Sharp's solar LED street lights incorporate seismic detection
September 9, 2008 The argument for switching to solar-powered street lighting seems very clear cut: they run on sunlight, emit no CO2 emissions, provide an off-the grid source of lighting during in an emergency situation and use efficient LED-based light which tends not to attract insects. Sharp Corporation has announced plans to roll-out two new models of solar-powered LED street lights in the Japanese market and these have the added bonus of in-built Seismic Motion Sensors which detect earthquakes of 5 or greater on the Japanese seismic scale and respond by switching to full illumination for two nights.
Sharp introduced its first solar-power LED street light in October 2005 and the latest models provide a significant improvement in brightness. The more powerful of the two, the 160W LN-LW3A1 has a luminous flux of 1,800 lumens, which is around six times higher than the previous model (LN-L19ZA) and rivals the light output from a regular 32-W fluorescent security light according to Sharp's release. This is bright enough to make out the general facial features of a pedestrian on a darkened street at night at a distance of up to four meters away.
The other, slightly shorter (3.7m as opposed to 4m) and less powerful LN-LS2A1 model has a nominal maximum output of 80 W and an instrument-measured luminous flux of 1,200 lumens. Both models use Sharp’s proprietary solar (photovoltaic) modules and high-intensity, long-life mercury free LEDs which last about 10 years before they need replacing. They use a 12 volt, deep-cycle, sealed lead battery that provides enough power in reserve to operate the lighting for a week without sunshine.
In terms of reducing emissions, Sharp estimates that the LN-LW3A1 model eliminates around 48 kg of CO2 emissions per year compared to units powered by conventional utility sources (44kg per year for the LN-LS2A1).
The LEDs don't emit ultraviolet light and this reduces the number of insects that congregate in the vicinity compared to fluorescent or incandescent lights, which tend to attract insects because they produce ultraviolet light in the 350nm wavelength range.
The ability to detect large earthquakes is particularly relevant to the Japanese market where Sharp puts the market for new installations at approximately 100,000 per year. The seismic motion sensor is located in the support pole of the main unit and when it detects shaking above five on the Japanese seismic scale, full nighttime illumination is automatically switched on for two days (or until the battery runs out).