In the current National Electrical Code (NFPA 70-2014), if you want to find information about energy storage devices such as batteries, capacitors, fuel cells, etc., you probably need a search engine. Batteries have a section of their own (Article 480) but if you do a search you will find batteries scattered throughout the Code for many different applications. If users agree, that could very well change in the 2017 Code. Proposals just approved by one of the NEC code-making panels would pull all of this information into a single, brand new Article 706 for Energy Storage Systems (ESS).
The general public will not get a chance to see what that will look like until July 2015 when the draft is published. People then have two months to respond with comments. Proposed changes in the new Article include a definition of an Energy Storage System. It can be one or more devices capable of storing energy for use at a future time. Examples include electrochemical storage devices (i.e., batteries) and flow batteries, but could also include capacitors and kinetic energy devices (including flywheels and compressed air). Utilization voltage can be ac or dc and can include such things as inverters and converters, up to 1,000 volts.
NFPA’s correlating committee originally chartered a task group to look into the feasibility of consolidating requirements into a single place. The task group pulled in requirements from Articles having to do with photovoltaic systems and wind generation systems as well as other applications for energy storage. Items to be addressed include predictable features such as:
- ESS locations: spaces around ESS components, ventilation, guarding of live parts, means of egress, and illumination
- Markings: directories showing sources of all electric power, and a directory on any building not connected to a utility service source
- Circuit requirements: nameplate rated current, including inverter input and output current, dc-dc converter current, neutral current, etc.
- Overcurrent protection
- Wiring methods
- Charge controls, including all adjustable means, diversion charge controllers, and dc controllers and converters.
- Battery and cell terminations, interconnections, and accessibility
- Flow battery classifications, electrolyte containment, and flow controls
Changes to the existing battery section, whether integrated into the new ESS or not, should have minor impact on data centers.
These requirements are still fluid, and task groups are still working to clean up a lot of the requirements. A lot more changes are likely after the public gets its first look in July 2015. Anybody can submit comments; you do not have to be a member of NFPA. The full impact of any new Article typically takes more than one code cycle to be felt.