The 2021 Western Assessment concludes resource adequacy risks to reliability are likely to increase over the next 10 years. WECC recommends entities take immediate action to mitigate near-term risks and prevent long-term risks. Approaches to evaluating and planning for resource adequacy must adapt to changes affecting the system and evolve to ensure future reliability. The world has changed. The West has changed. These changes appear not only destined to continue, but to accelerate. If reliability and resilience are to be maintained, our planning, analyses, and ideas about resource adequacy must also change.
Based on current projections, by 2025 each region and the interconnection will be unable to meet a 99.98% one-day-in-ten-year (ODITY) reliability threshold because they will be unable to eliminate the hours at risk for loss of load even if all planned resource additions are built and power is imported.
The assessment relies on data collected from BAs describing their demand and resource projections. It evaluates resource adequacy across the entire interconnection and each of the five subregions.
The assessment uses two approaches to evaluate resource adequacy. The first is an energy-based probabilistic approach that evaluates potential demand and resource availability for each hour over the 10-year study period (2022–2031) to identify instances in which there is a risk of load loss. The second approach combines information from the probabilistic analysis with a deterministic model to examine how the system reacts to specific system conditions. The deterministic approach highlights risks associated with a few extreme scenarios.
Several conditions create the backdrop for this assessment, including a shift in the diversity of the interconnection, changes in demand and resource variability, the rapid pace of change, and the fact that resource adequacy must be analyzed and addressed across multiple time frames.
WECC’s analysis of resource adequacy over the next 10 years reveals the following takeaways:
- Both demand and resource availability variability are increasing and the challenges they present appear worse now than they did in the 2020 Western Assessment of Resource Adequacy.
- Under current planning reserve margins (PRM), all regions in the West show many hours at risk of load loss over the next 10 years.
- To mitigate resource adequacy risks over the near-term (1 to 4 years) and long-term (5 to 10 years), PRMs need to be increased - in some cases significantly - or other actions taken to reduce the probability that demand exceeds resource availability.
- Resource adequacy risks could get worse before they get better if action is not taken immediately to mitigate near-term risks and prevent long-term risks.
Findings show historical approaches to resource planning, if unchanged, will result in a significant degradation of resource adequacy. The typical deterministic approach to resource planning finds the peak demand hour, applies a flat, fixed planning reserve margin, and compares this information to the expected generation capacity. This approach assumes when the highest demand hour is resource adequate, all other periods are as well. Previously, this approach has been successful because system variability was low, so entities could rely on consistent resource availability. However, system variability is growing, reducing the consistency and predictability of resource availability.
Looking ahead, as resource availability variability increases with the growing portions of renewables, the certainty of previous levels of imports decreases, leading to reliance on imports becoming more precarious. Reduced availability of excess generation, coupled with increased demand for imports, can result in several entities relying on the same resource for imports to be available.
WECC encourages planners adopt energy resource adequacy planning regimens, rather than capacity based, with a focus on times of highest constraint, rather than peak demand. WECC also recommends planning entities and their regulatory authorities consider moving away from a fixed planning reserve margin to a probabilistically determined margin. As variability grows, a dynamic planning reserve margin will better ensure resource adequacy for all hours. Further, WECC recommends planning entities regularly recalibrate PRMs when there are significant changes to resources or demand that may increase the variability on the system.
The 2021 Western Assessment includes additional analysis as well as in-depth findings for each of the five subregions. WECC is looking forward to working with stakeholders on resource adequacy through future Resource Adequacy stakeholder engagement events, expanding to meet the needs of the West’s ever-evolving bulk power system.