Backyard Aquaponics
A place to discuss aquaponics

I'd say so, even if you have 3 X 10W for a total 30W, it's only about 1/10 midday sun strength.

Ow now i just don't lknow what to do i can't run an 300w led in a closed plastic box

Thanks for all the answers anyway!

No its not a good comparison.
Gunna
1/10 th of the midday sum at what latitude?

If its only leafy greens and I have never used led's before and they are in the high kelvin (shorter nm) you may be able to get away with 30w. Close only to cover and with a mylar surround (and don't forget air movement).

Where is yabbies when you need him?

HAHAHA sleepe.

"i havent tried any of it but its not a good comparison".....

try standing in a small box with a 600w HPS and then try again with a 30w LED..... then come back and tell me which gives off the most heat (power, which is what is needed).....

go try grow a plant under a 30w LED..... LOL sleepe.


The only LEDs worth using for plant grow cost a lot of money (and are high powered), you wont get shit all growth from cheap chinese LEDs..... or household LEDs.....

I'm at 31S, 1200W/m^2 is usual here over summer, so up to 35-40N or S latitude. Even now in winter, when growth is slow, I'm seeing 650W/m^2.
However, Solar radiation intensity is measured on a flat plane, the intensity when measured with a face on detector is still over 1000W/m^2 at this time of year throughout the middle of the day.
As I type this at 8:15am, the solar radiation on the upwards facing detector is 246W/m^2, with the sun only 16deg above the horizon, and face-on the intensity is 892W/m^2.
(246 / cosine of sun's zenith angle of 74deg)

Does it matter.. Gunna' gave the mathematical answer as to what happen outside under typical insolation.
If plants have developed over time to grow under those conditions, then surely that is where you should start.

If you want to try something contrary, then just go for it and then come back and tell us we were wrong..

I have seen the reflective "tents" used with red/blue led lamps.
These tents help to reflect the light to all parts of plants.. and thus you could get growth at lower lamp powers..
If you still seek details, then try talking to hydroponics shops as to what power levels they recommend..

But if you want advice from most folk here, then understand that here, they are not into table top hydroponics ..
..
.

Yav

Heat is an unfortunate product of HPS and metal halide lights (not a useful product). I do have a 150w led High Bay array that I am sure you would not wish to be in a small room with for very long.

Gunna

The midday sun is not a good analogy of working out what is required to grow leafy greens.

Bui

As I said I am not familiar with leds for growing. At the time I used to know some very unusual people leds were not around.
This is why we need yabbies.

Perhaps, but I find the midday sun works quite well for me If you can light with similar intensity and spectrum, it will work. Of course that's not to say lesser levels of illumination wont work, after all, stuff grows in fairly gloomy places, but serious hydro growers don't mess around with 3 or 10W LEDs.

Gunna; I don't think he is a serious hydro grower the grow area is only 50 cm x 50 cm.
Lets say we only take the PAR spectrum and knock out a bit of the longer and really shorter wavelengths. Green and yellow can be seriously reduced and red is not terribly significant. So that leaves us with 20w blue (high kelvin) and 10w full spectrum (well white and red anyway). One of the concerns I would have is reflectors with leds.

Just so you don't think I am *sigh* myself, and for a bit of amusement here is a pic of an antique (I have rotated the lights sideways so you can see them). This was the smallest seedling growing cabinet I ever built (just larger than a bedside cabinet.
The circular T5 was a 22w high kelvin the sockets were for CFT's. Mylar would have been nice but flat white had to do. The lights were suspended by cabinet door magnets so they could be lowered or raised on two metal plates.
Air was drawn in through a false floor to the front of the cabinet and exited the top back via a volt reduced computer fan.
I never had the heart to throw it out or give it away.

the heat part was just as an indicator, obviously the light is what matters.
I think the sun in a very good analogue for lights, after all, when was the last time you heard someone say "needs 8 hrs of full LED" when talking about plants?
now, if a plant needs X amount of full sun light, i think that is a perfectly good starting point to find out what sort of lighting you might need for optimal growth.

Now im not saying 10w LED wont grow plants, i grew a seedling under a single LED that was on the back of a speaker to indicate that it was on, it grew about 5-10cm and put on its first set of leaves..... this took a good month or 2.

now is that the sort of growth rate we are taking about? or do we want something closer to what the plants would do outside?

If you want to compete with nature, you cant get away with trying to cheat.... you need to throw power at the plants.

I just looked up those high bay LEDs, They look the same as Cree LEDs, i have a torch with one of them in, they are very powerful, you can feel the light heat up your hand. There is no doubt that light of your would be good, but that is no where near a "normal" LED.

Do you know how many lumen that high bay puts out Sleepe? A lot i imagine.

Yav

I am playing silly buggers with something else at the moment. However 1 question. Why do you think most plant leaves look green to you?

because that is the only colour which our eyes can see that gets reflected by the leaves, the other colours (blue, red, etc) get absorbed by the plant.

Did you know that the first algaes and plants were purple leaved and that that is a more efficient colour for leaves to be?
did you know that shadows are actually purple? Edit: change that to, did you know shadows from plants are purple

yes i can pretend to know stuff about light too.

Most of the green light not all; you don't need to pretend as long as you understand it, (most people don't)

So do you still think that you need full sunlight for leafy greens?

no, however people (as far as i have seen) are already saying LED arent all they were touted to be, plants need more than blue and red.

the "full sunlight" thing is just what gets used for normal gardening as it indicated not shaded.... so if you need 6 hours of full sun for leafy greens (about what they need) and the area of the world they come from gets say half of what Gunna gets (500w/m) then you must realise that to get the same sort of growth rate as the plant would get in its natural setting, ytou must provide it with as close to 500w of light for 6 hours per day as you can get.

once again, it comes down to..... how fast / slow do you want things to grow? not.... will they grow under certain lights, because they will grow under almost any light..... just not well.

That comes as a serious worry to me; I grew grosse lisse tomatoes on a raised bed next to a green painted asbestos fence under the shade of a *frack* big honkey nut tree.
Aside from the naughty little birds and the caterpillars I ended up having to turn a lot into a very nice sauce.

Probably should have bought a Lotto ticket.