Comments on Feb 2, 2022 stakeholder call discussion

Flexible capacity needs assessment - 2023

Comment period
Feb 02, 01:00 pm - Feb 16, 05:00 pm
Submitting organizations
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Middle River Power, LLC
Submitted 02/16/2022, 03:10 pm


Brian Theaker (

1. Please provide your organization’s comments on the Draft 2023 Flexible Capacity Needs Assessment Methodology Feb 2, 2022 stakeholder call discussion:

Middle River Power (MRP) appreciates the opportunity to provide comments on the draft 2023 flexible capacity needs assessment methodology.  MRP’s comments are focused on the treatment of hybrid resources within the study and flexible RA program.  MRP understands the CAISO effectively will treat the separate components of hybrid resources as individual resources and consider only the renewable resource output as impacting the three-hour net load ramp, while the energy storage component would be used by load serving entities (LSEs) to meet their flexible RA obligations.  MRP believes this proposed method allows the CAISO to conduct the study in a simple manner, rather than combining the two components and estimating the 3-hour net load ramp contribution of the entire hybrid resource. 

MRP respectfully requests the CAISO consider two concerns:

First, while the CAISO is proposing to consider the components of hybrid resources separately for the purposes of the flexible RA requirements, in practice the CAISO does not treat hybrid resources as separate components in its markets because the CAISO does not manage the state of charge for the storage component.  Hybrid resources must follow their CAISO DOTs, which impacts the storage component’s state of charge if the renewable resource is unable to generate to its forecast.  This means that the hybrid resource may not provide the expected level of flexible capability during the three-hour net load peak hours.  MRP believes the CAISO should review historic data to better inform the renewable resource forecast and, consequently, the hybrid resource’s state of charge.  MRP believes the CAISO has the state of charge information for hybrid resources needed to perform this review.

Second, it may be reasonable to assume that the storage component can provide its respective effective flexible capacity (EFC).  However, a review of the CAISO’s EFC list shows that various resources have an EFC up to six times greater than their Pmax or NQC value.  MRP generally expects a maximum of two times the Pmax or NQC, but the EFC list includes EFC values that exceed this expectation.  MRP suspects that this is not the CAISO’s intention and therefore requests the CAISO to review its process so as to ensure the CAISO can confidently count on the EFC that may be shown on a supply plan to meet the three-hour flexible RA requirement rather than overcounting resources and running the risk of not maintaining reliability.

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