Reducing light pollution

US researchers have developed a system that uses about 20 per cent of the energy of conventional parking lighting systems while reducing light pollution.

Michael Siminovitch, a director of UC Davis’ California Lighting Technology Center, and his colleagues have developed a novel system that uses about 20 per cent of the energy of conventional parking lighting systems while reducing light pollution.

The system, unveiled this month in a UC Davis parking garage after two years of development and field testing, is a highly efficient and innovative package of technologies.

The system includes light-emitting diode (LED) lights that give off bright white light but use little electricity.

Each lighting fixture – called a luminaire – has three light bars containing 60 LEDs.

Compared to conventional metal-halide lights, LED lights use less power (85W versus 175W), last longer and contain no mercury.

The system also includes motion sensors that detect the motion of a person or vehicle within about 35ft.

When no motion is detected for a designated period of time (30 seconds to 30 minutes), the sensor switches the LED light from a high level to a low level that uses half the energy.

Even low level is bright enough to provide plenty of light for people entering the garage. And the switch from low brightness to high signals to people using the garage that there is another car or person moving nearby – providing information to security personnel too.

Siminovitch said: ‘Switching to LED lights and adding bi-level activity-sensing technology yields energy savings for the project of 50 per cent when the lights are at full power and 80 per cent when they are in low mode.

‘As for maintenance savings, we project they will be 42 per cent of what we spent on the fixtures that were replaced.’

He added: ‘Even at half power, the LED fixtures are delivering plenty of light to the space. We may be able to cut levels further, saving even more electricity and lengthening fixture lifetimes.

The new lighting system, part of UC Davis’ Smart Lighting Initiative, is already serving six UC Davis sites (three parking areas, one pathway network and two building exteriors), as well as Sacramento State University and Arcade Creek Park in Sacramento.

It is also being adopted by other users including UC Santa Barbara, Cal Poly San Luis Obispo, Tianjin Polytechnic University in China, University of Notre Dame, North Carolina State University and the University of Arkansas.

Michael Siminovitch, director of UC Davis’ California Lighting Technology Center, demonstrates how the lights switch from low power to high when they sense that someone is walking or driving nearby