LEDs with plastic, re-usable cover or glass CFL's?

[treez]

Supposing I have two lights, one LED and one CFL.

The CFL took much energy to produce because the glass had to be smelted, and that glass tube cannot be re-used unless smelted back down.

The LEDs would have a Perspex cover, which presumably takes less energy to manufacturer than the glass tube of a CFL?
Also, the Perspex cover over the LEDs can be re-used without smelting back down.

So anyway, am I correct in saying that it takes more energy to smelt glass into a CFL tube shape, than the energy required to make a transparent Perspex cover for LEDs?

 

[betwixt]

When you say 'cover' you seem to be comparing the glass of a naked CFL with an enclosure around LEDs. It would be fairer to compare like for like, an enclosure over both types.

To answer your question: probably - but think of the energy needed to produce the LED base material as well. Acrylic plastics are relatively easy to make and not particularly expensive but on the other hand glass is a form of sillica and is even cheaper to source but has higher energy requirements per Kg to produce.

Brian.

 

[treez]

Thanks Betwixt, I see your point, the actual LEDs themselves may mean that a LED lightbulb takes more energy to produce than a CFL?....even if the LED lightbulb comprises no aluminium heatsinks and no glass in it.

I still think that glass smelting is such a high energy process that CFL's with their glass tube are going to take the highest overall energy to produce?..because surely the LED chip is only small, and so not much energy needed to produce each led?

 

[betwixt]

I'm pretty sure the most 'eco' reason for using LEDs is their longevity. The actual bulk manufacturing cost probably isn't much different between the two technologies but taken over the lifetime of the product the cost per day should be much less for an LED. A CFL lamp has a typical life expectancy of 8,000 hours while an LED degrades to a 'half-life' over around 50,000 hours. So if the statistics are to be relied upon, an LED will still be working around 6 times longer than a CFL lasted. I may be both eco-excessive and a bit of a geek but I actually repair CFL lamps when they stop working. Apart from occasional damaged glass, the vast majority of dead lamps either have shorted capacitors, open circuit resistors or dried up electrolytics in them. I'm not sure if the CFL life expectancy is based on the whole product or just the glass part, my experience says they rarely reach 8,000 hours. I have yet to have a single broken domestic LED lamp to make a comparison.

Brian.

 

[treez]

I see your point, though I wonder if you believe that if a led lightbulb contains electrolytic capacitors then its lifetime really is no longer than a CFL?

 

[betwixt]

You are quite right about both type containing electrolytics but there is a significant difference in the way the PSU's work. A CFL generally has a high voltage, low value electrolytic, say 2uF/400V and the load on the psu changes dramatically as it starts up. An LED supply has the advantage that by 'stacking' LED junctions the need to drop the incoming voltage is much reduced and the V/I characteristic is much more linear over time. One of the failures I commonly see in CFL is the capacitor across the tube ends which is generally around 3.3nF with a 2KV voltage rating, they frequently go short circuit and dump all the power into the heater filaments. This of course not only stops them lighting up but causes damage to the filaments as well. As I stated, I have never seen a faulty LED light so I can't give a 'gut feeling' on how likely I think they would last. I would guess that the use of a heatsink would at least allow the heat to be directed away from any electrolytic caps, in a CFL everything is packed into a small unventilated space where it gets extremely hot.

Brian.

 

[Audioguru]

ALL traffic lights and ALL street lights in my fairly large city are now LED. They use much less electricity and do not need expensive and frequent replacement as the incandescent ones they replaced. But I see some of the individual LEDs not lighting anymore after a few years. Since each light has maybe 30 LEDs then having a few that failed does not matter. Maybe after 20 years then they must be replaced.

Following many rainy days it got very windy then a brand new LED streetlight slowly fell down. The city workers came and removed the LED part (before I stole it).

 

[treez]

With streetlights, I just hope that they re-use the huge alu heatsink that they must use with them..........and I don't mean smelt it back down....I mean, when the led streetlight eventually fails, they take the alu heatsink back to the factory, and stick a fresh led pcb to it (preferably the old led pcb with new leds affixed to it).....then put this assembly back into the streetlight.
Do you know if they do this?

Getting alu from bauxite takes prodigious amounts of energy.

 

[betwixt]

Audioguru & Treez, you should live here - there are no street lights! (but we do have wonderful dark skies full of stars instead!)

Brian.

 

[Audioguru]

Here we have street lights because some stupid people drive at night with no lights on their cars or their car manufacturer was too stupid not to make automatic lights. Some stupid kids ride bicycles or skateboards at night with no lights.