Dynamic Facades with Smart Controls

Smart windows that track the position of the sun and automatically dim to block out glare and heat sound futuristic, but many architects and engineers are already starting to integrate them into the design of new homes and commercial buildings. San Francisco International Airport, for example, is installing one of the largest dynamic window installations in an airport in the world.

Researchers believe that these dynamic windows and shades, combined with smart control systems, such as Model Predictive Control (MPC), could play a key role in our efforts to modernize the electric power grid and reduce the cost of electricity.  Principal Scientific Engineer Christoph Gehbauer led a team of researchers in this work, done in the Building Technology & Urban Systems Division at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

MPC is a form of predictive control algorithm that anticipates changes by predicting environmental conditions. While MPC originated in the chemical process industry, it is now the focus of research for building controls. However, this research often has not included the potential of dynamic facades as an active control element.

By taking into account peak and future pricing information from the utility, MPC can optimize Heating Ventilation and Air Conditioning (HVAC) and daylighting energy usage accordingly. In addition, more precise control of solar-optical parameters can reduce glare and heat inside buildings, leading to increased comfort for occupants. Enhanced with MPC, dynamic facades also have the ability to provide Demand Response (DR) to shift and shed loads at critical times of the day. This can help to align demand and supply of electricity to make the evolving power grid more reliable and resilient, a topic which is catching on nationwide.By including dynamic facades, MPC control can significantly decrease energy costs and increase net load management capabilities of benefit to both building owners and the evolving electrical grid, according to researchers in Berkeley Lab’s Building Technology & Urban Systems (BTUS) Division.

“By proactively anticipating weather and occupancy changes, MPC-based controls are fundamentally different from traditional building controls. Dynamic facade elements and HVAC setpoints can be adjusted ahead of time, which is very beneficial to the control of buildings,” said Gehbauer. “Our hope is that this initial study for California will raise public interest in applying MPC controls for dynamic facades.”

Gehbauer’s team studied the performance of an MPC controller in a south-facing perimeter office with electrochromic windows for a sunny week during summer and winter periods in both Oakland and Burbank, California. They found that MPC strategies reduced total energy cost of a perimeter office by up to 28% and critical coincident peak demand by as much as 43% compared to traditional control methods.