The invention relates to a system for storing and outputting thermal energy and a method for operating said system. The system operates according to the Brayton cycle, wherein a heat accumulator (14) is charged by means of a compressor (13) and a cold accumulator (16) is charged by means of turbines (15). Said cycle is reversed for discharging. In addition, according to the invention, the cold accumulator supplies a cooling circuit, which provides the cooling for a superconducting generator (36) by means of a cooling unit (33). A favorable generator weight can thereby be advantageously achieved in particular for wind turbines (22), because the generators are limited regarding the weight thereof due to being housed in the nacelle of the wind power plant (22). Thus, advantageously higher power can be converted in the wind power plant (22).