The largest power authorities in the United States rate the dependability of wind projects to deliver electricity during periods of peak demand at between 8% and 18.5% of their rated power capacity, according to a survey released Friday by the U.S. Energy Information Agency (EIA).
The EIA says Regional Transmission Organizations (RTOs), which manage about 60% of the power supplied to utilities in the U.S., recognize that the wind necessary to achieve a turbine's full generating capacity may not be available at the time of peak electric demand. In their long-range projections, planners count only a fraction of the nameplate capacity by applying a discount factor to it.
The EIA says its own benchmark discount for wind power reliability ranges from 15% to 30%, depending on geography.
The lowest reliability factor in EIA’s survey was 8% applied by the Midwest Reliability Organization (MRO), which serves Nebraska, Iowa, Wisconsin, Minnesota, most of South Dakota, eastern Montana and the Canadian provinces of Saskatchewan and Manitoba. MRO projects its total wind capacity in 2019 will be 8.75 gigawatts (GW) and that wind capacity available for peak periods will be 0.70 GW.
The highest reliability factor in EIA’s survey was 18.5% applied by the Western Electricity Coordinating Council (WECC), which serves the 11 most western states and the provinces of British Columbia and Alberta. WECC projects its total wind capacity in 2019 will be 26.19 GW and that wind capacity available for peak periods will be 4.85 GW.
Small variations discount percentages can have big consequences for power infrastructure planning, says the EIA. Hypothetically, if a region projecting 20 GW of wind capacity by 2019 decreased its capacity value by one percentage-point from 12% to 11%, and had to replace that lost wind capacity in order to meet its target reserve margin, it would require an additional 0.20 GW of capacity resources by 2019. That 0.20 GW could come from a variety of traditional sources (gas, coal), or represent the available-on-peak portion of approximately 1.8 GW of additional wind. A conventional natural gas combustion turbine of the required size might cost $195 million, says the EIA.
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