water has to be lifted farther, the strategies for

    moving it change.

    Shallow-well pumps

    These days, the most common pump for a shallow well is a

    jet pump. Jet pumps are

    mounted above the well, either in the home or in a well house, and draw the water up

    from the well through suction (see Single-Drop Jet-Pump System diagram on next page).

    Because suction is involved, atmospheric pressure is what's really doing the work.

    Think of the system as a long straw. As you suck on the straw, you create a vacuum in

    the straw above the water. Once the vacuum is there, the weight of the air, or

    atmospheric pressure, pushes the water up the straw. Consequently, the height that you

    can lift the water with a shallow-well jet pump relates to the weight of the air. While

    air pressure varies with elevation, it's common to limit the depth of a jet-pump-

    operated shallow well to about 25 ft. There is also deep well pump.

    Jet pumps create suction in a rather novel way. The pump is powered by an electric

    motor that drives an impeller, or centrifugal pump. The impeller moves water, called

    drive water, from the well through a narrow orifice, or jet, mounted in the housing in

    front of the impeller. This constriction at the jet causes the speed of the moving water

    to increase, much like the nozzle on a garden hose. As the water leaves the jet, a

    partial vacuum is created that sucks additional water from the well. Directly behind the

    jet is a Venturi tube that increases in diameter. Its function is to slow down the water

    and increase the pressure. The pumped water–new water that's drawn from the well by

    the suction at the jet–then combines with the drive water to discharge into the

    plumbing system at high pressure.

    Because shallow-well jet pumps and deep well water pump use water to draw water, they

    generally need to be primed–filled with water–before they'll work. To keep water

    in the pump and plumbing system from flowing back down into the well, a 1-way check

    valve is installed in the feed line to the pump.

    Solar Powered Water Pumping

    Any renewable energy source can make the electricity needed to power various

    appliances, including pumps. Solar electric power in particular is a reliable and

    economic choice for powering remote water pumping. Solar water pumping systems are in

    common use for garden fountains, livestock watering, and large-scale watering needs for

    commercial installations. 

    Cattle ranchers all over the world are enthusiastic

    solar pump users because their water

    sources may be spread over large areas of rangeland that lack utility power and where

    generator use would be expensive and impractical. Photovoltaic (PV) panels are therefore

    in widespread use for reliably producing electricity directly from sunlight to power

    livestock and irrigation watering systems. When properly designed, PV-powered pumping

    systems can result in significant long-term cost savings and a smaller environmental

    footprint compared to conventional power systems.

    System Design Considerations

    A typical solar-powered water pump system, which includes a solar array, controller,

    pump, and storage tank. (Source: “The Montana Agsolar Project – Expanding the

    Agricultural Uses of Solar Energy in Montana.”)

    A solar-powered water pumping system consists of four parts:  the actual pump

    which moves the water, the controller which adjusts the pump speed and output power as

    the solar panel input varies, the engine, and the solar panels. The specifics of the

    system design are determined by the following considerations:

    The site-specific available solar energy (or insolation).

    The volume of water required in a given period of time for the application at hand.

    This may include additional water to be stored for periods when the PV is not operating

    or has diminished output.

    The total dynamic head (TDH) for the pump (the equivalent height that water must be

    raised, taking friction losses in the pipes into account.)

    The quantity and quality of available water.

    The system’s proposed layout and hydraulic criteria.

    Pumps for Solar Pumping Systems

    There are two major types of solar pumps, direct current (DC) and alternating

    current (AC). DC solar pump

    s are generally suitable for small applications (garden fountains, landscaping,

    etc.) and are relatively low-priced, particularly because they do not require inverters

    to produce AC power from the solar panels. These pumps are generally designed to operate

    with minimum electrical power, so they have rather low flow rates. Such pumps often find

    use in submersible deep wells where a slow but steady pump rate is acceptable.

    AC solar pumps are driven by inverters producing AC power from PV panels. They are

    suitable for all kinds of applications from landscaping to irrigation, particularly

    large-scale applications such as farmland irrigation, desert control, and so forth. AC

    solar pumps are available in power output ranges from 150W to 55kW.

    Solar-powered pumps are characterized as either positive displacement pumps (e.g.

    diaphragm, piston, or helical rotor) or centrifugal pumps. Positive displacement pumps

    are typically used when the TDH is high and the flow rate (measured in gallons per

    minute) required is low. Conversely, centrifugal pumps are typically used for low TDH

    and high flow rates.

    There are many resources available that provide specific information and advice for

    implementing solar water pump

    s in a variety of situations. These should be consulted to meet the needs of

    specific applications.

    • Creado: 09-11-21
    • Última sesión: 09-11-21

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