Harnessing the wind

Press, 11 August 1979, Page 17

Harnessing the wind

Windmills for Home, Farm, and Cottage Industry. By R. F. Sewell. Coromandel Press, 1979. $3.50. (Reviewed by R. E. Chilcott)

In sailing and the use of wind-power, an ounce of practice is worth pounds Of theory. This booklet concentrates on sail-windmill practice. Construction details of a nine-metre diameter traditional Dutch-type windmill are presented which should allow an enthusiast to build a wood-and-canvas mill to drive such loads as water pumps and circular saws. Plenty of sketches, reminiscent of Leonardo da Vinci illustrations rather than working drawings, help get the ideas across. Pumping and sawing systems are emphasised and the reader is referred to a bibliography for further information.

One Of my windmill theories is that the more blades you have, the less likely you are to lose one. It is therefore reassuring to find that the author’s experience in New Zealand leads him to recommend a four-bladed windmill to drive an electric generator, rather than a high-speed two-bladed propeller. Operating at normal windspeeds, a windmill can be quite exciting; the sight and sound of a runaway windmill in a gale is awe inspiring, as we found recently with a 12-metre diameter Cretan-type sail windmill at Lincoln. This raises the question of safety and it should be remembered that the windmills described in the booklet do not have automatic controls: manual reefing or shut-down would be required in nor’westerlies or southerly gale conditions. To build these devices, the enthusiast needs spare time and

energy, a large back garden, and understanding neighbours. Alternatively windmills would make interesting school woodworking projects and, who knows, one day this could lead to a thriving replicawindmill kit-set export industry. Meantime a few slow-revving sail windmills in the Canterbury Plains landscape might become a popular tourist attraction for overseas visitors. This low-cost booklet is well illustrated and provides useful information for wind-power enthusiasts and students of molinology.

(R. E. Chilcott is a lecturer in agricultural engineering at Lincoln College where he has been experimenting with new designs for windmills suitable for New Zealand conditions.)