Control of supply air temperature and outdoor airflow and its effect on energy use in a variable air volume system

A VAV system in a commercial office building in central New Jersey has been modeled, with DOE-2 and a variable-base bin method, to assess control strategies that lead to reduce HVAC costs with no decrease in comfort. The goal is to minimize the sum of fan and heating/cooling power while providing sufficient air to maintain desired office temperatures and air quality. With the 55 F (12.8/sup 0/C) supply air temperature specified by the HVAC designer, fan energy is kept low at the expense of the chillers. Raising the supply air temperature to 60 F (15.6/sup 0/C) makes more use of outdoor air in temperate weather and reduces the chiller energy consumption by a predicted 33 MWh/year while increasing fan power by only 4 MWh, for a net savings in combined fan and chiller power of 23%. An additional 9 MWh of net fan and chiller energy savings can be achieved by varying the supply air temperature with outdoor temperature.