PSC: Dispatch of Energy Storage in MTEP and DPP Studies (20211012)

MidAmerican appreciates the presentation and strongly agrees that the dispatch assumptions for energy storage resources do not reflect real-world operation. Consequently, all benefits of energy storage are not equally represented and prevent a fair interconnection process. MidAmerican encourages MISO to reevaluate the assumptions and process for implementing energy storage resources in MTEP and DPP.

Madison Gas and Electric supports the comments of both WPPI Energy and Alliant Energy they submitted on the feedback item "Dispatch of Energy Storage in MTEP and DPP Studies."

Alliant Energy would like to thank MISO for investigating dispatch of storage in MTEP and DPP Studies. We strongly support this effort and believe that improvements to the way that storage is modeled will better align siting decisions for storage with the value that storage can provide to the MISO system.  We also appreciate MISO encouraging stakeholder involvement and comments regarding this topic.

Alliant Energy supports the recommendations shown below as provided by Clean Grid Alliance (CGA) in their presentation during the October 12, 2021 Planning Subcommittee (PSC) meeting.

1) Revise energy storage dispatch in MTEP and DPP models to remove unrealistic operating scenarios from units seeking full ER/NR interconnection rights

2) Accommodate the need for limited dispatch studies in MISO’s generator interconnection process so energy storage can be deployed to address transmission needs, which it is unable to do today

3) Capture energy storage asset capabilities in models to reflect the storage technologies seeking interconnection today as well as into the near future with long-duration storage

Our concern is that MISO’s current study dispatch methodologies for energy storage are not consistent with how these resources will operate.  This difference between storage dispatch in MTEP and DPP models and the actual dispatch during operations could prevent valuable grid functions and services from being made available on the MISO system. 

Alliant also strongly agrees that storage paired with variable resources reduces (not increases) the need for new transmission.  For example, storage paired with variable resources such as wind would reduce the need for new transmission by smoothing the output of the resource and making it truly dispatchable – charging during high wind periods that create transmission congestion and discharging during low wind periods when additional energy is needed to serve load.  If storage is modeled as adding generation during high wind periods and charging during low wind periods it may appear that additional transmission is required to accommodate even larger energy output swings when the storage was added specifically to reduce the output generation swings.  The result is that storage may not be added if the interconnection cost is prohibitive due to additional transmission being required.

Under MISO’s current modeling methodology, storage is dispatched as if it were not following MISO dispatch instructions. MISO’s real-time Security Constrained Economic Dispatch (SCED) instructs generation to run to mitigate transmission congestion and maintain system reliability. Through this dispatch MISO has functional control over all generation resources with economic penalties for not following instructions.  Beyond the penalties for not following MISO dispatch, resources maximize their profitability by following MISO’s instructions.  Given this real-world operation of storage in response to wholesale market pricing signals, the dispatch in MTEP and DPP models should also be modeled in such a way that transmission congestion is reduced, not increased.

Finally, storage resources can install software and hardware controls to prevent dispatch during specific, predetermined time periods or to ensure that a generation interconnection limit is never exceeded by a given resource.  With such controls in place, storage could provide additional capacity on the MISO without the need for new transmission.  For example, a 100 MW wind generator must secure transmission service to provide 100 MW to the system.  However, the same wind generation only provides about 15 MW during the summer peak under MISO capacity rules.  Storage at such a wind site could charge at night and discharge during the peak hours of the day thus increasing the Effective Load Carrying Capability (ELCC) up to the full interconnection amount without the need for any new transmission because the interconnection amount will never be exceeded.   This provides additional capacity to serve peak load with no additional transmission needed.

More accurate modeling based on realistic storage dispatch assumptions will allow MISO to capture the additional benefits that storage can provide and therefore reduce overall costs as compared to using unrealistic dispatch assumptions.

We commend MISO for investigating this issue further and strongly encourage MISO to continue this effort to encourage optimal siting and realize the benefits storage can provide to the MISO system.

Clean Grid Alliance Comments on Dispatch of Energy Storage in MTEP and DPP Studies
November 2, 2021

Clean Grid Alliance appreciates the opportunity to provide comments on Dispatch of Energy Storage in MTEP and DPP studies. This topic is very important to multiple MISO Sectors and stakeholders who seek to interconnect or benefit from the interconnection of energy storage on MISO’s system. Today, the generator interconnection process is required for all MISO stakeholders (except transmission owners) to interconnect storage to the MISO transmission system. Unfortunately, the dispatch methodology in the interconnection process presents significant barriers for storage to interconnect and additionally incents storage to locate away from the grid locations where it is most needed. For example, according to MISO’s own RIIA study, storage located near high variable generation pockets provides the greatest benefit to the MISO system. Storage in practice will generally be used to mitigate nearby constraints that result from high penetrations of renewable energy, but the current fuel-based dispatch methodology for storage studies storage as if it is aggravating the same constraints and leads to high Network Upgrades to interconnect.

Clean Grid Alliance strongly encourages MISO to separately look at two different potential changes that would be beneficial in eliminating significant barriers to storage interconnections: 

1)    To investigate elimination of the 100% injection dispatch scenario in the shoulder studies for full ER interconnection rights. The result of this request would be to study storage at 100% injection at peak load and 100% withdrawal in shoulder studies. This will facilitate siting of storage near wind resources, which optimizes benefits to the MISO system. Additionally, modeling storage control/dispatch to address (rather aggravate) constraints would better align with storage operating strategies and data.

2)    To consider creating a “limited interconnection” study option for storage with a narrow and specific intended application. Projects with “limited interconnection rights” that later seek to obtain full interconnection rights, would be required to re-enter the queue, similar to an ERIS project. 

We sincerely thank MISO for the opportunity to provide input on this very important topic, and look forward to further discussions. 

Sincerely,

Rhonda Peters, Ph.D.

Technical Consultant for Clean Grid Alliance

WEC Energy Group supports the comments submitted by Alliant Energy and looks forward to the opportunity to improve the dispatch of energy storage within the MTEP and DPP models.  As part of this effort, we support the review and enhancement of the dispatch assumptions for resources with Surplus Interconnection Service.

DTE would like to thank MISO for investigating battery storage dispatch assumptions in MTEP and DPP processes. DTE is supportive of the Clean Grid Alliance presentation at the last PSC meeting  and would like to see realistic assumptions around battery storage to be implemented for both MTEP and DPP. DTE is supportive of a process to investigate further and obtain agreements on what these assumptions should be.  

WPPI shares the view of presenter Rhonda Peters that current dispatch assumptions for battery storage are posing a hindrance to development of storage near concentrations of intermittent generation, thus depriving MISO of resources with substantial potential to provide reliability and economic benefits to the MISO system.  It appears current modeling of such resources makes them appear more problematic than other generation, when the reality would appear to be the opposite.  We encourage MISO to work with stakeholders to prioritize this issue for resolution.