So, what exactly is energy storage?

graphic image that says the words energy storage. The background is light orange and peach with two small blobs on it with various electricity equipment in them. One has a rechargable battery icon and the other has wind turbines, solar panels and energy storage batteries.

The term ‘energy storage’ appears often in news about Tesla battery products or in discussions about renewable energy generation and the future of electricity. You may have heard the term before, but not know what it means or the technology involved.

In this post, we do Energy Storage 101 and explore examples of the different technologies. We hope this helps you to understand the vast topic of energy storage and feel excited for the innovations happening in this field.

What is energy storage?

Energy storage is the ability to capture energy produced at one time and be able to save it for later use. Humans have been using different forms of energy storage for over a hundred years. Energy storage technologies are an important part of electricity infrastructure. It has become crucial as we add more renewable energy projects to the electricity grid. 


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Electricity is a form of energy. It has many applications and has created human civilization as we know it. It also has one major challenge: you can’t hold onto it or save it for later. When electricity is generated at a power station it must be used in the moment, regardless of the fuel type.
This isn’t a big issue with power stations that use fossil fuels, such as coal or natural gas. Whether it is a pile of coal outside the coal plant or gasses in the pipeline connected to the natural gas power plant. The energy is in the resource itself. If more or less electricity is needed to meet demand, then either more fuel is added to the furnace or less. These power plants are balancing the generated electricity with the electricity needed.
We know there are drawbacks when fossil fuels are burned for electricity generation. So, using fossil fuels is no longer an option for a healthy planet. We need to utilize more renewable, clean options and combine them with energy storage technology.

Why is energy storage important for renewable energy?

If the source of power is natural, such as moving water, wind, or sunlight, then the amount of energy available can change from day to day or from minute to minute. This is called intermittent, meaning that it is not constant or steady. For example, solar power works well when the sun is shining and often generates more electricity than is needed during the day, but no electricity is generated at night. Intermittent electricity generation without energy storage results in anything powered by electricity (such as lights, appliances, machinery, etc.), to be turned on and off constantly.

Energy storage is important as more renewable energy projects are added to the grid because it brings stability to on and off power sources. Electricity can be generated even if demand is low, and then can be stored and used at a later time when electricity demand increases, but the renewable energy source is not generating electricity.


How is energy stored for generating electricity?

There are many forms of energy storage for electricity. Batteries are the first technology that comes to mind, but the oldest are hydroelectric dams.

Hydro Dams are large reservoirs of water that are contained behind a dam. In a hydroelectric power plant, the mechanical energy of the flowing water through the dam is converted to electricity using a turbine. When there is higher demand for electricity, then more water is allowed to flow through the turbine. When there is less demand, then less water flows through. It’s like being able to turn a tap on and off. Hydro dams can be found in many countries around the world and have been used to generate electricity since the late 1800s.

The largest in Canada is the Robert-Bourassa hydroelectric generating station in northern Quebec.




Pumped Storage Hydropower stores energy in the form of the gravitational potential energy of water. When electricity is being generated but is not in demand, then the extra electricity is used to power a pump which moves water from a lower elevation reservoir to a higher elevation reservoir. When demand for electricity increases, the water in the higher reservoir is released, flowing down through a turbine and back to the lower elevation reservoir. The water continues to move back and forth between the reservoirs, depending on whether extra electricity is being generated or if there is demand for electricity.

The concept is simple and could be used in many locations, but the only facility in Canada is the Sir Adam Beck pump generating station in Niagara Falls, Ontario.

Photo credit: By Ontario Power Generation – Adam Beck Complex, CC BY 2.0,


Batteries store energy in the form of chemical energy. There are many types of batteries, from lead-acid (the first rechargeable battery) to the common and versatile lithium ion. The materials and chemicals used within batteries can differ. The idea is the same: when extra electricity is being generated it is directed into a battery and causes a chemical reaction. When electricity demand increases, the chemical reaction is reversed and electricity is generated.

Grid-sized batteries are being built all around the world, and the largest one in development at the time of this publication is in Australia.



Flywheels store energy in the form of rotational energy. When extra electricity is being generated it will work to accelerate a heavy flywheel at a very high speed. When the energy is needed, the flywheel’s rotational speed is reduced because that energy is transferred to an electrical generator.

The first grid-connected flywheel facility in Canada is located in Minto, Ontario. At this facility, the flywheels weigh 12,000 pounds (over 5000 kg) and spin at speeds over 11,000 RPM (rotations per minute).



Compressed Air Energy Storage (CAES) uses the potential energy of pressurized air to store energy. When extra electricity is being generated, it powers an air compressor which forces the air into a container and greatly increases the air’s pressure. When electricity is in demand, the pressurized air is heated and expands as it is released from the container. The expanding air moves through a turbine to generate electricity. To do this on a large scale, the container must be large. The most common use is old salt mines to hold the pressurized air because they are stable, and the air can’t escape.

The first CAES facility was built in Huntorf, Germany in 1978 and it is still in operation today! There is one of these facilities in Goderich, Ontario.



Hydrogen energy storage uses the chemical potential of hydrogen atoms. When extra electricity is being generated, it can be used to power an electrolyzer which separates water into hydrogen and oxygen. The hydrogen is stored in a fuel cell which acts like a battery. When electricity is needed, the chemical reaction is reversed. Energy is released as the hydrogen reacts with oxygen to form water again.

In Bela Coola, BC, there is a hydrogen energy storage system that works alongside a hydroelectricity generating station.


Gravity energy storage systems use the gravitational potential energy of heavy objects. Using cranes and electric motors, large blocks are lifted from the ground when there is extra electricity being generated and are placed at a higher elevation. When there is demand for electricity, the blocks are lowered and the kinetic energy of the falling block turns the motor in reverse which generates electricity.

In Oct 2021, there was an announcement for one of these facilities to be built in British Columbia, and each block will weigh 35 metric tons, which is the same weight as five large elephants! You can learn more about how this technology works by watching this video


Hopefully you have a better understanding and can store some of this info for later use.