The sodium-sulfur battery installation provided by NGK Insulators, Ltd., (deployed at Xcel in Lucerne, Minnesota, in 2008) to supplement wind-turbine generation contains 20 50-kW modules with 7.2 MWh of storage capacity and a charge/discharge capacity of 1 MW.

The DOE/EPRI 2013 Electricity Storage Handbook in Collaboration with NRECA has been released and is available for download (166 pp + appendices). The handbook was jointly authored by the Sandia (on behalf of DOE Energy Storage Systems program), Electric Power Research Institute (EPRI), National Rural Electric Cooperative Association (NRECA), and AECOM Technical Services, Inc.

The portfolio of electricity storage technologies can be considered for providing a range of services to the electric grid and can be positioned around their power and energy relationship. The comparisons given here are very general, intended for conceptual purposes only. Compressed air energy storage and pumped hydro are capable of discharge times in tens of hours, with correspondingly high sizes that reach 1000 MW. In contrast to the capabilities of these two technologies, various electrochemical batteries and flywheels are positioned around lower power and shorter discharge times.

The handbook is a how-to guide for utility and rural cooperative engineers, planners, and decision makers to plan and implement energy-storage projects. It also serves as an information resource for investors and venture capitalists, providing the latest developments in technologies and tools to guide their evaluations of energy storage opportunities. It provides information on

  • electricity storage services and benefits;
  • electricity storage technologies: cost, performance, and maturity;
  • methods/tools for evaluating electricity storage; and
  • storage system procurement and installation

and includes a comprehensive database detailing the cost of current storage systems in a wide variety of electric utility and customer services, along with interconnection schematics. A list of significant past and present energy-storage projects is provided for a practical perspective.