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Technology Frontier

Jul 2008 Issue

Saving Our Planet with Green Lighting

PolyU's newly invented high-power, energy-saving Lighting System

The world is facing many serious threats posed by global warming. Energy consumption is one of the major issues that have raised our concerns recently. If improper use of energy goes on, there will soon be no more blue sky and fresh air.

In view of this, a research team from the Advanced Optics Manufacturing Centre, led by Prof Lee Wing-bun, Chair Professor of the Department of Industrial and Systems Engineering of The Hong Kong Polytechnic University (PolyU) has developed a LED Street Lighting System (Patent Application Number: 200820001242.2 (China)) which is flexible, high-power and energy-saving. Adopting the precision machining technology and superior optics design, this newly invented lighting system is able to serve as a novel, flexible and environmental friendly product to save our planet.

LED is widely used in the past ten years. Nevertheless, without correct and appropriate optics design, its capacity can never be fully optimized. This newly developed high-power LED street lighting system is able to utilize the advantage of LED by incorporating with the freeform optics design to aggrandize the allocation of light. The saving of energy is thus achieved by the effective use of high-power LED on a modular lamp holder, together with the use of ingeniously designed freeform optical surfaces. The novel freeform optical surfaces with non-rotational symmetry lead to uniform light distribution and increase of light emission efficiency up to 90% or above.

The rapid development of wide bandgap semiconductors-related materials and light-emitting devices with one of the concepts of “Green Lighting” applies well on LED lighting system. The promotion of “Green Lighting” concepts began since the late 80s; people were advocating the use of highly-efficient, energy-saving lighting products in order to create a safer and higher quality living conditions as well as to minimize the light pollution. The cost of electric cable can also be reduced since LED needs less electric current which may save energy up to 75% - 90% or even more. Other advantages of the lighting system such as its outstanding outlook, environmental friendliness and the durability of lamp holder will definitely fit the market's need for “Green Lighting”.

Based on the characteristic and uniqueness of LED, the Advanced Optics Manufacturing Centre of PolyU has designed the freeform optics to enhance the quality of optical system, to optimize the product structures and to save energy consumption of LED lighting system. This can also avoid blinding and improve light allocation up to 70% - 80%.

In addition, the modular lamp holder of this new invention is composed of 5 LED heatsink braces in which the high-power LEDs are placed. The 5 LED braces are then installed on a main brace according to the requirement of light allocation. This unique design enables better heat dissipation and facilitates the replacement of defective individual LED without the need to dismantle the lamp holder. The energy required is only one fourth in comparison with the traditional lighting systems. This can facilitate the assembly of the lighting systems and fulfill the national road lighting standard in terms of light distribution. The design can also provide flexibility in making decision on the number of braces and the shape of heatsink ring required based on the power of LED. This development is not only applicable on high-power LED Street Lighting System, but also other LED lighting systems such as interior lighting systems, outdoor lighting systems, decorative and advertisement lighting systems.

Among the 1,000 over inventions from different countries, the PolyU research team won top honours in the 36th International Exhibition of Inventions, New Techniques and Products, Geneva in April 2008. The research team brought home with 3 most prestigious awards: (i) Grand Award - the International Press Prize (ii) Gold Metal and (iii) Special Prize.