MISO interconnection customers have the option of designating “hybrid” as fuel type when they submit an interconnection request before July 22, 2021, for the 2021 Definitive Planning Phase (DPP) cycle. In addition, there are nearly 5,000 MW of hybrid resources, mostly solar plus storage, waiting to be studied by MISO from the 2019 and 2020 cycles. But MISO does not have a tariff definition yet for hybrid resources.
MISO is preparing to file a hybrid resource definition at FERC next month because MISO expects more hybrid resource interconnection requests. Hybrid resources are not co-located resources, which happen to be at the same point of interconnection. And because storage is a big part of hybrid resource definition, there are many details that MISO is discussing with stakeholders, such as transmission charges if storage discharges to the grid as a hybrid resource and the capacity credit for a hybrid resource.
Setting the stage for hybrid resources
Almost a year after the FERC technical conference on hybrid resources, at MISO’s hybrid resources workshop held on June 21, 2021, MISO legal said they are updating the tariff to define hybrid resources, and they will report to FERC in July about this definition, asking for a 60-day effective date.
Even though there are no hybrid resources currently at MISO, four projects are pursuing a surplus interconnection process right now, which is outside the DPP cycle. FERC Order 845 allows adding generator interconnection requests at existing facilities to use any unused transmission reservation called surplus interconnections. Surplus generator interconnection request looks like a hybrid.
Definition of hybrid and co-located resource
MISO is proposing the following for a hybrid resource definition:
“A Generator that combines more than one type of Electric Facility for the production and/or storage for later injection of electricity.”
Hybrid resources should not be confused with co-located resources. The definition of a co-located resource is multiple generators located at the same point of interconnection.
In the energy market, the asset owner manages the offer for both co-located resources and hybrid resources. Ownership of co-located resources can be separate or affiliate at the same single point of interconnection. Both of those owners don’t have to own the asset at the point of interconnection.
What if a hybrid resource injects more than the generator interconnection studied amount?
When a stakeholder asked how MISO keeps track of interconnection rights and transmission, MISO legal said monitoring of hybrid resource output falls under the FERC Order 890-A requirement of “unreserved use of the transmission system,” and violation of the tariff is spelled out in the generator interconnection agreement. MISO also said penalties for excessive use of the MISO transmission system exist today in the interconnection tariff.
Additionally, MISO operations track whether interconnection services limits are met based on the unit output. Finally, the obligation exists on the interconnection customer as it relates to the interconnection performance limits.
MISO market participation model for hybrid resources
NextEra, Clean Grid Alliance (previously Wind On the Wires), and Customized Energy Solutions want MISO to keep the dispatchable intermittent resource (DIR) model for hybrid resources. But DIRs cannot provide regulating or spinning reserves.
A DIR model at MISO was first established for utility-scale wind resources. MISO recently got FERC approval for applying DIR to utility-scale solar resources. DIRs cannot provide ancillary services such as regulation, spinning, and non-spinning services but can provide energy, capacity, and ramp capability at MISO.
In response to a question regarding hybrids registering as a DIR, MISO said that it could allow frequent updates to the model registration process once the new model manager process is live. MISO also took the action item to review whether they can publicly post the registration types for resources. This was taken in response to a stakeholder question as to whether MISO can be transparent about how resources had stored energy resource type II market registration when they did not go through the generator interconnection process.
Hybrid resources capacity credit process
MISO gives 50% capacity credit for solar without running any analysis. To assign capacity credit for hybrid resources, MISO said they have a two-phase accredited process. In phase one, the accreditation for hybrid resources is the sum of the default Unforced Capacity (UCAP) ratings for Co-located resources upto the interconnection service amount.
In phase two, capacity accreditation is more operations-related as MISO gains experience dispatching hybrid resources. Unforced capacity considers the statistical data on forced outages and unplanned outages that are sometimes outside an asset owner’s control. Phase II is based on the forecasts provided by hybrid resources similar to DIRs or market offers for the top 8 daily peak hours in a season when MISO moves to seasonal resource adequacy construct.
Hybrid and Energy Storage are tied together
While MISO is preparing to implement Electric Storage Resource (ESR) on its current market platform to comply with FERC Order 841, MISO also filed for a rehearing request at FERC. Since hybrid resources are most likely to include a storage component, the question arises if transmission charges would be assessed when storage charges from the transmission grid for later discharge?
In response to that question on transmission charges, MISO said any withdrawal for later injection is treated as a load per FERC acceptance of MISO 841 compliance filing. So, hybrid resources that include storage won’t be charged for transmission when providing ancillary service.
On the other hand, MISO said battery energy storage systems (BESS) could incur network upgrade costs in response to another question on interconnection and transmission cost. A battery withdrawing energy from the transmission grid doesn’t change the requirements of the generator interconnection process.
An ESR market participation model’s benefit is that MISO has an “available” mode for electric storage resources that show the availability for an electric storage resource available for ancillary services but not participating in energy markets. Charging, discharging, emergency charging and emergency discharging, continuous, and outage are the remaining modes for ESR’s. This market feature is available after MISO implements ESR. Hence hybrid resources and storage resources fate is tied at MISO.
On hybrid resources at MISO, Great Plains Institute (GPI) conducted a survey, and the results should be announced by June 25. FERC staff released a white paper on hybrid resources a month ago. MISO is also planning to file at FERC the capacity accreditation process for hybrid resources in July.
With more hybrid resources interconnecting, we can expect the market to mature. The good news is that renewable developers have a path forward for including storage with solar interconnection requests.