Science@Berkeley Lab nameplate Berkeley Lab logo
January, 2007
Inexpensive Wireless Lighting Could Save Money and Cut Greenhouse Gases

WiLight is a new wireless lighting control system that dims or switches overhead lighting according to the occupants' preferences, or in response to building-wide demand. Developed by two researchers in Berkeley Lab's Environmental Energy Technologies Division (EETD), Francis Rubinstein and Dennis DiBartolomeo, WiLight was designed to be low cost, to encourage building owners to retrofit facilities for energy efficiency.

Image Spacer image
Francis Rubinstein with the transceiver of the WiLight wireless lighting-control system. (Photo by Anthony Ma, EETD)

Using a battery-less transmitter instead of a normal wall switch, a building occupant can switch and dim overhead lighting wirelessly. Using a radio bridge, a building manager can manually control the lighting system. Or the lights can dim or switch off automatically, in response to a signal from a demand-response server.

The WiLight transmitter uses a clever energy-scavenging technique developed by EnOcean Inc. to eliminate the need for batteries: the transmitter harvests the mechanical energy of the user's clicking on the switch to charge up a radio transmitter that signals the transceiver to dim or switch the lights. This avoids the maintenance headache of replacing batteries and reduces the environmental impact of the system.

Besides responding to individual occupants' needs, WiLight can read a wireless signal from the building's demand-response system to automatically dim down lighting to a lower level during a grid emergency, or when electricity prices are high. To accomplish this, the WiLight system was designed to work with another technology currently in development at Berkeley Lab, funded by the California Energy Commission's Demand Response Research Center. This new technology, called CLIR, allows buildings to automatically monitor the status of the electricity grid over the internet, via signals from utility servers. If the grid nears an overloaded emergency state, the CLIR box uses the WiLight radio bridge to send a radio frequency signal to the building indicating the seriousness of the crisis, whether moderate or severe. Nonessential energy uses are reduced, for example by lowering building lighting levels or raising thermostat settings on air conditioning units. WiLight reads the signals and lowers the lighting to preset levels.

The economical WiLight system accepts a variety of inputs to increase efficiency and reduce energy use of building lighting.

Many buildings in California now have bi-level switching, as required by Title 24 energy efficiency standards. This means that the lights in a room can be all on, half on, or all off. WiLight works with the bi-level circuitry to allow the demand-response technology to automatically choose the lower light level during a grid emergency. If a user turns on a light in the room during the emergency, WiLight allows the light to turn on to the lower level of lighting, but not to the maximum level until the grid emergency is over.

The system is compatible with existing lighting products and protocols and can work with emerging wireless technologies. "This makes WiLight an extremely inexpensive control system for retrofitting large commercial buildings," says Rubinstein, "since the cost of additional wiring has been the major disincentive to lighting control systems in large existing commercial spaces."

Commercial Building Energy Use

Berkeley Lab studies suggest that lighting controls could reduce energy used for lighting in commercial buildings by nearly one-half, by automatically turning off or lowering electric lighting when there is sufficient daylight to make electric lights unnecessary.

There are 60 billion square feet of commercial floor space nationally. Rubinstein estimates that if 30 percent of commercial buildings adopt lighting control systems by 2025 the nation could reduce its energy use by 700 billion kilowatt-hours, saving about $50 billion and reducing greenhouse gas emissions by 140 million metric tons — equivalent to the emission of 93 million automobiles.

WiLight's promise was acknowledged early on by its selection as a finalist in the 2006 Technology Breakthrough Award Competition managed by the Center for Entrepreneurship & Technology (CET) of UC Berkeley's College of Engineering.

Berkeley Lab's development of WiLight technology was funded by the California Energy Commission's Public Interest Energy Research (PIER) Program and the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy.