Riding the wind
WIND power has been used for centuries to lift water in farms, especially in countries like Australia and the us. Some problems inherent in the existing windpump designs - high initial cost, difficulty in local manufacturing, and the need for regular maintenance - have rendered this age-old technology nonviable in developing countries. Sandy Polak and Paul Dawson, at the uK-based Neale Consulting Engineers Ltd, have developed a modern windpump design, tailored to the needs of developing countries (Appropriate Technology, Vol 21, No 4, March, 1995).
Designers of this machine - called the Poldaw windpump - set certain design criteria stemming from their experience for developing it for individual farmers and small communities at an affordable price. While giving top priority to robustness and reliability of the machinery, they wanted to make it maintenance free. The aim was to have a windpump with a minimum 20-year lifespan for all its structural components. The design, it was felt, should use readily available low-cost material and should require the minimum of labour and equipment to manufacture.
The installation was aimed to be simple, quick and safe. Since carrying out assembly involved risk, requiring to be perched on top of a tower, the hazard could be avoided by assembling the entire machine with the tower lying on the ground and then winching the whole assembly upright. As the target was a small, affordable windpump, the minimum size criteria meant that a rotor diameter of at least 3 metre had to be maintained.
Keeping these criteria in view, the designers built a modified version of the windpump using low-cost, reliable components. The total weight of the machine, including a 6-metre high tower, is 400 kg. Built in steel, the pump uses standard ballbearings which require minimum maintenance. With its size changeable according to the size of the well, the machine works in winds with a speed as low as 6 miles per hour and has an automatic storm protection mechanism.
Construction and testing of the first machine was successfully carried out during late 1994. Currently, the design for a larger machine with a rotor diameter of 5 metres and twice the water out- put is underway. A demonstration machine is operational at the Centre for Alternative Technology, Macynlleth, Wales (UK).
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