Skip navigation to main content. National Renewable Energy Laboratory (NREL)NREL HomeInnovation for Our Energy Future
About NRELScience and TechnologyTechnology TransferApplying TechnologiesLearning About Renewables
Learning About Renewable Energy
Learning About Renewable Energy Home Renewable Energy Basics Using Renewable Energy Energy Delivery and Storage Basics Distributed Energy Energy Storage Batteries Compressed Air Flywheels Pumped Hydropower Supercapacitors Superconducting Magnetic Energy Hydrogen Advanced Vehicles and Fuels Basics Student Resources

Batteries

Batteries are the most common device used for storing electrical energy.

Advanced Batteries

Advanced battery technologies include lithium-ion, lithium polymer, nickel metal hydride, and sodium sulfur types. Advanced batteries offer much smaller "footprints" (i.e., they take up less space) than lead-acid batteries. They are typically CURRENTLY too expensive for large-scale utility applications, but are used for power quality and backup purposes at manufacturing plants. They are also used in consumer goods and automobiles. Lithium-ion batteries in laptop computers, for example, can provide twice as much operating time as conventional batteries. Sodium sulfur batteries can operate at high temperatures, and have proven safe even under extreme conditions.

Flow Batteries

Flow batteries work in a similar fashion to lead-acid batteries, but the electrolyte is stored in external containers and circulated through the battery cell stack as required. This external reservoir of rechargeable electrolyte can be as large as needed, and situated where convenient. Some flow batteries use two different kinds of electrolyte that are stored separately.

The great advantage to flow batteries is that their electrical storage capacity is limited only BY the capacity of the electrolyte storage reservoirs. They provide very high power and very high capacity batteries for load-leveling applications on the electricity grid. Zinc-bromine flow batteries are the most common type in use in the United States.

Lead-Acid Batteries

Lead-acid batteries are the most common type of battery. They are used in automobiles, and by both utilities and electricity consumers as a backup energy source for critical electricity needs.

The traditional lead-acid battery is made up of plates, lead, and lead oxide immersed in a solution consisting of 35% sulfuric acid and 65% water. This solution is called "electrolyte," and causes a chemical reaction that produces electrons. Various other elements are also used to change the density, hardness, and porosity of the plates.

A couple of variations on the traditional design have emerged:

  • Valve-regulated lead-acid (VRLA) batteries — are sealed and need no topping off with water, and so require less maintenance than regular lead-acid batteries.

  • Gel-type lead-acid batteries — are filled with a gel instead of liquid, making them much less likely to spill.