Low-frequency power-grid ancillary services from commercial building HVAC systems

With the introduction of volatile renewable energy sources into the grid, the need for inexpensive ancillary service increases. We propose a method to provide ancillary service by using the flexibility of demand in commercial building HVAC (Heating, Ventilation, Air-Conditioning) systems. In particular, we show how a regulation command transmitted by a balancing authority can be tracked by varying the cooling demand in commercial buildings in real-time. A key idea here is the bandwidth limitation of the regulation signal, which allows the building's HVAC system to provide this service with little effect on the indoor climate. The proposed control scheme can be applied on any building with a VAV (Variable Air Volume) system and on-site chiller(s). Simple calculations show that the commercial buildings in the U.S. can provide 47 GW of regulation reserves in the frequency band f ∈ [1=(60 min);1=(3 min)] with virtually no change in the indoor climate, while meeting current ISO/RTO standards for regulation.