Wind Project Performance 1994 Summary
WPRS performance results also have been categorized by horizontal or vertical axis machines. When comparing performance of horizontal and vertical turbines, it should be recognized that vertical axis turbines used in California at the present time represent relatively old technology. No new capacity has been added since 1986.
The California wind industry continues to be dominated by horizontal axis machines accounting for 94 percent of all capacity and 100 percent of new capacity. Comparison of performance indicates a 23 percent capacity factor for horizontal axis turbines compared to a 9 percent capacity factor for vertical axis turbines (Figure 12 -- Capacity Factors by Turbine Axis).
Performance by kWh per square meter was 810 for horizontal axis turbines compared to 513 for vertical axis turbines (Figure 13 -- kWh Per Square Meter production by Turbine Axis). WPRS data does not explain why the variation in kWh per square meter performance between horizontal and vertical axis turbines is so much less than the difference in capacity factor performance.
Note that other important turbine characteristics such as downwind and upwind configurations, number of blades, fixed or variable pitch blades, and braking devices are not tracked in WPRS reports.