Transportation / Mobility

January 14, 2011


Kokusai Kogyo Introduces White Roofed Buses to Improve Air Conditioning Efficiency

Keywords: Energy Conservation Non-manufacturing industry Transportation / Mobility 

Kokusai Kogyo Co., a Japanese bus transportation company, announced on September 6, 2010, that it had changed the roof color of its bus fleet from lime green to white and has started introducing new buses with white roofs in fiscal 2010. By reflecting direct sunlight, a white roof can curb temperature rises inside the bus and improve air conditioning efficiency in summer, having the end result of reducing carbon dioxide (CO2) emissions.

In August 2010, a field test was conducted to measure the temperature in both types of buses. In an ambient temperature of 40 degrees Celsius, the temperature in a conventional bus rose to 49 degrees, while the temperature in a white-roof bus rose to only 47, showing a cooling effect of two degrees. 

The test also measured the time taken to lower the interior temperature to 35 degrees Celsius (five degrees below the outside temperature) after turning on the air conditioner. It took 30 minutes for a conventional bus to reach this level, while the white roofed bus required only 18 minutes, a 12-minute reduction. This means that the white roofed bus will require less engine idling time to cool interior air before starting service. If this reduction is applied to all of the company's 895 buses, their CO2 emissions in the three summer months are estimated to drop by about 40 tons.

Kokusai Kogyo plans to increase gradually its number of white roofed buses. The company, which received Green Management Certification as an eco-conscious transport business in 2005, will continue to implement environmental initiatives, including introducing fuel-efficient vehicles and promoting eco-driving techniques.

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Posted: 2011/01/14 06:00:15 AM