Solar water pumping for farms and borewells

Most solar applications fight against a timing mismatch: generation peaks at midday while household demand peaks in the evening. Irrigation does not have that problem. Water pumped at noon is just as useful as water pumped at dusk, because you are storing water rather than electricity.

That single fact removes the battery from the system, and with it most of the cost and nearly all of the maintenance. It is why solar pumping is one of the strongest economic cases in solar, rather than a compromise.

What it replaces

• Diesel. A recurring fuel cost that rises, plus the labour of fetching and handling it.
• Dependence on the supply schedule. Agricultural feeders often supply power at inconvenient hours. A solar pump runs on its own daylight schedule.
• Unreliable three-phase supply. Low or unbalanced voltage damages motors. A solar-driven controller is not exposed to that.

Origian supplies solar water pump systems in three motor ratings: 3 HP, 5 HP and 7.5 HP. Which one a site gets is not chosen from a brochure. It is selected from the borewell’s head and the discharge you need, both measured during the site survey.

Head and discharge pull against each other. A deeper water level means more lift, and more lift at the same flow needs more power. A larger flow at the same lift needs more power too. So a deep borewell feeding drip lines and a shallow open well flooding a field can end up at the same horsepower for entirely different reasons.

The panel array is sized after the motor. It has to drive that motor for the hours of pumping your daily water requirement calls for, with some margin for mornings, evenings and cloudy spells when output is lower.

If a site needs less than 3 HP or more than 7.5 HP, the survey will say so plainly. The wider market range is set out in the section above, but these three ratings are what Origian supplies. Ask for the motor rating, the array size in kW and the expected daily water output to be written on the quotation, so you can compare offers on the same terms.

A few figures gathered before the visit make the survey faster and the sizing more accurate. You may know some of them already; a borewell driller or pump mechanic will have noted the rest.

• Static water level: how far below ground the water stands when the pump has been off for a while. This, not the total depth of the bore, sets most of the lift.
• Drawdown: how far the level falls once pumping starts. A bore that drops sharply cannot sustain a large pump, however big the array.
• Yield: how much water the bore gives per hour without running dry. The pump should not be sized beyond it.
• Delivery point: where the water goes and how high above ground, whether a field channel, a storage tank or a drip header.
• Pipe size and length: narrow or long pipes add friction, which the pump has to overcome as extra head.
• Crop, acreage and irrigation method: these set the daily volume. Drip uses far less water per acre than flood irrigation.

If your current pump is electric or diesel, note its HP and how many hours a day it runs in the peak season. That is a working record of what the land actually needs.

You can get a rough idea of yield yourself. Run the existing pump into a drum or tank of known size and time how long it takes to fill, then repeat after an hour of pumping. If the second fill is much slower, the bore is drawing down, and the survey should size for the lower figure, not the first one.

Measure in the dry season if you can. The water level in most bores falls through the summer, and a pump sized to a post-monsoon reading can fall short exactly when the crop needs water most.

Solar pumps come in two physical forms. A submersible pump sits down the borewell, below the water level, and pushes water up; it suits deep bores. A surface pump sits at ground level and draws water up a short suction pipe; it suits open wells, ponds and canals where the water is only a few metres down.

Motors are either AC or DC. A DC motor runs from the panels through its controller and uses the array’s power efficiently, which suits smaller, dedicated systems. An AC motor runs through a controller that converts the panels’ output, and it can be easier to source and repair locally. Both are in common use on farms.

Which form and motor type fit your site is a survey decision, made from the water source and the head. The controller matters as much as the motor: it starts the pump gently, protects it from running dry, and matches the motor to the sunlight available through the day.

Agricultural solar pumping is a separate subsidy scheme from PM Surya Ghar (which applies only to residential rooftop electricity systems): PM-KUSUM, covering standalone solar pumps and the solarisation of existing grid-connected pumps, administered through state nodal agencies — NREDCAP in Andhra Pradesh, TGREDCO in Telangana — rather than the PM Surya Ghar portal.

The PM-KUSUM subsidy scheme for solar pumps is not currently active in either Telangana or Andhra Pradesh. Origian installs standalone (non-subsidised) solar pump systems in this category.

If you also want rooftop solar for your home, that is a separate PM Surya Ghar application. For how the work runs once a system is agreed, see our installation process.

Because PM-KUSUM is not open in either Telangana or Andhra Pradesh at present, every solar pump Origian installs today is a standalone system, bought without a scheme subsidy.

In practice, that means three things for a buyer. The full cost is yours, so the decision rests on what the pump replaces: diesel, or hours lost to the agricultural feeder schedule. The paperwork is simpler, because there is no nodal-agency application to wait on. And the system is sized to your borewell and crop, not to a scheme’s fixed package.

Scheme status can change. If PM-KUSUM reopens in your state, the state nodal agency will announce it: NREDCAP in Andhra Pradesh, TGREDCO in Telangana. Until then, plan the purchase on its own merits.

A diesel pump costs money every hour it runs: fuel, the trips to buy it, and the servicing an engine needs. A solar water pump costs most of its money up front and very little after, because sunlight is free and there is no engine to service.

That makes the comparison a question of payback. The more hours a year you pump, and the higher the diesel price, the faster solar earns back its cost. The diesel pump to solar calculator asks for your pump size, the hours you run it each day, the days you irrigate in a year and the diesel price, then estimates the diesel you burn and the payback on a solar replacement.

Run it with your own season’s figures, not a guess. A pump that runs two hours a day for a few weeks a year makes a weaker case than one that runs six hours a day through two crop seasons.

A solar pump works on the sun’s schedule: little water at dawn, most around midday, little again by late afternoon. Farms that get the most from it plan around that rhythm rather than against it.

A storage tank is the simplest tool. Pump into it through the bright hours, then irrigate from it when you choose, by gravity or with a small booster. Water in a tank costs far less to keep than electricity in a battery, and it does not wear out with use.

Drip irrigation multiplies the benefit. It needs less water per acre than flooding, so the same pump covers more ground, and its steady, low flow suits a pump whose output rises and falls with the sun. With a smaller daily volume, the array can often be smaller too.

Cloudy days reduce flow rather than stopping it. A tank sized for a day or two of normal use rides through a dull spell without losing a watering.

When a site is short of water at peak times, there are two ways to fix it: a larger pump and array, or a larger tank. A bigger tank is usually the cheaper answer when the bore can supply the water but the hours of sunshine are the limit. A bigger pump only helps if the bore’s yield can keep up with it. Settle that question at the survey, with the yield figure in hand.

Installation follows a site survey that fixes the pump rating, the array and the controller. The array is mounted on a structure near the water source and cabled to the controller, and the pump is lowered into the bore or fixed at the source. Origian builds its rooftop systems on hot-dip galvanised structures with stainless steel bolts; ask for the same standard on a field structure.

Upkeep is light but not zero. Panels in open fields gather dust faster than rooftop panels, especially near ploughed land, so clean them every few weeks in the dry season to keep the flow up. Check the cables for rodent damage, keep weeds and shade away from the array, and watch the controller display for dry-run or fault warnings.

If you would rather hand upkeep over, ask whether an annual maintenance contract suits your pump site. Origian’s maintenance terms are on the annual maintenance page.

Origian works across Andhra Pradesh and Telangana. In Andhra Pradesh that covers Anantapur, Kurnool, Kadapa, Nandyal, Sri Sathya Sai, Tirupati, Nellore, Guntur, Vijayawada and Visakhapatnam. In Telangana it covers Hyderabad, Warangal, Nizamabad, Karimnagar and Suryapet. The surrounding areas of each are included. For a farm outside these towns, call with your village and mandal, and Origian will confirm whether a survey can be arranged.