What is the World’s Largest Energy Storage System? A Comparison of Energy Storage Technologies

Energy storage stocks have been booming in recent years. When discussing energy storage, all the focus is on lithium batteries. However, it’s not just lithium batteries that can store energy; many things can. The reason we keep talking about lithium batteries is because they are currently the most likely champion in the competitive arena. Today, we’ll spend three minutes building a systematic knowledge framework for energy storage systems.

Three Energy Storage Methods: Physical Energy Storage, Electromagnetic Energy Storage, and Electrochemical Energy Storage

Energy storage involves converting electricity into other forms of energy, storing them in an “energy storage device,” and releasing them when needed. During the charging and discharging process, energy is naturally transferred across time, much like a “reservoir” acting as a “peak shaving and valley filling” regulator: storing water when there’s an abundance and releasing it when there’s a scarcity. This is the role of energy storage.

Energy storage devices come in various forms. We can convert electrical energy into kinetic energy, potential energy, and chemical energy, etc. Corresponding to different energy conversion methods, the main types of energy storage are currently divided into physical energy storage, electromagnetic energy storage, and electrochemical energy storage.

The world’s largest energy storage system is pumped-storage hydropower, and its dominant position is unlikely to change in the short term.

Let’s first understand physical energy storage. Physical energy storage includes pumped-storage hydropower, compressed air energy storage, and flywheel energy storage. Besides generating electricity—what we usually understand as “hydropower”—pumped-storage hydropower units can also be used as energy storage batteries for power dispatch. Pumped-storage hydropower has a large capacity and low storage cost, making it a natural battery, and its dominant position is unlikely to change in the short term.

However, pumped-storage hydropower does not have much growth potential because its construction is entirely dependent on geographical conditions, meaning whether local water resources are abundant and have a stable supply. In recent years, almost all newly built reservoirs have faced ecological and environmental controversies and have been shelved. Since 2016, the global installed capacity of pumped-storage hydropower units has only grown by 0.6%. Compressed air energy storage, as the name suggests, uses air as an energy carrier. Electricity is used to compress air, which is then stored in abandoned mines, expired oil and gas wells or storage wells, on the seabed, in salt caverns, etc. When needed, the compressed air is mixed with natural gas, heated, and burned to drive a turbine to generate electricity. Although it still requires fossil fuels to operate, it is considered environmentally friendly. Its key features are high output power (MW level), long operating time (up to several hours), and long service life (up to 40 years, capable of tens of thousands of cycles). Disadvantages include high construction costs due to geographical limitations, hindering widespread application.

Flywheel energy storage, also as the name suggests, uses electricity to accelerate a cylinder at very high speed in a vacuum, storing electrical energy as kinetic energy, which is then converted back into electrical energy. Flywheel energy storage is commonly used in industrial uninterruptible power systems (UPS) or for frequency and voltage control on the power grid. Its key features are high energy storage efficiency (up to 90%), long service life, environmental friendliness, and ease of use. Disadvantages include low energy density, high maintenance costs, and poor cost-effectiveness.

Both superconducting and supercapacitor energy storage are currently very expensive and will not be widely used in the short term.

Electromagnetic energy storage includes superconducting and supercapacitor energy storage. Superconducting energy storage involves placing a coil made of superconducting material in a container at a critical temperature. Under such extreme temperatures, the resistance within the superconductor is zero, resulting in no power loss during energy transfer. The energy is stored in the magnetic field as direct current circulating within the superconducting coil.

However, achieving superconducting energy storage requires consuming energy to create the critical temperature environment, which is prohibitively expensive and environmentally unfriendly. Furthermore, the energy storage time is very short. Although superconducting energy storage products are available, their application in power grids is limited and mostly experimental.

Supercapacitor energy storage uses a special electrode structure that increases the electrode surface area by tens of thousands of times, resulting in a large capacity. Its key features are fast charging and discharging speeds and a high number of reusable batteries. When used in buses or subways, it can discharge rapidly during acceleration and recover energy during braking. Even frequent acceleration and braking do not affect battery life.

The fastest-growing energy storage system globally is electrochemical energy storage, with lithium-ion battery energy storage showing the strongest potential to become the champion.

Electrochemical energy storage has been the hottest topic and the fastest-growing type of energy storage in recent years. 2018 can be considered the inaugural year for electrochemical energy storage, a year of concentrated growth. There are many types of electrochemical energy storage, among which lead-acid batteries, with their very low cost advantage, are widely used in power batteries such as starter batteries for automobiles and electric bicycles, as well as energy storage batteries such as uninterruptible power supplies (UPS). However, their problems include short lifespan and lack of environmental friendliness.
Lithium-ion batteries’ biggest advantage is their high energy density, and their manufacturing cost continues to decrease with the scale effect of the electric vehicle market, making them the most widely used battery type in electrochemical energy storage.

There are several types of flow batteries, the most commonly heard of being vanadium redox flow batteries. Their technical characteristics include long lifespan, good charge and discharge performance, and capacities reaching the MW level, making them suitable for use in power systems, but their manufacturing cost is relatively high.

Sodium-sulfur batteries have a technical prerequisite: their operating temperature must be maintained above 300℃ to keep the electrodes in a molten state. In addition, the high manufacturing cost limits its large-scale application.

Another type is the aluminum battery, which has been frequently mentioned in recent news. Aluminum and graphite are abundant materials, making mass production cheaper than other batteries, and they also have a long lifespan and no organic solvents. Its disadvantage is its relatively low energy density, so careful selection of application scenarios is crucial.

When understanding or using energy storage battery technology, we must first accept the premise that there is no perfect energy storage technology in the world; we are simply making choices for different application scenarios. Each energy storage battery technology has its suitable application scenarios, its advantages, and its limitations.

Source: Green Academy Editorial Office 
https://greenimpact.cc/Articles/detail?cid=2&id=311
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