Electricity storage is the art of preserving electrical energy for future use. In the era of energy transition, this technology is of great importance. It makes it possible to compensate for the interruption of renewable energy sources such as solar and wind energy, and thus provides the key to a more efficient integration of these resources into our electricity grids. This article aims to provide a comprehensive overview of electricity storage, from its various traditional methods to emerging technologies. We will also explore their critical role in electric mobility, grid balancing and the prospects for a more sustainable energy future by  2050 .

How is electricity stored?

Electricity can be stored in several ways. Traditional methods include the use of batteries, hydro and thermal storage. Nowadays, modern technologies such as supercapacitors and flywheels are also used. Each of these technologies converts electrical energy into a form that can be stored and released as needed. The selection of the appropriate method depends on the specific system requirements and environmental constraints.

Traditional electricity storage methods

Conventional batteries

– How do you store electricity in the battery?
The battery stores electricity through a reversible chemical reaction between its components, represented by a single or two-terminal cell. When the battery is charged, electrons are forced to flow from the negative side (anode)  to  the positive side  (cathode) , which leads to an accumulation of electrical energy. Upon discharge, this reaction reverses, releasing stored electrons and generating electricity that can be utilized.

Conventional batteries are one of the most common ways to store electricity. They come in different types, including lead-acid, nickel-cadmium, and lithium-ion, each with their own distinct properties. Lead-acid batteries are reliable and inexpensive, but their energy density is limited, making them less suitable for high-performance applications. In contrast, lithium-ion batteries are widely used in mobile and stationary applications due to their high energy density, low self-discharge rate, and long cycle life. However, they can be more expensive to purchase.

Benefits:
–  Wide availability in the market.
–  Mature technology with diverse options.
–  Possibility of integration into many applications. Disadvantages:
–  The high cost of some technologies.
–  Possibility of performance deterioration over time.

Hydraulic storage

Hydraulic storage (also called  pumped storage ) uses water tanks at elevation to store energy in potential form. When electricity is needed, water is released to spin turbines, which then generate electricity. This method is particularly effective for large-scale storage and is often used in hydroelectric power plants. The advantages of water storage lie in its large storage capacity and its ability to respond quickly to demand, which makes it an ideal choice for stabilizing electrical networks.

Benefits  :
–  Large storage capacity.
–  Rapid response to requests.

Disadvantages:
–  Specific topographic requirements.
–  Potential environmental impact.

Thermal storage

– How to store thermal energy?
Thermal storage works by converting electricity into heat using electrical resistors or heat pumps. This heat is then stored in an insulating material, such as a thermal fluid or a phase change solid. When electricity is needed, the heat is converted back into electricity using a turbine or heat engine. Thermal storage is characterized by low cost compared to other storage technologies, and it is also an environmentally friendly technology for producing electricity.

Operating principle:
–  Converting electricity into heat.
–  Storing heat in the material.
–  Reconverting heat into electricity.

Applications and limitations:
–  Applications in solar thermal and geothermal power plants.
–  It can be used for heating or direct electricity production.
–  Limitations related to the efficiency of the heat conversion process.

Modern electricity storage technologies

Storage with supercapacitors

Supercapacitors store electricity in the form of ions adsorbed on the surface of porous electrodes. Unlike batteries, they do not involve chemical reactions, allowing for much faster charging and discharging. They are particularly suitable for applications that require fast charge and discharge cycles, such as electric vehicles and energy recovery systems.

Features:
-Very  long lifespan and fast charge/discharge cycles.
–  High energy density.

Energy storage by flywheels

–  What are energy storage flywheels ?
The flywheel stores energy in the form of mechanical rotation. Here’s how it works :

• Charging stage : When excess electricity is available, it is used to rotate the flywheel at high speed. This process converts electrical energy into kinetic energy, which is stored in the form of rotation.
• Energy storage phase : The flywheel continues to rotate at high speed. The resulting kinetic energy is conserved thanks to high-quality mechanical components and bearings, reducing friction losses.

• Discharge phase : When electricity is needed, the speed of the flywheel slows down, and in return the kinetic energy will be converted into usable electricity. This is done by reversing the primary process, using rotary motion to generate electricity.

Note:
Electricity cannot be stored as it is because it is actually moving energy. To preserve it, it is first converted into another form of energy. When we need it at some point, we convert it back into electricity. However, at each stage of these transformations, some energy is lost. This loss may be more or less significant, depending on the circumstances. It’s a bit like losing a little water every time you move it from one container to another.

Advanced battery storage

Advanced battery storage relies on the advanced use of new combinations of materials and technologies to outperform conventional batteries, such as lithium-ion batteries. Examples are lithium-sulfur and lithium-air batteries.

These developments aim to reduce the costs of electricity storage systems and increase the energy density generated, i.e. the amount of energy a battery can store per unit volume or weight. They are also exploring less expensive and more abundant materials, reducing reliance on scarce materials. Although these technologies are still in the research and development stage, they promise to revolutionize electricity storage by providing more efficient, economical and sustainable solutions to meet the growing energy demand.

Benefits:
–  Possibility of obtaining much higher energy densities.
–  Reducing the expensive and rare materials used in batteries.

Cryogenic energy storage

Cryogenic energy storage relies on the use of  cryogenic materials , such as liquid air or liquid nitrogen, to store energy. This innovative process works by cooling these gases to extremely low temperatures, turning them into liquids. The energy is then stored as a cooled liquid in insulated tanks to reduce thermal losses. When electricity is needed, the liquid is heated, causing it to evaporate and power turbines that generate electricity. This technology helps provide high storage capacity and the ability to store for long periods of time, which contributes significantly to progress towards a more sustainable and flexible energy system.

Storing electricity in aluminum

Electricity storage may become more efficient and affordable thanks to an innovative project: aluminum electricity storage. This revolutionary idea is based on aluminum’s ability to store large amounts of energy in a compact and low cost. By charging the aluminum, it is converted into a reactive material that can then release electricity when it is needed. Thanks to its high reversibility and the abundance of aluminum in our environment, this project offers a promising glimpse into the future of electricity conservation.

Why is electrical energy stored?

Electricity storage is a key pillar of our transition to a more sustainable energy system. Power plants store electricity for several important reasons :

• Demand and supply management:
  The rate of electricity consumption changes throughout the day due to differences in usage and needs. Electricity storage helps meet demand during peak periods, when usage is at its highest, and releases energy during off-peak periods, helping to maintain a balance between supply and demand.

• Power grid stability:
  Power grids are sensitive to sudden fluctuations in electricity demand or weather conditions. Electricity storage provides the ability to quickly provide surplus energy when it is needed most urgently, keeping the grid stable and reliable.
• Renewable energy integration:
  Clean energy sources, such as sun and wind, are intermittent and do not always produce electricity when demand is high. By conserving the electricity produced during periods of overproduction, renewable energy plants can provide electricity when needed.
• Energy Security:
  Electricity storage provides a strategic reserve that can be mobilized in emergency situations, such as power outages or natural disasters, ensuring a stable and reliable supply of electricity.

Storing electricity in homes

Storing electricity at home is a crucial solution to improving energy use. Home batteries store electricity produced from renewable resources, such as solar panels, and use them normally when demand is high or in the absence of local production.

Additionally, solar energy storage systems include a battery to store electricity during periods of excess production, making it available for later use. This approach promotes self-consumption and further reduces and saves electricity bills. By combining these new technologies with smart energy management systems, homeowners can maximize the efficiency of their electricity consumption and reduce their dependence on national electricity grids.

In conclusion,  electricity storage is an essential pillar of our transition to a more sustainable energy future. From traditional technologies to innovative emerging approaches, each approach helps maximize the efficiency of our energy grids. Whether it is through advanced batteries, thermal storage or innovative projects. This constantly evolving field paves the way towards a more reliable, flexible and environmentally friendly electricity supply.