Solar-powered agricultural irrigation is a steady and growing line of business for solar companies. The irrigation season largely coincides with the months of highest solar irradiation, which makes these systems naturally efficient. An irrigation project differs from a rooftop system, however: it is sized around the pump's needs rather than an electricity bill. This article covers what to collect during the site survey and what to state in the proposal when quoting a solar irrigation system for a farmer. Pump and array sizing is explained in detail in our solar irrigation sizing article.
Information to collect on site
| Information | Why it matters |
|---|---|
| Pump power (HP or kW) and phase | The basis for array and drive selection |
| Well depth, static and dynamic water level | Total head and the pump's operating point |
| Required flow and daily irrigation hours | Whether daily water demand can be met |
| Irrigation method (drip, sprinkler, flood) | Required pressure and operating hours |
| Cable distance from pump to array | Cable cross-section and voltage drop |
| Array area, slope and shading | Layout and production |
| Irrigation months and crop | Which month the system is sized for |
| Current energy source and annual cost | Savings and payback |
Photograph the pump's nameplate and the well records. Values given verbally by the farmer may differ from the nameplate; base the calculation on nameplate and measured values.
Comparing with the current situation
For the farmer, the key question is what the system will save. To answer it, establish the current energy cost accurately:
- Grid-supplied: bills for the irrigation season, tariff type and connection status.
- Generator-driven: fuel consumption, maintenance and repair costs, and time spent attending the generator.
- No grid connection: the cost and lead time of a new connection compared with a stand-alone solar irrigation system.
Where an agricultural connection is grid-tied, how surplus production is credited depends on current regulations and the distribution company's terms. State this in the proposal as an assumption, not as a firm commitment.
What the proposal should include
- System summary: panel count and arrangement, total capacity, pump drive and protective devices.
- Suitability assessment: compatibility of the existing pump with the system, motor current, recommended fuse and cable cross-section.
- Expected operation: in which months, at which times of day and for approximately how long pumping will take place.
- Assumptions: that well depth, water level and flow values are based on survey information, and that results will change if these values change.
- Scope: whether installation, mounting, cabling and commissioning are included, and whether well and pump work is excluded.
- Savings and payback: comparison with the current energy cost and the payback period.
- Protection and maintenance: dry-run protection, panel cleaning and pre-season inspection recommendations.
Common mistakes
- Looking only at pump power: two pumps of the same power deliver different flows at different well depths. Total head must be taken into account.
- Ignoring start-up current: the current a motor draws when starting must be considered when selecting the drive.
- Underestimating cable distance: the longer the distance between the array and the well, the larger the cable cross-section; cost and voltage drop must be calculated accordingly.
- Overlooking water storage: pumping into a tank during sunny hours and irrigating from the tank when needed gives a battery-free system valuable flexibility.
Agricultural energy systems in PVAGE
In PVAGE's agricultural energy systems module, you enter pump power (HP), well depth, daily irrigation time and cable length; the module calculates panel count and arrangement, motor current, recommended fuse and a suitability assessment. Calculation coefficients are shown on screen, and calculations can be saved and exported as PDF. Agricultural irrigation can be selected as a separate system type in the proposal module, and farm and irrigation are among the consumption profiles. See the agricultural energy systems page for details.