February 21, 2024

Zero-Export Storage Requires Utility Interconnection

At SEAC's January 2024 general meeting, Radina Valova led a discussion about interconnection procedures for zero-export energy storage systems and opportunities to improve state-level processes.

Integrating energy storage into the grid presents an opportunity and a challenge for utilities and consumers. On one hand, it enhances renewable energy capabilities and resilience. On the other, it introduces regulatory and technical complexities, such as ensuring safe integration without compromising grid stability.

At SEAC’s January 2024 General Meeting, Radina Valova, Regulatory Vice President at Interstate Renewable Energy Council (IREC), shed light on interconnection requirements for zero-export energy storage systems.

Valova also shared findings of a study that explored the impact of energy storage integration on the grid and proposed solutions to the primary obstacles that escalate cost and delay interconnection. 

Resolving Confusion About Interconnection Requirements

Zero-export storage systems are configured using protective relays or power control systems to not feed power into the grid.

A common misconception is that an interconnection agreement between a client and the utility is not required for zero-exporting systems.

Valova said, “If a system is running in parallel to the grid, even if it’s not exporting to the grid, my understanding is that it does require an interconnection application.”

A key reason for the confusion is inconsistent procedures dealing with storage interconnection. There are three ways that interconnection procedures currently address controlled export.

  1. Export controlled systems are not recognized. In this case, jurisdictions lean on the Federal Energy Regulatory Commission’s Small Generator Interconnection Procedures (SGIP), which regulate the connection of small generators to utility lines. SGIP procedures were last updated in 2013 and do not recognize export-controlled systems.
  2. There is a review process for storage, but it doesn’t screen for export control or identify acceptable export-control methods. States may have some form of review process for storage, but they don’t identify in detail or at all the acceptable export control methods. See, for example, the Code of Maryland Regulations (COMAR) 20.50.09.
  3. There is a distinct screen for export-controlled storage with details on acceptable export control methods.California has Rule 21, a tariff that contains operating requirements for grid-connected energy systems. Rule 21 provides detailed information on what methods of export control are acceptable to qualify as non-export for the purposes of the screen.

Keys to Smoother Interconnection

IREC’s Building a Technically Reliable Interconnection Evolution for Storage (BATRIES) project recommends ways to reduce the time and cost of interconnection and enable the unique capabilities and benefits of storage flexibility.

First, identify acceptable export-control methods. Support safe and reliable storage interconnection to increase transparency and predictability for utilities and applicants. Added clarity would provide interconnection customers with information necessary to design projects before applying.

As Valova said, “There’s a lack of standardization around what are acceptable export controls, and that leads to a lack of trust from the utilities in how storage will operate according to a schedule or profile.”

Moreover, states should explicitly incorporate these acceptable export control methods into interconnection rules and revise the interconnection screening and study process to accommodate the use of export controls.

Second, clarify the language. The current review process does not differentiate between a system’s nameplate rating and export capacity. Nameplate rating is the maximum rated power output of a system regardless of whether it is limited by export controls. Export capacity is the amount of power that can be transferred from the system to the grid. Export capacity might be less than or equal to the nameplate rating.

Under the current review process, utilities assume systems will always export 100 percent of the nameplate rating. Evaluating projects based on real export versus nameplate rating would speed up the process and reduce the cost for zero-export systems.

Third, allow for flexibility. Usually, a customer applies for interconnection, and the application goes through review. If upgrades are needed, the customer has two options: pay for the upgrade or withdraw, forfeit their place in the queue, and submit a new design and application. 

Allowing customers to modify designs post-application could be more cost-effective and efficient. Providing customers with information to understand the reasons for review failure, the necessity of upgrades, or alternative options to avoid upgrades would make the process more transparent.

Lastly, keep an eye on California as it seeks to clarify how the transition from Net Energy Metering (NEM) 2.0 to NEM 3.0 affects storage interconnection applicants with existing systems. Following Valova’s presentation, the California Solar & Storage Association notified members that existing systems can soon add capacity behind the same meter of a NEM system and maintain the NEM status of the original system if the new capacity is managed as non-exporting.

Storage Impacts on the Grid

Even in a limited or zero-export mode, storage can export small amounts of energy to the grid. As storage deployment grows and more systems join the distribution system, could they have negative grid impacts? 

Research from the BATRIES project concluded that storage systems can massively increase hosting capacity on the distribution system and the risks of inadvertent export are small in the aggregate. There are some differences depending on whether the systems are connected to urban or rural feeders.

The BATRIES research and toolkit provides a pathway to overcome the challenges of energy storage interconnection.

Download the BATRIES toolkit here.