Storage technology is now available for different stages of development, varying project scales, and for meeting both short and long-term energy storage needs. Short-term storage technologies can compensate for output fluctuations that only last a few hours, whereas longer term or seasonal storage technologies can bridge the gap over several weeks. There is no “one-size-fits-all” technology for storage. Along the entire supply and demand chain, different storage technologies are required – from second reserve for frequency stability to seasonal storage for several months. A cascade of different storage technologies is required to support: the local integration of power generation from variable renewable energy (VRE) in distribution networks; the grid infrastructure to balance VRE power generation; and self-generation and self-consumption of VRE by customers.
Short-term storage options include batteries, flywheels, compressed air power plants and pump storage power stations with high efficiency factors. The latter is also used for long-term storage. Seasonal storage technologies include hydro pumped storage and the production of hydrogen or renewable methane.

Figure 30 Overview storage capacity of different energy storage systems

From the REN21 report “Renewables Global Futures Report: Great debates towards 100% renewable energy”.