Given the urgency of climate change mitigation, it is crucial to increase the practical utilization of renewable energy. However, high uncertainty and large fluctuation of variable renewable energy create enormous challenges to increasing the penetration of renewable energy. Various energy storage technologies have been applied to renewable energy to handle the fluctuation and uncertainty problem. To enrich the knowledge about the effects o. Given the urgency of climate change mitigation, it is crucial to increase the practical utilization of renewable energy. However, high uncertainty and large fluctuation of variable renewable energy create enormous challenges to increasing the penetration of renewable energy. Various energy storage technologies have been applied to renewable energy to handle the fluctuation and uncertainty problem. To enrich the knowledge about the effects of energy storage technologies, this paper performs a comprehensive overview of the applications of various energy storage technologies and evaluates their capabilities of mitigating the fluctuation and uncertainty of renewable energy. The main techno-economic characteristics of the energy storage technologies, including: super-conducting magnetic energy storage, flywheel energy storage, redox flow batteries, compressed air energy storage, pump hydro storage and lithium-ion batteries, are analyzed. Moreover, supercapacitor storage, sodium‑sulfur batteries, lead-acid batteries and nickel‑cadmium batteries are also discussed in this study.••••The fluctuation and uncertainty in integrated energy systems are quantitatively defined.••Various energy storage technologies for handling fluctuations and uncertainties are overviewed.••The capabilities of various energy storage technologies for handling fluctuations and uncertainties are evaluated.••The development of energy storage technology is discussed.CAEScompressed air energy storageESSenergy storage systemESTenergy storage technologyFESflywheel energy storageHESShybrid energy storage systemIESEnergy storageIntegrated energy systemUncertaintyFluctuationIncreasing demand for energy and concerns about climate change stimulate the growth in renewable energy. According to the IRENA's statistics, the world's total installed capacity of renewable energy increased from 1,223,533 MW in 2010 to 2,532,866 MW in 2019, and over 80% of the world's electricity could be supplied by renewable sources by 2050. Wind energy and solar energy are the two most common types of renewable energy. The installed capacity of wind and solar energy in 2019 was 5.43 times as big as their size nine years ago and was expected to account for 52% of total electricity generation by 2050. However, due to always-changing natural and meteorological conditions, wind energy and solar energy are characterized by high uncertainty, which is usually represented by the inaccuracy of forecasts, and large fluctuation, which describes the instability of outputs. The increase in solar photovoltaic (PV) and wind power raises the requirement for flexible operation of power systems to an unprecedented level. Responding to the problems, many countries have issued grid codes for intaking renewable energy, and enormous research efforts have been paid to overcome the uncertainty and fluctuation problem,,.To technically resolve the problems of fluctuation and uncertainty, there are mainly two types of method: one is to smooth electricity transmission by contr.
