XI. Appendices
Chapter XI includes appendices that cover the following topics:
A. Unaddressed Barriers
B. Power Control Systems and the UL CRD
C. Research Supporting Voltage Change (Inadvertent Export) Screen Recommendation
D. Modeling, Simulation, And Testing: Technical Evaluation of Inadvertent Export-Inadvertent Export Research
E. Recommended Procedure Language
F. Recommended Language to Use in Interconnection Application Forms
Download the chapter file below to view each appendix in full. Or download the entire Toolkit and Guidance for the Interconnection of Energy Storage and Solar-Plus-Storage for all chapters, recommendations, and appendices.
A. Unaddressed Barriers
The project team identified a host of storage interconnection challenges that merit solutions development, and which were beyond the time and resources available as part of the BATRIES project. Given the volume of barriers, it’s likely that no single project would be able to address them all in detail. The project team provides the below table in order to facilitate future solutions development by other stakeholders.
| Storage Issues Identified During BATRIES Scoping Process and Not Pursued | Explanation |
| Interconnection Dispute Resolution | Defining or improving the process by which utilities and customers resolve an interconnection disagreement (e.g., timeline compliance or upgrade cost estimate disputes). |
| Timelines for Study, Construction, and Overall Interconnection Process | Reducing the length of time it takes to complete the review processes and approve an interconnection request. |
| Interaction Between Interconnection Engineering Review and Service Requests | Streamlining the utility process for handling new service requests and DER interconnections (e.g., single portal or direct interaction with service planning). |
| Interconnection Application Portals | Providing guidance on creating or improving utility web portals, which allow customers to apply for interconnection online. |
| Cybersecurity | Identifying ways to prevent and respond to cyber threats that could impact the electric grid, including how to address any risks that may arise from DERs and aggregators. |
| Automation | Streamlining the interconnection process through software automation and other solutions to improve the customer experience and internal utility workflows. |
| How to Inform Safety Protocols | Ensuring that requirements for storage system interconnection are coordinated with national standards and provide clear guidance on safe operation of ESS on the grid. |
| How to Develop Advisory Documentation | Providing guidance on documentation of conformity from manufacturers to ensure that it is readily available and consistent, which can help utilities understand new products, their capabilities, and whether or not they comply with certain utility tariffs. |
| Fiscal Certainty | Establishing transparent, clearly defined utility protocols that enable customers to understand the need for certain interconnection studies and their associated fees. Providing greater certainty around upgrade costs and other fees can reduce the financial risk related to developing a project. |
| Tariff Compliance | Streamlining utility review of a DER system to verify whether or not it will operate in accordance with a specified tariff, such as net energy metering. |
| Queue Withdrawal Penalties | Reviewing and providing guidance on the design and application of queue withdrawal penalties. If a customer decides to remove a project from the queue, they can face steep withdrawal penalties from the utility. |
| Interconnection to Networked Distribution Systems | Providing technical guidance on interconnecting storage and solar-plus-storage systems to networked distribution systems. Current guidance and procedures are very limited and apply conservative rules of thumb that may make interconnection more costly for these systems. |
| Ramp Rate Limits | Providing guidance on ramp rate limits, which involves controlling the rate of increase or decrease of power output through predefined limits. |
| Defining Telemetry and Metering Requirements for Specific Use Cases | Defining metering and telemetry requirements for the different configurations of storage and solar-plus-storage systems and the diversity of use cases to avoid redundancy and minimize costs. |
| Thresholds for Interconnection Review Screens | A review of eligibility limits and screening values in light of energy storage capabilities. |
| Vendor Documentation | Providing guidance on documentation from manufacturers to ensure that it is readily available and consistent, which can help utilities in their evaluation of interconnection requests. |
| Predefined Setpoints | Definition of selectable standardized settings for energy storage parameters. |
| Interoperability | Improving the capability of communicating across different networks and between technologies that have distinct settings. |
| How to Accommodate Project Ownership Transfer | Ensuring that there is clarity in the rules to allow for DER projects to be sold and ownership to be transferred to another customer. |
| Wholesale Market Participation Impacts on Storage Interconnection | Determining if ESS participation in wholesale markets through the provision of capacity, energy, or ancillary services will impact the interconnection process for ESS and the way those systems should be studied. |
| Rule Applicability | Identifying the types of regulations that can apply to all states and utilities and the types of regulations that need to be more state- or utility-specific. |
| Aggregate Impacts of Islands | Evaluation of the effect of concurrent disconnection or reconnection of multiple microgrids (intentional islands) on the electric system. |
| ESS Value Stacking | Understanding the challenges of providing multiple services to the grid to maximize ESS revenue streams. |
| Improving Distribution System Planning | Identifying better grid planning and forecasting practices to determine grid needs that can be met with DERs. |
| Applicability to Vehicle-to-Grid (V2G) or Vehicle-to-Home (V2H) | Understanding how solutions that address challenges related to stationary energy storage will impact V2G or V2H applications. |
In addition to the table, the project team briefly notes two particular storage interconnection topics that merit discussion but require significant further technical research to develop. By highlighting these issues, the project team intends to tee them up for potential future research and solutions development, such as by national laboratories or other stakeholders. Those issues include:
| Barriers Identified for Further Technical Research | Description | Recommendations |
| Addressing the risks of storage systems causing flicker or rapid voltage changes | When storage systems experience major changes in their output levels, this can result in flicker or rapid voltage changes (RVCs) on the distribution circuit. The methods for evaluating the impacts of energy storage system power transitions are not well known or defined, which can result in ambiguity during the interconnection process. This ambiguity is a barrier to fair and efficient interconnection of energy storage. | Some of the gaps that future research may need to address include the issues of what flicker or RVC impacts are likely to result from different distribution- and transmission-level use cases, and guidance on evaluations of flicker based on IEEE 1547-2018 requirements. |
| Addressing the impacts of storage system power transitions | Energy storage systems can undergo rapid changes in their charge and discharge levels, which can result in grid impacts. There is no standardized way to characterize ESS performance during power transitions or evaluate its impacts, as mentioned above. Additionally, there is no widely accepted specific guidance that exists on how ESS equipment should address power transitions for different use cases. | The UL 1741 Supplement SA should be updated to include the ability to test for limiting power ramps in the negative direction. Some of the gaps that future research may need to address include the issues of what distribution system impacts are likely to result from different distribution- and transmission-level use cases, and guidance on designing ramp rates for different use cases to avoid distribution system impacts. |
Download Chapter XI to see the full appendix.
B. Power Control Systems and the UL CRD
This appendix provides background information on Power Control Systems and the Certification Requirement Decision (CRD), summarizes the test protocol, and includes example configurations to support either export limiting or net energy metering (NEM) integrity. Download Chapter XI to see the full appendix.
C. Research Supporting Voltage Change (Inadvertent Export) Screen Recommendation
Consideration should be given to both the voltage and thermal impacts that inadvertent export could cause. Voltage regulator and capacitor controls are sometimes configured to respond in 30 seconds or less, making it possible for inadvertent export to cause tap operations that prematurely wear regulation equipment. An analysis of these impacts for different feeder, load, and inadvertent export scenarios is covered in Chapter V. Download Chapter XI to see the full appendix.
D. Modeling, Simulation, and Testing: Technical Evaluation of Inadvertent Export—Inadvertent Export Research
This appendix includes a discussion of the technical analysis of the impacts of inadvertent export on both an urban feeder and a rural feeder. Download Chapter XI to see the full appendix.
E. Recommended Procedure Language
This appendix compiles recommended model language revisions discussed in the Toolkit. The captured language is based on FERC SGIP, but states should easily be able to incorporate any changes into their own interconnection rules—whether they are based on FERC SGIP, IREC’s 2019 Model Rules, or any other model language. Language and screens that are not modified are not shown. Download Chapter XI to see the full appendix.
F. Recommended Language to Use in Interconnection Application Forms
This appendix compiles recommended model language revisions discussed in the Toolkit. States should easily be able to incorporate this language into their own applications forms (or portals used by utilities). Download Chapter XI to see the full appendix.
