Solar water pumping systems are an ideal alternative to diesel generators for a number of reasons including low maintenance costs, environmentally friendly and have a longer life cycle.
These benefits were highlighted by Titus Koech, Technical Services Manager SSA at JinkoSolar, during an online discussion titled Solar-powered water solutions for sustainable agriculture in SSA.
Koech further underlined that solar water pumping solutions not only provide water for irrigation systems but for domestic water supply as well as water for livestock, especially for most of the arid and semi-arid regions of sub-Saharan Africa.
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Explaining the difference in the installations, he said the pumps can be deployed as either a standalone or hybrid system. However, each configuration will have its own advantages and also limitations, according to Koech.
“In the case of standalone, where PV is the only source of energy, this may result to low yield because pumping occurs only during the day. But for hybrid systems where there is more than one source of energy like PV plus electricity from the grid and diesel generator, the pump will operate for longer hours, even at night. It also comes with the advantages of higher OPEX and high initial costs. The choice of the configuration when it comes to liability depends on the requirements,” says Koech.
Selection criteria for the configuration
To determine the suitable installation, Koech says JinkoSolar technicians would first conduct an assessment, what follows after the assessment is the sizing. “For the assessment, there are a number of factors that we look at like the water source, the water demand, solar resource, and solar radiation. We then use the assessment output to determine the sizing for the solar pumping solution and the PV array.
“What is also very important for solar pumping is the cost, not only the initial costs, but rather the lifecycle cost of the total project. While doing the cost analysis of the system, we also estimate, usually 20 plus years for the lifespan,” he says.
Factors that are considered include the CAPEX, the OPEX, the replacement costs and also the energy or fuel costs especially for hybrid systems.
Solar water pumps serving humanitarian sector
Adding to the discussion, Asenath Kiprono, Global Water & Solar Specialist at Oxfam, shared high-level experiences, findings and lessons for solar application for water supply in the humanitarian sector.
“In 2017, it was approximated that about $1.4 million was used on diesel related expenditure in the humanitarian sector. Water supply remains the biggest consumer of energy in this context,” she noted.
In the humanitarian sector, energy is being used in four categories; heating, lighting, cooking and powering, including powering pumping systems for drinking water and agriculture. Solar is a sustainable solution that addresses the energy challenge in the sector and specifically these four categories, says Kiprono.
She pointed out that one of the elements that makes solar very attractive is its cost-effective effectiveness over the long term. The capital costs of solar is higher than diesel, but over time due to the money saved by not buying diesel for the generator, the savings accrue very fast, with a system paying back within a very short time.
Kiprono continued: “We have done lifecycle cost analysis using present worth costs to determine the payback period, and the cost savings accrued over time. We have analysed over 200 water schemes in 10 countries around the world.”
The component with the highest lifespan is the solar panel and “even though we use 25 years to do the analysis, which is the expected lifetime of the solar panels, the cost benefit can be seen as early as 2-5 years. And so we don’t have to wait 25 years to see the cost of benefits”.
Using Uganda as a model example of the proper use of solar. Kiprono stated that they visited Uganda in 2017 – At the time when WASH agencies were responding to an influx of refugees into the West Nile region of the country – and at that time, only about 2-3 humanitarian organisations were using solar for water supply.
“When we went back one year later, over 150 water schemes had been solarised by about 20 organisations, bringing a projected cost saving of about $23,3 million over a period of 25 years, with 8.1 million being accrued in just the first five years. The carbon saving totaling to about 1.1 tonnes per year. These good examples have increased across the sector since that time,” she stated.
Design and selection of pumping systems for irrigation
Providing context when it comes to designing a solar water pumping solution that is tailored to the unique needs of a client. Simani Dube, the Technical Consultant at Samansco & Solarquest Group, said: “The first thing to do is to determine the kind of water source that you have; be it a damn, river, or a river that has been redirected for your system.
“The next thing after determining your water source is to size your hectarage. Even if you’re using your dam to irrigate your farmland, you have to make sure that the quantity of water is enough for the area chosen.”
The next aspect in the process is to determine the size of the pumping system advises Dube: “There are various pump suppliers worldwide that have a lot of water pumping solutions that range from purely DC pumps that will work with solar only to pumps that can function with both solar as well as an AC backup for those that would want to have overnight irrigation or an alternative to just pure solar on a day when they don’t have an adequate water supply.”
He noted that each pump has its own unique features and some brands have a wide range of solar water pumping solutions to fit the requirements of each client. “Some of these brands also have sizing software that you would want to use that are dedicated to the accurate sizing of the pumps you would want,” Dube added. ESI
Listen to the full recording: Solar-powered water solutions for sustainable agriculture in SSA