Optimal Scheduling with Non-preemptive Air Distribution for Precooling

The in-building section of a HVAC system is a major contributor to its overall energy consumption. This work looks into energy savings at the supply fan (which takes up to 30% of HVAC in-building energy consumption) while energy consumptions at the chilled water pump and the chiller are also taken into account. By elongating the cooling process, the energy consumption can be significantly reduced due to the nonlinear feature of the fan power consumption. To ensure that a computed assignment of mass flow rates is practically feasible, we developed an algorithm to check whether there exist a fan supply pressure and a damper opening to realize these mass flow rates.

We want to determine the minimum supply pressure at the entrance of the supply duct. After choosing any one supply pressure (which should be more than the minimum supply pressure), we can determine the pressure value at each node of the duct network. We are then able to determine the damper opening in each room based on their assigned mass flow rates. Since we are dealing with a scheduling problem, that means we are interested in steady-state mass flow rates or average mass flow rates in the very slow cooling process. By locking onto the values of damper opening and fan supply pressure, steady-state mass flow rates will appear in the duct network