Energy storage landscape 

According to data from the International Energy Agency (IEA), the share of renewable energy in global electricity generation is projected to increase from 32% in 2024 to 43% in 2030, while the share of variable renewable energy is expected to nearly double, reaching 28%. At the same time, by 2030, the growth rate of global electricity demand is projected to be at least 2.5 times that of the overall energy demand growth rate. By then, renewable energy and nuclear energy will account for half of the total electricity supply. 

The IEA emphasizes that grid congestion is a "critical bottleneck" in many regions, "hindering the deployment of new power generation, energy storage and demand-side resources." The organization also stresses that to meet the growing electricity demand, the annual investment in the grid needs to increase by 50% by 2030, and energy storage for "an increasingly weather-dependent power generation mix" is a priority. 

Two main energy storage technologies are already in operation. Pumped hydro storage (PHS) and battery energy storage systems (BESS) are regarded by investors as key low-carbon systems for complementing renewable energy assets. 

Hydroelectric pumped storage utilizes cheap electricity to pump water to high altitudes, and releases the water to drive turbines to generate electricity when electricity is expensive. It remains the only technology capable of storing gigawatt-hours, or even terawatt-hours of energy. Many countries choose to modernize and reinvest in existing systems, such as this project in Wales, or are planning new projects. A proposed development project in Scotland will more than double the existing electricity storage capacity in the UK. If approved, this will be the country's first large-scale pumped storage project in over 40 years. 

However, traditional pumped hydro storage is not suitable for countries lacking mountainous terrain or large reservoirs. In these cases, lithium-ion batteries are the preferred form of energy storage. But using batteries also has drawbacks. Traditional lithium-ion batteries are limited by their capacity (typically 4-6 hours) and the lifespan issues caused by continuous charging and discharging cycles. 

"Batteries have made significant progress, but it is difficult to scale them up to the level required by the national power grid," said Tony Sample, the chairperson of IEC TC 82, which is responsible for formulating standards for solar photovoltaic systems. "Longer-term energy storage solutions - such as hydrogen - will be essential, especially for industries where electrification is not feasible, such as the aviation industry." 

Lithium-ion batteries are widely used in many applications, but they also have other drawbacks, including dependence on key minerals and the risk of thermal runaway. Therefore, the search for new or improved long-duration energy storage (LDES) technologies is accelerating. Each method has trade-offs in terms of cost, efficiency, and scalability. 

According to Christian Noce, the chairperson of IEC TC 120, this technical committee is responsible for formulating standards for energy storage systems. "An EES system is very complex and consists of multiple subsystems and components. That's why IEC TC 120 adopts a system-level approach to create a universal framework for grid-connected EES systems, making the design, operation and safety more consistent and efficient." 

Fluid battery 

A flow battery is a rechargeable battery that uses two different chemical solutions (electrolytes) to store energy. These electrolytes are stored in external tanks. This technology is scalable as the storage capacity can be increased by enlarging the size of the tanks. It is also safer than lithium-ion batteries as it has no risk of explosion. 

The global market value of this technology will be 1.22 billion US dollars in 2026 and is expected to reach 2.88 billion US dollars by 2034. The current commercial flow batteries are based on vanadium and zinc chemical systems. Future commercial deployments include projects in Sweden, while the largest liquid flow battery in Europe is under construction in Laufenburg, Germany, with an energy storage capacity of over 1.6 GWh and an output power of over 800 MW. 

The Netherlands has developed a new type of flow battery. During charging, the salt water solution generates acidic and alkaline liquids, which are then stored in separate tanks. It is claimed that an Aquabattery can operate for 20 years and store energy for up to 100 hours. However, the flow battery technology requires a significant initial investment in tanks and electrolytes, and has a lower energy density compared to lithium-ion batteries.