LELABAPP
Case study

One hectare of yellow kiwis
irrigated by solar in South-West France

This study covers one hectare of yellow kiwis, about five hundred plants, fed from a river and already equipped with a micro-irrigation network. The current pumping, driven by the tractor power take-off, provides seasonal irrigation and frost-protection sprinkling. The project consists of transferring daily irrigation to a solar pump, while keeping the thermal set for night-time needs.

South-West France 1 ha of yellow kiwis Need: 40 m³/day Pumping from a river Micro-irrigation in place
The project

Site data and existing installation

The plot holds one hectare of trellised yellow kiwis, drip irrigated. The river lies at the foot of a bank about three metres high. The network and the filtration already exist; their reuse remains subject to checking the acceptable flow, the head losses and the level of filtration required. The project keeps the thermal installation for frost-protection sprinkling and assigns the new solar system to daily irrigation.

1 haof yellow kiwis, about 500 plants, under micro-irrigation
40 m³/dthe peak need calculated by LE LAB for one hectare of fruit trees
April to Octoberthe declared pumping period, the irrigation season of the orchard
20 mthe total dynamic head calculated, bank, delivery and head losses included
Step 1

Data entered in the application

The climate reference city is Toulouse. The use selected is irrigation, with the closest available category, “Citrus and other fruit trees”, applied to an area of 1 hectare, that is a reference need of 40 m³ a day. This choice serves as the basis for the need in the application; it is not an agronomic classification of the kiwi. The pumping period runs from April to October and the watering mode is drip irrigation. For the water intake, the study uses 3 m of height between the water and the bank, 2 m of delivery head up to the delivery point and 120 m of pipe. Neither backup power nor water reserve is declared. From these data, the application establishes a total dynamic head of 20 m.

Summary of the study in LE LAB: Toulouse in France, need of 40 m³ per day for 1 ha, pumping period from April to October, water depth 3 m, delivery head 2 m, 120 m of pipe, calculated total head 20 m, without backup power and without a reserve

The summary before calculation. The total dynamic head is calculated for you, it is not to be entered.

Composition of the total dynamic head. The 20 m break down as follows: 3 m between the water and the bank, about ten metres for the pressure available at the delivery point and close to 7 m of head losses in the pipe and the fittings. The bar reserved for the delivery point, that is about ten metres, on its own covers the 2 m of delivery head declared: those are absorbed and do not add to it. In this case, the pressure required by the drip network represents a larger share than the elevation of the plot alone.
Step 2

The solution selected by the study

LE LAB selects a GRUNDFOS SQF 5A-7, a 4-inch submersible with integrated electronics, whose envelope covers 9.0 m³/h and 50 m of head. The array counts 3 panels of 630 Wp in a single string, that is 1,890 Wp. Over the period from April to October, average production settles at 58.9 m³ a day for 40 required. The recommended pipe is HDPE Ø 50 mm PN 10, inside bore 44.1 mm, where the water travels at 1.46 m/s at the pump's maximum flow — and more slowly at the actual operating point —, within the window recommended by the application.

Solution selected by LE LAB: GRUNDFOS SQF 5A-7 pump in 4 inches, solar array of 1,890 Wp in 3 panels of 630 Wp, average production of 58.9 m³ per day

The solution at a glance: the pump, the array and the average production over the declared period.

A result tied to the conditions of the project. The three-panel array is explained here by a limited total dynamic head, a seasonal need concentrated on the brightest months and a pump with integrated electronics. This result cannot be generalised from the area of the orchard alone: the resource, the head, the pipe, the period and the daily need remain decisive.
Step 3

Monthly production and a typical day

Estimated average production reaches 65.5 m³ a day in July and 45.8 m³ in October, the least favourable month of the declared period and the sizing month of the season. Every monthly average from April to October stays above the need of 40 m³ a day. This reading is not a daily guarantee: a very overcast spell can produce less than the need. With no water reserve and no backup power, the organisation of irrigation must therefore keep the flexibility required for working at the pace of the resource. The winter months remain visible on the chart, even though the sizing covers only the declared period.

Estimated monthly production against the need of 40 m³ per day: from 45.8 m³ per day in October to 65.5 in July, critical month October, sizing over the period from April to October

The estimated monthly production, against the line of the need. The critical month of the period is stated under the chart.

The typical day in July shows the flow starting around 07:00, a maximum of 7.4 m³/h around solar noon and an estimated daily volume of 63.0 m³. The gap of 58% against the need indicates additional average capacity for this typical day; it does not on its own define a free watering window nor the coverage of every day of the month.

Daily output for a typical day in July: estimated hourly flow from 07:00 to 18:00, peak of 7.4 m³/h, volume produced 63.0 m³, daily need of 40 m³ covered with 58% margin

The typical day of the month chosen, hour by hour, with the peak flow and the volume produced.

The technical point

Conditions for a water intake in a river

The diagram of the study shows the array, the cabinet, the submersible pump at 3 m, the 120 m of pipe and the delivery point. In surface water, the pump can be installed in a sump fed by the river or in a suitable strainer housing, subject to complying with the manufacturer's requirements. A submerged installation stays flooded and does not require daily hydraulic repriming; its starting then depends on the automatic controls, the water level and the power available.

Installation diagram produced by LE LAB: photovoltaic generator of 1,890 Wp in 3 panels of 630 Wp, Grundfos IO101 and CU202 cabinet, SQF 5A-7 submersible pump installed at 3 m, 120 m pipe in HDPE Ø 50 mm, delivery point raised by 2 m, stop float switch and electrical protections

The installation diagram of the study. The arrival point is drawn as a raised reserve: here, it is the head of the micro-irrigation network, 2 m above the pump.

Motor cooling in open water. A submersible motor is cooled by the water that flows along its casing. In a narrow borehole, the geometry imposes this flow. In a sump or in open water, a flow sleeve may be needed to achieve the prescribed sweep velocity. It is listed in the LE LAB catalogue in 4 inches and is chosen according to the pump diameter, the flow and the installation conditions.

The existing filtration cannot be kept without checking. Its acceptable flow, its fineness, its condition and its head losses must remain compatible with the new pump and with the emitters. The pressure actually required at the filter inlet and at the head of the drip sectors must also be confirmed: the bar reserved at the delivery point is a study assumption, not a measured setpoint. Protection of the suction against coarse debris completes this filtration. The project must also check the low-water level, the variations of the river, protection against floods and the rules applicable to water abstraction.

Boundary of the scope

Frost-protection sprinkling stays with the existing system

Frost-protection sprinkling is triggered mainly at night and at dawn, outside the period of photovoltaic production. It also requires a flow available without interruption throughout the frost episode. The solar system at the pace of the sun presented here is therefore reserved for daily irrigation; the existing thermal pump keeps the frost-protection function.

At nightfrost-protection sprinkling starts when the temperature falls, outside the hours of solar production
A few nightsthe frost-protection function calls on the current set a small number of nights a year, in spring
April to Octoberdaily irrigation accounts for most of the pumping hours of the season
2 usestwo functions, two regimes: each keeps the means that suits it

Separating the uses avoids assigning to the solar system a function it cannot fulfil on its own. The thermal pump remains available for frost episodes, while the solar pump covers seasonal irrigation under the production conditions described by the study.

And for sprinkling during the day? A sprinkler, a gun or a centre pivot require a pressure held from one end of the window to the other, which the pace of the sun alone does not guarantee. There is a hybrid architecture for that, pairing the solar array with a backup source on the same pressure setpoint: this is the subject of the constant-pressure irrigation page, and the question of the backup source is dealt with in solar and generator. On the orchard described here, micro-irrigation works at low pressure and the path remains that of the pace of the sun.
Scope of the study

From the declared need to the technical solution

The application establishes the daily need from the crop and the area, takes the pumping period into account and calculates the total dynamic head from the hydraulic data entered. It then proposes a compatible pipe, pump and photovoltaic array, and presents the monthly production and a typical day for the site studied.

40 m³/dthe need calculated from the crop and the area, with no flow to enter
1,890 Wpthe array selected, 3 panels of 630 Wp in one string
58.9 m³/dthe average production over the period from April to October, critical month included
Ø 50 mmthe recommended pipe in HDPE PN 10, chosen on the water velocity
Data and limits. The results use the manufacturers' official performance curves and the climate data associated with the reference city. The hydraulic assumptions and the values used are those shown in the study. They must be confirmed on site before execution, in particular for the river level, the existing pipe, the filtration, the fittings and the regulatory conditions of abstraction.
Sources and method. The irradiation comes from PVGIS, on the optimal tilted plane calculated for the reference city, 37 degrees for Toulouse. The temperatures and the other climate quantities come from the NASA POWER series. The head losses are calculated with the Hazen-Williams formula on new HDPE. All the figures on this page come from the study replayed in the application.
To go further: the other case studies run the same exercise on other crops and other resources, and the application can be replayed freely with your own figures from LE LAB.

Study a comparable configuration

The application makes it possible to run this path again with the data of another project: crop, area, water resource, pumping period and characteristics of the pipe.

Size my project See the other case studies