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Balance of Power

Large grids can integrate more wind—without major burdens.

Fortnightly Magazine - May 2011

balancing services.

Finally, most balancing authorities are already integrating other wind and solar. As a result, the diversity of those resources coupled with the diversity of the developers’ proposed new wind plant reduces the need for new operating reserve capacity.

• S mall Balancing Authority: A small balancing authority has few resources that can be used to provide balancing needs. When asked to integrate new wind, this balancing authority asserts that it will need all new regulated resources in large amounts to integrate the wind.

Analysis of a small balancing authority, performed for a wind developer, concluded that the amount of operating reserve needed to integrate existing wind by the balancing authority was considerably less than what had been put in place.

Several insights were gained by examining the differences in the studies performed by Black & Veatch and the study performed by the balancing authority. First, it wasn’t clear how the balancing authority established its final hourly interchange schedules with other balancing authorities. The balancing authority didn’t keep records of the load forecast it used when it finalized its interchange schedule. And although the balancing authority engaged a wind forecasting consultant to prepare forecasts for the scheduled hour, it didn’t use those forecasts. It wasn’t clear what forecasts the balancing authority used because it didn’t keep those records.

Because current FERC rules make it difficult to change intertie schedules within the operating hour, forecasting and scheduling activities that are done “before the hour” are crucial for meeting CPS2 requirements. Changing the output of resources located within a balancing authority “within the hour” in order to maintain intertie schedules is clearly allowed; regional transmission organizations and independent system operators with centralized dispatch are designed to do exactly that. The small balancing authority that was the subject of the study, however, didn’t change any of its in-area resources within the hour, thus causing it to need more regulating reserves to meet its CPS2. It isn’t clear why these changes weren’t being made within the hour consistent with its ability to do so.

The Black & Veatch analysis of the need for regulating reserves for this small balancing authority doesn’t correspond with the balancing authority’s own study of its needs. However, both studies agree that if future additional renewables are provided from smaller plants in diversified locations, less new operating reserve will be needed than if added renewable generation comes from larger plants in more concentrated locations.

Findings and Recommendations

The analyses yield two recommendations to further assist and enable integration of large amounts of renewable generation into the grid.

First, wind developers should take a collaborative stance and work with existing balancing authorities rather than develop a wind-only balancing authority.

Second, balancing authorities should consider keeping records of load and wind forecasts used in actual intertie scheduling activities. These records will help the utility demonstrate that it is prudently scheduling its purchases and sales outside of its balancing authority.

Improvements in near-term forecasting of renewable generation output and power demand—coupled with geographic, generation and load diversity—will enable providers to integrate large amounts of