ERCOT readies to integrate a large future influx of wind generation and finds need for new, more flexible resources to provide ancillary services – preferably a zero-to-five-minute ramping...
Winds of Change Freshen Resource Adequacy
Intermittent and interruptible resources increasingly are being considered in regional resource adequacy calculations—but the approaches differ.
study, completed in July 2006, investigated each of these mitigating measures. After much discussion, AESO determined that the success of wind-power integration requires wind-power forecasting, although the other mitigation measures were not discounted. Forecasting was seen as the best first step. The majority of AESO stakeholders agreed, and most supported a centralized forecasting system, while others supported a decentralized forecasting system which may better support wind bidding into the market. The opinions as to who should pay for such a forecasting system were wide and varied. 2
The perceived benefits of a wind-forecasting system include: improved system operation and reliability, more efficient use of regulating reserves and wind following, and less chance of constraining wind-power potential. In October 2006, the AESO issued two requests for proposals for a wind-power forecasting pilot project. The first phase of the pilot will forecast meteorological data and convert it into wind power data for specific locations in Alberta for one year. The second phase of the pilot will analyze the results obtained in Phase I. This first-of-its-kind wind forecasting pilot could establish new precedents, protocols, and procedures for the interconnection of large quantities of wind capacity onto the grids of North America.
The Northeast: Three RTOs And Three Calculations
To sell power into the New York market, NY-ISO requires all generators over 10 MW to meet certain requirements (e.g., net dependable capability, outage schedules), this includes both interruptible (demand-side) and intermittent (wind and solar) power resources. NY-ISO determines each generator’s unforced capacity (UCAP) based upon the data it submits. If a generator has committed to meet a certain amount of unforced capacity, but fails to meet that commitment, the ISO will impose various financial penalties.
Unlike the New York ISO, ISO- New England (ISO-NE) does not have a required reserve-margin criterion. Required resources are planned based on meeting the standard LOLE/LOLP reliability criteria of not disconnecting any firm load due to resource deficiencies, on average, more than once in 10 years.
ISO-NE uses a multi-area reliability model, developed by the ISO-NE staff, to assess the resource adequacy of the New England bulk power system. This model considers forecasts for demand, generation, imports, transmission, and demand-side management. The model considers hydro, but does not appear to consider wind generation.
New England currently has only two operational wind-energy projects, which produce about 12 GWh annually. As of June 2006, 12 wind projects, totaling 924 MW are in the ISO-NE generator interconnection queue. ISO-NE estimates that the capacity factor for the 11 onshore wind generators will be 25 percent, and the capacity factor for the one offshore wind generator will be 38 percent. ISO-NE does not believe that the renewable projects currently in its generator queue are adequate to meet the state renewable requirements of Connecticut, Massachusetts, Rhode Island, and Vermont. While the ISO-NE 10-year Regional System Plan, which is updated annually, discusses the future incorporation of wind resources, it does not appear to include wind in the modeling process.
PJM performs its Reserve Requirement Study annually using two probabilistic models (GE MARS model and an in-house PRISM model)