Wind Project Performance 1994 Summary

Staff Summary

Industry Performance

Total Capacity. A cumulative capacity of 1,609 megawatts (MW) was reported operational during the fourth quarter of 1994. The 54.3 MW of new capacity installed during 1994 was higher than previous years. Cumulative capacity, however, declined due to continued attrition of older turbines.

Electricity Output. In 1994, the California wind industry produced more than 3.2 billion kWh of electricity, enough power to meet the annual electricity needs of almost 500,000 typical California homes. The amount of electricity generated during 1994 exceeded all previous years, including 1991 and 1992 when reported installed capacity was higher.

Electricity Production Percent of Projected. Although California wind projects generate a substantial amount of electricity, the industry as a whole produced only 79 percent of the total output projected for 1994. This figure, however, is an improvement from the 76 percent of total projected output attained in 1993 and is a significant improvement from the 45 percent of total projected output attained in 1985. Because many wind developers overstated output capabilities during the tax credit era, a number of older turbines with overstated projections lower the total average statewide percent of projected output. When turbines installed since 1985 are isolated, the percent of projected output for 1994 rises to 87 percent.

Capacity Factor. Capacity factor is defined as the ratio of actual energy output to the amount of energy a project would produce if it operated at full rated power for 24 hours per day within a given time period. As indicated previously, there should be standardized testing of all wind turbines for capacity factors to be truly comparable. With no such program, wind turbine ratings currently are based on widely varying test conditions and miles per hour specifications. Voluntary standards for testing wind turbines, however, have been developed by the American Wind Energy Association (AWEA).

Despite testing limitations, the capacity factor is still considered a strong indicator of wind project performance. The annual capacity factor is computed as the average of quarterly capacity factors calculated for each group of turbines reported. Only operating turbines are used to calculate capacity factors so that performance results are not skewed by non-operational capacity. For projects with new turbines, only one-half of new capacity is included in the capacity factor calculation during the quarter of installation because new turbines are not likely to operate for the entire quarter in which they are installed and new equipment typically needs a "debugging" period before operating at fully rated power.

Wind Figure 01

The resulting statewide capacity factor for 1994 is 23 percent, representing almost a 77 percent increase from the 13 percent capacity factors for 1985 and 1986 (Figure 1 -- Statewide Capacity Factors 1985 to 1994). The upper limit capacity factor achieved by some California wind projects continues to exceed 30 percent. In particular, one project has consistently reached this upper limit, including an annual capacity factor of 38 percent in 1994.

Wind Figure 02

Note that statewide average performance is still adversely affected by a number of older turbines that are less reliable and efficient than those currently being installed. When wind turbines installed since 1985 are isolated, the capacity factor rises to 27 percent (Figure 2 -- Capacity Factor for Turbine Stock).(3)

(3) All calculations of the turbine base "Since 1985" in this report exclude 3,430 - 100kW turbines installed in Altamont Pass because the project operator is reporting kWh production in the aggregate. Some of these turbines were installed prior to 1985 and some were not. Since the operator is reporting a single electricity-produced figure for this mixed urbine base, performance calculations in the category "Since 1985" cannot be made.

kWh Per Square Meter. Annual kWh per square meter calculations are anotherwind technology performance indicator. The advantage of this indicator is that it is based on blade-swept area, a wind turbine specification determined by standard measurements rather than non-standardized kW ratings used to determine capacity factors. Unfortunately, it is still difficult to develop directly comparable kWh per square meter results because data reported for some turbine models include new turbines that have not had the benefit of a full operational year. When any kWh per square meter calculation does not include a full operational year for all turbines, an asterisk has been placed next to the value on all summary tables in Section 6.

Wind Figure 03

Average kWh per square meter annual production for 1994 was 798, more than a 10 percent increase from the 720 kWh per square meter recorded for 1993. When turbines installed since 1985 are isolated, however, the resulting kWh per square meter annual production figure increases to 895 kWh per square meter (Figure 3 --kWh Per Square Meter Production of Turbine Stock).


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