On-line control strategies of supply air temperature for multizone VAV air-conditioning system

Two on-line optimal control strategies were proposed to save energy consumption of multizone VAV air-conditioning system. One is on-line optimal reset of supply air temperature set-point, which uses the signal of local controller of VAV damper as index of indoor relative load; another is on-line optimal on/off control of CAV boxes, which are designed for external zones because of solar heat gains. The two strategies were validated by the simulation tests under many kinds of weather conditions. The results show that comparing with the conventional control strategy, both of them can save energy and maintain indoor thermal comfort. In the partial load condition, especially in the condition of low outdoor load, they can not only save the overall energy consumption, but also make indoor air more comfortable.