The application of a multistage optimization technique to determine optimal operating strategies for HVAC systems is explored. Using this technique, the energy efficiency potential of the two most widely used operating strategies, namely, constant- and variable-air-volume, is examined. A single-zone space heating system, with a heat pump, a storage tank, a heating coil, a fan, and ductwork, is simulated. Typical building operation schedules, consisting of off-normal, start-up, and normal occupied periods, are considered. A multistage optimization problem is formulated and solved. Simulation results showing the trade-offs between energy storage, time-of-day rates, building schedules, zone loads, and air distribution strategies are given. It is shown that the variable-air-volume mode of operation in which both air-supply temperature and flow rate are continuously modulated is the most energy efficient strategy.

Units: SI