The Flywheel is the machine that provides the sole means of storage of Mechanical Power. Its primary purpose is to provide smoothing of Electricity requirements and/or to provide the player additional reaction time in case of a brownout. While other methods of energy storage can be built, such as thermal energy storage systems in the form of Steam Hi or Steam Lo in a Fluid Storage, the Flywheel is currently the only machine which stores energy losslessly and with instant access.
Physically it features a longitudinal shaft connected through several large weighted wheels. Energy is thus stored as momentum as a product of their rotational speed and mass.
When the Flywheel's shaft is connected to both a generator and a turbine, it will consume any excess Mechanical Power which is not being used to generate Electricity up until it is fully charged or excess power disappears. At full charge, it is capable of storing 80 MW-seconds worth of energy: more simply, 1 MW of output for 80 seconds, or 80 MW of output for 1 second, or 800 MW of output for 0.1 seconds, or any other multiple thereof. When there is greater demand on the shaft for Electricity generation than is being provided by the generator, the Flywheel will donate its energy to provide the additional Mechanical Power needed.