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Safeguarding Emerging Energy Storage Systems
UL worked with key stakeholders to develop an outline intended to result in new standards that address the risks inherent to new energy storage system applications.
WHY SAFEGUARDING EMERGING ENERGY STORAGE SYSTEMS MATTERS
Modernizing the world’s electrical systems is critical to meeting projected energy needs, including addressing environmental issues by integrating more energy from renewable sources and enhancing the efficiency of non-renewable energy processes.1 Energy storage systems (ESS) are growing in importance because of their ability to enhance the reliability and resiliency of energy delivery, provide grid stabilization and backup power services, improve grid operation and lower costs.2 Although there are significant economic and environmental benefits deriving from the increased usage of ESS, some of its applications have emerged in advance of sufficient safety standards, creating new risks and requiring new safeguards.
Energy-related emissions are responsible for 60 percent of the world’s total greenhouse gases and 80 percent of carbon dioxide production.3 This issue is the result of almost 80 percent of the world’s energy being supplied through the combustion of fossil fuels, which releases a number of pollutants into the atmosphere.4 In the foreseeable future, the potential impact on the environment could grow as global wealth expands, the world population reaches 9 billion by 2050 (up from 7 billion today) and electricity is provided to the 1.3 billion people who now live without it.5 To address the environmental effects of energy use, a shift toward renewable sources such as solar, wind and geothermal — along with greater energy efficiency in appliances, buildings, lighting and vehicles — is required.6
ESS technologies have been touted as critical for its ability to facilitate the integration of wind and solar energy onto the electric power grid.7 Today, although energy storage in the U.S. is equivalent to 2.3 percent of the nation’s current energy capacity — a level that lags behind Europe and Japan8 — there is tremendous growth and demand for ESS.9 Much of this is driven by energy utilities that see the economic and operational benefits related to grid balancing and load leveling (the ability to tap into stored energy when electric demand peaks without stressing utility output), and compensating for intermittency issues related to renewable energy sources (e.g., wind doesn’t blow and sun doesn’t shine 24 hours per day).10 Backup energy and support for microgrids are also fueling demand for ESS by companies, institutions and municipalities.11
Today, a variety of energy storage technologies are being used or explored across different applications, including stored/pumped hydroelectric, thermal (compressed air energy storage, or CAES) and specialized technologies such as flywheels and gaseous systems. However, the primary focus of the expansion and deployment is battery-based energy storage systems, and the principal technology for these systems is lithium-ion.12 There are four types of potential safety risks associated with ESS:
- Energy – fire, explosion and burns
- Electrical – shock, arc flash and burns
- Mechanical – pressure, noise, moving parts and sharp edges
- Chemical – exposure to toxic or hazardous substances
It is imperative to mitigate these risks for energy storage technology to fulfill its promise relative to supporting renewable energy expansion and electric grid efficiency and reliability.13
WHAT DID UL DO?
UL has worked with key stakeholders to develop a new outline in response to the potential hazards related to ESS that is intended to ultimately result in new safety standards. These stakeholders include component manufacturers, material suppliers, system integrators, pack assemblers and controls manufacturers within the manufacturing supply chain and distributors and retailers, integrators and system owners, Authorities Having Jurisdiction (AHJs) and regulators, insurers, and first responders.14 The outline, UL 9540, covers systems that are intended to store energy from power or other sources, and provide electrical or other types of energy to loads or power conversion equipment.15 The ESS may include equipment for charging, discharging, control, protection, communication, controlling the system environment, fuel or other fluid movement and containment. The system also may contain other ancillary equipment related to the functioning of the ESS.16
UL 9540 addresses key issues associated with ESS, including: battery system safety, functional safety, grid connectivity, interconnection with premise wiring systems, environmental performance, containment and fire detection and suppression. The new standard is intended to safeguard the uses of emerging ESS technologies across different types of systems, a variety of usages and functions, and a range of potential system users.17
The standard also specifies a series of tests, which is designed to help protect users, facilities and the environment.18 Included in these tests are:
- Electric tests, covering normal operations, dielectric voltage withstand parameters, grounding and bonding, and insulation resistance
- Mechanical tests to examine overspeed, faulted securement and broken part performance
- Fluid containment tests related to leakage and strength
- Environmental impact tests19
UL 9540 is the foundation of a certification process that includes both listing certifications and field evaluations.20 Listing certifications focus on self-contained, factory packaged ESS and would cover:
- Compliance to UL 9540
- Listed under UL CCN (FTBW)
- Ongoing production inspection
- A UL Listing Mark21
Field evaluations focus on engineered and field constructed ESS and limited production products, and include:
- Test of an installed product with cooperation of an AHJ
- Non-destructive evaluation
- No production inspections
- Field-label marking22
Investigations may be for complete systems or may use a modular approach of preliminary construction review followed by complete system testing and certification.23
UL continues to work with key stakeholders to address deployment issues related to ESS, including:
- Working with first responders to holistically support the necessary tactics and equipment to deal with more and larger distributed ESS.
- Addressing standardized performance assessments for ESS
- Researching and addressing the safety risks of repurposed electric vehicle batteries, which still have a useful life in stationary applications such as ESS
- Safeguarding “V2X,” vehicle to grid and related technologies, that enable connectivity between EV batteries and electric grids24
As ESS deployment expands into the infrastructure at increasing rates, we will continue to work with the technical and Code communities to proactively address safety issues in a holistic manner. We will also continue our efforts in safety science to help enable a safe and sustainable energy storage infrastructure.25