Energy saving and improved comfort by increased air movement
In this study, the potential saving of cooling energy by elevated air speed which can offset the impact of increased room air temperature on occupants’ comfort, as recommended in the present standards (ASHRAE 55 2004, ISO 7730 2005 and EN 15251 2007), was quantified by means of simulations with EnergyPlus software. Fifty-four cases covering six cities (Helsinki, Berlin, Bordeaux, Rome, Jerusalem, Athens), three indoor environment categories - I, II and III (according to standard EN 15251 2007) and three air velocities (<0.2, 0.5 and 0.8 m/s) were simulated. The required cooling/heating energy was calculated assuming a perfectly efficient HVAC system. A cooling energy saving between 17% and 48% and a reduction of the maximum cooling power in the range 10-28% has been obtained. The results reveal that the required power input of the fan is a critical factor for achieving energy saving at elevated room temperature. Under the assumptions of this study, the energy saving may not be achieved with the methods for air speed increase, such as ceiling, standing, tower and desk fans widely used today when the power consumption of the fan is higher than 20 W.