What is UL 9540?

UL 9540 is a safety system listing for energy storage systems. UL 9540 evaluates the compatibility and safety of the various components that make up an ESS but integrated as a system.

 

According to the current edition of UL 9540*:

 

A common misconception is that UL 9540 only applies to lithium-ion UPS systems. It is important to note that it can be imposed on a variety of UPS, ESS, battery types and designs.

 

For more detailed information on UL 9540:

What is a UL 9540-listed system?

A UL 9540-listed system can be a variety of different designs.

 

Typically, there is an energy storage device such as a battery, capacitor, or electro-mechanical piece of equipment. Then, to provide that stored energy, a converter of some sort converts the stored energy to the proper voltage and power levels that are appropriate for the application. 

 

Examples of UL 9540 systems could be:

• A UPS with lithium-ion batteries
• A bidirectional inverter with Valve Regulated Lead Acid (VRLA) batteries
• A UPS with super capacitors (electrochemical)

The various component configurations and designs are integrated as a system and need to be evaluated and tested for UL 9540 compliance. This includes varying numbers of battery cabinets or other energy storage components.

Why is UL 9540 important?

In recent years, installation codes and standards have been updated to address modern energy storage applications which often use new ESS technologies. The most prescriptive safety codes and guidelines in the UPS industry are:

• National Fire Protection Agency (NFPA) 855: Standard for Installation of Stationary Energy Storage
• International Fire Code (IFC)
• Occupational Safety and Health Administration (OSHA)

 

Some important considerations within UL 9540 and NFPA 855 codes include, but not limited to:

• Currently, NFPA 855 states any lithium-ion battery system over 20kWh shall be certified to UL 9540.
• The current edition of UL 9540* has requirements that limit the maximum energy capacity of individual nonresidential electrochemical ESS to 50 kWh unless they comply with the separate UL9540A fire test criteria that is specific to battery systems (Florence & Hopper, 2020).
• ESS larger than 50 KWh or with separations less than three feet cannot be listed to the current edition of UL 9540 without complying with appropriate UL 9540A fire test performance requirements (Florence & Hopper, 2020).

In the example below, a UL 9540-listed system allows the UPS and battery cabinets to be side-by-side, creating a footprint advantage over systems without a UL 9540 listing, if a site requires NFPA 855 and IFC regulations.