Choosing a Wind Farm Site on a Ridge
A power company is selecting one of three sites for a 12-turbine wind farm (60 MW) on a coastal ridge. Site A has the strongest average wind speed (9.8 m/s) but is 800 m from 22 homes and 11 km from the nearest transmission line. Site B has a wind speed of 8.4 m/s, is 1.5 km from the nearest home, and 7 km from the grid. Site C has the best wind resource (10.4 m/s), is 4 km from the grid, but lies on conservation land and includes a known nesting site for a threatened bird. The company must meet a 42% capacity factor to be financially viable. Geotechnical testing shows Site A has shallow bedrock, Site B has soft soils requiring piled foundations, and Site C has unstable slopes. The consent hearing will consider noise, landscape, ecology, and transmission costs. The company has a fixed budget and needs to choose one site within six months.
1. Rank the three sites using a weighted decision matrix. Explain the criteria and weights you choose.
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Criteria and weights: wind resource 35% (financial viability), distance to grid 20% (cost), social and noise impact 20%, ecological impact 15%, foundation and geotechnical risk 10%.
Site A: wind 9.8 m/s (best), grid 11 km (worst), homes 800 m (worst), ecology moderate, bedrock (best). Site B: wind 8.4 m/s (lowest), grid 7 km (middle), homes 1.5 km (best), ecology moderate, soft soils (worst). Site C: wind 10.4 m/s (best), grid 4 km (best), ecology worst (conservation land and threatened bird), unstable slopes (worst).
A weighted ranking places B first because its social and ecological risks are lower and its grid distance is manageable; C last because ecological and geotechnical risks are high despite the best wind; A middle because strong wind is offset by noise conflict and grid cost. The exact ranking changes if wind is weighted at 50%, which could favour C or A. The key is that the 42% capacity factor threshold must be tested, not assumed.
2. Explain how uncertainty in the data could change your ranking.
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Wind data may come from a short period or a single mast, so Site B's 8.4 m/s could be underestimated or Site A's 9.8 m/s could be a local gust. Nesting counts are seasonal; Site C's threatened bird may be absent in some years but critical in others. Foundation costs are estimates; soft soils at B could double. Noise and landscape effects are contested and depend on turbine model and layout. Grid connection costs can change with consent conditions.
A sensitivity analysis should test: if B's wind is 10% lower, does it still meet 42%? If stabilising C's slopes adds $8m, is it still viable? If A's nearby homes expand by 20, does noise become unacceptable? The ranking is a decision under uncertainty, not a fixed answer. The company should collect at least 12 months of on-site wind data and a full ecological survey before choosing.
3. Recommend one site and justify it, including one condition to reduce adverse effects.
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Recommend Site B. It has the lowest social risk (1.5 km from the nearest home), moderate grid distance (7 km), and avoids conservation land. Its wind speed is lower, but 8.4 m/s can still be viable if the capacity factor is verified; the company should not risk the ecological and legal delays at C or the noise conflict at A. The soft soils add foundation cost, but this is a known engineering problem.
Condition: a noise limit of 40 dB at the nearest home, a community liaison group, and a habitat offset for any ecological loss. If wind monitoring shows B cannot reach 42%, the fallback should be A with a reduced layout, not C. This is a precautionary judgement: avoid the highest-consequence risks first, then optimise engineering.