L.E.D. vs HALIDE/T5/VHO

[Ron99]

Eugene is correct. Unless you are running them right above your water without a splash shield then salt creep and corrosion should not be a big problem. There was one guy in the candlepower forums IIRC that posted a picture of an emitter he had been running over a salt water tank for a long time and it was covered in salt and corrosion but it still lit up.

Heat is really the enemy of LEDs. Like any lighting system it all depends on how it's designed and put together. If it is designed well and has adequate cooling you can expect the advertised life out of the LEDs. If it is not well cooled you can expect the LEDs to degrade faster. But LEDs themselves have been used on myriad different types of equipment in all sorts of environments so I would still argue that their reliability is well understood.

As Eugene pointed out the LEDs are best run at less than 80 degrees. The lower the better. I haven't measured the temperature of my heatsink exactly but what I can do is put my finger in one of the holes on top of the fixture and touch the heatsink. After running for several hours it feels just barely warm to the touch so it can't be above 40 degrees. I may add a temperature sensor hooked up to the Arduino when I get to that point.

As for cars, which ones seem unreliable? I have heard of some issues on Cadillacs but Hondas and Audis seem pretty reliable from my understanding. Again, Eugene is correct that the stresses on automotive components are far higher with greater temperature shifts and shocks and bumps and vibrations etc. Not generally a problem for aquariums.

So I think your criticism of LEDs could apply to T5s or MHs as well as there are good reliable systems and poorly built and unreliable systems. Doesn't matter what the technology is. Part of the problem you mention about difficulty in repairs is that in order to save on manufacturing costs the LED emitters are set up on modules in many systems and if one LED goes down the whole module has to be replaced as it is usually not simple to replace a single emitter once its on the PCB. I do give kudos to Maxspect as each of their LEDs is on a discrete star PCB and can be replaced individually if need be. Not so with the AI or several others where you have 3 to 6 emitters on one PCB. So again, depending on the design of the system, the fix could be as simple as replacing one emitter or having to replace an entire module. But replacing a module should not be more difficult or more onerous then replacing a ballast in a T5 fixture.

[sphelps]

Kind of my point guys. LEDs are rated for 10 years before a 30% drop in intensity occurs just like halides are rated for 5 years. So yeah halides only last a year before par is too low so how long will the LEDs last? It would seem obvious and fair to say they won't last the full tens years before requiring replacement.

Also yes all lights have failures which was also my point but the bulbs can easily be replaced while LEDs cannot be easily replaced. Based on the design of the fixtures I've seen it appears that once the LEDs fail or become too worn the fixture is basically trash unless you have the skills to fix it which in my mind isn't fair to assume we all do. In addition the shear number of LEDs is much higher than other alternatives so the chance of failure is greater.

Like I said looking more promising these days but it's too early to say too much about the reliability and lifespan of LED fixtures which is why I wouldn't recommend the option to most people. Enough said.

[Ron99]

The difference between LEDs and Halides and T5s etc. is that LEDs spectrum does not shift as they degrade. They simply lose output. With MH and florescent lights the spectrum shifts to undesirable wavelengths which compounds the loss of PAR. LEDs should last longer because they will only lose some output but not shift in spectrum. So 6+ years is a reasonable estimate for LEDs.

The added difficulty of changing LEDs will only be an issue if their lifespan is far less than what is estimated and I guess that's the crux of the argument. You either think they will last or you believe they won't. I suppose only time will tell.

[sphelps]

I'd agree that six years would be a reasonable estimate at this time. That being said with the current design of LED fixtures the energy savings will likely never give a payback if you have to essentially replace the fixture every 6 years. That's without my concerns of premature failure which seems fairly likely with what I've seen with current fixtures on the market and the lack of a decent warranty period on newer fixtures.

On the topic of par vs spectrum I don't believe you're correct, just because the spectrum of the bulb changes doesn't mean the par will also change. Certain halide bulb and ballast combinations will last far past the year mark in terms of par while spectrum is a separate issue.
http://reefkeeping.com/issues/2007-04/ac/index.php

I see LED taking more of a role in supplemental lighting in combination with halides or some other type of HID lighting of the future.

[OceanicCorals-Eugene-]

Originally Posted by sphelps

I'd agree that six years would be a reasonable estimate at this time. That being said with the current design of LED fixtures the energy savings will likely never give a payback if you have to essentially replace the fixture every 6 years. That's without my concerns of premature failure which seems fairly likely with what I've seen with current fixtures on the market and the lack of a decent warranty period on newer fixtures.

On the topic of par vs spectrum I don't believe you're correct, just because the spectrum of the bulb changes doesn't mean the par will also change. Certain halide bulb and ballast combinations will last far past the year mark in terms of par while spectrum is a separate issue.
http://reefkeeping.com/issues/2007-04/ac/index.php

I see LED taking more of a role in supplemental lighting in combination with halides or some other type of HID lighting of the future.

PAR decreases as spectrum shift due to a few factors. PAR is a measure of Photosynthetically Active Radiation as bulbs shift in color they generally move either towards the right of the spectrum graph or the left, most bulbs we know move towards the right as can be seen in high kelvin bulbs as they go from blue to white-ish. As this happens PAR values drop as the spectrum is now shifting and you get less of both red/blue spectrum that most corals utilize. The point is even if the PAR is still high enough the corals no longer get there needed spectrum so there colors become dull or brown and none of us like that

[sphelps]

Originally Posted by OceanicCorals-Eugene-

PAR decreases as spectrum shift due to a few factors. PAR is a measure of Photosynthetically Active Radiation as bulbs shift in color they generally move either towards the right of the spectrum graph or the left, most bulbs we know move towards the right as can be seen in high kelvin bulbs as they go from blue to white-ish. As this happens PAR values drop as the spectrum is now shifting and you get less of both red/blue spectrum that most corals utilize. The point is even if the PAR is still high enough the corals no longer get there needed spectrum so there colors become dull or brown and none of us like that

Bulbs with a lower K rating typically produce higher PAR because, as you said, it's related to the amount of useful radiation (more of it in lower spectrum bulbs). So if PAR and spectrum wear where directly tied together, as you stated, then with certain bulbs you would see an increase in PAR as the spectrum shifts in the lower K direction. We of course know this isn't the case and the article I linked suggests that the change in par and spectrum overtime are independent not dependent. The decrease in PAR is related more to the decrease in intensity not the shift in spectrum. Of course certain bulbs preform differently so some may be more effected by the spectrum shift but avoiding such bulbs is pretty easy these days with all the information we now have.

So just because an LED doesn't suffer the same spectrum shift as other bulbs doesn't mean the PAR rating will be unaffected, it simply means you won't notice a change in color overtime, only intensity.

[OceanicCorals-Eugene-]

Originally Posted by sphelps

Bulbs with a lower K rating typically produce higher PAR because, as you said, it's related to the amount of useful radiation (more of it in lower spectrum bulbs). So if PAR and spectrum wear where directly tied together, as you stated, then with certain bulbs you would see an increase in PAR as the spectrum shifts in the lower K direction. We of course know this isn't the case and the article I linked suggests that the change in par and spectrum overtime are independent not dependent. The decrease in PAR is related more to the decrease in intensity not the shift in spectrum. Of course certain bulbs preform differently so some may be more effected by the spectrum shift but avoiding such bulbs is pretty easy these days with all the information we now have.

So just because an LED doesn't suffer the same spectrum shift as other bulbs doesn't mean the PAR rating will be unaffected, it simply means you won't notice a change in color overtime, only intensity.

your forgetting those spectrums that were already in the two extreme zones of red and blue, where do they go? Those gets pushed further right into the 800nm (reds) range that we cant see, nor can corals utilize so you lose a good portion of the spectrum that you would if the bulbs were new, so you see a decrease in PAR output. The decrease in PAR is not just about the intensity decrease, losing red spectrum and blue spectrum decrease par values quite a bit as well

The way spectrum works is, too far right, the spectrum isnt used, and same goes for to far let. if the bulbs we had originally were spiked at 450nm and spectrum shift it to 500nm in a year, all that blue light turns into green. Corals dont utilize green light very well and the and useful PAR goes down. Then everything in the 650nm-700nm range literally just disappears from the usefull radiation spectrum and moves into IR range.

[Ron99]

Originally Posted by sphelps

Bulbs with a lower K rating typically produce higher PAR because, as you said, it's related to the amount of useful radiation (more of it in lower spectrum bulbs). So if PAR and spectrum wear where directly tied together, as you stated, then with certain bulbs you would see an increase in PAR as the spectrum shifts in the lower K direction. We of course know this isn't the case and the article I linked suggests that the change in par and spectrum overtime are independent not dependent. The decrease in PAR is related more to the decrease in intensity not the shift in spectrum. Of course certain bulbs preform differently so some may be more effected by the spectrum shift but avoiding such bulbs is pretty easy these days with all the information we now have.

So just because an LED doesn't suffer the same spectrum shift as other bulbs doesn't mean the PAR rating will be unaffected, it simply means you won't notice a change in color overtime, only intensity.

It's actually more complicated then that. The spectral shift of bulbs actually makes a big difference in PAR. First have a look at this figure that shows the peak absorption wavelengths for chlorophyll:



You can see that chlorophyll likes blue and red but not much in between. Now here is a good article on the spectral output of various MH lamps:

http://www.personal.psu.edu/sbj4/aqu...omparison.html

Here is the output of a 10,000K Ushio bulb as an example:



So as that big blue peak not only decreases but shifts over the the right you get less real useable PAR since the green part of the spectrum is less efficient then the blue and red in terms of photosynthesis. The situation is probably even worse with 14,00K and 20,000L bulbs that have more blue and less red in their spectrum. Here's a 20,000K bulb:



So yes, the lack of spectral shift in LEDs is a big advantage in that you stay in the peak output frequencies for photosynthesis. I imagine the T5s etc. put out similar spectrums as some of the MH lamps so the situation is similar.

[sphelps]

The other day you seemed to agree that 10 years wasn't reasonable, what's changed??

Originally Posted by Ron99

LEDs should last longer because they will only lose some output but not shift in spectrum. So 6+ years is a reasonable estimate for LEDs.

Perhaps changing a ballast is as easy as changing a driver, that's fair enough, but how many drivers are used to drive 250W of LED compared to the number of ballasts for 500W of halide?
How is changing an LED as easy as changing a Halide or T5 bulb? Even the shear number of LEDs to replace in comparison, it wouldn't take much longer to start over. Sorry but if you have to break out a soldering iron it's not that easy. Plus I'd like to talk about actual fixtures not DIY approaches. Like I said let's stay in the real world.

My assumptions were very little, you're assuming way more including price drop when more realistically the LEDs you need to replace down the road will be extinct and difficult to source. You'll have to adapt new types of LEDs into the fixture which will add more complication. Maybe perhaps someone could provide a manual from a supplier of an LED fixture that shows the user how to replace the LEDs? I imagine such thing doesn't exist, for obvious reason.

[superduperwesman]

I say we design LEDs that are easy to replace and make a killing