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What are some different types of energy storage?

While batteries are the most common form of energy storage in everyday life, used in phones, tablets, watches, remotes and many other household items, they are not the only type of energy storage device. Each type is suited for different applications. Here are 3 different types of energy storage devices and the different ways they are used.

Batteries

Batteries are electrochemical devices, generating electricity through chemical reactions. Connected with an external circuit, electrons inside the battery flow from one electrode to the other, creating an electrical current that powers the load. Particular combinations of materials do not react in the same way, and each chemistry can store different amounts of energy and operate at different voltage ranges. Lithium-ion batteries are the most commonly used nowadays, favored because of their high capacities, stability, low self-discharge rate, and relatively low need for maintenance. Lithium-ion batteries can also be charged and discharged many times while maintaining its integrity and safety. Alkaline batteries are another common battery chemistry, used to power remotes, flashlights, toys and many other items. Lead-acid batteries are used in cars to start the motor.

In smaller applications, batteries are quite favorable; phones, tablets and other portable devices can last for a day before needing to be recharged. However, when it comes to larger applications such as electric vehicles or grid storage, their capacity still falls short. Batteries are the heaviest and most expensive part of an electric vehicle, and most still do not hold enough capacity to match up to internal-combustion engine vehicles. Further improvements in batteries will eventually even out the playing field, allowing for the same size of batteries to store more energy than before, increasing its competitiveness and viability for large-scale applications. 

Redox flow batteries

Redox flow batteries are another type of chemical cell, but they operate in a completely different way than typical cell batteries. Flow batteries are liquid based, consisting of two half-cells each connected to an electrolyte tank. The half-cells are filled with the cathode and anode solutions and energy is released or store through the continuous circulation of the electrolytes through the half-cells.

Unlike lithium batteries, flow batteries are favorable for larger-scale, albeit, stationary, applications. Energy capacity is easily scalable by using bigger tanks and more concentrated electrolyte solutions. However, since they are typically quite large in size, they are not the best choice for portable applications. With some experts suggesting that they can last up to 30 years, they are being explored as a cost effective alternative for large-scale energy storage.

Supercapacitors 

Supercapacitors, on the other hand, store energy statically rather than chemically. An electric field is created when ions present in the electrolyte migrate from one metal electrode plate to another. 

Supercapacitors are very different from chemical-based energy storage devices. They do not have high energy density, holding only 1 to 30 Wh/kg. However, they have very high power densities, meaning that it can release a large amount of energy, as well as recharge, in a short period of time. 

The nature of the supercapacitor makes it suitable for high-powered applications such as regenerative braking. In grid storage applications, the supercapacitor can act as a buffer to meet peak-load demand, quickly releasing energy into the grid when there is a sudden spike in demand, before the main energy storage can kick in.

Each type of energy storage device has their advantages and limitations. Some are looking at how to combine different types and capitalize on their advantages. Researches at the Queensland University of Technology are working on a hybrid of batteries and supercapacitors to create a device that can have the energy capacity of batteries with the power density of supercapacitors. These kinds of innovations will help push energy storage forward and create more efficient solutions for the future. From batteries, to flow batteries, to supercapacitors, Arbin Instruments has high quality equipment to test different types of solutions. Talk to an expert today to find what suits your research and development needs.

Introduction to Supercapacitors

Though most common, chemical batteries are not the only way to store energy. Another device that is constantly being researched and improved is the supercapacitor. The supercapacitor stores electricity as static rather than chemical energy. While they can’t match up to batteries in energy capacity, they do have clear advantages that secure them a place in our energy-efficient future.

 How does a supercapacitor work

A supercapacitor is made up of two metal electrode plates separated by a thin and porous insulator usually made from carbon, paper or plastic that has been soaked in an electrolyte.

When a charge is applied, ions in the electrolyte migrate toward the plate with the opposite polarity. An electrical field is created by this movement, and energy is stored in the intense electric field between the ions and electrodes that keeps them together. During discharge, electrons move toward the circuit load, releasing the ions from the plate.

What is the difference between supercapacitors and batteries?

While both store energy, the supercapacitor and battery are extremely different. The energy density of the supercapacitor is only around 1 to 30 Wh/kg, compared to the 100 to 265 Wh/kg of modern lithium ion batteries. 

Conversely, the supercapacitor greatly surpasses batteries in power density. Because it does not rely on chemical reactions to release energy, the supercapacitor can release a large amount of energy in a short amount of time. The specific power of a supercapacitor can be up to 10,000 W/kg, while that of general lithium-ion batteries is around 1,000 to 3,000 W/kg.

This also means it can charge very quickly. The average charging time of a supercapacitor is 1-10 seconds, whereas batteries would need to charge for 10 minutes to up to an hour to reach full charge. 

Supercapacitors have a much longer cycle life because the materials do not degrade through the energy release process. In batteries, the chemical reactions would eventually wear down the materials and cause loss of capacity. 

Supercapacitor Applications

Despite all these advantages over batteries, the one thing that greatly holds back supercapacitors are their energy capacity. Nonetheless, they are well suited to high power applications that need to charge and discharge quickly without the need for long-term storage. 

Some small devices that make use of supercapacitors include flashes for cameras and small electrical tools. Because these devices do not need a constant flow of electricity but rather quick bursts of energy, the supercapacitor is perfect in these instances.

Though not energy dense, supercapacitors are used in certain types of electric transportation. In China, some of their electric buses in Shanghai run on supercapacitors, charging up at stops while passengers alight and board. Because they can charge in seconds, buses can keep running for the whole day without worry of running out of charge. Certain trams and light-rails in various places across Europe also make use of the same principle. 

In electric vehicles, supercapacitors can be used in regenerative braking systems, quickly absorbing and releasing energy. In this way, the supercapacitor would support the battery in powering the car, especially during acceleration where a quick burst of power would be needed.

In grid applications, another important area in the future of energy storage, supercapacitors can also be paired with batteries to bridge power gaps when there is a sudden surge of demand for energy. The supercapacitor would act as a buffer between the grid and load, quickly releasing energy when there is a sudden surge of demand so as to limit disruption of the energy flow, as well as the strain on the grid.

Testing supercapacitors

Because of supercapacitors’ many advantages, exploring ways they can play a role in energy storage is an important part of the conversation. Arbin has high quality supercapacitor testing equipment for research and development purposes. Like all of our other equipment, the supercapacitor test systems support real-world simulation charge/discharge cycles. Available for cell, module and pack testing up to 800v.