Articles
Below is the text of an article I wrote, based on interviewing SME's, as well as other independent research.
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LEDS: Illuminating the Issues
Light-emitting diodes (LEDs) are playing an ever-larger role in energy efficiency. LEDs have the potential to provide efficiency, long life and low maintenance, but careful consideration should be given to just where and how they’re used.
LEDs developed out of the world of computers—they are basically semi-conductors, the same components found in computer chips. Because LEDs are based on semi-conductors, their development is following a path very similar to the development of computer chips and components, with rapid advances in performance, and decreases in price.
While performance increases are being seen in energy efficiency, a more critical advance has been technological: the ability to produce a white light with LEDs. One way of making white light with LEDs is by mixing colors, notably with the inclusion of blue. It wasn’t until the 1990s that blue LEDs became available, thereby making white LEDs possible. A white light makes a wide range of applications possible, such as streetlights. But there are still a number of issues that need to be taken into account when considering an LED lighting project.
The Matter of Thermal Management
Successful LED lighting is very application-specific, and careful consideration must be given to the environment in which they will be used. LEDs are very “thermally dependant”: They work very well in cold environments, but there are performance decreases in both light output and device lifespan in hot environments.
One very successful application of LED technology today is in exit signs. Because exit signs are ubiquitous in most buildings, are usually in stable and moderate temperatures, are on 24/7 and require little light output, using LEDs is a very energy-efficient choice for many buildings.
At the other end of the spectrum are LED streetlights. This is a more complicated application than exit signs, and a number of issues need to be considered carefully. In regions where it stays hot at night, LED streetlight systems might not be a good choice, given that high temperatures could decrease energy efficiency and lifespan of the lights. However, because streetlights are generally only on at night, when the temperature in most regions is cool, an LED streetlight system can be a viable option in many areas.
Replacing incandescent lights with LEDs can lead to some unexpected problems. One recent project was undertaken at an airport, where standard lights on the landing field were replaced with LEDs.
When the retrofit was completed, it appeared to be successful. However, a problem was discovered when snow arrived. The heat from the old incandescent bulbs used to melt the snow that landed on them, keeping them visible. But the LEDs didn’t get warm, so the snow just covered the lights. The solution was to install heaters around the LEDs to melt the snow, eliminating the energy efficiency gains.
The Status of Standards
LEDs technology is evolving faster than standards bodies can keep up with. For example, there are currently limited industry standards for testing product lifespan. Manufacturers have claimed product lifespans of up to 100,000 hours, or 20 years, but many of these claims are for devices that are only five years old. Although recent developments have created standards for light output and efficiency, there are still limited testing standards or other metrics. Because of these uncertainties, and no track record of long term maintenance costs, it’s difficult to determine an accurate return on investment.
In addition to a lack of standards, it’s difficult to know if a switch to LEDs is a good move today, since there are big performance gains currently being made in the industry. This makes it difficult to determine if ‘now’ is the time to move to LEDs, or if it’s better to wait for the bigger gains that are sure to come. But one thing that’s clear is that LEDs have a bright future.
