Question 6.17: Energy Estimate Using the Capacity Factor Approach. The Whis......
Energy Estimate Using the Capacity Factor Approach. The Whisper H900 wind turbine has a 900-W generator with 2.13-m blades. In an area with 6-m/s average windspeeds, estimate the energy delivered.
Using (6.65) for capacity factor gives
CF \ = \ 0.087 \bar{V} \ – \ \frac{P_{R}}{D^{2}} \ = \ 0.087 \ \times \ 6 \ – \ \frac{0.90}{2.13^{2}} \ = \ 0.324The energy delivered in a year’s time would be
\text{Energy} \ = \ 8760 \ {h}/{yr} \ \times \ 0.90 \ kW \ \times \ 0.324 \ = \ 2551 \ {kWh}/{yr}Of course, we could have done this just by plugging into (6.66).
\text{Annual energy} \ \left({kWh}/{yr}\right) \ = \ 8760 \ \cdot \ P_{R} \left(kW\right) \ \left\{ \ 0.087\bar{V} \ \left({m}/{s}\right) \ – \ \frac{P_{R}\left(kW\right)}{\left[D \left(m\right)^{2}\right]} \ \right\} (6.66)
For comparison, the spreadsheet approach yields an answer of 2695 kWh/yr, just 6% higher.
In these winds, this little wind turbine puts out about 225 kWh/mo—probably enough for a small, efficient household.