March 13, 2017
Randy Fish, Engagement Manager and Safety Working Group Chair
In a fast-moving and innovative industry like energy storage, it is easy to get caught up in the excitement to deploy this versatile and flexible energy technology as quickly as possible. That said, while the industry should continue to strive to quickly commercialize and deploy energy storage, we must also stress the safety and reliability of these technologies.
In February of 2017, numerous battery researchers and engineers, codes and standards aficionados, and safety and emergency response stakeholders descended on Santa Fe, New Mexico, for two and a half days of storage and safety discussions at Sandia National Laboratories' 2nd Energy Storage Systems Safety (ESS-S) Forum. The Forum’s goal: to assess the energy storage industry’s latest safety and reliability findings and best practices as well as updates on the latest ESS-S research and development.
A brief primer for those new to the ESS-S space (and the alphabet soup of acronyms):
Sandia and Pacific Northwest National Labs (PNNL), with support and funding from the US Department of Energy Office of Electricity (DOE-OE) and Energy Storage Research Program Manager Dr. Imre Gyuk, have led the country in energy storage research, development and deployment (RD&D) for many years now. As the market organically grew over the years, DOE-OE realized that safety best practices and information, a critical consideration and enablement for any emerging technology and market, was lacking. In 2014 DOE-OE developed an Energy Storage Safety Strategic Plan, and created an Energy Storage Safety Working Group (ESSWG) with three subgroups: 1) Safety Validation and Risk Assessment R&D, 2) Codes, and Standards, and 3) Outreach and Incident Response. The image below indentifies the scope of each.
Subgroup leaders (Dave Conover, Summer Ferreira and David Rose) have steadfastly spent the last two years directing interested stakeholders in the creation of helpful guidelines and products including:
Model ESS Installation Code, picked up by the National Fire Protection Association (NFPA) and now being developed as NFPA 855
Recently, the subgroups merged and initiatives in all three areas will henceforth be tackled through topic-specific task forces. Anyone interested in participating should reach out to energystorage@sandia.gov.
ESS Safety Forum Highlights
Although a majority of the discussions focused on lithium-ion batteries and lithium-ion ESS have gained broad traction in the market, a number of other ESS-S developments were also covered in detail. In Part 1 of this series, we will review the non-lithium-ion insights:
First responder outreach and education is being led by the National Fire Protection Association (NFPA). In addition to their role as a standards development organization (the National Electrical Code [NEC] is an NFPA-developed code), NFPA has an emerging technologies division that is developing safety tools and training for first responders who are called to scenes involving alternative fueled vehicles and energy storage systems. Combine this with just-kicked-off development of a new ESS installation standard (NFPA 855), the NFPA is at the forefront of ensuring that fire departments and first responders are well educated and prepared for large scale ESS deployment.
Fire hazard and risk assessment RD&D is a key area for further work to ensure safe ESS and appropriate codes and standards are developed. ConEdison, NYSERDA and DNV GL sought to address this in 2016 by conducting fire tests on a variety of lithium-ion chemistries, as well as lead acid and vanadium flow batteries. With input and data request from FDNY, the project sought to determine appropriate ventilation and extinguishing requirements for each chemistry. The data will be incorporated into FDNY’s ongoing energy storage code development activities and the full report and results are found here.
Codes and standards development leverages the latest ESS hazard R&D to ensure safe technology and installations, although ESS hazards and risks are still relatively poorly understood from a physics and materials science perspective. In addition to the International Electrotechnical Commission, UL is a leading standards development organization (SDO) and nationally recognized testing laboratory (NRTL). If you're curious how codes and standards address the hazard of ESS fire propogation, UL's Judy Jeevarajan's presentation uses UL 1973 as an example. UL standards previously covered only the components of ESS, such as the inverter (UL1741), lithium ion battery cells (UL1642), and stationary battery ESS (UL1973). However, there had not been a single overarching standard that covered the entire ESS from component to module to commissioning - until the publication of UL 9540.
FDNY’s view of ESS Response, presented by Lt. Paul Rogers, offered a window into the mind of how a fire fighter thinks about ESS and related incidents. From initial inspection and fire operations, to ventilation and post-fire overhaul, a fire fighter’s concerns are important to understand and address when designing and installing systems. Since codes, standards, and regulations are behind technological innovation, each fire department decides when to issue - or deny - an ESS installation permit. Before allowing lithium-ion ESS, FDNY is contemplating how to identify the battery’s failure mode using BMS data, verifying that no hazard still exists from latent, undetectable, and deep seated exothermic reactions, and how to turn the site over to a qualified individual and a “reach back” telephone number to the manufacturer or other knowledgeable, responsible party.
Assessing a battery’s state of health and charge is a surprisingly challenging task - especially in real time when the batteries are already deployed. Developing an accurate methodology could lead to better in situ monitoring and management of damaged or dying cells, enabling problems to be averted or poor performing cells to be immediately replaced. Daniel Steingart and his lab group at Princeton University have successfully tested a novel technique similar to how geologist search for oil: sending acoustic signals (sound waves) through batteries at different states of charge and seeing how the signals reflect back.
Flywheels have been around for thousands of years (see Wikipedia) and have experienced safety incidents in the past (including one or two recently), but no real safety standard existed. Sandia published a flywheel safety guide in 2015 and the technology has since been included in UL 9540. The two hazards to avoid are rotor failure and a loose rotor, and the key flywheel safety parameter, according to the presentation by Sandia’s Don Bender, is related to velocity. Since the stress experienced by the flywheel is directly proportional to the rotational velocity (there were equations to back this up), generally speaking, you should avoid being in the vicinity of flywheels with tip (i.e., the furthest rotating point from the center) speeds greater than 400 meters/second.
Molten salt thermal energy storage, usually connected to massive concentrating solar panel plants, is being commercially proven around the world (See the DOE Global Energy Storage Database). Sandia’s own test facility is open for business (and tours) if you’d like to learn more about emerging salt media. Clifford Ho at Sandia lauded the key aspects of molten salt storage and suggested there are minimal unpredictable safety risks (except for a recent tower fire) - just don’t try to touch the salt or get between the CSP mirrors and tower!
Inorganic sodium-based batteries, such as sodium-air, sodium-ion and sodium-bromine, are being tested at Sandia’s facility in Albuquerque. While the all-inorganic chemistries potentially offer a relatively low-temperature (≤200°C) and non-flammable electrolyte, Research Scientist Erick Spoerke is still working to refine and improve the electrochemical performance potential and cost to rival presently commercial technologies..
Vanadium redox flow batteries, featuring a non-flammable electrolyte, recently became the second battery chemistry (after advanced lead-acid) to receive permitting approval from the New York City Fire Department for grid-connected deployment in the city, according to UniEnergy Technologies CEO Gary Yang.
The Forum made clear that experts from a wide variety of stakeholder groups and fields are actively pursuing the development of safer energy storage systems while making sure that the public - and officials responsible for keeping the public safe - are sufficiently educated on how to mitigate the potential risks of energy storage.