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| Fig. 1: Te Uku Wind Farm on the way to Raglan. (Source: Wikimedia Commons) |
New Zealand is looking toward the future, with a target of 90% renewable energy by the year 2025. [1] Wind power is a relatively small share of the country's renewable energy sources, but with the great potential the country has for wind power that share is sure to increase. Despite the generally positive reactions to renewable energy sources, there can be opposition to the installation of wind farms for various reasons.
New Zealands latitudinal location leaves it subject to the Roaring Forties, a powerful and consistent Westward wind that hits most prominently between 40° and 50° latitudes. The combination of the three factors led to early sailors effectively halving their travel times from Europe to Asia. [2] These three factors include the Earth's rotation, the relative lack of other land serving as windbreaks, and the displacement of air from the equator towards the south pole. In modern times, the roaring forties are more useful because of the way they give wind farms a consistent source of power.
The Conservation of Mass is a fundamental rule of physics that states that mass cannot be created or destroyed. In the context of wind turbines this means that the amount of air flowing into the turbines must be equal to the amount of air exiting it. The German Physicist Albert Betz found that this means the most energy you can theoretically extract from a wind turbine is equal to 16/27 (59.3%) of the total kinetic energy of the air flowing through it. [3] More precisely, the maximum power output P is given by
| P | = | 8 27 |
ρ v3 A |
where ρ = air density, v = velocity, and A = effective area of the disk. Because wind is essentially free, it makes wind power an extremely effective method for energy production.
Despite the positive reactions one might expect to a sustainable energy project being proposed, in reality there are a variety of negative aspects of almost every project proposal. The aspect that gets the most complaints is due to the Not In My BackYard (NIMBY) phenomenon. One example is a Wind Farm proposal that received 519 submissions (49%) against it. [4] A personal example of NIMBY I've seen comes from my mother who regularly hints at her dislike of the sight of wind turbines (Fig. 1) on our drive from Hamilton to Raglan, a small beach town on the West Coast of the North Island of New Zealand.
© Sam Perry. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] M. R. W. Walmsley et al., "Minimising Carbon Emissions and Energy Expended for Electricity Generation in New Zealand Through to 2050," Appl. Energy 135, 656 (2014).
[2] I. C. B. Dear and P. Kemp, eds., The Oxford Companion to Ships and the Sea, 2nd Ed. (Oxford University Press, (2001).
[3] K. Grogg, "Harvesting the Wind: The Physics of Wind Turbines," Carleton College, 13 Apr 05.
[4] D. Bell, T. Gray, C. Haggett, "The 'Social Gap' in Wind Farm Siting Decisions: Explanations and Policy Responses," Environ. Polit. 14, 460 (2005).
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