Widespread use of energy storage on the electric power system grid will require a coordinated effort by technology developers and utilities to ensure that systems are designed to adequately address utility needs. Utilities must understand the technical and cost characteristics of the various technologies being advanced by developers. System providers must offer energy storage systems that meet the requirements that will be placed on those systems. It is that latter objective that has been the central motivation of the project documented in this report.
The project, one element of the Electric Power Research Institute (EPRI) Energy Storage Program to accelerate the grid-readiness of energy storage systems, has brought together all of the stakeholders—including utilities, manufacturers, and system operators—to define some of the basic functional requirements for storage owned and operated by utilities, as well as for customer-sited storage systems that may provide value to utilities. The report focuses on the applications of high priority identified by the utility participants.
Energy storage is receiving increasing attention from utility engineers and regulators for its potential to solve a variety of technical challenges in the management of electric power. However, utilities, vendors, and regulators must develop a common ground on which to base their understanding of energy storage application requirements.
This report presents a set of functional requirements for energy storage systems connected to the electric power system to be used in specific ways (use cases and operating modes). By steering procurement and development efforts so that they are consistent with these requirements, utilities and developers can work with a common understanding to develop the most effective storage solutions to utility problems.
The project employed a public, open-source approach by bringing together high-level energy storage stakeholders, including representatives from utilities, renewable energy project developers, equipment developers and manufacturers, regulatory bodies, independent system operators, power pools, and government and educational institutions. After a first draft of application requirements was developed, the project was opened up for public comment and received increasingly detailed input from stakeholders through public webinars, while application-specific work groups refined the individual functional requirements.
The report provides functional requirements for four key energy storage applications: substation-based storage, distributed energy storage systems, customer premises energy storage systems, and energy storage to integrate renewables. Energy storage to integrate renewables is further divided into three subcategories: solar photovoltaic ramping support, wind ramping support, and load- and resource-shifting applications.
The requirements for each application include details related to specific use cases and operating modes, power output and duration, system ratings and effectiveness, physical requirements, communications and data flow, and operational and safety issues.
Application, Value and Use
This report will provide significant value to energy storage manufacturers and system integrators by communicating grid requirements for each of the energy storage applications. The report will help utility system planners who are considering the role that energy storage can have with regard to the management of the grid and the temporal differences between economic energy supply and customer energy needs. The report provides generalized requirements for storage systems, independent of the technologies of interest, suitable for helping engineering and procurement personnel develop the more detailed specifications required in a procurement action. The report will also help power system operators to communicate with the developers of large-scale wind and solar farms and the developers of energy storage systems, so that each can bring value to the operation of the electric grid and therefore bring value to the electric consumer.
The results will also help commercial, industrial, and residential customers who install energy storage for their own use, consistent with an incentive tariff, to allow utility control under defined circumstances for mutual benefit. The customer energy storage system requirements will ensure that installed equipment will be consistent with utility standards, procedures, and operating requirements.
Recommendations for further study have been included in the report. Many of the recommendations relate to the need for data and information to assist in development of storage operating modes and value propositions.