Storing energy


The two main types of batteries that are commonly used are ‘single-use’ and ‘rechargeable’. The single-use batteries, sometimes referred to as primary types, are commonly alkaline batteries, and these are readily available in supermarkets and shops.

All batteries are available in a range of sizes and shapes - tiny batteries known as button-cell batteries power calculators and hearing aids, while very large batteries power cars and trucks.

Lithium button-cell batteries displayed on a white background alongside a calculator.
Button-cell batteries in a calculator

Mobile phones rely on battery power to run their software and to allow them to be portable. The most desirable combination for users is a small battery that provides as much power for as long as possible.

Common forms of batteries used in homes are AA and AAA, and both typically produce around 1.5 volts (V) per battery. A larger PP3 battery, often used for smoke alarms and medical equipment, typically produces 9 volts (V) per battery.

Three batteries, AA, AAA and PP3, are shown next to each other for comparison.

Once a battery runs out it has to be replaced unless it is rechargeable, in which case it is connected to a mains power source to be recharged.

A set of four AA rechargeable batteries on charge.

Rechargeable batteries:

  • are more expensive to purchase than single-use batteries
  • can be recharged
  • are more economical in the long term
  • have a limited lifespan

Rechargeable batteries can only be recharged a number of times before they lose battery life, in the same way as smartphone batteries lose battery life over time.

Batteries can be recycled to prevent them ending up in landfill sites. Batteries contain harmful chemicals and metals that are bad for the environment if disposed of incorrectly; these elements can contaminate the ground or poison the wildlife that may eat them.

Kinetic-pumped storage systems

A kinetic-pumped storage system is a fast-acting electrical energy storage system to top-up the National Grid power supply at peak times when more electricity is needed. A kinetic-pumped storage system works by having two reservoirs and a hydro-electric dam system.

During the night excess electricity is produced by other electrical energy stations, meaning the cost of the electricity is much lower, so a kinetic-pump plant will pump the water from a lower reservoir up to a higher reservoir, where the water remains. When there is a sudden need for more electricity (spike) during the daytime, the dam is opened and the water from the top reservoir passes through pipes, spinning turbines to quickly produce the electricity needed.

A kinetic-pumped storage system turning the flow of water into electricity. Water flows from a reservoir through a turbine before being pulled back up again.

Different types of energy can be described as being in different ‘stores’. It cannot be created or destroyed but it can be transferred, dissipated or stored in different ways.

Type of energyExample of how it could be storedApplications
KineticIn a flywheelIn a spinning top toy or a gyroscope
InternalIn heated solids or liquidsA storage heater stores thermal energy during the evening or at night when the cost of energy is low - the heat is then released in the day, as it is needed
Elastic potentialIn materials that are stretched or squashedIn the foam sole of a modern running shoe
Gravitational potentialIn an elevated weightA skier at the top of a hill
ElectricalIn electrochemical devices, eg batteriesIn batteries, eg lithium-ion batteries found in most portable consumer electrical devices
MagneticIn supercooled, superconducting coilsAlthough highly efficient, these are still experimental and high-cost systems and are only used for manufacturing facilities requiring very ‘clean’ energy, eg microchip fabrication factories
A diesel-powered engine with two large spinning flywheels

Flywheel for storing kinetic energy

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