NextEra Energy Resources energy storage facility

How does a battery energy storage system work?

 

Battery energy storage can provide valuable services to help balance and improve the efficient operations of the larger power grid. Storage can also complement renewable generation by storing wind and solar energy when its plentiful and distributing it to customers when its most-needed. Batteries can make more renewable energy available over more hours of the day – modeling a traditional power plant. 

Energy from the power grid or from renewable energy sources is delivered via a bi-directional inverter, which converts the energy from alternating current (AC) into direct current (DC). Today's batteries can only store DC. This energy goes into an array of batteries that is typically housed within a battery container or a building structure. 

When the energy is needed on the power system, the inverters are then used again, but this time to convert the DC from the batteries into AC. Once the power has been transformed, it is stepped up in voltage and subsequently sent to an on-site substation or directly to a distribution or transmission line. 

A Battery Management System monitors the individual cells and controls the voltage, temperature and current for the safe, reliable transfer of energy. The system automatically shuts off if the batteries are operating outside of predefined parameters.  

The electricity is then distributed to homes, schools, businesses and other consumers. 

NextEra Energy Resources – Battery energy storage equipment

What are the components of a battery energy storage sytem?

 

A battery energy storage system consists of: 

  • Individual battery cells.
  • These cells are collected into modules and housed in a specially designed, climate-controlled sotrage container.
  • The racks fill containers, not unlike a storage container you’d see on a ship or truck.
  • The containers are paired with inverters to convert DC-AC electricity.
  • Can be paired with a renewable energy asset (solar, wind) or stand alone.

Battery storage container

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Individual battery module

What kind of batteries are used for energy storage?

 

We primarily use lithium-ion battery technology, which has benefitted from years of research and development and has been proven to be safe, efficient and cost-effective for utility-scale battery energy storage. We are always evaluating other battery chemistries and technologies to continue to advance this growing industry.

 

Can the batteries be recycled?

 

The materials used in battery energy storage facilities are valuable even after more than 20 years of use. Many of the battery manufacturers we work with offer to reclaim their lithium batteries as the parts can be recycled and used in new products.

In addition to re-use in new battery cells, the recycled materials extracted can be used in a wide variety of consumer products such as lithium grease, concrete additives and some glass products.

  • NextEra Energy Resources requires our vendors to provide recycling certificates to ensure all applicable regulations are followed in the recycling and disposal of battery storage related equipment.
  • Following EPA guidelines, we do not dispose of batteries in municipal landfills.
  • Requirements for the disposal of lithium-ion batteries are found in Part 273 of Title 40 Code of Federal Regulations.

If maintained properly, depending on the use case, a battery system can last 20 or more years and can be replenished over time.

Sources:

[1] Title 40 Code of Federal Regulations Part 273: Standards for Universal Waste Management

NextEra Energy Resources employee using safety gear: Hard hat, gloves and safety yellow vest.

Do battery energy storage systems present a fire risk?

 

Fires involving battery energy storage systems are rare. At NextEra Energy Resources, the safety of our employees, neighbors and the public are always our highest priority. Responsible energy production begins with preparation from day one.

  • Batteries used in our facilities undergo rigorous industry testing and certification by Underwriters Laboratories (UL). This ensures that the cell and module designs are robust.
  • Battery modules are housed in fully enclosed containers, like shipping containers.
  • Each container is equipped with fire protection and explosion control systems to comply with National Fire Protection Association.
  • We have sensors that alarm when an abnormal condition arises. Additionally, our facilities are monitored 24/7 by our Renewable Operations Control Center, which can remotely shut down any affected site.
  • We work and train with local first responders and fire officials to coordinate any response, in the unlikely event of a fire.