Growing with LED lights

[Aceetobe]

Unfortunately, LED isn't a searchable term, so I'll include the term diode in here so its findable.

I know the startup costs of LEDs are ginormous, but it looks like they are coming down.

I live in San Diego, and am mostly an outdoor grower. However, I have a basement (a rarity for California), which holds at about 65 all year round. I was thinking I could set up a little "tent", and grow some of the cooler more humid loving orchids. This would be about 5x5 area or so.

Now if you take one of these indoor tents and seal it up, all of a sudden of course the heat is going to increase. Toss in the lights, and that 65 becomes more like 80. After doing some research, it appears that the amount of heat generated by the LEDs is negligible, so I was wondering if any of the setups had been used, and whether or not they really put out as much light as they say they do.

[Ross]

LED lighting has been discussed here a lot over the last year or so. I think (this is my take on it) the state of the science, is that the lighting isn't quite up to what we can provide with t5 banks. LEDs certainly are attractive in the electrictal usuage arena. But they don't really deliver right now in the foot-candle arena.

[Ray]

Part of the problem with LED's is the VERY narrow spectrum each puts out.

While most setups do use bulbs in the two peak wavelengths that react with chlorophyll, it actually reacts with a range of wavelengths surrounding each peak, so there is a lot of wasted "acceptance bandwidth".

[Oscarman]

But they do make excellent flashlights!

[jrhennek]

I use the blue (B60XB) for Phal seedlings and the plants grow like crazy. The plants were able to be repotted into 3 1/2" pots in about half the time my seedlings that are not unfer the light. Light is on about 14 hrs per day just like my 600w HPS.
Would I do a whole setup with LED's (I DON'T THINK SO)

Jayme

[Aceetobe]

While most setups do use bulbs in the two peak wavelengths that react with chlorophyll, it actually reacts with a range of wavelengths surrounding each peak, so there is a lot of wasted "acceptance bandwidth".

As long as they hit the max absorbance, it won't matter. One molecule of chlorophyll can absorb 1 quanta of light per time unit. At the absorption peak, the extinction coefficient is the highest, meaning the highest percentage of interacting photons are actually absorbed. By having different wavelengths, you lower this probability, and thus become inefficient. Now there maybe some other benefits to other wavelengths beyond just chlorophyll, however I see no efficiencies in using anything other than peak absorbance. I don't know what the relaxation time for chlorophyll is though. I'm guessing its on the order of milliseconds.

Which brings up another point. Do people usually run LEDs under DC or AC conditions? If the lights are under AC, this could be part of the reason why they are inefficient.

Anyways, I'm glad you pointed this out to me. I looked in the "lighting forum" and found the other threads. It seems like its marginally cost effective if you put together your own system. And completely not cost-effective if you buy pre-built ones.

Once again, my primary concern is heat, because I'll be right up against the limit of the cool growers.