BESS (Battery Energy Storage System)

Definition

BESS (Battery Energy Storage System) is a battery-based storage system that stores extra electricity and supplies it back when needed. It is the most common type of Distributed Storage (DS) and therefore a type of DER. In the overall power system, BESS acts like an energy bank—it stores unused electricity and releases it later to keep the grid stable.

The Problem That Led to It

After introducing DER, many local generators such as solar panels and wind turbines produced electricity only when nature allowed. Solar panels generate power during sunny hours, while wind turbines depend on the wind. Unfortunately, people often need electricity when these sources are producing little or none.

Instead of wasting extra electricity during the day and running short at night, engineers needed a way to save electricity now and use it later. This led to BESS.

What Problem It Solves

BESS stores excess electricity when production is high and releases it when demand is high or generation is low. This:

• Reduces wasted renewable energy.
• Provides backup power.
• Helps balance supply and demand.

What Happens If Not Used

Extra solar or wind energy may be wasted, and the grid must rely more on traditional power plants when renewable generation drops.

Easy Wording

BESS is a large rechargeable battery that saves electricity for later use.

Layman Example

Think of a water tank at home.

• When water is available, the tank fills up.
• When the water supply stops, you use the stored water.

A BESS does the same thing, but with electricity.

Technical Example

Before BESS

• Solar panels generate extra electricity at noon.
• Homes cannot use all of it.
• The extra electricity is wasted or curtailed.
• At night, electricity must come from the main grid.

After BESS

• Solar panels generate extra electricity.
• BESS stores the unused electricity.
• At night, BESS supplies the stored electricity.
• The main grid provides only the remaining demand.

Limitation

BESS only stores electricity—it cannot create it. It always needs a power source, such as solar panels, wind turbines, or the main grid, to charge.