California Updates Wind Stats–Finally

By Paul Gipe


In February, the California Energy Commission issued its long-awaited update on the performance of the state’s wind industry.

The Wind Performance Report Summary 1996-1999 eliminates some confusion, while adding its own. Because the CEC collects data directly from the state’s electric utilities on energy deliveries, the report of electricity generated by California’s wind turbines is the most accurate and reliable of the data found in the report. However, the CEC is dependent upon wind companies for calculating the total number of wind turbines and wind-generating capacity in the state. Historically this has proven problematic.

Some wind projects have changed hands so many times no one on staff knows they have a legal obligation to report the number, size, and type of turbines on their sites. Some operators simply don’t cooperate. Others inexplicably fail to add new projects to their reports. For example, the CEC’s Juan Guzman says that after issuing the Performance Report he learned that Enron was operating the Cabazon project in the San Gorgonio Pass. Enron did not report the 40 MW project of Zond Z-750 turbines in their 1998 filing.

Enron’s failure to file the Cabazon data, coupled with other operators’ failure to file reports with the state, led the CEC to issue a surprising disclaimer. Though the Wind Performance Report data says there were 1,406 MW of wind capacity at the end of 1999, the CEC believes there was actually 1,670 MW. The CEC reports that the discrepancy has steadily increased since the last state report was issued.

Independent analysis for WindStats found 1,620 MW operating in 1999.

The CEC report also doesn’t include the growing number of small turbines in the state, nor the two turbines installed on San Clemente Island. Nevertheless, California’s Wind Project Performance Reporting System is the most authoritative assessment of what is operating in the state.

When the CEC issued its first report in 1985, California accounted for more than 90% of total worldwide wind capacity. Since then the burgeoning growth of the wind industry has, for the most part, passed California by. In 2001, the state’s wind turbine fleet, probably one of the most varied in the world, represented only 6% of world wind capacity.

The CEC’s report confirms what WindStats has been reporting since 1996 that total installed capacity has been declining from its peak in 1991. Despite assertions by the U.S. Department of Energy and the industry’s trade association to the contrary, the decline has been steady. Recent repowerings have slowed but have not reversed this trend.

According to the CEC’s data, by year end 1999 total installed capacity in California had fallen by 16% from 1991. WindStats’ independent analysis estimates the industry has closed the gap to within 4% of the peak.

Total annual generation has fallen by a similar amount: 1999 generation was 12% less than that in 1994. Poor winds and construction activity related to several major repowerings cut total production a staggering 27%, indicating the range of volatility wind turbine owners and power planners can expect from large-scale wind development.

The CEC’s Guzman reports that 2000 was a particularly good year. In 2000 the state’s wind turbines produced 3.175 Terawatt-hours or within 1% of the industry’s peak generation in 1994.

Fortunately, yields statewide have held their own. Since its peak in 1994, statewide annual specific yield in kWh/m2 have declined only modestly from 5% to 8%. The aging fleet of first and second generation turbines is being offset by the introduction of more modern turbines through repowerings in the San Gorgonio and Tehachapi passes. Repowerings have been stalled in the Altamont Pass by legal and environmental obstacles. When these will be resolved remains uncertain.

California’s wind industry suffered a devastating blow by the state’s experiment with utility deregulation. Since the mid 1990s the future of wind companies in the state has been uncertain. First was a decision by the Federal Energy Regulatory Commission thwarting the construction of new projects, quickly followed by Kenetech’s bankruptcy, then a brief dalliance with so-called green power projects, and more recently by the bankruptcy of Pacific Gas & Electric and the near bankruptcy of Southern California Edison during the sates power crisis. It’s been a wild ride, but the state’s wind turbines, for the most part, remain standing and delivering a much needed 1% of the California’s electricity even when large segments of the industry hadn’t been paid for months on end.

Those who track the industry will quickly realize that the numbers in the report don’t always add up or match those published previously. The CEC staff acknowledges that there are discrepancies and faults the complexity of the contracts between wind companies and the utilities, as well as to uncooperation of some wind companies. For example, the CEC’s report lists San Gorgonio Farms as selling the exact same number of kilowatt-hours in 1996 and 1997. Not only is this highly unlikely, the capacity factor SGF produces, 53% is surprisingly high as well–even for SGF, one of California’s most productive wind farms. The CEC report lists SGF as generating 1,328 kWh/m2 in 1996 and 1997. In 1994, the last time SGF produced 1,300 kWh/m2, SGF’s turbines were reported delivering a more modest–and believable–capacity factor of 38%.

Similarly, the CEC reports that in 1996 AB Energy generated an impressive 1,700 kWh/m2 from its 31 Vestas V27s. Even with such productive and reliable turbines as the V27, few sites in the world have produced comparable annual yields: La Ventosa in Mexico, Wellington, New Zealand, and possibly some sites in Spain. Yet AB Energy only generated 22.4 million kWh in 1996. The actual yield for the turbines is 1,260 kWh/m2. The CEC report lists AB Energy’s annual yield correctly for 1997, but misplaces the decimal point for the capacity factor.

A more egregious error is a 1996 listing for five Taiwanese-built Delta turbines. The CEC reports that these relatively unknown turbines produced 2,300 kWh/m2 in 1996 with a 53% capacity factor. Or the listed production of the 20 WEG MS2 turbines in the Altamont Pass. Though historically productive turbines, there is little likelihood that they generated 4,550 kWh/m2 in 1996 for a capacity factor of 85%!

Clearly, one needs to use the CEC data with due care.

Even with the addition of nearly 1,700 MW of new capacity added outside the state last year, California’s fleet still represents about one-third of the total wind capacity operating in North America. As such, California remains an important source of data on the long-term performance of wind turbines. The CEC realizes this and hopes to re-establish annual performance reports now that the legislature, stung by relying on an unregulated electricity market to provide an essential public service, has given its support.


Paul Gipe is the author of several books on wind energy and is a contributing editor to Wind Power in View: Energy Landscapes in a Crowded World recently published by Academic Press.