Bright Future for MTR Travelers

Some MTR passengers may have found reading on their journey more illuminating, after the MTR Corporation started to install High Brightness Light Emitting Diodes (HB-LEDs) array modules for saloon lighting in one of its train carriages on the Tsuen Wan Line in mid October. Whiter and brighter light giving sharper definition to printed words is just one of the advantages provided by this new form of indoor lighting. Energy efficiency, longer service life and greater environmental friendliness are among other benefits provided. This new technology is being adapted for use by the MTR in a joint project with HKUST. Such an application is among the pioneers in large scale solid state lighting (SSL) around the world.

Recent tests by HKUST show that the newly developed HB-LED array modules consume 30% less electricity than traditional fluorescent light tubes used in households. In MTR carriages, the saving is around 20% given the energy-saving arrangements already in place. In addition, HB-LEDs are ‘cold light’ sources, which generate no heat radiation, resulting in further saving on air-conditioning cost. HB-LEDs typically last up to 100,000 hours, which offer 10+ years of service life in MTR trains. This is at least six times longer than the existing fluorescent light tubes, leading to lower replacement costs and less waste.

HKUST project leader Professor Ricky Lee, Department of Mechanical Engineering, said that each newly developed lighting module consists of 56 HB-LEDs, with the light intensity generated being equivalent to the original 30W fluorescent light tube. He also indicated the biggest challenges in this project have been to optimize electrical power consumption and optical output, and to generate an acceptable uniform light field, subject to several existing constraints. Through extensive testing and analysis, HKUST’s R&D team designed and fabricated HB-LEDs array modules that could generate sufficient light intensity, using the original power supply, and fit into the limited space inside the train’s existing lighting bay. The mounting and pitch of components and the arrangement of driving circuits have been optimised for a uniform light field, minimal electrical power consumption and best thermal management.

“The Corporation is the first public transport operator in Hong Kong to try out HB-LEDs as indoor lighting,” said Mr Wilfred Lau, Head of Operations of the MTR Corporation. “The company is very pleased to work with HKUST on this project.” The current pilot run is set for 12 months during which period the MTR will monitor the durability and efficiency of this new lighting technology. The Corporation will then decide whether to replace all in-train lighting with HB-LEDs and also consider this SSL technology for its station lighting and advertising panels. According to the rail operator, there are more than 25,400 fluorescent lights on the MTR's 106 trains, while there are an average 1,300 lights in each of the 50 stations. In addition to opening up a huge potential market in this region, this “HB-LEDs array modules for SSL” project also reflects HKUST is playing a key role in the development of Hong Kong by forging partnerships with business and industry.