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Sun powers Sharp's LED street lamp

04 Aug 2004

Sharp harnesses solar energy to power its latest LED-based street lamp and illumination panel.

LED-based torches, bicycle lights, traffic signals and car brake lights are beginning to find their way in modern society. But now Sharp has taken this one step further. The firm will launch a solar-powered LED-based illumination panel and street lamp onto the Japanese market by the end of the year.

"By combining two environmentally conscious goals - creating energy using solar cells and saving energy using mercury-free LEDs, Sharp has developed a new generation of lighting products," said the firm in a statement detailing the products.

The transparent illumination panel makes use of what Sharp calls a crystalline thin-film tandem solar cell that combines amorphous silicon and crystalline thin-film silicon technology.

"This new cell achieves a conversion efficiency of 7.3%, approximately 1.5 times higher than conventional amorphous silicon cells," says Sharp. "These cells offer excellent temperature characteristics and because the material can be made as thin as 2 microns, it also helps to conserve resources."

Starting from a base reflecting electrode, the panel comprises a crystalline thin-film silicon solar cell topped by an amorphous silicon solar cell and a transparent electrode.

The panel also contains mercury-free white LEDs which are said to have a lifetime of 40000 hours. According to Sharp's specifications, the illumination intensity at a distance of 2 meters is approximately 30 lux.

Unlike the panel, the 3.7 meter-tall street lamp uses a polycrystalline solar cell and ten 1 W LEDs. The illumination intensity measured directly underneath the lamp at a height of 1 meter above ground is said to be around 18 lux.

"The design conceals a secondary battery and control circuitry mounted inside the pole," says Sharp. "Construction work to install overhead of buried power cables is completely eliminated. The lights can be installed in a single day and turned on immediately. The light will operate even during power interruptions or power failures resulting from natural disasters."

The street lamp will be introduced on September 15 and Sharp plans to produce around 2000 units per month. The suggested retail price is around 500,000 yen ($4500). Made-to-measure LED-based illumination panels could be lighting everything from tourist attractions to railway platforms from November 2004.

Author
Jacqueline Hewett is technology editor on Optics.org and Opto & Laser Europe magazine.

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