8 steps to streamline energy storage interconnection

Nexamp installed energy storage on two community solar farms in the grid-constrained ISO New England. The Clark Road community solar farm (pictured has 7.1 MW solar capacity and 3MW/6.1 MWh storage. (Courtesy: Nexamp)

The most significant obstacle to reaching ambitious renewable energy goals in the United States is the time-consuming and costly process of tying projects into the grid.

Biden’s administration is aiming for 5 million homes to be powered through community solar projects by 2025. That’s 700% more capacity than 2021. Developers say that lack of transparency and urgency in interconnection could put this goal at risk.

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The long wait in the interconnection queue is a common problem for asset owners and renewable energy developers across the country. So it is not surprising that interconnecting solar+storage hybrid energy plants and energy storage have their own challenges.

For example, the National Renewable Energy Laboratory published an analysis that showed that paired solar PV systems and battery storage systems, as well as a defined operating agreement between utilities and developers, could help to save time during interconnection.

But the analysis found two primary pain-points for renewable energy deployment: the utility-developer relationship remains tenuous, and the interconnection process is seen by many as the biggest threat to meeting climate goals.

Mark Frigo (Vice President Storage at Solar and Storage Developer Nexamp) said that he is often faced with interconnection issues.

Frigo stated that “Parties deal with this stuff commercially” via contracts and not regulatory requirements. Renewable Energy World.

The Interstate Renewable Energy Council released recently a toolkit to overcome eight regulatory and technical obstacles to interconnecting energy storage project to the distribution network.

Known as “BATRIES” (Building a Technically Reliable Interconnection Evolution for Storage), the multi-year project was supported by the Department of Energy’s Solar Energy Technologies Office, the Electric Power Research Institute, Solar Energy Industries Association, California Solar & Storage Association, New Hampshire Electric Cooperative, PacifiCorp, and Shute, Mihaly & Weinberger, LLP.

The toolkit will provide solutions for eight obstacles to storage interconnection

1. Energy storage defined

IREC stated that most interconnections between states’ distributed energy resources (DER) were not designed with energy storage as a primary goal at the foundational level.

Interconnection procedures must clearly describe: energy storage; operating schedule, operating profile; use of power control (PCS); and the maximum output that takes in export capacity. This is consistent with a DER’s nameplate rating. IREC also recommended states that utilities keep current all relevant interconnection documents, agreements, application forms, study agreements.

2. Standardize reliable and safe export controls

It is important to update interconnection procedures to identify acceptable methods that can both be trusted and relied on by the utility and interconnection customer. The PCS should be included on the list of eligible export controls. The limits set by the PCS should also be considered when enforcing export capacity as specified in the application.

3. Grid impacts of limited-export and non-export systems should not be underestimated

IREC estimated that DER storage could be significantly increased if utilities accurately evaluated the grid impacts of limited-export and non-export systems. It stated that interconnection procedures don’t properly account for export controls.

After a utility verifies the applicant’s export control, eligibility for fast-track interconnection should be determined on export capacity and not nameplate rating. This is to reflect the importance of export controls. IREC stated that applicants should be eligible to fast track interconnection if their inverter-based projects do not exceed 50 kW and have an export capacity of less than 25 kW.

Separate screenings may also be justified to distinguish between nameplate ratings and export capacities.

4. How to stop accidental export

IREC stated that DERs can accidentally export power to the grid if load drops off suddenly. Utility companies need to be aware of the potential impact of inadvertent export events on the grid.

IREC conducted a time-series study of both an urban feeder and a rural feeder with exporting photovoltaic system and non-exporting storage. This was done to better understand the worst-case scenarios.

Its analysis showed that feeders can hold more DER capacity if the DER is controlled export. This can be viewed as increasing the feeder’s available hosting capacity for nameplate DER or as a more efficient use of existing feeder capacity for DERs. This finding was supported by both urban and rural feeder assessments. However, the extent of hosting capacity that can be increased will depend on feeder characteristics and the location and size the exporting DER.

5. Transparency of distribution grid

IREC found that preapplication reports and hosting capacity analyses (HCA), which allow applicants to access information before they submit an interconnection application, can improve transparency of the distribution grid.

HCA results can help developers design energy storage systems that don’t limit charging during peak load hours. This helps to avoid grid constraints. HCA tools should include the latest DER queue to properly inform developers. IREC said that utilities, regulators, developers and others will need to take action.

6. Allow developers to make changes in order to reduce gid impacts

The interconnection application review process generally does not support design modifications to avoid grid impact without losing their place in the queue. IREC said that this is a key barrier to interconnection of energy storage.

Utilities must share data from failed interconnection screens with customers in order to enable them to make necessary design changes and give clear guidance as to how an application might pass.

7. States should adopt current standards

IREC believes that interconnection standards and guidance documents like the IEE 1547 standards play an important role in ensuring devices are interconnected safely and reliably to the grid.

Some of these IREC recommendations include:

-Interconnection applications must be reviewed to determine if a PCS has been included in the DER system design. If so, it should be identified

-IEEE 1547 defines a reference point of application (RPA), so it is clear at which physical point in the system configuration the requirements of the standard must be met for testing and evaluation as well as commissioning.

-In order to ensure that DERs are properly addressed by technical requirements, any stated execution or parameter change performance requirements must align with or refer to IEEE 1547-2018

-The interconnection assessment process should include an understanding any interactions between storage system usage cases and export or imported limits or other functions.

8. To evaluate operating schedules, define rules and processes

IREC said that current interconnection procedures do not properly value energy storage’s ability for operation according to a predetermined timetable that governs both the power exported and imported as well the timing.

Standardization should be established to describe energy storage operations, with particular import and export restrictions. While regulators are limited in their ability develop standards, they can create a sense o urgency and expectation.

IREC recommended that regulators encourage or actively develop field testing programs to validate the performance and profile of a deployed system against a fixed operating schedule.

Mark Frigo of Nexamp stated that storage interconnection presents challenges due to procedures based on legacy technology as well as equipment from a 100 year-old distribution system. Utilities usually classify assets as either a generator or a transmission and distribution asset. However, storage can be classified in any of these categories.

Frigo stated that Nexamp has found commercial solutions to its problems. Although a storage asset offers a nonwires alternative to distribution, and solves a grid reliability issue, utilities still levy an annual demand charge. Nexamp sends the exact same bill back the reverse way.

There is no standardization in this process, so Frigo’s team must negotiate individual contracts with each utility.

He said, “That’s not an elegant solution, but it works.” “Until the rules are really clarified, that’s what’s going on behind the scenes.”