Determination of Cost Savings Using Variable Speed Fans for Cooling Servers

This paper addresses how different control schemes for fans used to cool servers can affect energy consumption. An analytical model that includes physical parameters of a heat source/heat sink/fan was developed. As a case study, an air duct with a DC fan, heat sink and heat source was built. Experiments were performed to generate physical parameters used as inputs to the model. Three fan control methods - variable speed, on/off and low/high speed fan controls - were modelled using MATLAB and Simulink to compare fan speed behavior, target chip desired temperature and saving in fan electrical energy. Potential savings in air conditioning power were also estimated. Simulation results show that variable speed fan control can save more energy than other fan control types, especially on/off control. The model developed can also be used by practitioners to explore the trade-offs between fan and air conditioning power.