What Qualifies as an Intermittent Renewable Resource in ISO/RTO Markets?

How CAISO defines intermittent renewable resources

In the California Independent System Operator (CAISO) market, intermittent renewable resources are referred to as “Eligible Intermittent Resources” (EIRs). These are typically variable energy resources like wind and solar that are subject to weather conditions beyond the control of the facility owner or operator. To qualify, these resources must meet specific criteria, including:

Participating Generator Agreement: EIRs must execute agreements like the Participating Generator Agreement or Pseudo-Tie Participating Generator Agreement, binding them to CAISO’s tariff rules.

Forecasting requirements: CAISO oversees the development of forecasting tools for EIRs, ensuring accurate energy predictions. Resources can also use their own forecasts if certified by CAISO.

Minimum capacity: Participating Intermittent Resources must have a rated capacity of at least 0.5 MW and be electrically connected at a single point on the CAISO-controlled grid unless otherwise permitted by CAISO on a case-by-case basis.

These rules ensure that intermittent resources are integrated into the market efficiently while maintaining grid reliability.

How MISO approaches intermittent resources

The Midcontinent Independent System Operator (MISO) defines intermittent resources as those powered by variable energy sources like wind or solar. However, MISO distinguishes between intermittent and dispatchable resources based on their operational characteristics.

Intermittent resources: These are resources that cannot control their output due to the variability of their energy source. For example, wind turbines depend on wind speed, and solar panels rely on sunlight.

Registration requirements: MISO requires intermittent resources to register under specific categories and align their megawatt capacity with interconnection studies to ensure market compatibility.

MISO’s approach emphasizes the importance of aligning resource capabilities with market needs, ensuring that intermittent resources contribute effectively to energy and operating reserve markets.

How PJM defines intermittent renewable resources

PJM Interconnection, which serves the Mid-Atlantic region, defines intermittent resources as those that rely on renewable energy sources with variable output. These resources are integrated into PJM’s capacity and energy markets under specific guidelines.

Variable energy sources: Wind and solar are the primary examples of intermittent resources in PJM. Their output is influenced by weather conditions, making accurate forecasting critical.

Market participation: PJM allows intermittent resources to participate in both day-ahead and real-time markets, but they must adhere to PJM’s forecasting and scheduling requirements.

PJM’s focus is on ensuring that intermittent resources can reliably meet their commitments while maintaining grid stability.

ERCOT’s unique perspective on intermittent resources

The Electric Reliability Council of Texas (ERCOT) takes a slightly different approach to intermittent renewable resources. ERCOT refers to these as “Variable Renewable Energy Resources” (VRERs) and emphasizes their role in the state’s energy-only market.

Forecasting and telemetry: ERCOT requires VRERs to provide real-time telemetry and forecasting data to support grid operations.

Market integration: Unlike other markets, ERCOT does not have a capacity market, so VRERs participate solely in the energy market. This makes accurate forecasting and real-time responsiveness even more critical.

ERCOT’s approach highlights the importance of flexibility and real-time data in managing intermittent resources in an energy-only market structure.

How SPP manages intermittent resources

The Southwest Power Pool (SPP) defines intermittent resources as those powered by renewable energy sources like wind and solar, with output that cannot be stored or controlled by the facility owner. SPP’s Markets+ initiative further integrates these resources into its day-ahead and real-time markets.

Forecasting requirements: SPP produces hourly forecasts with a rolling 48-hour projection for wind and solar resources. Participants must provide meteorological data to support these forecasts.

Dispatch limitations: In the physical unit commitment process, SPP limits the maximum dispatch of intermittent resources to the lesser of their output forecast or the submitted maximum in their resource offer.

SPP’s focus on accurate forecasting and dispatch limitations ensures that intermittent resources are effectively integrated into its markets while maintaining reliability.

Why understanding these definitions matters

The way ISO/RTO markets define and manage intermittent renewable resources has significant implications for market participation, compliance, and grid reliability. Each market tailors its rules to its unique operational needs, creating opportunities and challenges for resource owners and operators.

By understanding these definitions and requirements, market participants can better navigate the complexities of energy markets, optimize their operations, and contribute to a more sustainable energy future.

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