Why LED lamps need cooling and incandescent lamps don't - Page 1
Forum section: electronics / beginners

author: BeBuLamar
author_rank: Super Contributor
timestamp: January 12, 2024, 02:00:58 am
content: Why something like a 50W LED lamp (that is a LED lamp that actually consumes 50W not one that delivers equivalent light intensity as a 50W incandescent lamp) would need cooling but a 50W incandescent lamp doesn't. While the amount of energy wasted as heat in a lamp is high but a LED is more efficient then why the cooling need?

author: IanB
author_rank: Super Contributor
timestamp: January 12, 2024, 02:18:37 am
content: Quote from: BeBuLamar on January 12, 2024, 02:00:58 amWhy don't you think about this for a moment and see if you can come up with the answer by yourself? If you do think about it, you will find the answer is really obvious.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 12, 2024, 02:19:53 am
content: The transport and shedding speed of "excessive heat" is determined by a lot of factors (surface area, moving air) and also by the temperature difference. Incandescent bulbs can become very hot without issues (the tungsten wire is literally glowing with heat (1800 celcius?) and the rest is made of glass and metal, and those materials can also take a lot of heat.LED's however degrade quickly when they become hot. And the hotter they get, the lower their life expectancy. Even temperatures as low as 50 degrees centigrade already start degrading LED expectancy. LED's often also have built-in driving electronics and a lot of those parts also have quite low temperature limits.Note this also has an effect on light armature design. Armatures designed for incandescent light bulbs do not need very much ventilation but must be able to withstand the heat of the incandescent bulb (they also radiate quite a lot of IR). Armatures for LED lighting should have an "open" design to encourage air movement and cooling of the LED. The E27 fitting was very common for incandescent bulbs (which also needed regular replacement), while LED armatures tend to go into fancy "completely custom" designs with the LED's even not replaceable. Part of this may be planned obsolescence, but partly it is also because with an integrated design, you can make the heatsink for the LED a part of the armature itself.

author: xrunner
author_rank: Super Contributor
timestamp: January 12, 2024, 02:24:05 am
content: Quote from: IanB on January 12, 2024, 02:18:37 amRight.A 50 W LED produces as much light as a 500 W halogen according to the internet. That halogen element is going to be very hot. But some things are inherently robust per the materials used, and some aren't so ... think.

author: Stray Electron
author_rank: Super Contributor
timestamp: January 12, 2024, 02:26:53 am
content: The short answer: Incandescent lights need a lot of heat to make the filamentincandescentso that it will emit light. LED lights are solid state devices (diodes) and don't need heat to produce light and, in fact, even small amounts of heat will quickly destroy them just as it does with any solid state device.

author: TimFox
author_rank: Super Contributor
timestamp: January 12, 2024, 03:35:32 am
content: Look up the melting temperature of tungsten and other high-temperature metals, and compare with typical semiconductors, including GaAs.

author: globoy
author_rank: Frequent Contributor
timestamp: January 12, 2024, 05:11:33 am
content: In addition, incandescent bulbs emit most energy as IR radiation so the heat is able to escape. If the following chart is to be believed only 18% of the energy into an incandescent bulb turns into heat locally. The rest is radiated away (only 10% ends up as visible light.https://www.researchgate.net/figure/Figure-2-Energy-Distribution-Diagram-of-Incandescent-light-bulb_fig2_267598738Ultra efficient LED bulbs might convert 50% or more of the energy to visible light (with no IR) *but* the remaining energy is local heat. And as someone else said, LEDs are very sensitive to temperature and degrade quickly at high temperatures so that heat has to pulled away from the LED chips with a lot of heat-sinking. Also other power supply components need to be kept reasonable cool to have long life.

author: radiolistener
author_rank: Super Contributor
timestamp: January 12, 2024, 06:50:07 am
content: Led lamps have driver circuit which consists of capacitor and other components (include leds) which is very sensitive to heat and can be easily damaged due to overheating.Incandescent lamp don't have temperature sensitive components and can heat to much higher temperatures with no issue.

author: Andy Chee
author_rank: Super Contributor
timestamp: January 12, 2024, 06:57:12 am
content: The physics of light emission of an LED and tungsten filament are different.LEDs work on the physics principle of electroluminescence. Tungsten filaments work on the physics principle of black body emission.These two different laws of physics have direct consequences on the quantity of heat and light emitted from the device, and the physical construction of how the heat and light are removed from the device for correct operation.

author: radiolistener
author_rank: Super Contributor
timestamp: January 12, 2024, 06:59:10 am
content: Quote from: BeBuLamar on January 12, 2024, 02:00:58 amthat claim is not quite accurate, both LED and incandescent lamps emit exactly as much light power as they consume. But incandescent lamp power is radiated in very wide light spectrum, while LED lamp emits all power within very narrow area of the spectrum.So, it's not correct to compare light emission power of LED lamp vs incandescent lamp by comparison of their light intensity at some specific wavelength.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 12, 2024, 07:03:37 am
content: To be more specific, think about it: the incandescent bulbhasto be internally at around 2500 degC to emit light; so quite obviously it must be able to handle that temperature without dying. On the other hand, the LED semiconductor die dies (pun intended) at maybe 150 degC. It's also tiny!

author: IanB
author_rank: Super Contributor
timestamp: January 12, 2024, 07:14:30 am
content: It's also wrong to think that an incandescent lamp doesn't need cooling. It absolutely does. If you try running an incandescent lamp in an enclosed space where it doesn't have adequate cooling, it will have a much shorter life.A simple energy balance tells you that 60 W in equals 60 W out. If you don't remove 60 W of heat from a 60 W incandescent bulb (i.e. provide 60 W of cooling for the bulb), then the bulb will fail.The difference between an incandescent bulb and and LED is the operating temperature. The incandescent bulb operates at temperatures that will sizzle your fingers if you touch it, which makes it much easier to remove the heat. (Heat removal rate goes up as operating temperature goes up.) An LED bulb will self-destruct if it gets that hot, so much different cooling arrangements are needed.

author: tszaboo
author_rank: Super Contributor
timestamp: January 12, 2024, 08:59:06 am
content: The short answer is: because they operate at different temperatures.

author: sparkydog
author_rank: Regular Contributor
timestamp: January 12, 2024, 08:46:00 pm
content: Quote from: radiolistener on January 12, 2024, 06:59:10 amThat'sverymisleading. Both types of illuminators emit exactly as muchenergyas they consume, yes, but kinetic (i.e. convected or conducted heat) energy is not "light" or even radiant energy of any sort. Moreover, most people would consider "light" synonymous with "EMR in the visible spectrum".