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Quantum Dot LEDs: the future of lighting?
I don't mean to hijack this thread and make it about Aurora, but the book has some details that might be relevant. Dialing down the lighting for human comfort is a good point, but efficient agriculture may impose other requirements. In Aurora, their lighting can provide 120,000 lux which is brightest sunlight on Earth. Typical overcast at midday is 1000-2000 lux. In one biome, lighting units have failed and KSR writes:

Loc. 3783
Their artificial sunlight varied in luminosity from 120,000 lux on a clear midday to 5 lux during the darkest twilight storms. This was all well regulated, along with a moonlight effect at night ranging from a full moon effect of 0.25 lux to 0.01 lux, on the classic lunar schedule. But when the lighting elements had to be refurbished or resupplied, then it was as if unscheduled eclipses were occurring. Crops were therefore affected, their growth delayed in ways that stunted them at harvest time.

So you might have to wear sunscreen after all, at least in the crop-growing areas. These are lighting units, visually weighted, lumens, lux, etc. You don't need as much power if you don't supply the full spectrum of sunlight, though if you are trying to simulate Earth as closely as possible, you need to know what plants and animals use from that spectrum. Bees use UV, etc. Today, 300 W/lumen is a high but demonstrated LED luminous efficacy. For this level, according to an online calculator I found, 120,000 lm/m^2 is 400 W/m^2.

Aurora is truly a closed habitat with no resupply or external resources at least until they reach their target star system. And in the book, they have done well, surviving for 160 years (they have some pretty amazing 3D printers to recreate any device they need from recycled and stockpiled materials). But systems are breaking down due to subtle but cumulative long term effects. Overcoming these problems is one of the threads of the book. Others are social and psychological problems. It's really fascinating. I will need to read it again one of these days!

Wander some day to a indoor farming sight. Full spectrum lighting is never used, waste of resources and slows growth. The proper selection of red, green, or yellow LED's are used for the particular crop. Example; red only for tomatoes.
This just shows the current state of lights.
Cool! I wish they had done the math to compute cost per hour. So I did it; they're all roughly comparable, with LED bulbs (as shown) being the most expensive, and halogen after that.

But their prices for LED bulbs are outdated; I've been buying them at Home Depot for about $5 each. At that price, they're about half the cost of incandescent bulbs, and comparable to CFLs as shown.

Of course, I don't buy the lifetime shown (and claimed by the manufacturers) for CFLs, either. I used those for quite a while, and was constantly replacing them. I took to marking the date on the base when I installed, so I could see exactly how bad it was when I replaced them... and typically, it was about a year or two. Pure marketing bunk there. CFLs were a brief misstep in the technology chain, and I'm happy to see them go!

LED bulbs, on the other hand, have not failed me even once so far. It's definitely the future of lighting, unless we come up with something even better!

Joe Strout
Lead Developer, High Frontier


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