LED vs MH integrating sphere measurments

[tankslave]

I know Sanjay has done a lot of PAR mapping on different LED vs Metal Halide fixtures, but I couldnt find any real absolute total radiated output measurements. Having access to a 40" integrating sphere, I decided to try to start doing some comparative measurements. If you guys don't know what an integrating sphere is, it basically captures all the radiated light from a source, no matter what the angle, elimating the effects of the optical system (reflector, distance from the source, etc). You can read all about it on the internets. What it gives you is total power radiated at each wavelength. Anyhow, I started with an Ushio 14K 250W lamp with an Ice Cap electronic ballast (not the newest, but that's what I had on hand). The bulb was new, however. Then I took a Kessil A350W (this was about 6mo old), and turned both channels up all the way. Now the kessil only uses 90W, whereas the 250W metal halide ballast uses about 300W at the wall-plug.

Here is the absolute (raw) data:



If you integrate the radiated power from 400nm to 700nm, you get about 12W radiated for the Kessil (that comes to 13.5% efficiency). The Ushio metal halide radiates about 41W (13.7% efficiency). Scaling the graphs according to input power, you can see that they are pretty closely matched:



If anyone is interested, the Duv (distance from the white point on the color chart) on the Kessil was -0.093, whereas the MH was-0.007, substantially closer.

My conclusion: from a radiometric standpoint, both are about equal in terms of total radiated efficiency, but obviously the spectra are weighted differently. The MH is still considered a "white" source (spectrum is more evenly spread out), but the Kessil is more like a blacklight (very high blue/red ratio).

Obviously we don't necessarily care if one is more white than the other, only how our corals do (and look) under the lights, so take what you want from this data, I dont want to start any arguments, just show some data.

The only thing I thought was interesting is that the Kessil did not provide nearly as much of a boost in efficiency as I thought it would (I thought the total output would be at least half that of a 250W MH, but it was more like a third).

Might have to reconsider how many you need to replace a traditional 250W MH...

I'd like to test out a Radion G3 Pro, if anyone is willing to loan me one for testing purposes (hard for me to justify buying one just for this test)...

 

[machote]

so then kessils are better?

 

[coit]

Is there any weighing for efficiency by frequency / photon energy? Someone with actual qualifications (maybe you? ) could explain this better, but is there any point to measuring past 700nm? Does the MH being a really good UV/IR emitter boost it's paper efficiency meaningfully after the weighting?

 

[tankslave]

Yeah, if you weigh the curve for photon flux density (number of photons, rather than energy), the curve will shift up on the right (red) end of the spectrum. Since it takes less energy to generate red photons than it does blue, you get more bang for your buck (that's why grow lights are usually reddish).
However, PAR readings also cutoff above 700nm, so that extra energy the halide lamp puts in the infrared (700-1000nm) basically just goes to heat up your tank. The halide does have more UVA (360-400), which corals do use/need.


Since the halide has more red/blue, you should expect get slightly higher PAR readings with the metal halide lamp, but keep in mind that corals are usually better adapted for the blue end of the spectrum, which PAR readings don't really take into account (doesnt really tell you if they're red photons, or blue photons, just adds them all up).

Basically, I think what this says is that you get about the same amount of light per watt with either system, but the kessil might have an advantage with coral growth, as it dumps more of its energy into the blue.

Dont know if that answers your question...

 

[coit]

Yep that's pretty much what I was half remembering

One other question I have about the spectral plots, are they both read from the same sensor? The MH next to it looks like it has a fairly high resolution, are they both measured the same way? I vaguely remember there was a fight around here a while ago about how "smoothed out" some data sheets for LEDs were vs allegedly much spikier looking reads if they were read directly at a high resolution from a spectroradiometer. Is the Kessil really that smooth?

 

[tankslave]

They were both measured on the same sphere and sensor; I dont have any control over the smoothness/averaging, so yes, it does look like the Kessil is quite smooth compared to the metal halide.

 

[coit]

Sweet, good to know. Thanks for putting this together by the way, it's not a toy I'd ever heard of anyone breaking out for reefing purposes before. Roughly how much does an integrating sphere cost off the shelf? Is it an 'if you have to ask...' sort of thing ?

 

[LakeShow]

These graphs are great, Kessil claims that their new A360we is around 30% stronger than the 350w's. It would be awesome to see them side by side on a graph like that if you can get your hands on one.

 

[tankslave]

Sweet, good to know. Thanks for putting this together by the way, it's not a toy I'd ever heard of anyone breaking out for reefing purposes before. Roughly how much does an integrating sphere cost off the shelf? Is it an 'if you have to ask...' sort of thing ?

For the one we have, you're probably looking at $20-30k... There are smaller ones, that are more "reasonably" priced, that you could use for small LEDs and such, but not really something you can put a foot long bulb in.

 

[tankslave]

These graphs are great, Kessil claims that their new A360we is around 30% stronger than the 350w's. It would be awesome to see them side by side on a graph like that if you can get your hands on one.

Yeah, I'm kinda curious as well. Still waiting for them to send me a demo unit...

 

[tankslave]

So I took advantage of the sale at MD and got an XR15W. I will probably end up returning it, as I don't think its enough juice for the 60 cube I'm planning, but I at least got to test it out and get a nice apples for apples comparison:



To put some numbers behind the pretty pictures, if you integrate the graphs from 400nm to 700nm (the visible spectrum), you get the total radiated output in watts (total energy output per second). Again, this is independent of the lens angles, distance to the fixture, etc. This is collecting all the energy that the fixture puts out that we can see. (It is interesting to note that the Kessil actually looks like it has a bit more UV than the Radion)

So here's the numbers. Wall plug power was measured with a Kill-A-Watt:

Ushio 250W (14K): 41W Radiated/ 250W input = 16% Efficiency
Kessil A350W (both channels high): 13W Radiated/ 90W input = 14% Eff.
Echotech Radion XR15W (all channels 100%): 17W Radiated/ 73W = 23% Eff

Haven't done the conversion to total PAR (total photon flux) yet, but will try to post that next. I think the total radiated power efficiency kinda gives you a more practical feel for what you get, rather than all these PAR maps anyway.

 

[GroktheCube]

Interesting. Surprised that the Radion is so much more efficient than the Kessil. 23% is pretty good!

 

[jda]

Are you able to test the Radion and Kessil at settings/programs more like how people use them? I don't know of anybody who uses either at 100% on all channels.

If you want to test more MH, send me a PM and I will ship some to you. I really appreciate this study/data and your efforts.

 

[coit]

The XP-Es these days are pretty insane efficiency wise

http://www.cree.com/LED-Components-and-Modules/Products/XLamp/Discrete-Directional/XLamp-XPE

IIRC there is a lesser but still noticeable improvement with a few of the other emitters they use on it too.

It would be interesting to see what the generational improvement is from the first two cluster radion to the xr-30 as well. I thought the A350W would get crushed but going from launch dates .. at max power it adds up to 11.5% gain per year or so? And the kessil emitter is a tiny multichip-alike (dense matrix or whatever they call it).

 

[tankslave]

Yeah, supposedly the A360 had some efficiency improvement, but I haven't gotten my hands on a new one yet. I think most MH lamps are probably going to be in the same efficiency range, but if there's one in particular that everyone really wants me to test, let me know.

Obviously certain LED's are more efficient than others, and running all channels at 100%, just gives you an average of all of them, but since that also corresponds to the "12K" preset, it seemed like a good starting point. I can try other settings too, I'm not really sure what's the most "popular" setting is. Any other setting just dims one or more of the channels though. If you really want to be thorough, you should just measure each channel one at a time, and do the calculation for each one on its own. Maybe if I have some time over the weekend...

 

[greaps]

Great date, hope you get more fixtures, and bulbs, would be interested in the Chinese light comparisons.

 

[rgulrich]

Nice read, great info - keep'em comin'!

 

[Fredfish]

That's some very cool testing you're doing. So the Echotech is quite a bit more efficient than the Ushio (in the range of 40%).

The difference in efficiency between the Echotech and Kessil is quite surprising.

 

[Christian J]

If you guys don't know what an integrating sphere is, it basically captures all the radiated light from a source, no matter what the angle, elimating the effects of the optical system (reflector, distance from the source, etc).

But effects of the optical system is an important consideration when comparing light fixtures. According to http://www.advancedaquarist.com/2012/10/aafeature

"Good LED lenses are compact in size and, at the same time, can help to transfer up to 90 percent of produced light through the water surface. For comparison, when using conventional bulbs with reflectors usually only 40% of light penetrates the surface. Best reflectors (often cumbersome) can yield up to 60% of light penetration, and the bulb itself partially blocks the light returning from the reflector."

if you weigh the curve for photon flux density (number of photons, rather than energy), the curve will shift up on the right (red) end of the spectrum. Since it takes less energy to generate red photons than it does blue, you get more bang for your buck (that's why grow lights are usually reddish).
However, PAR readings also cutoff above 700nm, so that extra energy the halide lamp puts in the infrared (700-1000nm) basically just goes to heat up your tank.

Not sure if I understood the above --are you saying the integrating sphere measured heat from the MH bulb too? Doesn't that make the whole comparison between LED and MH meaningless? The very definition of efficiency is to convert less electricity to heat and more to visible light.

 

[sahin]

tankslave: this is awesome work. Love seeing hobbyists taking time out to do this sort of research. :beer:

Are you able to provide data for either the Radium 20K 250w or 400w?

I would love to see Raw (absolute) data and scaled by input power graphs.