Powering Agriculture: Irrigation

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Agriculture is the backbone of the majority of developing and emerging countries. Therefore, access to reliable and affordable irrigation water for agriculture is a crucial factor for the economic development of the country.

Definition

Irrigation is the controlled application of water for agricultural purposes through manmade systems to supply water requirements not satisfied by rainfall. Crop irrigation is vital throughout the world in order to provide the world's ever-growing population with enough food. Irrigation can be defined as replenishment of soil water storage in plant root zone through methods other than natural precipitation.

Background

Irrigation water is brought to cultivated land through artificial means, such as pipes, hoses or ditches. The irrigated land usually contains crops, grass or vegetation which would not receive enough water from rainfall or other natural sources. Sometimes the reason to irrigate a portion of land is that it happens to be a dry season with less-than-average amounts of rainfall, or it might be necessary to do so because the land would never receive enough water on its own to be fertile. The water used for irrigation might be taken from nearby lakes, reservoirs, rivers or wells.

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 and emerging 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.

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Sustainable Irrigation

What is sustainable irrigation and how can it be promoted? Around 93% of human water consumption is utilized for irrigation. Most of this water needs to be moved, often from below the ground. Yet, water distribution is often inefficient and requires significant amounts of energy, mostly supplied through diesel generators.

The ability to move water is critical for irrigated agriculture in most areas of the world. Both surface and underground water resources are commonly tapped for irrigation. Around 57% of current irrigation water demand is covered by the former, the remaining 43% by the latter source of water (World Bank, 2010).

In particular irrigation from underground sources requires an energy input. In off-grid areas of the world, this is currently covered to a large part through diesel generators. The disadvantages of this fossil energy supply are known. High operating costs and frequent maintenance, environmental damage through ground water soiling with fuels and lubricants or CO2 emissions are the most significant drawbacks of the status quo. Using renewable energy (RE) sources is an attractive alternative as they feature several economic, managerial and ecological advantages.

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Types of Irrigation

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

  • Surface irrigation. Subtypes:
    • Borders (strips of land are irrigated)
    • Furrows (water is fed into small channels)
    • Basin irrigation (entire field is flooded)


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
  • Required labour input
  • Capital requirements and availability
  • Costs and benefits


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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 done by diesel or petrol motors as well as by electric motors that fed from the grid or are run by diesel generators. The utilization of renewable energy sources is steadily increasing but still on the minority side.

The following table gibes an overview on the main energy sources for water abstraction and conveyance in irrigated agriculture:

Table: Overview of energy sources of irrigation water pumping
Source of energy
 Description

Petrol engine

Small petrol-driven pumps are a very common option for smallholder agriculture. The pump motors have usually an output in the range of 1.5 to 5 horse powers (hp), but are also available with higher performances. Petrol-driven pumps are characterized by low initial costs, a low weight, a comparatively small lifespan and high fuel consumption and high maintenance requirements.

Diesel engine

Diesel engine-driven pumps are generally available with higher capacities and outputs starting from 3.5 hp. Higher performance engines are available and cater also for medium-size farms.

Diesel-driven pumps are characterized by their high initial costs and the high costs for spare parts and maintenance. Their lifespan is much higher than that of petrol-driven pumps. Operational expenses are quite low due to their goof fuel efficiency of diesel engines and the low price (often subsidized for agricultural use) for diesel in most countries.

Natural gas engine

In some countries like Morocco propane gas engine-driven pumps are in use due to a heave subsidization of propane household gas and lacking utilization restrictions. Here, small petrol-driven pump engines are converted to run on propane gas with similar characteristics as petrol engines. Operational expenses are much lower as to compare to petrol engines due to the large price difference between propane gas and petrol.

Electric engine

AC or DC electricity-driven pumps are quite common with a large variety in the actual source of electricity. Their output starts as low as 0.5. hp and can extend flexibly to large scale purposes. Electric pumps are generally very efficient and low on maintenance requirements (if operated within their designed input power range).

A distinction has to be made according to the actual source of electricity:

  •  Network/grid-supplied electricity;
  •  Generator (diesel, petrol)-supplied electricity;
  •  Photovoltaic-generated electricity;
  •  Electricity generated from other off-grid RE-sources (biogas, biomass generators).

Wind powered pumps

In remote areas around the world windmills have been in use as a common technology to lift water from wells and aquifers for agricultural purposes. This technology has partly been used for irrigation on smallholdings in connection with an intermediate water storage high tank enabling gravity flow into a low pressure system (or traditional surface irrigation). This technology is characterized by an extreme variation of water availability due to varying wind speeds and a high maintenance requirement for the mechanical system of the windmill. Initial costs are low.


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Hybrid Solutions

RE-based water abstraction and conveyance are still in its early stages as far as the larger scale utilization of PV-technology is concerned. Very often, PV water pumping is built into a multiple energy source mix on farm level, but rarely a standalone solution.

Hybrid solutions can generally be distinguished in two categories:

Separated systemsusually comprise a RE-option (predominantly PV) as the preferred source of energy for the water pump(s). A conventional energy option, mostly a diesel or petrol engine-driven pump or a grid-supplied (or generatorsupplied) electric pump are available as a back-up or stand-by option (in case the RE-source is not available). This set-up is often chosen by farm managers to minimise risks.

A quite common occurrence is also the parallel operation of the RE-option with conventional energy options to reduce operational expenditure.

Integrated systems combine two or more RE-sources or combinations of renewable and conventional energy sources. These systems are usually quite sophisticated and capital-intensive as they require investments in several modern technologies (e.g. PV- and wind-generators) or an automated or semi-automated system integration of conventional and RE-technologies.

Integrated high-end products (e.g. AC/DC compatible PV pumps) are available on the market.

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Solar powered Irrigation Systems

Among the renewables, solar Photovoltaic (PV) is often the most attractive option. It features a near-absence of running costs, little maintenance requirements and ease of use. In terms of CO2 emissions, an off-grid solar pumping system that replaces a typical diesel generator unit will save about 1 kg of CO2 per kilowatt-hour of output (GIZ, forthcoming). Due to falling costs for the components necessary for a PV pump, the renewable powered systems have become increasingly attractive from an economic perspective. However, many farmers in remote areas of the world do not know of these advantages of solar powered pumps, or if they do, non-technical barriers such as access to finance hinder an increased adoption of the systems.

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. However, demand in this regard will have to be largely generated from the rural farm households themselves.

A study was conducted with the purpose of taking stock and analysing the status quo of irrigation systems, its energy input and water conveyance methods. The study is based on desktop research enriched with information from country case studies in Chile, India, Kenya and Morocco.

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Challenges

  • 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
  • The fact that operating costs are drastically reduced comes as a double-edged sword: the net income of farmers can increase as running costs are reduced. but the farmers no longer have a cost barrier imposed on their water access. A consequent threat to the sustainable use of water resources arises. .
  • Choosing the appropriate water conveyance method is a challenge itself

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Case Studies

Solar-Powered Pumps for Improved Irrigation in Honduras, Nepal and Zambia: iDE’s Clean Irrigation Solution (CIS) can compete with fossil fuel pumps both in terms of cost and enhancing agricultural productivity. CIS’s universal piston pump can run on a variety of power sources (solar steam power, photovoltaic power, and grid-connected alternating current (AC) where available). The system accesses groundwater from deeper depths than conventional pumps, and maintains a slow, steady discharge rate. iDE will work with local businesses to sell and service the CIS. Recently, field testing of pumps have been started in Nepal.

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Micro-Solar Utilities for Small-Scale Irrigation in Senegal: Earth Institute’s solution will enable a small group of farmers to use a central solar energy unit to power multiple AC pumps for irrigation. The proposed solution takes advantage of the benefits of solar without the high costs associated with DC-powered pumps and battery storage. This power will be accessed by farmers with prepaid electricity cards issued by a micro-utility, and sold through local vendors who will benefit from a small commission. Recognizing that a major obstacle to technology adoption is financing, a tariff-based financing model will allow customers to cover their appliance loans in small payments added into their micro-utility bills.

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Solar Powered Irrigation Systems in Egypt and the initiative "RaSeed": This initiative aims to promote the use of Photovoltaic (PV) systems in drip irrigation farming in order to support cost-effective and sustainable agriculture. Therefore, the aim is to introduce high capacity solar operated water pumps - of up to a pump size of 100kW - to the Egyptian agricultural sector. Furthermore, soil in the “New Lands” is mostly sandy, and water used for irrigation is ground water. Hence, it is crucial to use water efficient irrigation systems. RaSeed targets farm specific optimization of drip irrigation systems that enable maximum fuel savings and water efficiency by taking into account soil compositions and environmental conditions. In order to further the initiative, a Private Public Partnership (PPP) was established with a solar energy firm that is supported by the multi-donor initiative: ‘Powering Agriculture - an Energy Grand Challenge for Development’. Together with its partners, RaSeed establishes a network, providing high quality solar energy technology and training in Egypt.

►Read more here.


Further Country Case Studies:


Further Case Studies


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Further Information

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