Powering Agriculture: Irrigation

Irrigated agriculture is the backbone of local economic development in the majority of developing countries. Reliable and affordable access to irrigation water is a crucial factor.

Background

Manual lifting of irrigation water significantly reduces the scope of cultivation and the efficiency of irrigation – it does not, for example, allow for pressurized systems that are required for water saving drip or sprinkler irrigation techniques. In the absence of reliable electricity supply due to lack of grid connection or intermittent service, farmers in developing countries have hence to rely often on diesel-driven pumps for water abstraction and conveyance. These diesel-driven pumps create high operation costs and are prone to service gaps due to an insufficient fuel supply and technical defects. A reliable and cost-effective supply of irrigation water is therefore a core problem in many rural areas in developing countries.

The perspective of grid extension and the establishment of uninterrupted and affordable electricity supply into rural areas is a distant vision in many of these countries. Rural electrification in economically weak rural areas in Africa, Asia and Latin America will be largely based on investments into local off-grid solutions.

Types of Irrigation

There are various irrigation methods, each requiring an experienced farmer to determine the quantities of water to apply and the timing of the irrigation. The most commonly used modern irrigation methods are:

• Surface irrigation. Types:
  

Basin irrigation (entire field is flooded)

Furrows (water is fed into small channels)

Borders (strips of land are irrigated)

• Sprinkler irrigation
  
• Drip irrigation
  

A number of factors determine the suitability of the various methods:

• Natural conditions: soil type, slope, climate, water availability, water quality
  
• Type of crop
  
• Type of technology
  
• Previous experience with irrigation
• Capital requirements and availability
  
• Costs and benefits
• Labour input
  

Energy sources for irrigation water pumping

Motor-driven water abstraction and conveyance requires a reliable energy source – or a reliable combination of energy sources. The vast majority of water pumping for irrigation purposes is to date effected by diesel or petrol motors or electric motors fed from the grid or from diesel generators. The utilization of renewable energy sources is steadily increasing but still on the minority side.

• Petrol engine
• Diesel engine
• Natural gas engine
• Electric engine: distinction has to be made according to the actual source of electricity
• Network/grid-supplied electricity
• Generator (diesel, petrol)-supplied electricity
• PV-generated electricity
• Electricity generated from other off-grid RE sources (biogas, biomass generators)
  
• Wind powered pumps
  

Solar-powered irrigation systems

In regions with high solar insolation levels, electricity from solar cells open up new options for lifting and distributing water in an efficient, reliable and economically viable and ecological-sound way. The technological option of solar-powered irrigation is rarely taken into consideration due to a lack of pertinent experience and the comparably high investment costs of the past. Nevertheless, as prices for solar modules have fallen substantially in recent years, governments, extension services and technical cooperation are reconsidering PV water pumps to be employed in agricultural production and beyond. Demand in this regard will have to be largely generated from the side of the rural farm households themselves.

Barriers

• Farmers and extension services are not aware of the variety of new technologies that may be appropriate for them
• CES (clean energy technologies) are relatively new, therefore farmers have limited access to distributors for installation, parts, and service
  
• Farmers often do not have the means to cover high capital costs associated with clean energy upgrades – and financing is seldom available
  

Further Information

• Solar Energy for Powering Agriculture
  
• Photovoltaic (PV) Pumping Systems for Irrigation
  
• Article on Agriwaterpedia
  
• Practical Action: Fact sheet on the advantages and disadvantages of solar photovoltaic water pumping, including real world application.
  
• Climate Tech Wiki: Solar Water Pumps