LEDs are being touted as the future of residential lighting, but there are still some burning issues the technology has to overcome.

LEDs offer an exceptionally long life, brighter light and the capability to produce a lumen per watt value that dwarfs that of incandescent bulbs. However, all of these benefits are pulled into question when too much heat is added to the equation.

All forms of lighting convert electricity into heat in some form. As well as light, incandescent lamps produce infra-red (IR) emissions while fluorescent and metal halide sources emit IR, ultraviolet (UV) radiation and heat as well as light.

With LEDs, only 15-25% of the energy they consume is converted into visible light, the rest is heat created at the junction. This must be removed by conduction or convection to heat sinks or alternative solutions or the performance of the device will be significantly compromised.

Excess heat that is not dissipated can result in discolouration, reduced light output and depreciation of lumens; ultimately shortening the lifespan of the product.

Lighting Council Australia technical manager Owen Manley says there is a basic reason for this.

“Because an LED is a semiconductor, it generates heat as well as light. A classic rule of semiconductor technology is that if you add 10°C to a product’s temperature you half its life,” he says.

The primary cause of lumen depreciation is heat generated from drive current, thermal path and ambient temperature at the LED’s junction. The higher the drive current, the greater the heat created. The amount of heat that can be removed is reliant on the design of the LED system itself and the temperature of the surroundings.

Owen says that correct thermal management has to be in place to maintain the high performance LEDs are capable of and also to preserve the reputation of the product as a whole. 

“There is potential for LEDs and other solid state lighting sources to represent 60 to 70% of the lighting market by 2020, so it definitely has huge prospects. However, people still need to have a better understanding of the technology.

 “People are misrepresenting what the technology can do and choosing LEDs for the wrong applications. If you use an LED in the correct scenario it can be great. In instances such as truck tail lighting and sign lighting LEDs have revolutionised the industry because the right product was chosen for the right application.

“The current problem is that energy savings are being promised to commercial projects which do not correspond with the product’s capabilities. They are being touted as being able to cut your energy bill in half, but they can also significantly reduce the amount of light if not utilised properly.”

Owen’s concerns don’t end at the negative effect of excessive heat output, he also believes there are potential implications on the product’s future success.

“Around 25 years ago people paid a significant amount of money for compact fluorescent lamps (CFLs) as they were considered state-of-the-art, but many didn’t perform so people still have poor perceptions of the technology. The same risk applies for LEDs.

“There is a possibility of disrupting the rollout of the technology because of poor performing products and misrepresentation of claims. Irrespective of all that, when you have a good installation and a good product for the intended purpose, LEDs will perform well.”

Adequate heat management and temperature of the operating environment is paramount to the success of LED applications. With superior heat sink designs in place, the junction temperature will be minimised, maximising performance and preserving the lifespan for years to come.