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| State of the art white LED efficacy? |
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| splin:
The most efficient LEDs available at Digikey are 229 lumens/Watt form Everlight though Seoul, Osram and Samsung are close behind. Cree used to regularly boast about setting new efficacy records, but the last was in 2014: https://www.cree.com/news-media/news/article/cree-first-to-break-300-lumens-per-watt-barrier 303 lumens/Watt (in the lab). So are we likely to see 300+ lumens/Watt in the foreseable future or has development hit a plateau? Most domestic lighting LED bulbs seem to top out at around 117 lumens/Watt - how much of the shortfall from the best available LEDs is likely to be down to: 1) Using cost effective, lower efficacy LEDs 2) Driver efficiency loss - 10% perhaps? 3) Losses due to light absorbtion by the encapsulation/diffusers etc? 4) Use of lower colour temperature (2700K), lower efficacy LEDs because of customer demand for 'warmer' lighting? Given that LED bulbs can last a very long time if properly designed, with decent quality drivers, surely there must be some demand for state of the art efficiency bulbs albeit at a somewhat higher price? A decent 1521 lumen, 13W bulb can retail at £10 in the UK; 1521 lumens equates to 40 of these 3500K, 80 CRI LEDs: https://www.digikey.co.uk/product-detail/en/seoul-semiconductor-inc/S1W0-3030358003-0000003S-00001/897-1400-2-ND/9997401 They would cost £2.12 at Digikey prices. So with markups and taxes that might add £5 to £10 to the cost (with a high efficiency driver included) at retail. I'd be happy to pay £15 for a bulb that is 30% more effiicient, for locations where the lights are on for a long time. 30% CO2 reduction would be welcome and the extra cost could be recovered in 12 to 18 months; clearly you need to expect a decent lifetime from an expensive bulb, but the higher efficiency would help by reducing the thermal stresses. The 30% more efficient comes from 213 lumens/Watt less 10% driver loss and 15% optical losses = 164 lm/W compared to the 117 lm/W of a 1521 lm, 13W bulb. Do such bulbs exist? |
| mzzj:
add to your list 5. operating temperature: specified at 25C junction temp, real-life situation is closer to 100C Based on Cree's PCT tool modern medium-power white leds drop lose about 10% in efficiency if junction temperature rises 60C from theoretical marketing value. E27 light bulb just sucks as a led form factor. High efficiency led lightning is easy to find in fluorescent tube replacements. Philips has 4000K tubes with 172Lm/W. |
| splin:
--- Quote from: mzzj on January 16, 2020, 10:19:31 pm ---add to your list 5. operating temperature: specified at 25C junction temp, real-life situation is closer to 100C Based on Cree's PCT tool modern medium-power white leds drop lose about 10% in efficiency if junction temperature rises 60C from theoretical marketing value. --- End quote --- Good point, but witrh higher efficiency, temperatures will be lower. Samsung LM301B LEDs lose 6% flux at 85C, but forward voltage drops by 3% so efficiency loss should only be 3% from 25 to 85C provided the driver is suitably designed. --- Quote ---E27 light bulb just sucks as a led form factor. High efficiency led lightning is easy to find in fluorescent tube replacements. Philips has 4000K tubes with 172Lm/W. --- End quote --- That's much better but it can't all be down to the form factor. Perhaps it's because tubes are generally bought by companies who value the electricity cost savings (and maybe additional air conditioning power savings) rather more than domestic customers. |
| OwO:
Are we talking about bulbs? as in those that screw into incandescent bulb sockets? If so there is no way you can dissipate 10W in that form factor without heating to near 100 degrees C. Ditch the bulb form factor and you can do far better. Here in new homes you rarely see bulb based fixtures anymore. It's almost always big ceiling mounted lights using LED strips internally, with area big enough to keep the LEDs cool. |
| DaJMasta:
Don't know if the bulbs exist as what market would they be for? There's virtually no residential or commercial application where that level of efficiency would be a significant benefit over baseline performance that would use a standard bulb. The cost would be substantially more because of the price of the LEDs themselves, so with the exception of products emphasizing tiny form factor over almost all else, it's going to be hard to justify the expense. I do think you can get somewhat better than 90% efficiency on the power supply conversion, though, especially when a string of LEDs can be driven at a fairly high voltage (close to mains). You can get drivers better than 95% efficient, so if you were looking for power savings in bulbs, it may actually be more economical to optimize the driver and then get the slightly better luminous efficiency LEDs. The combination of the two could probably shave off a few percent of the total losses from a standard bulb for maybe twice the price, whereas going for the ultimate in LED tech and driver optimization could maybe get a few more percent for several times the price. Hard to say. Looks like what's commercially available is to about 230lm/W, but the price for LEDs seems reasonable (~10 cents each in a few thousand quantity). I wonder if they really just jump on the bargain basement LEDs to make consumer grade LED bulbs. |
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