Energy storage describes the storage of energy in times of low   energy demand (demand less than production) and the release of   stored energy in times of high energy demand. 

With the development of renewable energies such as solar modules or wind turbines, the area of energy storage also grew. Due to unstable energy production, e.g. when the sun does not shine all day, redundant energy must be stored for times when its production is below demand. From huge pumped storage power plants with an output of up to 3,000 MW to batteries for private households, many different technologies and processes have been developed.

The most common technologies for electrical energy systems to balance the electrical load in a grid (ensuring a balance between electricity demand and supply) are pumped hydroelectric energy storage (PHES) and compressed air storage (CAES).

Pumping water up a hill into an artificial lake using redundant energy capacities increases the energy potential of water. This potential energy is used in times of energy scarcity by letting the water flow to a lower level and converting its potential energy into electricity. CAES works on a similar principle by pumping air into natural underground caves or air tanks during periods of low energy demand, releasing the air and generating energy during periods of high energy demand.

PHES accounts for 99% of all energy storage capacity worldwide and operates on a simple principle of using water flow and gravity.

While PHES and CAES technologies are being developed for electrical energy systems that require an already installed and functioning power grid, home batteries can be connected to the home or district power grid. The best known technology is Tesla’s home battery called Powerwall. It consists of lithium-ion batteries (the same batteries as a laptop and even all Tesla car models) that can store electrical energy and return it when needed. Home batteries do not require any power grid infrastructure, they can easily be connected to any power generating device such as solar panels or wind turbines and make the user independent of the public power grid. Especially for developing countries where there is no grid infrastructure or installation is too costly, home batteries have enormous potential to provide electricity.



Since our fossil resources on this planet are limited, renewable energy will be the only way we can produce energy in the future. Natural volatility in production is one of the biggest problems and can only be solved with efficient energy storage both in the grid and for private users.

Literature: Huggins (2016): Energy Storage. Heidelberg: Springer