Experimental determination of dynamic models for commercial HVAC loads

Abstract

The intrinsic energy storage built into many electrical loads can be leveraged to ease the integration of time-intermittent renewable generation into the electrical grid. The thermal storage of buildings makes HVAC systems just such a load. Here, we focus on large commercial HVAC systems that are controlled by building automation systems (BAS). Via the BAS, the temperature set points of many or all of the thermostats may be changed in a global, coordinated fashion to modify the power consumption of the HVAC system. Global set point control has many advantages including ease of implementation, maintenance of minimum ventilation requirements and, perhaps more importantly, a known impact on end-user comfort and satisfaction. A significant drawback is that the electrical load is only indirectly controlled via the global set point changes. We present the results of our experiments on the time response of a large commercial HVAC system to global set point control and the reduction of these results to a dynamic model suitable for design of a feedback system to control HVAC electrical load. Scott Backhaus