Integrated controller or solar drive:
250 m³/day in Andalusia
In the Guadalquivir valley, a drip-irrigated orchard draws its water from a 120 m borehole and fills a raised pond. Peak demand is 250 m³ a day, there is no power line on the plot and the grower does not want one. LE LAB proposes two solutions at this duty point: a LORENTZ PSk2 controller and a GRUNDFOS SPE permanent-magnet motor on an RSI drive. Here is how LE LAB separates them, and why one drive feature, real as it is, counts for nothing here.
An orchard, a pond, not a power socket
The layout is that of thousands of Andalusian plots: a borehole, a pipe rising to an irrigation pond, and drip lines fed by gravity from the pond. The pump therefore does not have to follow the emitters' demand, it has a single duty, filling the pond within the day. A grid connection is not considered: the substation is far away, and solar at the pace of the sun suits this kind of filling exactly.
The input data
Seven answers are enough. The irradiation reference city is Córdoba, water depth 120 m, lift to the pond 5 m, pipe run 150 m. LE LAB computes the total dynamic head on its own, 132 m, adding friction losses to the elevation. The backup power box stays on no, and that answer counts as much as the others.
The summary before calculation. The total dynamic head is computed for you, it is not to be entered.
The selected solution: an integrated controller
LE LAB selects a LORENTZ PSk2-40 fitted with the C-SJ42-19 pump end, a 6-inch assembly accepting up to 62 m³/h and 200 m of head. The array counts 76 panels of 515 Wp, that is 39,140 Wp, wired as four parallel strings of nineteen panels in series. Average production settles at 276.4 m³ a day for 250 required.
The solution at a glance: the pump, the array and the average production, with the seasonal range stated without fuss.
The two solutions at the same duty point
LE LAB does not show a single answer. At 250 m³ a day and 132 m of head, it proposes two solutions, one per drive family, ranked by the size of the photovoltaic array they demand.
| Solution | Photovoltaic array | Average production | Equipment |
|---|---|---|---|
| LORENTZ PSk2-40 C-SJ42-19 | 39,140 Wp · 76 × 515 Wp | 276.4 m³/d | integrated PSk2-40 controller |
| GRUNDFOS SPE 32-19 | 39,200 Wp · 80 × 490 Wp | 280.0 m³/d | RSI 30 kW drive, sine-wave filter, temperature sensor |
The two arrays are almost the same size: 39,140 Wp against 39,200 Wp, a gap of 60 Wp, and 76 panels against 80. At this duty point the integrated controller therefore buys no installed power, and the SPE even produces a little more on average, 280.0 m³/d against 276.4. What separates the two solutions lies elsewhere, in the equipment to be fitted. The choice between the two Grundfos motors on a drive is covered on its own page, SP or SPE.
Production, month by month
On the real irradiation of the region, production runs from 206.6 m³ a day in December to 347.0 in July. Sizing is done on the average month, and the range is shown as it is: the winter months fall below the 250 m³ required. For an orchard that is the right trade-off, since peak irrigation falls precisely when the sun is there. A grower who needed the 250 m³ in December would read this chart and size on the least favourable month, which the application offers.
Estimated monthly production, against the line of the need. The blue curve is rainfall, it tells the irrigation season better than a calendar.
The RSI alternating-current input, and why it counts for nothing here
The GRUNDFOS RSI solar drive has a feature the PSk2 controller does not have as standard: it accepts alternating current. The photovoltaic array and a three-phase supply connect to the same drive input terminals, through a source changeover that prevents them from being connected at the same time, and the manufacturer presents this supply as a backup in case the solar array is interrupted. It is a real advantage, provided you need it.
On this orchard nobody does. The criterion therefore separates nothing. The ranking goes by array size, and here the two arrays are 60 Wp apart: what really separates them is the equipment, a matched controller on one side, a drive and its sine-wave filter on the other. In a country next door, on a far deeper borehole and with the grid at the substation, the same question gives the opposite answer, and for good reasons.
Two arrays of the same size, two sets of equipment
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