Solar-Powered Window Sensors for Smarter Buildings

Sensors are the next step needed on the road to developing smarter buildings, and a new, very-low power device has been developed to allow information about window to be transmitted to a control system for a building without a need for extra building wiring or power supply. The sensors are self-powered by the sun through a tiny solar cell on top of the unit.

The sensors, developed by the Fraunhofer Institute, are small enough to fit inside the gap between the two panes of a typical double-pane window. The solar cell itself and the sensor electronics and transmitter are so small that they sit flat on the spacer and do not block any of the visibility between the two panes.

The sensor is able to detect when a window is opened or closed, and can transmit that information wirelessly to a building management system (BMS) controlling the building. Used in conjunction with motorized operators for the windows, this can allow for a building to be opened up for fresh air when conditions permit, and to close the building back up when needed, even if the room is unoccupied.

The sensor can also serve an intrusion detection function, if the window is jostled or changes position unexpectedly. The sensor uses solar power, and is able to charge an internal battery to allow it to continue to operate even at night (currently able to span about 30 hours of darkness). Putting the sensor package between the panes also minimizes the problems that could come with occupants tampering with the sensor.

Since a single room could have many windows, the wiring to provide this level of information to a BMS system has been prohibitive in most cases. But this could be a point where a new degree of smart materials helps make a building more responsive and allow occupants a greater degree of control over their environment in conjunction with an intelligently managed building system.

Originally published at on September 21, 2015.