Can LED's reach the same efficiency (Lumen per W) as Low Pressure sodium lamps?

[eveares]

I don't know how much additional power percentage wise relative to the bulb a SOX lamps ballast takes up, but can LED's achieve the same or greater lumen per what ratio that Low Pressure Sodium/SOX achieve?

I am well aware of the awful colour rendering and CRI of SOX lamp's mono chromatic light output, however I do like them from a nostalgic perspective.

Reagrds: Elliott.

 

[ericmark]

The Son and LED both have good and poor control gear, it is not being Son or LED which makes one better to other, it is the control gear used. A LED lamp can actually produce 120 lumen per watt, most good ones are around the 100 lumen per watt, however most dimmable are down to around 75 lumen per watt.

It is harder with Son as the bulb and control gears are separate, same with a fluorescent fitting, so you can neither look at the bulb to get lumen or control gear as coatings in the bulb effect lumen per watt and methods used to start and run them, plus any power factor correction. Added to that we can see more in Orange light than other colours, however as to street lamps Son has one big problem, it is not reflected by some hi-vis safety clothing, seem to remember railway workers have a set colour because of this, but not people on the road, however the street lamp outside my house has been changed to LED, so now when I wake I have no idea if still night and light from street lamps or if day light.

I think churches look really good under son lamps, the orange looks good, using LED does not really cut it. But with LED the size of lamp is easier to select being just big enough, with son and fluorescent we seem to have huge jumps in size, it seemed most are 70, 200, or 400 watt with very little between those standard sizes, because of course they have to match the control gear, we see it with fluorescent 58W fluorescent tube replaced with a 24W LED output much lower but it was spread which was required rather than lumen output so dropping from 5400 lumen to 2400 lumen often is not a problem.

 

[Iggifer]

We recently fitted out a factory with LED Lo-Bays, I'll be honest I was skeptical but the light output was brilliant. Lumen per watt was probably not equievelant but would you rather run something at 400w or 50-80w for the same brightness? I know what I'd choose

 

[ban-all-sheds]

would you rather run something at 400w or 50-80w for the same brightness?

I don't really understand that.

LPS is 100-200 lm/W, so 400W is going to get you 40,000 - 80,000 lm.

Even at 120lm/W (Eric's top-end figure), a 50-80W LED is going to get you 6,000 - 9,600 lm.

 

[flameport]

but can LED's achieve the same or greater lumen per what ratio that Low Pressure Sodium/SOX achieve?

Theoretically they can, although they do not yet exist in products you can buy.

However it's more complex than just the lumen output, as the human eye is not equally sensitive to all wavelengths of light, so comparing a monochromatic light source to a white light source is not valid.

 

[motorbiking]

120 lumen per watt is the max output of the LED in a cooled environment. Output normally drops substantially after the first minute. If they aren't thermally managed you have to run them a lot less than the typical 3A bench test.

However Cree XM-L2 and XP-L both come close to 200 lumen per watt in the higher bins. Though this will be under test conditions.

 

[aptsys]

Indeed, any efficacy figures are given with a die temperature of 20 or 25C. Output drops significantly when temperature. The first LEDs which quoted 120lm/W were driven at about 10mW to get that number