reply to post by speculativeoptimist
Originally posted by Char-Lee
Originally posted by Berenai
So now we can put these on spaceships and have a food supply for long journeys to Mars or....
We can use them in our ELE bunkers...what they were made for maybe.
Cree is a world leader in LED tech and they have had DoD funding
Gotta keep people healthy in deep underground bases somehow! Mostly just vitamin
d, certain leds can produce the requried wavelengths.
Disclaimer; I have a commercial interest in LED lighting technology. I can't go terrifically in depth with some scientific aspects or technical design
for this reason.
The reason leds are beginning to take over the world of lighting and open new doors in farming;
Lumens are a photopic measurement for human eyes, with maximum sensitiviy in lime green and minimums at UV(deep blue) and iR (Deep red). Plants don't
see in lumens they see photosynthetic efficiency - number of photons of a given wavelength range (colour to us) and ease of absorbtion. Leds can
target peak photosynthetic efficiencies, with much more usable energy than any other technology for the same power input. Plants can adapt for other
wavelengths outside of these peaks, however the peaks are where the efficiency is.
One of the most important factors is that the spectrum of light can be manipulated to control many factors of plants from algae to coral to food
crops, in turn water transpiration in land based crops and growth type, speed and other characteristics. Much of the 1000w/m2 the sun puts out is
reflected as infrared energy off the plants around you, so the actual required density for photosynthesis is far less. This is also why infrared tuned
solar panels are more efficient in general.
And direct sunlight may be more efficient in some cases, but as a single point source it looses out in dense plots or any vertical farming.
Most high temperature, high end light bulb tech is a large single point source, without reflectors
(360 degree emission) they are pretty much
the same lumen efficiency as top end leds under typical working loads. However traditional tech has less micromole/W efficiency, due to spectrum, plus
added effects of heat but will also begin to degrade in a few thousand hours. Metal halides (amber) used in streetlights are 20,000 hours or more,
with poor light quality but excellent efficiency and longeivity. Yellow is also very close to the green peak sensitivity for human eyes.
LED has the advantage of being smaller, cooler, less intense and most importantly easily arrayed or spread out, so maximum surface area can be covered
and thus a higher average level of brightness, instead of just in one direction. NASA showed this alone can gain 25% food yield with the same amount
of light being used! Just like many streetlamps along a road vs one huge one. The setup you see in the photos of the test facility is far from optimal
at the distances the LEDs are being used, this is not where LEDs 'shine' the best.
Someone stated the heat generated by a vertical farm would be wasted - heat from leds can be used to preheat water or run any nearly heating system in
the building. This is near 100% efficient. Incandescent lightbulbs in cold climates are also near 100% efficient because of this! They heat your room.
Spend more $ on heating + leds or spend on incandescent light and less heating.. It's not always just about light output, it's about application.
A properly designed LED system could last anywhere past 100-200k hours. At 8 hours a day 7 days a week, that's a light bulb change in 31 years @ 100k
hours. Thing is you probably wouldn't have to change it, because the drop would be approx 5-10% in measured brighness, which is barely visible... see
where this is going? Infact it's more likely the LEDs power supply will fail than the LED.
The reason LEDs aren't taking over;
Beancounters plus chinese mass manufacturing has given leds a bad name. Most consumer led tech is poorly made and 5+ years behind the curve because
people don't want to pay for 'just a light'. Cheap christmas lights, overheating fixtures and blueish white, cheap torches are hardly a good poster
child. If you want it done properly, then get someone who knows what they're doing to design it for you. Don't expect to pay peanuts for it either;
cutting edge technology plususually a time consuming build - one that could likely outlive you.
With tomatos at $15/kg here, it's worth investing in LEDs for winter. Higher yeild, upside down plants for no damage with large fruit, nearly no pests
and any excess light can illuminate my living room. Seasonal stuff all year round. Plus then you know what's really in them, limiting radiation
exposure from rainfall, which is an issue with external crops currently.
LEDs will probably save the human race in the future. Just sayin'..
edit on 15/8/11 by GhostR1der because: edit for italics and extra