Experimental investigation of the additional energy consumed by building HVAC systems providing grid ancillary services

Commercial buildings offer vast thermal energy storage capability. Control of building heating, ventilation, and air conditioning (HVAC) systems can potentially be used to balance variations in renewable generation and load. Specifically, buildings can provide ancillary services to the grid by decreasing and increasing consumption with respect to their baseline, making them appear as a battery to the power system operator. However, a recent study has shown that buildings providing these services tend to consume more energy, resulting in a low effective round-trip efficiency. To explore this phenomenon further, experiments were conducted on three buildings on the University of Michigan campus. The buildings were chosen to represent a variety in structure, size, and HVAC system layout. They were instrumented in early summer of 2017 and baseline power and building automation system (BAS) data were collected for several months. The building thermostats were then perturbed through predefined patterns emulating ancillary service events, enabling detailed investigation of the resulting electrical energy consumption. This paper presents experimental results, focusing on the additional energy consumed and effective input/output efficiency. We find that the efficiency of building response depends on the magnitude and polarity of the temperature setpoint changes. Our results are consistent with past experimental results, but inconsistent with past modelling results. This indicates that the models need to be improved in order to capture the energy impacts of ancillary service provision by buildings.