Grid Energy Storage

Introduction

Grid energy storage is a collection of methods used to store energy on a large scale within an electricity grid. Electrical energy is stored at times when electricity is plentiful and cheap (especially from variable renewable energy sources such as wind and solar), or when demand is low, and later returned to the grid when demand is high and electricity prices tend to be higher.

In order to cope with both high and low load situations, as well as the increasing amount of renewable energy being fed into the grid, the storage of electricity is of great importance. However, the large-scale storage of electricity in the grid is still a major challenge and subject to research and development. 

The following technologies and approaches can, or are hoped to, provide a solution to storing electricity and balancing supply and demand in modern electricity grids.

Pump storage hydropower

A pumped storage hydroelectricity system (PSH) consists of two water reservoirs at different elevations. Low-cost surplus electric power is typically used to pump water into the upper reservoir. During periods of high electricity demand, the stored water is released through turbines to generate electricity.

PSH is a well established technology. In 2023, world pumped hydroelectric storage (PHS) was the largest storage technology, with a capacity of 181 GW.

Green Hydrogen

Green hydrogen could be used as a long-term storage option: In times of surplus renewable energy, additional unused electricity could be used to produce hydrogen, which would then be stored. During periods of additional demand or low renewable energy production, this hydrogen would be burned in fuel cells to generate emission-free electricity.

Today hydrogen is most commonly stored as a gas or liquid in high-pressure tanks for small-scale mobile and stationary applications. However, hydrogen is less dense than gas, which makes it hard to store and requires more space than gas for the same amount of energy. For future large-scale application further options are needed. There are several options, one being compressing it into underground salt caverns.

Hydrogen can also be converted into a liquid for long-term storage, which requires very cold temperatures. Another option would be to convert hydrogen into liquid ammonia with the advantage of using already existing infrastructure for safe storage and transportation.

Further Information

• Grid Portal on energypedia
• Balancing Supply and Demand in Electricity Grids
• Green Hydrogen