Energy storage: 10 steps for improving US interconnection processes

• ‍US interconnection delays increasing – 680GW of storage now queued
• ‍Wait for storage interconnection has now increased to five years
• Procedures don’t clearly define storage or explain why projects fail screening

The battle to secure grid connections for US renewable energy projects is becoming fiercer. The annual data on interconnection queues published by Berkeley Lab – a US Department of Energy Office of Science national laboratory managed by the University of California – show that total capacity in the queues is growing year-on-year. More than 1,350 GW of generation (of which 1,250 GW constitutes renewables), as well as an estimated 680 GW of storage capacity, was left waiting in queues as of the end of 2022. Worse still, the wait for interconnection is increasing. The figures showed that the typical duration “from connection request to commercial operation” increased from around two years for projects built in 2000-2007 to nearly four years for those built in 2018-2022, with a median of five years for projects built in 2022.

Indeed, getting stuck in an interconnection queue proves fatal for the majority of renewable energy projects. Berkeley Lab said that “among a subset of queues for which data are available”, only 21% of the projects (and 14% of capacity) seeking connection from 2000 to 2017 have been built as of the end of 2022”.

Of the zero-carbon generation capacity seeking transmission access, solar accounts for the biggest share (947GW), with wind accounting for 300GW (of which 113GW, or 38% is offshore). The data also shows the growing popularity of hybrid solar-storage projects – this is the fastest growing resource in interconnection queues, accounting for 80% of new capacity entering the queues in 2022. In fact, over half of the battery storage capacity in the queues is paired with some form of generation, most commonly solar.

With regard to the geographical breakdown of queued capacity, Berkeley Lab said that there was substantial proposed solar capacity in most regions of the US, while queued wind capacity was highest in the NYISO [New York Independent System Operator] region, the non-ISO West, PJM, and SPP [Southwest Power Pool], with a growing proportion of that capacity taking the form of offshore projects. Meanwhile, queued storage is primarily in the West and the CAISO [California Independent System Operator] region, but also strong in the ERCOT [Electric Reliability Council of Texas] area, the MISO [Midcontinent Independent System Operator] region, and PJM. As Berkeley Lab pointed out, much of this storage is part of hybrid configurations.

The majority (73% or 695GW) of the queued solar is scheduled to come online by the end of 2025, compared to 69% (472GW) of the storage and 48% (145GW) of the wind capacity.

The figures indicate that hybrid solar and storage projects are becoming increasingly popular. A total of 52.4% (358GW) of queued storage projects are in hybrid configurations, as are 48.2% (457GW) of queued solar projects. However, only 8.1% (24GW) of queued wind projects are in hybrid configurations.

Why storage faces unique connection challenges?

Interconnection is clearly a challenge for all US renewable energy projects, but energy storage schemes face unique challenges. They include a lack of clarity on how interconnection rules apply to storage in states interconnection rules. Meanwhile, BATRIES (Building A Technically Reliable Interconnection Evolution for Storage) – a project that is supported by the Department of Energy’s Solar Energy Technologies Office and led by the Interstate Renewable Energy Council – has claimed the evaluation of non- and limited-export systems is based on unrealistic operating assumptions that lead to overestimated grid impacts.

BATRIES argues that the clear identification of standardised methods of controlling export in interconnection rules would provide interconnection customers with the information they need to properly design energy storage system projects prior to submitting interconnection applications. “This regulatory certainty reduces the time and costs associated with ESS interconnection by minimising the amount of customised review needed and by empowering customers to design projects that avoid the need for distribution upgrades,” BATRIES says. “Today, many state interconnection procedures do not yet recognise export-limiting capabilities at all, and even fewer concretely identify the acceptable methods of control.”  In addition, storage developers also suffer from a lack of information about the distribution grid and its constraints, which can inform where and how to interconnect storage.

How to improve interconnection prospects for US storage

So what should be done to improve the interconnection prospects for energy storage in the US? Here are ten steps that should be taken: 

1. Energy storage should be more clearly defined in interconnection procedures, which should also “clearly state” that the procedures apply to the interconnection of new standalone energy storage, and storage paired with other generation, such as solar, according to BATRIES.

2. Interconnection procedures should also define and describe the requirements and use of power control systems (PCS), a vital tool for capturing the advanced capabilities of storage.

3. Because relying on a customised review of the export controls for every interconnection application is a significant barrier for ESS deployment, interconnection procedures should be updated to identify a list of acceptable methods that can be trusted and relied upon by both the interconnection customer and the utility.

4. When an interconnection application is submitted, interconnection rules provide the utility with a period of time to review the application for completeness and verify the screening or study process that the application will be first reviewed under. Interconnection application forms should be updated to include information about the energy storage system and, where export controls are used, the type of export control and the equipment type and settings that will be used, BATRIES says. During its completeness review, and once screening begins, the utility should verify that the equipment used is certified, where necessary, and/or is otherwise acceptable for the intended use.

5. In determining eligibility limits for simplified and fast track processes, interconnection procedures should reflect export capacity, not just nameplate rating, in the screening thresholds.

6. Interconnection applicants should be permitted to use the simplified process for screening purposes for certain inverter-based projects if the nameplate rating does not exceed 50kW and the export capacity does not exceed 25 kW.

7. Utilities should provide data on the state of the distribution system at the point of interconnection via pre-application reports and basic distribution system maps. This information should include existing and queued generation, load profiles, and distribution system lines maps. Interconnection applicants can use distribution system data to help inform project site selection and energy storage system design and installation.

8. Interconnection procedures should provide more information about why a project has failed screening. To ensure customers have sufficient information to make design decisions, interconnection procedures should provide specific guidance on what information results should convey to the interconnection applicant, including the specific screens that the project failed and the technical reasons for failure, “as well as details about the specific system threshold or limitation causing the failure”, according to BATRIES.

9. Standards should be developed that describe the scheduling of energy storage operations, especially time-specific import and export limitations. UL 1741, the primary standard for the certification of inverter functionality, should be updated to address scheduled operations, BATRIES argues.

10.  While regulators do not have direct control or authority over standards development bodies or processes, they can create a sense of urgency and expectation by incorporating scheduling functionality into interconnection rules.

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