What Is Energy Called When It Is Stored?

Energy storage is the capture of energy produced at one time for use at a later time. It allows us to overcome mismatches between energy supply and demand. Energy storage is an important component of efforts to utilize renewable energy sources like solar and wind power. Since the sun isn’t always shining and the wind isn’t always blowing, energy storage provides a way to store excess energy when it is available and hold it for when it is needed. Developing better methods of energy storage will be key to increasing the use of renewable energy and reducing our reliance on fossil fuels.

Energy can be stored in a variety of ways, including as chemical energy, gravitational potential energy, electrical energy, thermal energy, and more. The ability to store energy allows for greater flexibility and reliability in our energy systems. This article will provide an overview of the different forms energy can take when being stored.

Kinetic Energy

Kinetic energy is energy associated with motion. An object that has motion – whether it is vertical or horizontal motion – has kinetic energy. The amount of kinetic energy depends on the mass of the object and the speed of the object. The greater the mass and the greater the speed, the more kinetic energy is present. Some examples of kinetic energy include:

  • A moving car
  • A soccer ball being kicked
  • Wind
  • A flowing river

Kinetic energy is sometimes called energy of motion. Anytime an object is moving, it possesses kinetic energy. Kinetic energy plays a role in many everyday activities, processes, and tasks around us.

Potential Energy

Potential energy is the energy stored in an object due to its position or arrangement. For example, a ball sitting at the top of a hill contains potential energy because of its height above the ground. The higher it is above the ground, the greater its potential energy. Other examples include a compressed or stretched spring, objects being held at an elevated position, and separated electric charges. In all these cases, the object contains potential energy because work was put into placing it in that configuration. The object is not actively expending energy, but energy is stored within it. This stored energy, dependent on the object’s position, is referred to as potential energy.

Potential energy represents the capacity of an object to do work by virtue of its position or state. An object at rest has potential energy if it can release energy and do work by virtue of its present position and state. For instance, a ball held high up can fall downwards and release kinetic energy in the process. The potential energy was stored in the ball due to its elevated position, and this potential energy converted to kinetic energy as it fell. Potential energy is thus intrinsically linked to an object’s placement or arrangement.

Chemical Energy

Chemical energy refers to the energy stored in the bonds between atoms and molecules. It is energy released when a chemical reaction occurs. Some common examples of chemical energy include:

chemical energy stored in batteries and food

  • Batteries – The chemical reactions that take place between the anode, cathode, and electrolyte in a battery produce an electric current that can power devices.
  • Food – The bonds between molecules like carbohydrates, fats, and proteins contain chemical energy that is released when we digest food.
  • Fuel – Substances like coal, oil, gasoline, or natural gas undergo combustion reactions to release chemical energy that can be used for transportation, electricity generation, and heating.
  • Explosives – Explosives and propellants contain unstable chemical bonds that, when triggered, undergo rapid decomposition reactions that violently release chemical energy.
  • Biochemicals – ATP and glucose are examples of biomolecules that store chemical energy in their bonds to power cellular processes in living organisms.

In all these examples, chemical energy is stored in the molecules until specific chemical reactions are initiated to convert it to other forms of energy for use. Chemical energy is an efficient way to store and transport energy in compact molecules and materials.

Electrical Energy

Electrical energy refers to energy stored in the form of an electric charge or field. Some common examples of storing electrical energy include batteries, capacitors, and the separation of positive and negative charges.

Capacitors are a device used to store electrical energy. They consist of two conductors separated by an insulator or dielectric material. When voltage is applied, opposite charges accumulate on the two plates, storing energy in the electric field between the plates. The amount of energy stored depends on the capacitance of the capacitor and the applied voltage.

Batteries also exploit separated electric charges to store energy. In a battery, reduction and oxidation chemical reactions create a charge imbalance between the anode and cathode, establishing a potential difference. This potential difference can then drive electrons through a circuit and do electrical work.

Another example is the separation of charges that occurs in some materials or structures. For instance, rubbing certain materials together can strip electrons away, leaving net positive and negative regions. This charge separation constitutes stored electrical energy that can create sparks or drive currents in a circuit.

Nuclear Energy

Nuclear energy comes from the splitting (fission) or fusing of atomic nuclei. There are two main types of nuclear energy:

  • Nuclear fission – Atoms are split apart to form smaller atoms, releasing energy. Nuclear power plants use nuclear fission to generate electricity. In fission, uranium atoms are bombarded with neutrons, causing them to split apart into lighter elements and release energy in the form of heat. This heat is used to boil water into steam that spins a turbine to generate electricity.

  • Nuclear fusion – Light atomic nuclei are combined or fused together to form heavier nuclei, releasing energy. The sun produces energy through nuclear fusion when hydrogen atoms fuse together under intense heat and pressure to form helium. Scientists are researching fusion as a future energy source, but the technology is still in development.

Nuclear energy is considered a clean energy source, as it does not produce air pollution or carbon emissions. However, there are concerns around radioactive waste and safety. Properly managed, nuclear power provides reliable baseline electricity unaffected by external conditions like weather.

Mechanical Energy

Mechanical energy is the energy stored in objects by tension or motion. Some common examples of mechanical energy storage include:

  • Springs – The tension in a compressed or stretched spring stores energy that can be released as kinetic energy.

  • Flywheels – Spinning flywheels store rotational kinetic energy that can be tapped by slowing down the flywheel.

  • Compressed air – Compressing air stores potential energy that can be released to drive turbines.

  • Hydraulic accumulators – Energy is stored as potential energy by pumping fluid into an accumulator cylinder under pressure.

  • Weights – Raising a weight to store gravitational potential energy that can be released as the weight falls.

In each case, mechanical energy is stored in the configuration of the objects and released to do work. Mechanical batteries are essentially reservoirs of mechanical energy storage.

Thermal Energy

Thermal energy refers to the internal energy present in substances due to the motion and interaction of molecules and atoms. It is directly related to the temperature of matter. The higher the temperature, the greater the thermal energy. Thermal energy is important because when it is transformed, it can produce mechanical energy that powers many everyday devices.

Thermal energy is often stored in matter until needed. Some examples of matter that can store thermal energy include:

  • Molten salt – Salt that has been liquefied by heating can retain thermal energy that can be used to drive steam turbines for electricity generation.
  • Water – Hot water contains thermal energy that can be used for heating buildings or industrial processes.
  • Bricks – Bricks absorb heat during the day and release it slowly at night, helping regulate building temperatures.

Other materials are also capable of storing significant amounts of thermal energy for later use. Understanding thermal energy allows us to better utilize this useful form of energy storage across many applications.

Gravitational Potential Energy

Gravitational potential energy is the energy stored in an object due to its height or position. The higher up an object is, the more gravitational potential energy it possesses. This energy can be converted into kinetic energy if the object falls. Gravity causes objects to be attracted to one another, so the higher an object is above the ground, the more energy it has available to do work. Gravitational potential energy depends on the mass of an object, its height, and the strength of gravity. It is calculated using the formula:

Gravitational potential energy = mass x gravitational acceleration x height

As an example, imagine holding a book in your hand while standing at the top of a staircase. The book has gravitational potential energy due to its position above the ground. If you were to drop the book, as it falls its potential energy would be converted into kinetic energy – energy of motion. The book gains speed as it drops because its potential energy is transformed into kinetic energy. When it hits the ground, all of that gravitational potential energy will have become kinetic energy.

Gravitational potential energy can also involve changes in vertical position. For instance, when you lift an object upwards, you have to use energy to increase its height and give it more potential energy. The higher the object is lifted, the greater its stored energy. This stored energy can later be released as the object falls back down. Gravitational potential energy is directly proportional to mass and height – double either one, and the stored energy also doubles. In summary, the potential energy of an object depends on its mass, height, and the strength of gravity.


In summary, there are many different forms that stored energy can take. The main types discussed here included kinetic energy, potential energy, chemical energy, electrical energy, nuclear energy, mechanical energy, thermal energy, and gravitational potential energy. While the specifics of each form may differ, what they all have in common is that they represent energy in a stable state, ready to be released or transformed when needed to do work. Understanding the different ways energy can be stored is key to effectively harnessing these resources for human purposes, whether it be heating our homes, powering transportation, or running complex machinery. Recognizing how abundant stored energy is all around us underscores how essential it is to all aspects of our daily lives.

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