Why do so many of the bulbs run hot? Like so hot you can't hold them in your hand if they were on when you unscrewed them. Isn't this a lot of wasted energy?
All bulbs produce heat, both from the LEDs and the electronics. Incandescent bulbs were blazing hot, too, and they radiated IR on top everything else.
A high efficiency LED assembly is still producing on the order of 50% light and 50% heat.
blazing is undertaking, the filament is over 2500K
High efficiency is only 50%? Isn't that terrible? Are LEDs really that bad?
Incandescents used to be 5% visible light at best, with 95% of energy turned into non-visible radiation.
Partly because they are running tiny cheap power supplies pushed near their limit, and also because many of the actual LEDs they use aren't nearly as efficient as they could be. Also available surface area, in order to fit in most standard bulb locations they need to be small leaving little room for adequately sized heat fins.
yes theres multiple kinds of inefficiencies concerning the external circuitry etc, but there is also the intrinsic inefficiency of current LEDs: some of the high energy photon are downcoverted to a low energy photons by phosphors, so there is non-radiative (heat) generation in the phosphor itself. In theory it is perfectly possible to use "quantum cutting" i.e. 1 photon -> 2 photons instead of 1 photon -> heat + photon. There is quite a lot of research on quantum cutting phosphors, both for LED's and for VUV excitation etc, so these higher efficiencies will probably come, but I don't know how far out in the future. If someone knows of commercially available quantum cutting phosphors (or products using them) I would be very happy to know about them for some physics experiments...
I think they might have began quoting the LED lifetime on boxes, which is still true, but in reality something else in the bulb usually breaks before the LEDs themselves. I guess manufacturers have either taken it upon themselves or have been forced to reduce the quoted lifetime since the famous 100,000 hours marketing.
Or they quote the lifetime figure for a single LED, but then wire up a dozen or more in series to make the light. Any one of them fails and the whole assembly goes dark.