Street Lights - 150-watt high-pressure sodium (a fairly common lamp) at 14,400 mean lumens (over life of the lamp), and 75 lumens/watt.
Um, 14400/150 = 96. I presume they are calculating both optical transmission losses and ballast losses in the 75lm/W.
And a 400w metal halide = ~32000 lumens.
Is 32000 initial or mean lumens? I know output from metal halides degrade faster than other HID lamps, like Sodium. I suspect the mean lumens, accounting for ballast losses and optical losses might then be closer to 50.
I know Cree did a proof of concept street light where they said they achieved higher efficiency than high pressure sodium, and a lot of people on the boards scoffed at that because in terms of bulb-lumens output, high pressure sodium produces over 150 lumens/watt. However, that's cut at in half or worse when you account for the bad optics and lossy ballasts used in most street lights. Cree LEDs with properly designed ballasts and efficient TIR optics could actually do better, even if the emitters themselves are only 100 lumens/watt. Especailly when you consider degradation over the life of the bulb, which could be minimal if temp of the LEDs is kept low.
Further, using an array of LEDs and optics they could also direct those lumens a lot more efficiently -- I'd say of most street lights I see, less than half of the light that makes it out of the fixture actually lands some place where it's useful. An array of LEDS will be a lot easier to control exactly where the output goes. Finally, unlike HIDs which can take sevral minutes to start up, and longer to "restart" (as they generally need to cool down first), LEDs can be switched off/on immediately, meaning the lights could also be rigged with motion sensors to go OFF when noone is around. Power consumption for street lighting and light pollution could both be 20% of what they currently are by using LEDs.
140lumens per watt isnt overly impressive.
Especailly not if they mean lumens per watt of MICROWAVE INPUT, and not electrical input, which I very strongly suspect is the case. I hate inconsistent and/or deceptive reporting of units.
