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Solar-powered irrigation: A solution to water management in agriculture?


Stéphanie Roblin

Stéphanie Roblin explores the use of solar power in farming and explains why it could be an ideal solution to irrigation in developing countries.

Farmers have always played a significant role in our society as they provide the world’s population with food. However, one may forget that, not only do they provide food but they also provide energy, which nowadays, is of paramount importance, especially as in light of renewable energies. Indeed, farmers can produce energy from the wind, the sun or the biomass and they can use it for their own farm, or, if they have a surplus, resell it to companies.

Solar energy might be one of the easiest ways for farmers to produce energy. Indeed, farmers usually have several large buildings whose roofs are directly under the sun, without being hindered by the shadows of the trees, turning them into an ideal place to settle a photovoltaic system. Therefore, the use of solar energy in agriculture is becoming increasingly popular and the energy produced from this renewable source can be used either on the farm or in the local power grid, providing the farmer with an additional income. 

One of the areas in agriculture that benefits the most from solar energy is irrigation, especially in arid regions. The main reason is that using the sun for irrigation represents a virtuous circle: when the sun shines, it feeds the irrigation system, well, we know that crops needs more water when the sun shines a lot. Therefore, a large quantity of energy is available when it is actually needed.

How does a solar irrigation system work? 

The pumps used for the transport of the water are equipped with solar cells. The solar energy absorbed by the cells is then converted into electrical energy via a generator which then feeds an electric motor driving the pump. Most of the traditional pump systems mainly work with a diesel engine or with the local power grid. However, these two modes of operations present disadvantages compared to solar pumps.

In many rural areas, especially in developing and emerging countries, the access to the electricity grid is not always guaranteed. In this case, farmers cannot rely on the traditional irrigation system. Thus, using an independent and alternative energy system can be a solution for the farmer to secure a safe power source and for the public grid to avoid saturation.

Diesel pumps are slightly more efficient than AC powered pumps as they allow greater flexibility. However, one of the main constraints is that this system relies on the fuel availability, added to a greater impact on the environment. Diesel-driven pumps are cheaper than solar-powered pumps but the operating costs are quite high and depend heavily on the diesel price. In solar-powered systems, it works the other way round, that is, although this system is relatively expensive, the source of energy is free, therefore, after the amortization period, there are no longer operating costs (only the maintenance costs must be considered). Therefore, solar pumps turn out to be a viable long term investment.

As several studies, such as Water for wealth and food security by AgWater Solutions Project, have shown, the access to water for agricultural purposes remains critical in some areas such as in arid regions of Africa and Southern Asia. Many Indian and African farmers fetch the water directly from the well or the rivers and irrigate their fields using buckets. If farmers of those regions could have access to a motorized pump, they would increase their yield by 300%

Therefore, nowadays, R&D tends to focus on creating solar pumps that are affordable in arid regions. The company IBC SOLAR has developed with Siemens, a solution to replace diesel engine by solar-powered engine. In this case, the whole irrigation system including the pump can remain as it is; only the diesel engine is replaced by a photovoltaic system and the so-called “IBC pump drive controller”. A prototype of this system was tested in 2015 in a farm in Namibia and according to the manufacturer, turned out to be quite efficient. The main advantage lies in the fact that there are low acquisition costs as the existing infrastructure is used.

Where is solar irrigation happening?

The installation of solar pumps in arid regions such as in Africa, India and South America is also part of many development projects, aiming at increasing local farmers productivity and as a consequence, improving their living conditions. One of the successful example of this is the initiative of a Physics teacher in a school in Blankenese (Germany) where students have developed two solar-powered pumping systems in cooperation with the company SET GmbH from Wedel. They installed these systems in two farms in Nicaragua to pump underground water. This project could also be achieved with the collaboration of the UNAN University in León, which deals a lot with the exploitation of solar energy. Indeed, the project has been running for over 10 years and 30 pumps are in operation now in Nicaragua. It is supervised by the Nicaraguan company Enicalsa that helps farmers benefit from solar irrigation. The use of solar pumps allows the latter to produce all year round, even in dry season and thus to increase their income and strengthen their position in the local market. 

Aside from the regions previously mentioned, there is also an increasing interest in solar irrigation systems in Europe. Just a few months ago, a mobile solar drip irrigation system from Austria has reached the production stage. The Austrian company Wien Energie carried out this project which pursues a dual objective: on the one hand, reduction of CO2 emissions owing to the use of solar energy, on the other hand, achievement of 30% water savings thanks to the drip irrigation method versus the traditional sprinkler irrigation.

The principle of the drip irrigation method is quite simple. With the use of various valves, hoses and pipes, water drips slowly and at regular intervals to the roots of the plants. Therefore, there is no water waste as water goes directly where it should go, contrary to a sprinkler system in which water evaporates into the air or seeps into soils where no plants grow. Therefore, drip irrigation method enables to grow more crops with less water, turning it into a highly efficient irrigation method.

In the Wien Energie solar irrigation system, a mobile solar energy system with photovoltaic modules (up to 3kW) is connected to a wheeled pump which can pump from wells or rivers. Thanks to an app on your smartphone, you can determine the amount of energy produced by the system. The solar-powered pump then distributes the water through the hoses, directly to the crops. After a successful test on a 3.5-hectare organic cornfield in Guntramsdorf, Austria, this system is now ready for production.

Therefore, in countries which suffer from high temperatures and scarce water resources, the drip irrigation system could contribute to an efficient water management. This is all the more important as farmers have to face three challenges: save water, money and energy. Mobile solar drip irrigation systems shall turn out to be the perfect answer to face these challenges. Although these systems are still quite expensive and complicated to settle, many R&D projects are working on the democratization of the use of solar power in agriculture, which, in the future (and even now), could play a vital part in the management of the food and energy crisis.

 

ABOUT THE AUTHOR

Stéphanie Roblin is the community manager for Machineryzone.eu. 

 

FURTHER INFORMATION 

http://www.machineryzone.eu/

 

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This article is featured in:
Energy efficiency  •  Policy, investment and markets  •  Solar electricity

 

Comments

ANUMAKONDA JAGADEESH said

07 August 2016
Good article.
The key barrier to the large-scale dissemination of solar PV water pumps is the high capital cost incurred by farmers compared to the much lower capital cost of conventional pumps. It is portrayed Solar PV is a competitive option in the face of diesel, its adoption being contingent on the ease of access to subsidies. Another factor to be considered is the space requirement for the installation of a solar PV pump set. This factor limits adoption by small-scale farmers to whom land availability is a major constraint.
Some of the limitations of Solar Pumps:
1.Low yield: Solar pumping is not suitable where the requirement is very high. The maximum capacity available with solar is very low.
2. Variable yield: The water yield of the solar pump changes according to the sunlight. It is highest around noon and least in the early morning and evening. This variability should be taken into consideration while planning the irrigation.This is taken into account in some solar pumps which are costly.
3. Dry operation: The submersible pump has an in-built protection against dry run. However, the surface pumps are very sensitive to dry run. A dry run of 15 minutes or more can cause considerable damage to a surface pump.
4. Water quality: As with any other pump, solar pumps work best if the water is clean, devoid of sand or mud. However, if the water is not so clean, it is advisable to clean the well before installation or use a good filter at the end of the immersed pipe.
5. Theft: Theft of solar panels can be a problem in some areas. So the farmers need to take necessary precautions. Ideally, the solar system should insured against theft as well as natural hazards like lightning.
The criticism for electric pump sets is that in many areas power cuts. At least during nights the Farmer can water his crops when the power is there. On the other hand intermittent nature of sunlight will forbid sustained water supply for crops like rice. For dry crops unless water runs through pipes, evaporation of water takes place of the limited water supply by the Solar Pump. I had experience of electric, diesel and solar pumps. At a site where the water table is 150 ft. I could not use solar pump. So the solar pump is used to pump water from a sump to the nearby pond which is waste water.
“The Indian power sector provides significant opportunities for reducing energy
consumption by addressing existing inefficiencies of technical, operational and economic nature. Replacement of inefficient agricultural pump sets has been identified as one of the key policy initiatives, which to date, has been limited
to a few pilot projects. The policy objectives are to: replace inefficient pump sets,
improve distribution grids and provide metering. Adequate readdressing of economic inefficiencies, in terms of electricity pricing, remains a long-term objective. The scalability of such a policy proposal across the country offers many challenges(A Policy for Improving Efficiency of Agriculture Pump sets in India:
Drivers, Barriers and Indicators ,Anoop Singh, Climate Strategies, September 2009)”
As a Renewable Energy Expert I very much welcome deployment
of Renewables and Solar pumps are no exception. What I stress is reliability of power to pump water on demand . Here is a simple solution to use Electric pump sets efficiently. A 5 HP electric pump set costs about Rs 30,000 and a subsidy of Rs 25000 can be provided to replace the inefficient old electric pump sets. This can be funded by Union/State/International organisations. Energy saving yields immediate results compared to energy generation. When Rs 5 lakhs is provided as subsidy out of Rs 6 lakhs for a solar pump, mere Rs 25,000 per electric pump set is peanuts. Enormous electricity can be saved by this. Electricity is a high grade energy which is badly needed for lighting, computers, Industries
etc. Moreover such ambitious plans like Solar Pumps replacing 26 Million
irrigation pump sets often end up in HIGH PROMISE AND LOW PERFORMANCE as witnessed in some of the Renewable Energy Projects earlier in India.
Each Kwh saved is each Kwh generated.
Has any thorough cost benefit analysis on solar water pumps been made? Solar Water pumps efficiency is low and fit for open wells which are not very deep. For bore wells (with its intermittent nature) solar water pumps are least effective. Subsidies mean public money. On the other hand most of the irrigation pump sets are very old and inefficient. A scheme can be chalked out to replace the old and obsolete irrigation pump sets with more efficient ones. This will save enormous money and increases reliability. On the other hand power tariff for small farmers in many states is nominal or nil. As such how many Farmers will be willing to invest their share in Solar pumps which are not reliable? Here is a pertinent point. For centuries Water pumping windmills were in use. Why they vanished? Because of least reliability. In the eighties thousands of water pumping windmills were installed across the country under a Demonstration Programme by DNES (Now MNRE). None of them worked beyond a year. I am afraid the same fate may be for solar pumps. Agriculture needs water on demand. The Farmer won’t mind installing even diesel pump set so long as he gets reliable water supply for crops. A Government which is showing so much enthusiasm to promote solar pumps, why is reluctant to promote solar cookers which are efficient and reliable? The solar cookers will be best suited for rural areas.
The agricultural sector accounts for about 30% of electricity consumption in India. The largest population of inefficient pumps and systems is also to be found in this sector. Two factors that adversely impact electricity consumption are, efficiency of the pumping system, and inadequate standards for motors and pump-sets.
ICPCI{ International Copper Promotion Council (India)} is involved in several initiatives targeted at improving the equipment and distribution system efficiencies in the Agricultural sector. They have expertise and experience in :
1. Propagate the use of Energy Efficient Motors for energy savings, in Industries.
2. Promote the use of high efficiency motors and pumps in the Agricultural sector.
Expertise from organisations like ICPCI can be availed by Government of India and State Governments in going in for high efficient agricultural Electric Motors. Even a 10 to 20 % efficiency in Electric Motors contributes much to the power demand in the country.
Dr.A.Jagadeesh Nellore(AP),India
Renewable Energy Expert

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