What are the Advantages of Dimmed LED Street Lighting?

LED street lights provide massive savings over traditional high-pressure sodium (HPS) lamps. However, the next generation of dimmable LED street lighting takes operational savings, environmental impact, decentralization, customization, and safety to an all-new height. The reliability and longevity of dimmable LED streetlights make them a feasible replacement against former designs.

The average payback time to replace HPS with dimmable LED street lighting is around 11.5 years. This time is also reducing due to the expected 80% decrease in its prices within 4-5 years. There are many advantages to using dimmed LED street lighting, and the research behind its use is promising. This blog will build a solid knowledge base on street lighting, its design, and alternate options. Afterwards, we will analyze the technological improvements in dimmed LED street lighting and how they affect urban living.

What is an LED Street Light?

LED streetlights power light-emitting diodes to illuminate streets for pedestrians and vehicles. The light-emitting section is mounted to a pole at an angle to ensure focused lighting. The light from the LED fixture forms a cone with a diameter roughly equal to the height of the fixture on the pole. Street light fixtures ensure that roads are adequately illuminated while minimizing light pollution.

Safety is the primary objective of street lighting. It directly affects the response time of vehicle drivers and provides environmental awareness for pedestrians. In the past, the cost of operating street lights was high, mainly due to high-pressure sodium, metal halide, and fluorescent bulbs. Let's compare the popular high-pressure sodium street light bulbs with modern LED street lights.

▪ HPS Vs. LED Street Lighting

High-pressure sodium (HPS) streetlights were introduced in 1965. They were bright and energy-efficient compared to their predecessors. HPS uses sodium vapor to produce light that is yellowish-orange in color and closer to the sun's lighting. Currently, they are the most common type of street lighting worldwide. However, their use is gradually declining due to modern LED street lighting technology. Government regulations and incentives are driving this change, leading to the rise in LED street lighting. Here is a table differentiating HPS and LED street lights:

▪ Nondimmable Vs. Dimmable LED Street Lighting

Non-dimmable LED street lighting illuminates roads using a drive circuit and a light source. It provides a fixed brightness level and can be turned on or off through a centralized switch that receives a signal through a controller. Compared to predecessors like HPS or HID bulbs, adapting non-dimmable LED street lights is great for power consumption. However, dimmable LED street lights are a big step ahead in decreasing energy consumption and offering high customization options.

Dimmable lights can reduce illuminance, which, in turn, leads to lower power consumption. Dimmable LED street lights are best for areas where full-bright LEDs are applicable only during specific times within 24 hours. They require an additional voltage regulator or pulse width modulation (PWM) circuit that dims the LED light. More on the internals of LED lights will come in the next section.

Typical Design of an LED Street Light

The primary purpose of LED street lights is to ensure that bright, focused, and energy-efficient light appropriately disperses to the ground. A high-end LED street light can produce 119 lm/W. LED lights have several components that convert electricity into light. Here are the components and their purpose:

● Case: Heat Conductor and Ingress Protection

The housing incorporates all the components of an LED street light. It protects the internal components and removes their heat. Manufacturers ensure that the case consists of heat-conducting material. The casing also acts as a heat sink. Around 30% of the electrical energy converts to heat, as some components of an LED are less efficient than the diodes themselves.

Most LED street lighting manufacturers use aluminum alloy die-casting as their material of choice. The surface is treated with protective layers against ultraviolet and corrosion to ensure longevity. The case should also have an IP (Ingress Protection) rating that includes

● PCB with LEDs

The printed circuit board (PCB) holds all the LEDs and gives them power. Manufacturers can use metal or fiberglass PCBs, which are ideal for heat dissipation in LED streetlights.

● Driver

A driver is the power supply of the LED and converts the electrical line supply to the desired electrical requirements of the LEDs. Manufacturers embed it inside the casing at a location where proper heat dissipation is required.

● Thermal Dissipation

LED lights produce heat, and the driving circuit also requires heat dissipation. LED lights have thermal pads, and thermal pastes that enhance heat transfer. The metal casing is the final interface with the environment that removes heat.

● Seals

LED street lighting has seals to prevent water and dust from entering the housing, ensuring an ingress protection (IP) rating. The seal can be polyurethane or silicone sealing foam.

● LED Cover or Lens

A lens dissipates the light in directions in front of the LEDs to ensure balanced luminance within the light projection cone.

Can LED Streetlights Be Dimmed?

Yes, LED streetlights can be dimmed as long as they have the required circuitry. However, only some LEDs can be dimmed, as specialized circuits are needed to reduce brightness. Two popular methods to achieve dimming are a 0-10 volt dimmer or pulse with modulation (PWM).

▶ 0-10V Dimmer

A separate dimmer connects to the LED driver using a grey and purple sheath wire. It changes the voltage output between 0V and 10V. Zero voltage output means the LED is OFF, and 10V implies that it's at maximum brightness. The driver maintains a fixed current to the PCB, which consists of light-emitting semiconductors. The driver is the main component that should feature dimmable properties. Manufacturers usually mention their LED fixtures as dimmable if they feature a driver that supports variable-brightness LEDs.

▶ Pulse Width Modulation (PWM)

It is a device that turns the LED on and off at a higher rate than the power supply frequency. The turning on and off is fast enough that it's invisible to the eye. The percentage of ‘ON’ time for the LED is called the duty cycle. 75% duty cycle means that the LED will remain off for 25% of the time in an electric pulse.

Government Policies and Public Feedback on LED Street Lighting

Government policies and public feedback will continue to shape the future of LED street lighting. Typically, no specific government organization regulates the use of LED street lighting, but organizations such as the National Capital Planning Commission (NCPC) and the American National Standards Institute (ANSI) provide general guidelines.

Various government projects worldwide incentivize the use of LED lighting. However, in some locations, locals want to retain their traditional-looking lights. Let's analyze a few cases to understand public response and government policies.

★ Government Policies and Guidelines for LED Street Lighting

Let's take the NCPC's Washington D.C. streetlight conversion proposal. The key concerns about the conversion include excessive lights from the Washington Globe fixtures, which cause light pollution and disrupt wildlife. Moreover, using a 3000K LED color temperature had more blue, causing an increase in skyglow. There were also concerns about the circadian rhythm disruption due to the blue light. NCPC guidelines suggest the following to counter these problems:

Like NCPC, the International Dark-Sky Association (IDA) and the American Medical Association (AMA) also have guidelines to reduce light pollution and blue light effects on the environment and human health.

★ Public Feedback Considering Standard LED Street Lighting

◢ Denver Colorado LED Lighting Issue

Denver changed their HPS street lights with LED street lighting without a dimming feature. It led to a backlash significant enough to make it to the news on Apr 23, 2019. The primary concerns of the residents were:

● The streetlights invaded their homes. They were so bright that they had to close the blinds to prevent the light from coming in.

● Some residents suggested the lights were a great addition but should have a dimming feature.

● The light pollution that these bright blue lights were producing was too high. The light was reflecting off of surfaces and causing undue light.

◢ Washington D.C. Street Light Conversion Project

These were some of the public feedback received from the implementation of the D.C. Street light conversion project:

● Linnea Warren: "Scattering light indiscriminately instead of directing it where it’s needed is an environmentally unacceptable waste of energy."

● Laura Phinizy: "The vast majority of light emanating from the globes goes outward or upward, not downward toward the ground."

● Wayne Savage: "The anachronistic Washington Globe fixtures are incompatible with a modern street-lighting system that limits light pollution."

● Bonnie Garrity: "I have noticed significant glare emitted from these fixtures, impairing my vision instead of illuminating my view."

● Lee Mayer: "LED lights should have a color temperature of 2700 K or less, especially in residential neighborhoods."

The Advantages of Dimmed LED Street Lighting

Now that we know how LED street lights operate, their dimming function, government policies, and public feedback regarding LED street lighting, we can understand why dimmed LED street lighting is the best. A pole-mounted dimmable LED street lighting is ideal for saving energy while considering environmental and human health issues. The dimming feature allows for adjusting brightness and focused lighting to the ground.

✔ Energy Saving with Lower Power Consumption

LED street lighting provides massive energy savings compared to former technologies like HPS, Fluorescent, and metal halide. Making it dimmable further increases lighting efficiency. Combining dimmable street lights with intelligent systems can allow better control and public satisfaction.

Intelligent street lighting systems can turn on/off or reduce brightness based on timing or solar conditions. Similarly, the PIR (Passive Infrared Sensors) can increase the brightness of relevant light while keeping the others dimmed for energy savings.

✔ Environment Friendly

Dimmable LED street lighting systems directly affect human health, ecosystems, and the environment. The ability of these light systems to reduce their brightness provides several advantages:

● Reduced skylight in line with the International Dark-Sky Association (IDA)

● Dimmable LED street lighting allows warmer color temperatures between 2700 and 3000k, ensuring the human circadian rhythm is not disturbed.

● Mercury-free design reduces the use of harmful chemicals.

● In residential areas, the low brightness of dimmed LED street lights can reduce the incidence of light invasion in homes at night.

✔ Improved Safety

Dimmable LEDs can run at total capacity in areas where enhanced lighting is essential. However, they can be reduced to low power mode when the need is reduced. Street lighting is vital to reducing crime. Variable brightness based on PIRs or proximity sensors adds another aspect of safety improvement.

✔ Longer Operational Life Cycle

Like high-pressure sodium street lighting, reducing the brightness of LED street lighting improves its lifecycle. The DImming feature of LED street lights can extend the operational life of an LED light to 200,000+ hrs.

✔ Seamless Integration with Smart City Systems

Dimmable LED street lights can integrate with wireless centrally controlled systems or localized control cabinets that utilize PIDs, proximity sensors, and solar sensors to change brightness. Here are some of the configurations that cities or localities can apply for intelligent city systems:

● Remote Control on with Turn ON/OFF and Brightness Adjustment Feature

● Adaptive Brightness Based on Traffic Conditions

● Public Input Integration to Adjustment of Lighting Conditions

● Auto Brightness Adjustment Based on Low or High Activity

Conclusion

If you are considering dimmable LED street lighting for your locality, then it's essential to thoroughly understand the technology before making the big move. Dimmable LED street lighting provides massive savings and customization. Considering the public's backlash regarding installing bright LED lighting, dimming is a productive way forward. In short, dimmable LED streetlights provide the following advantages:

● High customization concerning the area requirement

● Reduce light pollution

● Enhanced safety with motion sensors

● Respect the human circadian rhythm

● Long Operational Life

Dimmable LED street lighting is a modern and reliable street lighting system. Government policies and public opinions suggest the use of dimmable LED street lighting.