The flywheels have a low energy density of 5-30Wh/kg and high power loss due to self-discharge. Flywheels also cannot provide continuous base load supply, unlike batteries or conventional pressurized fluid system energy storage machines, such as pumped-storage hydroelectricity. This efficient design allows for rapid charging and discharging, optimizing energy transfer and reducing mechanical energy loss. By lowering energy loss. . Using energy storage technology can improve the stability and quality of the power grid. Compared with other energy storage systems, FESSs offer numerous advantages, including a long lifespan, exceptional efficiency, high power. . What are the disadvantages of Flywheel energy storage systems? One of the most important issues of flywheel energy storage systems is safety. Here we will explain some of them. While the technology has been around for decades as a form of Uninterrupted Power Supply (UPS) to provide power when main sources fail, it has more recently begun to be. .