LED Street Lights – Potential Risks on the Environment and the Power Industry Press Conference

ledThe ‘Hong Kong Climate Action Plan 2030+’ shows Hong Kong’s commitment to saving energy and reducing carbon emissions. It states that by 2030, Hong Kong will reduce its carbon emissions by 65-70% compared to 2005. As part of this initiative, Hong Kong’s Highways Department is proposing to transition its outdoor street lights to LED lights. However, World Green Organisation (WGO) has found that when outdoor LED lights are exposed to weathers such as rain and thunderstorm, it could result in heat dissipation problems and harmonic distortion (noise). In result, the lifespan of LED lights could become shorter, which means that they would need to be frequently replaced, resulting in an increased amount of e-waste. This might also affect the stability of the power grid.

The use of outside LED lamps is following the international trend
Many international governments have long since switched from traditional high-intensity discharge lamps (HID) to LED lights for their outside street lights. In fact, the Hong Kong Highways Department piloted an outdoor LED lighting program in 2009. Although LED lights outperformed the HID lights in terms of energy-saving and colour effects, LED lights were still much more expensive and not very cost-effective which is why the LED street lights were not implemented on a large scale. In recent years, technological advancements in LED lights have enabled the price to be more affordable. In light of this, the government is starting the transition to switching all HID street lights in the road, sidewalks, and cycling paths to LED lights. In 5-7 years, the government hopes to replace 4,500 overhead and roadside floodlights and 10,000 footbridge and tunnel lights with LED lights in order to save energy and reduce carbon emissions.

LED lights’ technology has become more advanced since the 60’s. The energy efficiency of LED lights has turned more mature that it now can save more than 40%-70% of energy than traditional HID lights.

Improper use of LED lights can lead to environmental risks and problems to the power grid
WGO found that the improper use of outdoor LED lights may end up hurting the environment and affecting the stability of the power grid. WGO hopes to raise public awareness of the potential risks and propose solutions when implementing a city-wide replacement to LED street lights by examining international standards and past industry experiences. WGO will also work with Intertek Hong Kong to publish materials on introducing the technologies of outdoor LED street lights.

LED lights have become much more technically advanced since the 60’s. In the past, heat dissipation problem existed in LED lights and as a result the light source module was being damaged. With technological advancements, cooling technologies have greatly improved, which significantly helped dissipate the heat of the lights. The energy efficacy of indoor LED lights has also greatly improved, including the lower colour temperature LED lights (such as yellow LED lights). In fact, indoor LED lights have proven to save more than 40%-70% of energy than traditional HID lights.

To resolve heat dissipation problem of outdoor LED lights, it is recommended to relocate the power supply system away from the LED light source module, which could reduce the needs for road closure and using scaffolding to repair them.

Outdoor weather can cause increased harmonic distortions and affect the stability of power supply
Being able to successfully operate LED lights indoors is very different from operating it outdoors. Outdoor lamps are subject to weather changes and other environmental factors which can affect the stability of the LED light performance. In addition, installing the LED lights outdoors may also cause environmental problems.

The current outdoor LED lamp design is composed of three main parts; 1) driver/ light source module, 2) LED light source, and 3) switching mode power supply (SMPS). They all have different requirements and conditions to fulfil in order to ensure that the LED lights are safe to use outdoors. There are three biggest problems that must be tackled. First of all, since the lamp is outdoors, the SMPS, full of components like circuits and electrolytic capacitors, is exposed to rainfall, thunderstorms, or dust, which could accelerate the aging of these components and increase the probability of parts failing. In other words, the lifespan of the whole LED lamp could decrease and lower the efficiency of the heat dissipation, which increases the risk of heat related problems such as induction thunder or other overvoltage intrusions. The chance of causing harmonics, in which is a frequency multiple of the safe fundamental frequency, could also increase, resulting in total harmonic distortions. The harmonics will increase the amount of current flow in conductors and raise the temperature in transformer, switch and cables and so on, possibly affecting the stability of the whole power grid.

To reduce the interference of harmonic, WGO recommends increasing of the capacity of filters in the SMP, or considering using the design of HID lamps as it uses a passive type driver that does not contain an active oscillating circuit. The government should also set up a stricter standard that regulate the percentage of harmonics can produce. Although currently, the government has certain regulations on harmonics of outdoor LED lamps (BS EN 61000-3-2 and BS EN 61000-3-30), it was often doubted that after factory leave, the quality of which can no longer be guaranteed for fulfilling the regulation completely. It is suggested to include quality test after the factory leave. Regarding the issue of thunderstorm, the power supply system could still be damaged if the protection against lightning could not pass all the energy of lightning impulse to the ground. WGO therefore stresses the importance of setting up an effective grounding system.

WGO recommends using the ‘stove-type’ cooling fins as the bottom design of LED lights as well, or large smooth surface of metal to be the LED lamp to allow any potential build up to be removed.

Heat dissipation problems
The second problem is the setting of power supply system in LED lamp affects heat dissipation. When the power supply is on, only a small percentage of the power is turned into light. The rest is transmitted as heat. In the current design of LED lamp, the power supply system is placed near the LED light source module. The LED module, in addition to the heat that is produced by the diode in it, will also be affected by such power generating heat. Plus, the aging power supply system will generate additional heat. All these accumulated sources of heat will cause the lifespan of the module to decrease. To avoid poor heat dissipation and increase the lifespan of the power supply system, the outdoor LED light design should place the power supply system away from the light source module. This will also allow easy access for repairs and maintenance.

The third problem is the shape design of LED lights. Some countries use a ‘stove-type’ cooling fins to enhance the cooling function. However, because the fins are on the top, dust and bird faeces may accumulate. This causes the cooling fins to be blocked in return, which can lead to lower heat dissipation efficiency and serious heat issues. WGO recommends the cooling fins design to also be used at the bottom part of the LED lamp. This will allow any potential build up to be removed by strong winds and rain. Another solution will be using a large smooth surface of metal to be the LED light source. High quality of LED light source module chip and heat sink can also be considered, but these options will be more expensive.

Dr. William Yu, Chief Executive Officer of WGO stated,

Technological developments have drastically increased the quality of LEDs. In order to ensure quality, the International Electrotechnical Commission (IEC) issued a safety standard to regulate the production of LED light, such as the IEC-62471 certification standard that regulates the exposure of harmful light radiation. IEC, however, has yet to set up a standard for outdoor LED lights. During the transition to switching all HID street lights, we have to be more aware of the problems” He added, “Changing the old street lamps into LED lights is meant to save energy and protect the environment. That is why it is essential to address all the potential risks of having outdoor LED lights and avoid additional environmental pollution problems.

Appendix – Outdoor and Indoor lighting photoelectric parameters:

Outdoor lighting photoelectric parameters
Type of Lamp Power (Watts) Effective Light Output (Lumens) Input Power (Watts) Luminosity Efficiency (Lumens/Watts) Average Lifespan (hours)
Outdoor LED Lamp 68 8000 75 120 >20000
HID Lamp 150 7500 190 90 About 10000
Indoor lighting photoelectric parameters
Type of Lamp Power (Watts) Effective Light Output (Lumens) Input Power (Watts) Luminosity Efficiency (Lumens/Watts) Average Lifespan (hours)
T8 CFT – Cathode Fluorescent Tubes 36 1700 40 90 About 10000
T8 LED Tubes 13.5 1800 15 120 >20000
E26 Incandescent Bulbs 100 1000 100 10 About 10000
E26 CFL – Compact Fluorescent Bulbs 18 1000 22 55 About 10000

About Us
The World Green Organisation (WGO) is an independent non-governmental organisation concerned with environmental conservation and environmentally related livelihood and economic affairs by proposing an integrated, three-pronged solution that combines social, environmental, and economic aspects, leading to an environmental revolution. Through science-based policy research and community projects, the WGO aims to enhance the quality of the environment, promote a greener economy, and improve people’s livelihoods. In particular, it will focus on the social concerns of underprivileged groups and on the creation of a green economy to help realise its vision of sustainable development. For more information, please visit http://www.thewgo.org/

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