A Carbon-Fibre Flywheel for Data-Centre Ride-Through: Rotor Stress, Stored Kinetic Energy, Bearing Loss and Vacuum Housing for Twenty Usable Kilowatt-Hours

This paper sizes a carbon-fibre flywheel storage system for a data centre requiring uninterrupted supply across the interval before standby generation starts. The duty calls for 20 usable electrical kilowatt-hours delivered at a rated power of 200 kilowatts. Working from a stated specific energy of 45 watt-hours per kilogram, an energy density of 60 watt-hours per litre, a usable depth-of-discharge fraction of 0.85, and a round-trip efficiency of 90 percent, the calculation gives a gross stored energy of 23.5 kilowatt-hours, an active-store mass of 523 kilograms, a complete system mass of 941 kilograms, and a complete system volume of 706 litres (0.706 cubic metres). Full discharge at rated power lasts 0.1 hours, and a full recharge takes 0.124 hours at the stated charge power. Losses amount to 2.48 kilowatt-hours per complete cycle, appearing as heat at average rates of 10 kilowatts during charging and 12.4 kilowatts during discharge. Standing loss is 8 percent of the stored energy per day. Life is limited by the calendar limit, giving 6e+03 effective full cycles, about 20 years at the assumed cycling rate, and a lifetime delivered throughput of 120 megawatt-hours. All values are computed from the stated assumptions; the system is a design study and has not been built or measured. Status: SIMULATED, NOT MEASURED.