Integrated control of dynamic facades and distributed energy resources for energy cost minimization in commercial buildings

Controllable window, shading, and daylighting technologies provide an interesting opportunity to manage end use demands on distributed energy resources (DER) in ways that both complements the peak output profile of solar photovoltaic (PV) electricity generation and counteracts the peak demands on the utility grid produced by daytime commercial activities. The objective of this study is to explore whether dynamic facade technologies can play an enabling role in supporting a desired level of electricity service at either minimum operating cost or minimum carbon footprint through optimized integrated control with distributed energy resources. A proof-of-concept control system was developed by approximating non-linearities as piecewise-linear and determining the control state of both the demand and supply side components through global optimization. Annual simulations of a south-facing office zone with switchable electrochromic windows, solar photovoltaic electricity generation, and battery storage indicated that with optimized integrated demand–supply side controls, the utility grid load profile could be lowered to nearly zero demand (5 W/m²) during the daytime when energy costs are highest. A full-scale outdoor field test in Berkeley, California verified this performance, demonstrating that during a week of sunny winter weather, electricity bills could be reduced by 63% compared to heuristic control of electrochromic windows without the photovoltaics and electrical storage. In both the simulated and measured cases, the photovoltaic system was sized to meet the peak perimeter zone load and the electrical storage was sized to be fully discharged by the end of the peak day. Technical and market challenges for achieving reliable optimal control for widespread applications are discussed.