By Tom Kleckner
AUSTIN, Texas — The growth of distributed energy resources is not yet causing reliability problems, and accurate mapping and localized pricing signals should address concerns in the future, ERCOT said last week.
Based on installed capacity and current growth rates, DER does not pose “an immediate or near-term reliability concern,” the Texas grid operator said in a report released Thursday.
The report says ERCOT’s DERs are “characterized by a combination of low energy prices and an absence of regionwide regulatory incentives, leading to a penetration growth rate” much slower than in California and other regions.
“[We] are making sure we don’t have any reliability issues,” COO Cheryl Mele told members of the Technical Advisory Committee during its monthly meeting. “No current issues exist. That’s not the driver here, other than trying to stay ahead of what can be a growing resource in the ERCOT grid.”
Mele said the ISO’s first priority is to begin discussions with transmission and distribution service providers (TDSPs) about mapping resources larger than 1 MW. Those discussions will take place within the TAC’s Reliability and Operations (ROS) and Wholesale Market subcommittees.
ERCOT estimates there were 900 MW of DER interconnected with the grid as of December 2015, based on annual reports filed at the Public Utility Commission of Texas by TDSPs in competitive-choice areas. Another 200 MW are thought to be deployed in non-opt in entity (NOIE) service territories (those not competing in the ERCOT market).
The ISO said there were about 90 registered DER units, primarily diesel generators and some rooftop solar, as of March.
“As these resources grow, deployment of DER with capacity greater than 1 MW could result in some reliability concerns, depending on their location and level of concentration on the grid,” the report said.
ERCOT currently compensates DERs with zonal prices. Mapping those resources will allow for locational pricing and result in their more appropriate response to transmission constraints.
Definitions
The report said DER can be anything from large, fossil-fueled reciprocating engines to small rooftop solar systems. It includes an updated definition of DER: “Generation, energy storage technology or a combination of the two that is interconnected at or below 60 kV and operates in parallel with the distribution system.”
Further discussion will be needed if the definition is expanded to include demand response, ERCOT said.
The ISO said it believes “the foundation to the reliable and efficient management of this future distributed grid is visibility” through more detailed collection of DER data from TDSPs. It does not propose to model or operate the distribution system, leaving that to the distribution providers.
However, ERCOT said it will work with market participants through the stakeholder process to develop a standardized method for mapping DER units to their loads. The ISO said this will improve situational awareness of DER activity on the grid and “allow for stakeholder consideration of localized pricing signals” to support reliability.
The ISO also proposes working with stakeholders on a process for competitive choice and NOIE distribution providers to monitor the accumulation of clusters of unregistered DER (less than 1 MW). It estimates there are more than 11,000 such facilities in its market and more than 12,000 in NOIE territories.
When the combined connected capacity of these smaller units exceeds an agreed-upon threshold, the TDSPs would work with ERCOT to determine the best method for mapping them.
The new report updates a concept paper published in August 2015 that laid out a potential framework for DER participation in the wholesale market, which identified reliability concerns from a large deployment of DER.
The TAC is expected to refer the report to the ROS and WMS at its April meeting.
