A refrigeration cycle, an air conditioning system, and a method for controlling a refrigeration cycle are provided. The refrigeration cycle includes an outdoor unit, an indoor unit, a controller, and an inverter. The controller controls a compressor and an outdoor fan of the air conditioning system so as to minimize a total electric power consumption of the air conditioning system. The inverter controls the outdoor fan in a rotation state predicted from a capacity demand in an air conditioning space depending on an operation mode and sensor values. The controller predicts the capacity demand and controls a rotation rate of the outdoor fan based on a prediction of the capacity demand.