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Electricity from Fresh Air


Paul Botha is a South African who is firmly established in New Zealand after moving here 22 years ago. He spoke to Plimmerton Rotary on 1 November 2016.

Paul is a mechanical engineer and keen sailor who has spent most of his working life in the wind energy field. He has been with Meridian for 12 years, currently as their Strategy Manager for Wind Generation.

Paul gave us a well-illustrated and stimulating talk on the wind energy industry and its prospects.

Demand for electricity flattened off in 2007, meaning that no new generation capacity was needed. Growth has now returned, probably linked to population growth. Generation costs have shifted, and are now quite similar for each source: wind, hydro, geothermal and hydrocarbon.

Because air is much less dense than water, wind turbines are much larger than for hydro. Their efficiency depends strongly on wind-speed and blade size. Finding the best sites is critical, so measurement and monitoring, and modelling the results, is a key activity. Once a site has been chosen and all the consents obtained, the main challenge is a logistical one: bringing the huge components of the windfarm onto the site. Nearly all of the mechanical and electrical elements are imported, but the civil works and assembly are done locally.

The design of windmills varies: they can be horizontal or vertical, upwind or downwind, and 1, 2 or 3 bladed. The very biggest ones can have gearboxes and alternators at the top of the tower weighing 700 or 800 tons.

Meridian’s two local windfarms, Mill Creek and Westwind, have 88 turbines and provide enough energy for 90,000 homes.

Windmills can be noisy but there is a national noise standard which Meridian meets. Birdstrikes are fairly rare.

In answer to a question about domestic self-generation, Paul said that community windmills would be more efficient than individual ones, but less efficient than large commercial ones. The economies of scale are very powerful in this business.

Paul was introduced by Alistair Taylor and thanked by Ron Lucas, (who can see the Westwind turbines from his lounge).

Electricity from Fresh Air

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