To consume as little energy as possible and reduce the size of the PV supply, low- energy appliances working on DC will be preferred.
The farm has a well situated 200 m from the house. The water table is 25 m deep. Because of the distance from the house, we will propose a solar pumping installation independent from the rest. We refer to this as ‘pumping system’ and to the other, which supplies the house and the goat shed, as ‘main system’. The vegetable beds will be located close to the well, on a gentle slope so that trickle irrigation can be used. The water therefore has to be pumped to a height of 30 m (counting the tank and the depth of submersion of the pump), and stored in a tank at ground level. The size of this tank is calculated to allow storage of 4 days in summer, to allow for bad weather, so as not to interrupt supply. The resulting size is 4 x 400 = 3600 l minimum (or 4 m3).
The occupants, who are used to drawing water from the well for their domestic requirements, do not want running water. They will come to fetch water from the tank in jerrycans for their domestic consumption. The goats will drink from a trough, which will be fed directly from the tank by gravity (Figure 5.59).
To fill this tank, a pump is needed, able to lift between 550 and 900 l/day to a height of 30 m.