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Reference

Wind Pumps

by Peter Fraenkel

Windpumps are windmills for pumping water. They are usually used for pumping drinking water (either for livestock or human consumption) from boreholes in remote arid and semi-arid rural areas. Other less common applications include small-scale crop irrigation, pumping of seawater brine for sea-salt production and dewatering of waterlogged land.

The majority of windpumps in use today are entirely mechanical devices, with multi-bladed 'fan' rotors, based on technology developed originally in the USA during the latter part of the nineteenth century. It is no exaggeration to say that the windpump was the key to the exploitation of the American prairies for commercial livestock, and the technology is of renewed interest today for development applications in poorer countries with many similar physical conditions to those in the richer countries where windpumps have in the past proved to be vitally important.

The so-called 'American Farm Windpumps' are still manufactured in a form that has changed little since the 1890s; in fact there can be few areas of technology where engineering products are still being sold commercially today that have changed so little in the last hundred years. Despite the obsolete nature of most windpumps they are still in production by about 50 companies world-wide and in the region of a million or more units are in regular use mainly in countries with large cattle ranching industries such as Argentina, Australia, the USA and South Africa.

Attempts have been made in recent years to develop wind-electric pumping systems and although these may have a bright future, few are available at present. It is not easy to achieve the high efficiency of the old fashioned mechanical windpumps when converting mechanical energy to electricity and then back again, so the first generation of wind electric pumping systems tended to be less efficient and more expensive. However, new improved models are beginning to appear and may eventually supersede the original mechanical windpumps. Also the high solidity 'fan' rotor of the old windpumps allows operation in wind speeds down to 2 to 2.5 metres per second. This makes them viable in much less favourable wind regimes than are necessary for virtually all other kinds of wind power generation.

The reason this obsolete technology survives at least in some markets is that the windpump can be cost competitive (compared to diesel or solar pumps for example) in many locations. However, most of the customers who buy them do not undertake detailed economic analyses on cost-competitiveness to justify their purchasing decisions (although farmers commonly have a good feel for what is cost-effective and are well known the world over for being conservative and cautious in spending their money). Rather, their prime reason for using windpumps is that they are a technology that can offer high reliability and great longevity with minimal human intervention. Most windpumps can run 6 or 12 months between maintenance and even then only require greasing or a top-up with fresh oil. In the livestock industry this implies that a remote water point served by a windpump can generally function unattended for weeks at a time unlike when almost all other forms of water pumping machinery are used. Also, when a windpump requires occasional maintenance or repairs, it is generally a well-understood and simple form of technology that can readily be handled by most competent farm mechanics.

Mechanical windpumps declined in use from their heydey in the 1920s when there were 6 million units in use in the USA alone. Since the 1980s there has been something of a revival of interest in the technology but the windpump market has not grown significantly, but unfortunately not much in the developing countries but more in its traditional markets, the larger semi-arid countries with open grasslands and major livestock industries, notably Argentina and South Africa.

One reason cited for this disappointing performance is that the technology required is not sufficiently developed (in terms of performance, economic viability and technology appropriateness) for widespread dissemination; another is that it is generally obsolete. Perhaps another factor is that the main manufacturers are small companies only, interested in their local market, so most of the technology neither lends itself to technology transfer, nor are there many manufacturers interested in trying to transfer it.

Also, although it is a relatively simple technology once suitable experience has been gained, it is fraught with problems for those lacking any grounding in this field. This discourages its successful take-up in regions having the right conditions and needs, but lacking any pre-existing experience of the technology. However a plethora of small windpump manufacturers have appeared recently in several developing countries, particularly in India and China, and it seems possible that there will be a reasonably revival of the use of windpumps over the next few years since the need is widespread in many areas having the right physical conditions.

More information

Windpumps: A Guide For Development Workers, S Lancashire, J Kenna & P Fraenkel, 1993, IT Publications, ISBN 1-85339-1263.

• Reference
• UK Wind Energy Database