In the past decade, LEDs have changed seriously with increased light output, increases efficiencies and drastic change in price points. LED fixtures in outdoor solar street lamps come with great benefits and among the best benefits is to the environment and nature. We take a look at how LEDs have evolved compared to HPS (High-Pressure Sodium).

A breakdown of LEDs in outdoor solar street lamps

LEDs were initially so blue that installing it outdoor solar street lamps could cause low visibility, mass problems with circadian rhythms, and wildlife disturbance. The evolution of LEDs has resulted in a drastic reduction in the blue light and increase in light output in terms of Lumens/Watt efficiencies (LpW). That is, the same wattage that will produce 50 LpW can now produce 130 LpW. The improved efficiencies and lower wattage translate into a lower power requirement to produce the better or the same light output in outdoor solar street lamps.

As LEDs now feature lower blue light, which translates into improved visibility. Improved visibility translates into improved security and safety for pedestrians and drivers during the night. Improved visibility means when people take a walk or drive, there is less chance of an accident as they can see their surrounding very clearly. Additionally, it looks like 4K light color is even producing just as good or better visibility that has reduced blue spectrum because there is no to little Lumen loss, and some light fixtures even have increased Lumen.

The low power requirement of LEDs makes room for improved dark sky compliance, which means lesser light pollution. LED optics enable the light to be task-specific, pointing the light to the desired area. This prevents the light from casting in unwanted areas and thereby causing light pollution. Additionally, LEDs boast of very long lifespan compared to other sources of lighting with LEDs lasting between 50,000 and 100,000 hours and more.

Notwithstanding, LEDs tend to be expensive compared to other lighting solutions with the up-front cost usually high.

A breakdown of old-style HPS outdoor solar street lamps

HPS lights are a certain type of gas-discharge light, as the name indicates, high-pressure sodium lights work at high internal pressure inside the lamp. The lamp arc tube is composed of aluminum oxide and the sodium metal is mixed with numerous elements such as Mercury that act as counter-balances to the yellow glow with some light blue to white emissions.

To keep the optimal level of performance for HPS light, it needs to be replaced nearly every year and if the lights are operated on a 24 hours basis then you need to replace them more often. Depleted bulbs will send out light at diminished levels, which is not good for outdoor lighting.

However, considering that it is cheaper than LEDs, it easier to replace. HPS lighting has been produced commercially for a long time as it is generally effective in covering a large area. Not minding their long warm-up time of 5-10 minutes, its energy efficiency means it is still used in areas like car park, roadside, highway, etc. They are also more long-lasting than many fluorescent bulbs, incandescent bulbs, and other high-intensity discharge lamps generally. Only the recent invention of the now widespread and increasingly affordable LED lights have surpassed HPS consistently in terms of lifespan and efficiency.

However, old-style HPS lighting can cause light pollution with its refractors that push light in every direction in addition to the high wattage required to power it because it has low LpW efficiency. Additionally, HPS light has a poor color rendering with its dark yellow glow producing low-quality light. It is monochromatic, and as a result, the illuminated objects will look shadowy black instead of the usual color it has in the day.



The lower wattage and higher Lumen output mean that LEDs used in outdoor solar street lamps provide a better cost-effective solution compared to the old-style HPS light used in traditional street lighting. The lower wattage translate into higher light levels and less solar requirements with the same power requirements used before. Although the initial cost of HPS light is lower, however, the high cost of maintenance is still higher than LEDs. The lifespan of HPS light even thou is higher than most conventional bulbs in the market, it is still no match for LEDs.

Additionally, HPS is omnidirectional, that is they produce in 360 degrees and as a result, the light needs to be redirected to the needed area. On the other hand, LEDs used in outdoor solar street lamps are directional as they produced light in 180 degrees causing less light pollution compared to HPS lights. As result LEDs can meet dark sky compliance and provide needed lighting for security and safety without disturbing migratory patterns of animals and wildlife in general.