Solar pump to drive drip system?

jerryk1234jerryk1234 Registered Users Posts: 2
Hello,

I have about an acre here in suburbia. A lot of grape vines, fruit trees. City water is getting expensive, and I'd like to utilize my well. It's a shallow dug well. The county well guy says it might date from the 19th century. I have been fabricating a cover for the well of welded steel. It's a long term project. We have been building up a fairly extensive drip irrigation system also. I would like to use a solar system to drive the well pump - that way, I don't have to run wires out from the house, get a permit, etc etc ( the well is already permitted ).

I'd like to run the drip system directly from the well, and use an irrigation controller to turn the pump off when it's not needed. It would probably run a couple hours every other day. Existing literature that I've perused says that you fill a storage tank from the well, and then run the drip off the storage tank. I'm not sure I understand why that's necessary. Why not just drive the drip system direct from the well?

The well is in a basin on one side of my property. The water would have to be transported up to the top of my hill, about 70 feet higher. Say a total lift of 100 feet ( or less ) from the water level in the well to the top o the hill.
But then all the drippers are downhill from that point.

I also need to choose a pump. I wouldn't say price is no object, but I can go a grand or so. Keeping in mind that I also have to buy the solar panels, and a mount ( or steel to fabricate same ).

Comments?

Comments

  • mike95490mike95490 Solar Expert Posts: 8,170 ✭✭✭✭✭
    The way I understand plumbing and wells, is the water is below ground and does not run uphill. So a pump is lowered in, and pressurizes a 40 gallon tank with 55psi water. There is an air balloon in the tank that expands and provides pressure for when the pump does not run. If you don't have a pressure/accumulator tank, the pump starts and starts many times in a few minutes and overheats the starting winding in the motor. I would expect a solar pump to have the same limitations, and the ability to have pressure if a cloud obscures the sun for 10 minnutes, would keep the irrigation cycle going.
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  • AnawaAnawa Solar Expert Posts: 209 ✭✭✭
    I'm using PV as the power element in a water distribution system using above ground storage. Part of the system includes a drip irrigation field for our 1/2 acre garden. PV is only an element in the system and in some respects, the most uncomplicated part.

    Above ground water storage can simplifiy the process because it does away with the need for batteries in the PV system. You size the tank according to your needs, then add a couple of days more storage capacity for cloudy weather. Start by determining your maximum daily water demand. Also, it's a lot easier to trouble shoot and service a gravity water system than sophisticated PV electronics and batteries. Stuff will happen.

    If you decide above ground water storage is the route for you (and your budget permits), your post suggests that the water tank would be best situated on the "hill" between the well and where you would irrigate. Makes sense to me. This design would be best suited for a submersible pump placed in the well that "pushes" the water up-and-out of the well and continues to push it up to the tank. If the hill is unobstructed, you could mount the PV panels in conjunction with a water storage tank structure. I recommend that you consider protecting the tank from weather (very important) and vandalism (if the threat exists). Such a setup would require trenching for the pipe (probably 1-1/4") and laying the buried cable in the same trench (I'm guessing a minimum of 10awg).

    A high quality submersible pump that should take care of your water needs with necessary valves, fittings, controllers, cable, etc. could cost up to $3,000 installed. This assumes that you would be involved in a lot of the installations. Then, you will need the PV array and racking system, probably another $1,200 to $1,500. And additionally, a tank, foundation, controls housing, and other stuff that you may find necessary. I have 1,500 gal tanks that cost me $900 delivered, but not installed. Water is heavy, some type of foundation is required.

    There are many other possible designs and many people far more knowledgable in this area than me, I offer this scenario simply because it has, and still is, working for me and suits my overall needs.

    Oh, one more thing, drip irrigation needs high quality and filtered water, otherwise you'll be spending a lot of time maintaining your system and less time enjoying the fruits of your labor.

    Paul
    Paul 
    in Georgia

    System 1: PV- 410w Evergreen, Mppt- Blue Sky Solar Boost, Batt - 225ah Deka AGM, 12v led house lighting,
    System 2: PV- 215w Kyocera, PWM - Morningstar PS30, Batt- 225ah Deka GC's, 12v led house lighting, Dankoff 12v water pump,
    System 3: PV- 1.5kw Kyocera, Grundfos 11 SQF well pump, 3000 gal above ground water storage, dom water & irrigation,
    System 4: PV- 6.1kw Kyocera, Mppt- Outback FM80-2ea, Inverter- Outback FX3648-2ea, Batt- 804ah GB traction, Grundfos BMQE booster pump 240v, Mitsibushi mini-splits 240v, 18k and 15k
  • jerryk1234jerryk1234 Registered Users Posts: 2
    It's about 400 feet from the pump to the top of the hill. So that would be 400 feet of 3/4" schedule 40 PVC pipe. Giving me a virtual "tank" of 14.7 cubic feet, or about 110 gallons, at an average height of 50 feet, yielding back pressure into the pump of 50*.43 or 21 PSI. Also, do these small submersible solar pumps have sensing of outlet pressure? My understanding was that they pump as long as the power is applied, and depend on the electricity being switched to not pump when they're not needed.

    I suppose I could just get the pump and install it and test it. Sit there with an oscilloscope watching the current into the pump. If said current shows a lot of surges, then yes, I'd have to do something.
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,276 ✭✭✭✭✭
    A typical RV pump like a shurflo or flojet does have a pressure switch built-in. The pump will turn on when the pressure gets low and turn-off at the max pressure set-point. The store here has them. If you buy the right controller for the solar panel you will not need a battery. They can help you so give them a call. This may be too small for the number of plants and trees and you still have to get the water out of the ground and deal with the head pumping. Save the scope for something more challenging.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BB.BB. Super Moderators, Administrators Posts: 28,624 admin
    It also depends on how fast your well recharges and what the irrigation water usage rate is...

    You may, for example, need to "slow pump" the well over 6-24 hours to provide for 2 hours of irrigation. Then a good size tank at the top of the hill would be required to meet your irrigation needs and store sufficient water from the well to avoid pumping dry (and damaging your in-well pump).

    Before you buy anything... You will want to measure you well's output flow/recharge rate (use a cheap pump and genset if needed) for your first calculations. Then compare against your irrigation needs.

    And you should make several design option drawings and see what works best for you. If you can do this without batteries (i.e., in-well pump to cistern on hill for storage+pressurization)--That would probably be ideal. In general, as soon as you add batteries, the PV system becomes 4x more expensive, and you now have batteries to water and replace every 3-7 years or so.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • AnawaAnawa Solar Expert Posts: 209 ✭✭✭
    The configuration I'm suggesting would be a simple gravity system. The pump start/stop cycle is controlled by the water level that uses a float switch to open/close the circuit. When the tank is topped off, the pump stops automatically. As the water is drawn from the bottom of the tank into the drip irrigation and it reaches a predetermined level, the pump turns on, automatically. There is a water supply line (from the well) that is used to fill the tank and a water discharge line that feeds the drip irrigation field. Separate lines that are both connected to the tank.

    Using the pipe to store the water is a very creative idea, I'm not sure how the water flow would be regulated without check valves and some kind of pressure control vessel, such as suggested my mike95490 previously. I'm sure it can be done, but not without electronics interacting with some mechanical devices.

    Another thing, when you begin pump selection, not only do you need to know your maximum water demand, you must know if your well can supply the water. For example, you may determine that you will need 300 gallons a day for irrigation, but your well can only supply 100 gallons with a complete draw-down and it may require another 24 to 48 hours for it to "re-fill" just to able to draw 100 gallons. Since the well was existing, you may not have this info available which is understandable. Unless you know without-a-doubt that the well re-charge capacity will not limit what you want to do, you may want to consider contacting a local well drilling contractor and have them check it out. There are ways to find this info. Otherwise, you may be spending time and money that will not do anything that you hoped for. Saying all this another way, find the well re-charge rate and design your system accordingly.

    Paul
    Paul 
    in Georgia

    System 1: PV- 410w Evergreen, Mppt- Blue Sky Solar Boost, Batt - 225ah Deka AGM, 12v led house lighting,
    System 2: PV- 215w Kyocera, PWM - Morningstar PS30, Batt- 225ah Deka GC's, 12v led house lighting, Dankoff 12v water pump,
    System 3: PV- 1.5kw Kyocera, Grundfos 11 SQF well pump, 3000 gal above ground water storage, dom water & irrigation,
    System 4: PV- 6.1kw Kyocera, Mppt- Outback FM80-2ea, Inverter- Outback FX3648-2ea, Batt- 804ah GB traction, Grundfos BMQE booster pump 240v, Mitsibushi mini-splits 240v, 18k and 15k
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,276 ✭✭✭✭✭
    There is alot of really good advice for you here. With a (1500 gallon?) tank, the well daily flow rate is less critical as long as your usage is reasonable. The daily rate in gallons for your trees is what you need to measure first. Then you need to do what Bill suggests by using a cheap pump and a generator, or hire someone to do this. Once you know both of these numbers you can make a decision on what to do.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • jonrjonr Solar Expert Posts: 1,239 ✭✭✭✭
    You can go on ebay and search for "24V Submersible Deep DC Solar Well Water Pump". 100' is fine but you would have to think about the GPM you need.

    I am available for custom hardware/firmware development

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