Skip to main content

Rensselaer Polytechnic Institute (RPI)

Scientists Develop Simple Alternative for Harvesting Daylight and Saving Energy

April 19, 2006

Scientists Develop Simple Alternative for Harvesting Daylight and Saving Energy

Troy, N.Y. — Scientists at Rensselaer Polytechnic Institute’s Lighting Research Center (LRC) have developed a simple, cost-effective, energy-saving device designed to harvest daylight automatically. The DaySwitch™ was designed as an alternative to traditional dimming ballast systems that adjust light levels by reducing the lamp current.

The DaySwitch™ consists of a photosensor (bottom) that measures daylight levels and sends a signal to the microcontroller (top) that switches the luminaire on and off.
Photo by Rensselaer/LRC

“The DaySwitch™ is designed to build end-use efficiency by reducing light energy usage in commercial buildings and maintaining occupant satisfaction,” said Peter Morante, director of energy programs at the LRC. “It is estimated that the DaySwitch™ will be able to reduce lighting energy consumption by 30 percent in buildings with significant daylight contribution through windows or skylights, allowing for a payback period of approximately three years.”

Typical dimming systems have several drawbacks, including high initial cost and difficult photosensor programming and installation. As a result, dimming systems have not permeated the market, according to Morante.

The DaySwitch™ development team, led by Morante and Richard Pysar, an electronic design engineer at the LRC, created a low-cost prototype to control individual light fixtures, unlike traditional systems where one sensor controls numerous lamps. Individual control provides flexibility for on/off control and simple installation.

The DaySwitch™ works with all conventional fluorescent ballasts—the device regulating voltage and current supplied to the lamp. Because of its simple circuitry and on/off operation, the cost to produce the device is minimal and far less expensive than traditional daylighting control systems that utilize dimming ballasts, according to the LRC research team. 

“The DaySwitch™ offers a low cost option for harvesting daylight that is simple, accurate, and convenient to install,” said Andrew Bierman, senior research scientist at the LRC. “By taking advantage of natural light and using systems like the DaySwitch™, we can significantly reduce energy consumption and the growing strain on the nation’s power grid.”

The United States Department of Energy estimates that lighting accounts for one-quarter of the total energy consumed by U.S. commercial businesses.

How the DaySwitch™ works
The DaySwitch™ eliminates wasted or unwanted electric light by sensing when sufficient daylight is available to take the place of electric light, and then responds by turning off the fixture. When daylight decreases, the device turns the light back on. 

A built-in microcontroller automatically calibrates the DaySwitch™, allowing for self-commissioning and easy installation and maintenance. The design also includes a light-to-frequency photodiode that, together with the microcontroller, provides accuracy over a wide range of light levels (1 to 12,000 lux).

According to the LRC research team, commercial customers can expect a two- to five-year payback in retrofit applications and a one- to three-year payback when the DaySwitch™ is built into fixtures installed in new construction.

Project partners
The LRC recently received a $198,745 award from the New York State Energy Research and Development Authority (NYSERDA) to further develop, demonstrate, and evaluate the DaySwitch™, all in an effort to commercialize the device. The LRC is partnering with Dynamic Hybrids, Inc., of Syracuse, New York, to manufacture the DaySwitch™ prototype and is currently seeking a demonstration site within New York state to install and evaluate the device.

Initial research into simple concepts for daylight harvesting was funded by the Daylight Dividends program, a national effort, administered by the LRC, to educate and provide evidence, guidance, and perspectives supporting the use of daylighting in commercial and educational facilities. Daylight Dividends sponsors include California Energy Commission, Connecticut Light and Power Company, Efficiency Vermont, Iowa Energy Center, NYSERDA, North Carolina Daylighting Consortium, Northwest Energy Efficiency Alliance, and the U.S. Department of Energy. The initial research results are published in Lighting Research & Technology volume 37, issue 1. 

The LRC also received a $75,000 Energy Innovations Small Grant (EISG) to develop the first DaySwitch™ prototype. EISG is a California Energy Commission Public Interest Energy Research (PIER) program designed to establish the feasibility of new, innovative energy concepts.  

About the Lighting Research Center
The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute of Troy, N.Y., and is the leading university-based research center devoted to lighting. The LRC offers the world’s premier graduate education in lighting, including one- and two-year master’s programs and a Ph.D. program. Since 1988 the LRC has built an international reputation as a reliable source for objective information about lighting technologies, applications, and products. The LRC also provides training programs for government agencies, utilities, contractors, lighting designers, and other lighting professionals. For more information, visit

Contact: Mary Cimo
Phone: (518) 687-7174


Reeve Hamilton
Director of Media Relations and Communications

(518) 833-4277

For general inquiries:

About Rensselaer Polytechnic Institute

Founded in 1824, Rensselaer Polytechnic Institute is America’s first technological research university. Rensselaer encompasses five schools, 32 research centers, more than 145 academic programs, and a dynamic community made up of more than 7,900 students and more than 100,000 living alumni. Rensselaer faculty and alumni include more than 145 National Academy members, six members of the National Inventors Hall of Fame, six National Medal of Technology winners, five National Medal of Science winners, and a Nobel Prize winner in Physics. With nearly 200 years of experience advancing scientific and technological knowledge, Rensselaer remains focused on addressing global challenges with a spirit of ingenuity and collaboration.