New flexible solar cell technology developed by a group of engineering researchers at McMaster University, Hamilton, Ontario, has been installed at a bus shelter on campus to power lighting for nighttime transit users. The researchers are hoping the prototype will help boost efforts to commercialize the new technology.

“Our goal is to provide a clean, affordable power source for bus shelters that will let transit companies run Internet-based scheduling updates,” said Adrian Kitai, a professor of engineering physics at McMaster who guided the project. “The solar technology can also be used to light up bus shelter signage and provide lighting for general safety.”

The flexible solar cell project started as a master’s thesis for Wei Zhang, who subsequently worked as an engineer in the Department of Engineering Physics. Julia Zhu, a research technician in the department, and Jesika Briones, a master of engineering entrepreneurship and innovation graduate, also helped develop the initiative.

The ability to bend the solar cells to fit the curved roof of the bus shelter is one of the main features of the technology. The flexibility is achieved by tiling a large number of small silicon elements into an array, mounting them onto a flexible sheet, and connecting them through a proprietary method. The two solar strips installed on the McMaster bus shelter are about 90 centimeters long and 12 centimeters wide. Each strip has 720 1-cm-square solar cells and generates up to 4.5 watts of power.

The group mounted a solar strip at each end of the bus shelter roof and connected it to two energy-efficient, multiLED luminaires. Each lighting fixture uses only 600 milliwatts of power and produces about the same light output as a 3 watt regular tungsten bulb. The lights are bright enough for easy reading.

The solar cells capture sunlight during the day and convert it to electricity to recharge batteries located in each lighting unit. The batteries can hold enough charge to illuminate the shelter for most of a night.

The solar cell research team is monitoring the installation to determine how much solar power is required to fully recharge the batteries based on weather conditions. Winter months will be a particular focus as shorter and overcast days, snow and cold can affect the charging ability of the solar cells and batteries.