Solar water pumps- a good investment

Solar water pumping technology has come a long way since the first home-grown units were installed in Namibia’s rural areas. It has now improved to the point where investing in a solar pump is worthwhile, even though it is difficult to get insurance for a unit on an isolated farm, writes Servaas van den Bosch.
Issue date : 16 January 2009

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Solar water pumping technology has come a long way since the first home-grown units were installed in Namibia’s rural areas.  It has now improved to the point where investing in a solar pump is worthwhile, even though it is difficult to get insurance for a unit on an isolated farm, writes Servaas van den Bosch.

Solar power supplies cannot yet compete with conventional electricity suppliers because they don’t provide the same capacity, but farmers could save thousands by converting diesel water pumps to run on solar power. NGOs in Namibia are working with commercial banks to promote the use of these clean and easy-to-maintain pumps.

A suitable alternative
A feasibility study by the Namibian Ministry of Mines and Energy conducted in 2006 found at least 20 000 boreholes in the country no deeper than 100m with the ability to deliver 5 000â„“/day, ideally suited to solar-pump technology. Although deeper boreholes delivering more water require more energy than could economically be supplied by a solar system, solar technology makes sense on most if not all farms. “The savings are impressive,” says Robert Schultz, coordinator of the Energy Desk at the Desert Research Foundation of Namibia (DRFN).

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“Depending on the water level and volume to be pumped, the economic break-even point of a solar pump can be reached 20 months after installation. Most solar panels come with a 20-year warranty.” The DRFN study of the advantages of solar pumps takes into account initial cost, replacement cost and maintenance/operational cost.
While a diesel-powered pump is slightly cheaper to buy, Schultz warns that it may have to be replaced within five years. In contrast, he says, a solar pump’s submerged units last seven years.

Add the maintenance cost of a diesel pump and it becomes twice as expensive. But the big savings come from operational costs – the price of diesel, and of transporting it to the borehole. The all-inclusive cost over a 20-year period is estimated at R102 000 for a solar-powered pump, against R590 000 for a diesel-powered water pump.
Heinrich Steuber, the manager of Soltec, a company in operation since 1996, agrees.
“The solar pump is presently the most feasible water-pumping solution in the Namibian environment,” he says. “Only a grid-powered pump is cheaper, provided you have an existing grid point close to the borehole.”

Different technology
Solar water pumps are nothing new. Since the 1980s, several have emerged on the Namibian market. Early designs were either too complicated, with many moving parts and solar panels, or weren’t robust enough for Namibia’s harsh climate.
In the 1990s, a Namibian solar pump called the Juwa enjoyed short-lived popularity. It was robust and cost-effective, but eventually couldn’t compete with cheaper, easier-to-maintain products and production was halted. Nevertheless, some 300 Juwa pumps are still operational on Namibian farms.

Made for the emerging market
Today the market is dominated by two suppliers – the German-made Lorentz and the Danish Grundfos. The All-power pump, manufactured in South Africa, is also still sold, although it’s becoming slightly outdated. The Lorentz pump’s control unit is installed above ground, while that of the Grundfos is submerged, has to be properly sealed and is more prone to lightning damage.

Both pumps are easy to install. “It’s really plug-and-play and you don’t have to worry about pipes, as you do with the Juwa,” explains Schultz. The Lorentz pump is also easy to self-maintain, while the Grundfos is slightly more complex and requires professional service. Despite the apparent advantages of the Lorentz, some farmers shy away from it after experiencing wet-end failure and motor and control unit problems. Sorting out the warranty on the pump can also be time-consuming and difficult.

Both systems consist of the same basic components: a pump motor, a control unit, a water sensor, a water pipe, electric cables and a safety rope. The power cable is connected to a pole-mounted photovoltaic panel to ensure the underside doesn’t get too hot and enough air passes over the unit.The maintenance of the latest generation panels is as straightforward as keeping the surface free of dust that would shut out the sun’s rays.

Anti-theft measures
“The only big drawback is theft,” admits Schultz. “Because water pumps are often spread out all over the farm, they’re hard to monitor. But the perception of theft is greater than the real loss – the actual number of solar panels stolen lies somewhere between 1% and 2%. “However, because of these perceptions, insurers are hesitant to cover them,” says Schultz. “Some farmers surround their pump units with a hedge of cactus or sisal, or use arched ladders to gain access to the units.”

There are other security measures. A permanent presence, such as a labourer’s home, can be established at the pump site. Or the panel can be marked with the farm’s name and contact details. The underside can be painted with non-removable paint in a recognisable colour. It’s also wise to keep a record of the serial numbers.
A more elaborate strategy is to mount the panels on a 6m steel pole set in concrete with guy wires as an anchor. Cement is poured into the pole and razor wire is fitted under the panels. Although it’s a bit of work, it also safeguards the panels against vandalism by baboons.

“We’re collecting data to convince insurers the risk isn’t as high as it seems, but it’s also farmers’ responsibility to protect their assets,” adds Schultz.
Contact Robert Schultz on (+264) 612 3172.     |fw

Photovoltaic systems

  • A photovoltaic (PV) system converts solar energy to electricity through solar cells at an efficiency rate of 17%.
  • PV technology is based on semiconductors such as silicon.
  • In 2001, 101 pumps were sold.
  • In 2005, 225 pumps were sold.
  • Most boreholes are on commercial farms south of the veterinary cordon fence.
  • Diesel pumps, licks and interest on capital constitute 35% to 40% of farming operational costs.