SPIS Toolbox - Irrigation System
Irrigation System
Water is the most important input required for plant growth in agriculture production. Irrigation is the controlled application of water through man-made systems to supply water requirements of plants not satisfied by rainfall alone. Various methods can be used for irrigation (starting from simply watering plants with a pot or a bucket). The choice of a particular irrigation system mainly depends on the crops to be irrigated, the underlying water availability, irrigation water requirements and energy supply as well as the financial capacity of the farm household. Solar pumps pump up water to the farm, from where it can be collected for further distribution by hand. Alternatively, it can be pumped directly to the field through a system of canals (surface irrigation) or pipes (sprinkler and drip irrigation). In principle, solar pumps can be used for supplying water to any kind of irrigation system. The size (and cost) of the PVgenerator is mainly determined by the water and pressure requirements of the irrigation scheme. However, it is important to consider that SPIS are relatively expensive, requiring producers to grow high-value crops to guarantee its financial viability. In addition, water savings will have a positive influence on the invest-ment costs of the solar pumping system and the environment.
Surface irrigation systems are not always suitable for high-value crop production and they are far from being water-efficient. However, SPIS with surface irrigation systems are widely used asthey do not require the producer to adopt a new irrigation method. SPIS are seldom combined with sprinkler irrigation because sprinkler irrigation requires relatively high water pressures to operate, which demands expensive PV generators.
Water-saving irrigation technologies working at comparably low operating pressures are the preferred option in connection with PV pumping systems.
Drip irrigation systems normally operate at high pressures of 1–10 bar. Fortunately, the technology has been adapted to cater for low pressures and a more simplified operation. These low-pressure drip irrigation systems can give 80% uniform water application even from a few meters pressure. The performance is very much dependentof the pressure, the size and shape of the field being irrigated. Solar-powered drip irrigation is the “marriage” of two systems that go very well together. Drip irrigation is ideal for high-value crop production such as vegetables and fruits, and due to its high efficiency the solar pump can be quite conservatively sized.
Suitability of irrigation methods to PV pumping
|
Distribution method |
Typical water application efficiency |
Typical head |
Suitability for use with PV pumps |
|
Flood irrigation |
40–50% |
0.5 m |
barely cost-efficient |
|
Open canals |
50–60% |
0.5–1 m |
depends on local conditions |
|
Sprinkler |
70–80% |
10–20 m |
No |
|
Low pressure drip irrigation |
80% |
1–10 m |
Yes |
|
High pressure drip irrigation |
85–95 % |
10–100m |
No |
