As renewable energy adoption accelerates, energy storage solutions face critical challenges in scalability and efficiency. This article explores the three most widely used energy storage technologies, analyzing their strengths and limitations. Originally published by Vu Phong Energy Group, the post provides foundational insights into pumped-storage hydropower, flywheel systems, and batteries. Vu Phong Energy Group adds practical perspectives on their real-world applications, such as Vietnam’s growing demand for grid stability and sustainable energy growth. The discussion includes technical details, case studies, and future trends in energy storage technologies.
With the increasing integration of renewable energy sources for developing a green and sustainable economy, energy storage solutions are becoming critically important, attracting significant investment in research and development. The following discusses some of the most widely utilized and promising energy storage technologies globally, crucial for ensuring grid stability and maximizing the utility of intermittent sources like solar power and wind power.
Pumped-storage hydropower
Pumped-storage hydropower stands as one of the most efficient forms of energy storage currently available, accounting for over 90% of all grid-scale electricity storage worldwide. In this system, electricity is utilized during off-peak hours (when demand is low and surplus generation might be available) to pump water from a lower reservoir to a higher reservoir for storage. During peak demand hours, water is released from the upper reservoir to the lower one, passing through turbines to generate electricity. This process effectively stores potential energy in the water.
The benefits of pumped-storage hydropower include its ability to store massive amounts of electricity, a long operational life (typically 70-80 years), and a high economic return. The primary limitation of this technology is its dependence on suitable geographical terrain—ideally, mountainous regions with significant elevation differences adjacent to large rivers or streams. Countries like Japan, the United States, and China have the highest power output from large-scale pumped-storage hydroelectricity facilities. In Vietnam, there are at least ten high-potential sites for pumped-storage hydropower projects. The Bac Ai Hydroelectricity Facility in Ninh Thuan province is the first such plant under construction in the country. Phase 1 of this project was completed in March 2021, with Construction Joint Stock Company 47 (an associate company of Vu Phong Energy Group) serving as the leading construction contractor. These types of projects are integral to developing robust energy storage systems for renewable energy.
Bac Ai Storage Hydropower Plant in the construction process of Phase 1
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Flywheel system and supercapacitor
Flywheel and supercapacitor systems represent green energy storage technologies that offer rapid charging and high reaction speeds, ideal for applications requiring quick bursts of power. In a flywheel device, energy is stored as the kinetic energy of a rapidly rotating mass. Electricity is used to spin the flywheel at very high rates, sometimes up to 100,000 rpm, thereby increasing its kinetic energy. When energy is needed, the flywheel releases its stored energy by imparting torque to a mechanical load, which in turn slows its rotational speed. This kinetic energy is then converted back into electricity. Flywheels are increasingly employed in wind and solar power systems to store excess energy, acting as a “battery” or a backup generator to provide power when required.
Supercapacitors, in contrast to flywheels, store energy in the form of capacitor potential energy. They retain power through an electrostatic charge, without the chemical reactions involved in battery charging or discharging. Supercapacitors boast several advantages: they can hold a substantial amount of power, are extremely robust, and charge very quickly. However, their voltage drops rapidly due to internal leakage between the two poles, and they do not hold a charge for extended periods. Consequently, when integrated with renewable energy systems, supercapacitors are often combined with traditional batteries. Electricity generated from renewable energy storage options (such as solar and wind power) is initially stored in the supercapacitor, which then gently recharges the main battery. This approach ensures the battery remains fully charged and ready for use, while simultaneously extending the lifespan of the supercapacitors, making them excellent candidates for best energy storage solutions for intermittent renewables.
A 500kW flywheel is being lowered into the tunnel at the production facility of Temporal Power – a flywheel company for testing (Image: Temporal Power)
Types of energy storage batteries
Various energy storage technologies are employed in battery form, including lead-acid batteries (accumulators), lithium-ion batteries, solid-state batteries, and vanadium redox flow batteries. Each type presents distinct characteristics suitable for different applications.
Lead-acid batteries remain widely used due to their low production costs. They are commonly found in automobiles, where they provide the high surge currents needed for engine starting. However, this battery technology has drawbacks, such as the use of hazardous chemicals and a limited battery life (typically only about 300-500 charge and discharge cycles). Consequently, lead-acid batteries are primarily utilized for small-scale power storage requirements.
Lithium-ion battery technology is increasingly prevalent, favored for its substantial storage capacity and low self-discharge rate. These batteries are ubiquitous in modern devices, from domestic electrical appliances and electric vehicles to security systems and various storage applications. Lithium-ion batteries are often regarded as a “key” to unlocking a future free of fossil fuels and are a fundamental component of the Fourth Industrial Revolution, supporting the widespread adoption of renewable energy.
80MW storage station built from commercial Tesla Powerpack 2 Lithium-ion battery blocks, in California (Image: Tesla)
Despite their advantages, lithium-ion batteries do have limitations. For instance, they are reaching a safe energy density limit for certain applications, and the availability of rare earth elements for their manufacturing is a concern. Furthermore, the waste treatment process for manufacturing, destruction, and recycling is quite complex. As a result, multinational corporations and leading research institutions are investing significant human and financial resources into overcoming these limitations and developing new energy storage technologies. Solid-state batteries are one such outcome, predicted to become a viable alternative to lithium-ion batteries due to their enhanced energy storage capability, faster recharging times, and reduced heat emission. The main hurdle for these advanced energy storage technologies is their current lack of widespread commercial availability.
Energy storage is a pivotal element for the sustained expansion of the renewable energy industry. This sector is projected to attract investments totaling USD 620 million by 2040. In Vietnam, energy storage is also gaining traction, particularly as grid infrastructure endeavors to meet the growing potential and demand for renewable energy production. Dr. Nguyen Huy Hoach of the Vietnam Energy Association emphasizes the urgency: “It is past time for us to seriously examine the study and manufacturing of energy storage batteries, particularly for solar power, in order to assure energy security and sustainable growth.” As a key player in the Vietnamese renewable energy sector, Vu Phong Energy Group actively contributes to these discussions and the implementation of reliable energy storage solutions.
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Source: Vu Phong Energy Group JSC
