Welcome to Toyota 'LED Town' (1)
Imagine what it would be like if there is a town illuminated only by LED lamps?
In October 2008, we wrote a story about the residential area "Green Avenue Azabu no Oka" developed by Toyota Smile Life Inc (See related article). The area, which uses only LED lights for all outdoor lighting, is now for sale in lots.
This time, Nikkei Electronics actually visited Azabu no Oka and interviewed Tsutomu Ochiai, lighting designer of Member & Ochiai Design Office, which created the plans and designs for illuminating this residential area, and Toyota Smile Life's employees.
Nearly 1,000 LED lamps used
The LED lights installed in Azabu no Oka illuminate public areas including streets, sidewalks and parks as well as private areas such as the gate, porch and walls of each house. There will be a total of 204 houses built in this residential area when it is completed. Currently, 21 houses (including one model home) have already been completed and other houses are under construction. It will take four years to build all the houses.
When completed, Azabu no Oka will have a total of about 1,000 LED lights with each house having four or five lights. To create relaxing and warm atmosphere, all the LED lights in the area are white LEDs that emit light similar to that of light bulbs and have a color temperature of slightly less than 3,000K.
In addition, the LED lights are laid out to indirectly illuminate wide areas of streets and walls to create a vivid scenery. The LED lights do not directly enter the human eye, preventing "glaring," which is sometimes a concern about LED lights. This measure was adopted because "glaring is unfavorable for residential lighting," Ochiai said.
The illumination of Azabu no Oka was designed by leveraging the characteristics of LED lights, which have a low power consumption and can easily highlight objects through indirect lighting, Ochiai said. LEDs emit light in one direction unlike other light sources that emit light in all directions, making it possible to efficiently provide indirect lighting, he said.
In addition, only LED lights with high luminance efficiency were used to illuminate only the minimum necessary areas. Furthermore, the irradiating areas of LEDs were widened so that people can see wider illuminated areas and feel more brightness than the actual value. Through these methods, power consumption was reduced by about 75% compared with normal light sources, Ochiai said.
LEDs directly connected to AC 100V power source
Japan Outdoor Lighting Mfg Co Ltd supplies the LED lights for Azabu no Oka. Each light incorporates white LED modules manufactured by Toyoda Gosei Co Ltd. About five types of LED modules were used to make the LED lights, according to Japan Outdoor Lighting Mfg.
The LED modules are directly connected to an AC 100V power source, without using an AC-DC converter. Though long life is sometimes a selling point of LED lights, which are resistant to deterioration, some say that the operating life of LEDs is affected by deterioration of power supply circuits. From this perspective, LED lights used in Azabu no Oka are free from such problems.
For lighting LEDs through direct connection with an AC 100V power supply, it is common to connect 20 to 30 LEDs in series. With this method, 3-4V is applied to each LED, making it possible to light LEDs (in the case of GaN-based LEDs such as white and blue LEDs). Though details of the method employed this time were not disclosed, it is possible that this common method was applied to the residential area.
Also, all of the subdivisions are equipped with an exterior LED light as well as an AC 100V outlet, which is intended for plug-in hybrid cars, in the vicinity of the parking area. There is no wonder that Toyota Smile Life Inc, which belongs to the Toyota Group, highlights the environmentally friendly feature that utilizes the next-generation automotive technology.