Lighting Plants

[Jackalope]

Hi,

This thread seeks to encourage the discussion of lighting plants for the purposes of indoor gardening. Since many of our members come from the US and other places which have sub-freezing winters, consideration of lighting suitable for growing plants is timely.

Gary

[ElfNori]

I've been researching LED grow lights as they are less expensive to build and run and can be tailored to what you need (greenery or blossoms/fruit). From what I've read, the growth is better than the best full spectrum lights. I've got a personal friend who is using LED lights in his basement and he backs up what I've read on the internet. The best I've come up with yet is a company that sells kits.

14w grow light kit

The same company has a 50w kit as well.

Nori

[jack@badflas]

I think that is a lot of money. If you go to Walmart, Lowes, or Home Depot, you can get a 4' shoplight for about $10 and a pair of daylight bulbs for $5. For $15 you get full spectrum light that will cover a 2' X 5' area and draw 80 watts. at 1' this is plenty of light. I've been growing plants using this for years.

[ElfNori]

Sure you could, but the interesting bit here is that plants use red and blue light most efficiently to produce growth. They won't grow under green light at all and yellow light is pretty worthless to them, so full spectrum light is a bit of a waste.

Plants use blue light to produce foliage and red light to produce blossoms and fruit. More blue light is required than red as more foliage is required than flowers and fruit. Nasa used LEDs in space to grow stuff. More info here.

I'm working toward reducing our wattage. Using full spectrum lights might be easier/cheaper in the beginning, but I don't want the heat or the extra power consumpsion. LEDs will be better in the long run. They won't burn the plants, no matter how close they're set, they will use less power, produce less heat, use less energy and will last much longer.

Nori

[ElfNori]

Here's a hands-on test of the led array

http://greenpinelane.com/homegrownlights_test.aspx

Nori

[jack@badflas]

Hardly a waste, but suite yourself. Shoplight produce all the right light you need, enought to saturate the plants. Anything beyond that is a waste. a 30 watt savings would take a very long time to pay back, especially if you figure the interest on the difference in the up-front cost. A shop light covers a much larger area as well, so cost per square foot is considerably less, even considering the power. 80 watts covers 10 square feet (2'X5'), vs. 14 watts covering 3 square feet. 8 watts/ft2 vs. 4.6 watts/ft2. The shop light is actually cheaper to operate. So considering the up front cost, power usage, etc. the shop light wins. The only thing that the LED does better is last a long time.

it would take 3 14 watt units costing about $150 (once you include shipping) to do the same thing as a $15 shop light. I can replace the whole thing 10 times for the same cost, and I'm still ahead with power. FL lights don't put out enough heat to worry about either.

[GaryD]

Hi Nori,

Thanks for posting this information.

I've been interested in the idea of indoor growing for some time but the cost of running metal halide or high pressure sodium lights makes the whole business prohibitive.

This may be less of an issue if the waste heat from the lights is used to keep a fish tank at the optimum temperature (for example) but I'm certainly attracted to the idea of LED's given all of the benefits that are claimed for them.

Since the 14 watt light was only large enough of itself to get a single tomato plant to a foot high, I wonder how many 14 watt arrays would be necessary to grow plants in a space of (for example) 16 square feet.

Jack.....does the arrangement that you mentioned have two fluorescent tubes in it? Could we have more information about how it works and what sort of results you achieved with it?

Gary

[ElfNori]

I take your point, but I only have a finite number of available watts available right now. Once the house is in and we get moved up the hill I'll be better of (watts to waste), but for now I have to stay small. As I'm only covering a small aeroponic tub, not a bed of any kind, the 14w will do nicely.

N

[ElfNori]

Very true, but that's all I need for that particular app.

I saw, in one of my searches, someone who built an LED grow light out of strings of Christmas lights. I thought that was pretty trick.

Nori

[Dufflight]

I don't think metal halide chew that much power. The fluorescent lights come in red and blue spectrum. MH in a room with a fish tank would warm the water and provide a heat sink for when the lights are off.

Over here the temp outside is not much of a problem. I can see the benefits of using the lights outside to extend the light to plants grown out of there normal seasons.