IDEAS: Issue #1: DER Definition
è Issue Identified:
What is the ERCOT definition of DER? Answering this question is necessary to determine the lexicon for Section 2 of the Nodal Protocols with respect to Distributed Energy Resources, and it is also necessary as a foundation for framing clear and precise discussion and consideration of this subject.
è Issue Development:
The current definitions for Resource types as described in Section 2 of the ERCOT Nodal Protocols are deemed not sufficient to describe the “DER” resource type, due to the potential market entry by Resource Entities that are representing, or intend to represent, assets connected on the distribution system at 60 kV or below that may consist of generation and/or storage, or an aggregation of generation and/or storage, or an aggregation of generation and/or storage and/or load resource, but never a load resource by itself, and that are capable of injecting electrical energy onto the distribution system.
Further, given that there may be different levels of market engagement by a DER, to include nodal vs load-zone settlement, or self-responding vs SCED-dispatched, it becomes necessary to establish definitions for the sub-types of DER.
In the ERCOT Concept Paper on Distributed Energy Resources in the ERCOT Region Submitted to the Distributed Resource Energy & Ancillaries Market (DREAM) Task Force on August 19, 2015, the draft definition for Distributed Energy Resources is,
“A generation or energy storage technology, or combination of generation and/or energy storage technologies, that is interconnected at or below 60 kV, operates in parallel with the distribution system, and is capable of injecting electrical energy onto the distribution system.”[i]
This issue and this draft definition are framed by the existing regulatory framework, which includes the following:
Substantive Rule §25.501(h) says that,
“ERCOT shall use zonal energy prices for loads […]”.[ii]
ERCOT Nodal Protocols Section 2.1 define Load Resource as,
“A Load capable of providing Ancillary Service to the ERCOT System and/or energy in the form of Demand response and registered with ERCOT as a Load Resource.”[iii]
One of the sub-sets of Load Resources, Aggregate Load Resource, is defined within the ERCOT Nodal Protocols Section 2.1 as,
“A Load Resource that is an aggregation of individual metered sites, each of which has less than ten MW of Demand response capability and all of which are located within a single Load Zone.”[iv]
ERCOT Nodal Protocols Section 2.1 define Generation Resource as, “A generator capable of providing energy or Ancillary Service to the ERCOT System and is registered with ERCOT as a Generation Resource. The term “Generation Resource” used by itself in these Protocols does not include a Non-Modeled Generator.”[v]
One of the sub-sets of Generation Resources, Aggregate Generation Resource, is defined within the ERCOT Nodal Protocols Section 2.1 as,
“A Generation Resource that is an aggregation of non-wind generators, each of which is less than 10 MW in output, which share identical operational characteristics and are interconnected at the same POI and located behind the same Generator Step-Up (GSU) transformer (with a high-side voltage greater than 60 kV).”[vi]
Neither existing Load Resource or Generation Resource definitions, nor the draft DER definition, allow for the full variety of asset arrangement and market engagement schema described by industry representatives, and so does not give these resources open access to the market.
Given that a DER may at times act as a Generation Resource, may at other times be inclusive of a Load Resource, and at other times may be more like a Non-Modeled Generator, it may then be reasonable to also think of DERs in the context of an All-Inclusive Resource.
All-Inclusive Resource is defined within the ERCOT Nodal Protocols Section 2.1 as,
“A term used to refer to a Generation Resource, Load Resource and a Non-Modeled Generator.”[vii]
Also, a Non-Modeled Generator is defined within the ERCOT Nodal Protocols Section 2.1 as,
“A generator that is:
(a) Capable of providing net output of energy to the ERCOT System;
(b) Ten MW or less in size; or greater than ten MW and registered with the PUCT according to P.U.C. Subst. R. 25.109, Registration of Power Generation Companies and Self-Generators, as a self-generator; and
(c) Registered with ERCOT as a Non-Modeled Generator, which means that the generator may not participate in the Ancillary Service or energy markets, RUC, or SCED.”[viii]
è Detailed Explanation:
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This definition takes the basic concept that a DER is a single generation resource or an aggregation of various generation/storage and load resources that is a net injection onto the system.
è Analysis:
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How is storage (including EVs) treated in definition? Storage is treated as a generation resource in this definition. However, EVs are a little different if they are only used to stop charging and not discharging to the system, the latter of which most EVs are not currently capable. If only stop charging then that would be considered DR.
How does Wholesale Storage Load treatment factor into the DER issue? It only factors into the COP status or settlement of the overall resource.
è Solve/Solution:
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Given the issues and analyses above, the following definition for Distributed Energy Resource is proposed:
Distributed Energy Resource
An individual generator or storage device, or an aggregation of any combination of generators, storage devices, or Load Resources, interconnected at or below 60 kV, interconnected in the same Load Zone, and capable of injecting electrical energy onto the distribution system.A Generation Resource, which may be an energy storage device, or an aggregation of Generation Resources (which may include a energy storage devices), or an aggregation of Generation Resources (which may include energy storage devices) and Load Resource(s), but never a Load Resource by itself, which is interconnected at or below 60 kV, dispersed in the same Load Zone, and is capable of injecting electrical energy onto the distribution system.
DER-Minimal
[to be discussed further in Task Force meetings] Status Quo-similar to current DG treatment; self-responding; settled at Load Zone.
DER-Light
[to be discussed further in Task Force meetings] A DER that is self-responding and has a finer locational settlement than Load Zone.
DER-Heavy
[to be discussed further in Task Force meetings] A DER that is SCED-dispatched and has locational settlement, approximately commensurate in grid topology detail with modeled Generation Resources, but which may not include a Load Resource as part of the DER.
DER-Heavy(Z)
[to be discussed further in Task Force meetings] A DER that is SCED-dispatched and that is settled at the Load Zone.
This definition addresses what is a DER. The above definition takes the high-level stance that it does not matter what is in the aggregation. Rather, what matters is whether, or not, the Resource is a capable of a net injection to the system.
[i] ERCOT Concept Paper on Distributed Energy Resources in the ERCOT Region Submitted to the Distributed Resource Energy & Ancillaries Market (DREAM) Task Force on August 19, 2015. [Version 1.0]
[ii] CHAPTER 25. SUBSTANTIVE RULES APPLICABLE TO ELECTRIC SERVICE
PROVIDERS.
Subchapter S. WHOLESALE MARKETS.
§25.501. Wholesale Market Design for the Electric Reliability Council of Texas.
(h)Zonal energy prices for loads. ERCOT shall use zonal energy prices for loads that consist of anaggregation of either the individual load node energy prices within each zone or the individualresource node energy prices within each zone. Individual load node or resource node energy pricesshall be the locational marginal prices, consistent with subsection (e) of this section, resulting fromsecurity-constrained, economic dispatch. ERCOT shall maintain stable zones and shall notify marketparticipants in advance of zonal boundary changes in order that the market participants will have anappropriate amount of time to adjust to the changes.
[iii] ERCOT Nodal Protocols 2.1
[iv] ERCOT Nodal Protocols 2.1
[v] ERCOT Nodal Protocols 2.1
[vi] ERCOT Nodal Protocols 2.1
[vii] ERCOT Nodal Protocols 2.1
[viii] ERCOT Nodal Protocols 2.1