Get on the bus

19 Jun 2009

Prototype solar power source is put through its paces for possible mass-transit applications.

Brighter bus shelter

McMaster University in Canada has installed solar cells that fit the curved roof of its campus bus shelters in a bid to commercialize the prototype design and aid night-time travellers.

"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 headed up the project. "The solar technology can also be used to light up bus-shelter signage and provide lighting for general safety."

The ability to bend the solar cells to fit the curved roof of the bus shelter is a key feature 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.

In terms of the specifics, two solar strips (each about 90 cm long and 12 cm wide) are installed on the bus-shelter roof. Each strip comprises 720 1 cm² solar cells and generates up to 4.5 W of power.

One solar strip is mounted at each end of the roof and connected to two energy-efficient, multi-LED light fixtures. Each light fixture uses only 600 mW of power and produces about the same light output as a regular 3 W tungsten bulb.

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 light the shelter for most of the night.

The McMaster team is now monitoring the installation to determine how much solar power is required to fully recharge the batteries based on varying weather conditions.

The flexible-solar-cell project started out as a master's thesis for Wei Zhang, who subsequently worked as an engineer in the university's department of engineering physics. Julia Zhu, a research technician in the department, and Jesika Briones, a master's of engineering entrepreneurship and innovation graduate, also helped with the initiative.