Energy supply security is an increasing concern for many countries worldwide as more of the energy generation shifts from fossil fuels to renewables. Oil, natural gas and coal may be finite resources but can be stored in their natural state, while energy generated by solar and wind systems are infinite but due to their intermittency, require long duration energy storage solutions (LDES) to keep supply and demand in balance across the grid.
The share of renewables in global electricity generation is expected to expand from 32% in 2024 to 43% by 2030, while the share of variable renewable energy sources is set to almost double, reaching 28%, according to the International Energy Agency (IEA).
Regardless of source, delivery of the electrical energy to the users depends on cabled grids for transmission and distribution. The IEA highlights grid congestion as “a critical bottleneck” in many regions, “slowing the deployment of new electricity generation, storage and demand.” The organization also stresses that meeting the increasing demand for electricity requires annual investment in grids to rise by 50% by 2030, with storage of “an increasingly weather-dependent mix of power generation sources” a priority.
Regarding storage of the energy, there are two principal technologies in operation; pumped hydro and battery energy storage systems
With pumped hydro, water is pumped uphill when energy is cheap and released to drive turbines and generate power when energy is expensive. It remains the only technology capable today of storing gigawatt (GW), let alone terawatt (TW) hours. Yet conventional pumped hydro is only suitable in places with mountainous geography or large water reservoirs. In other places, lithium-ion batteries are the preferred form of energy storage. Traditional lithium-ion batteries are, however, limited by capacity (typically 4–6 hours) and lifespan caused by constant charge-discharge cycles. Lithium-ion batteries are also reliant on critical minerals and the risk of thermal runaway. Consequently, the search for new or enhanced LDES is moving at pace and comes with trade-offs in cost, efficiency, and scalability.
Various other types of rechargeable battery technologies are under development at different stages, such as:
Flow batteries that use two different chemical solutions (electrolytes) to store energy.
Compressed air energy storage (CAES), which works by compressing ambient air and storing it under pressure underground using surplus or off-peak power.
Thermal energy storage technologies, such as using a closed-loop system of molten salts and steam, and also Concentrated Solar Power (CSP) systems which store excess heat energy gathered during the day collected by various types of focusing mirrors.
Renewable energy converted into hydrogen for longer term storage via electrolysis.
Within the IEC, there is work in process with standards for the different technologies. Innovation in the field of energy storage is, however, rapid, so one must ensure that the standardization is not made too narrowly around today’s technologies and become barriers for tomorrow’s technologies.
Further information about this theme may be seen here.
(This article is based on an article in IEC’s etech newsletter; edited by T.Sollie)