Optimal supply air temperature with respect to energy use in a constant air volume system

As a general rule, the built environment in the EU uses about 40% of the total energy use. A major part of this is used to provide buildings with the necessary heating and cooling. The energy use of a building can be decreased by proper controlling of the ventilation and indoor climate system. One way to decrease the energy use is to control the supply air temperature. This paper presents a method for an optimal supply air temperature regarding energy use for a ventilation system with constant air volume (CAV). A one-zone office with a CAV system, heating radiators and chilled beams was considered. The optimisation was done by minimising the sum of the different powers to heat the air, heat the radiators, cool the air, cool the chilled beams, run the fan and condense the vapour when the air supply air temperature was cooled below the dew point temperature. The energy saving potential was also analysed when the optimal supply air temperature is applied in a northern European climate. The annual energy use can be decreased significantly if the supply air temperature is optimised. An optimised supply air temperature should be possible with the controllers available on the market but the implementation of such a control strategy requires further research.