Growing fruit / veg indoors - artificial lighting - Help

[veggiechicken]

I read those calculations early this morning, didn't understand them then, and I still don't I would prefer to tailor my crops to fit the seasons, not try to bend the seasons to suit my taste buds, especially given the cost involved!

[kazborn]

my partner says you could get all complicated with the math or you could just place your hand on the nearest leaf to the light and move the light closer to your hand till it feels just the right warmth, 30w cfl's are good a mere inch or 2 from the foliage if using lots of low power lights the 'wasted' light all builds into a nice aura thet feeds the whole plant...no weak lower nodes as you normally get for the more used and 'better' top down hps bulbs (or mh for veg).

[Dusty Rhodes]

I take your point kazborn, it is rather complicated I was just trying to get a rough idea.
I mean the room I am in is 12x12 foot and if it had a light bulb for every square foot it would be pretty hot in the room, I think it might feel similar to being in the middle of the sahara!

Now were my 100 watt bulb surrounded by a circular lampshade with surface are of one square foot, that surface would be in similar conditions to the surface of the sahara on a hot day.
Now if there are reflectors above the light bulbs you are getting about 100watts per square foot.

The UK is at a latitude of 53.1142�, if my maths is correct we get the cosine of that which is 0.6, rather more than I thought, or our room is full of 60 watt light bulbs!! But we also have more losses in the atmosphere as it has more to travel through at that angle.

But we are on a tilt an only at that angle on the equinoxes, which are March and September I think, we get more in summer and less in winter.

Now you could use maths to work out a suitable distance for your light bulbs I believe.

What you need to do is work out the radius of a sphere with surface are of 1 foot, assuming you are using a 100 watt light-bulb.

so...let's do that!!

The surface are of a sphere is 4 pi x radius x radius ( 4pi.r^2) so 4pi.r^2 = 1

r^2= 1/4pi so r = square root of (1/4pi)

4pi = 12.5, 1/4pi = 0.08, sq_root(1/4pi) = 0.282

So you want 0.282 feet or 3.385 inches.

That would be at the equator though


Here you need about 0.68 of a foot or 8 and 1/4 inches if my maths is correct.

[square root of (0.6/4pi) feet]

That assumes you are using a bulb emitting the same spectrum as the sun, grow lights are different usually. They are somewhat artificial as they miss out the green light.
I don't know if that affects plant growth much, id guess if speeds them up if they get extra blue and red to compensate.

Of course you don't get sun all day either but I doubt all day full sun does any harm, more good I expect.

It probably would be easier to drive to Stonehenge for the answer and skip all the math

[esbo]

I read those calculations early this morning, didn't understand them then, and I still don't I would prefer to tailor my crops to fit the seasons, not try to bend the seasons to suit my taste buds, especially given the cost involved!

Fair enough, a lot of people probably do not under stand them, however I am pretty good at maths, got A grade B and I am pretty sure they are correct. I had does similar ones before when I wanted to work out how much stronger the sun was at various times of year and at various places on the planet and I think they are broadly correct although there are some things which complicate it such as the light has to travel through more of the atmosphere when it is at an angle so more of it gets scattered.

But I thought people who grow under lights might be interested, ie it is probably harmfully if you put the light too close. But the proof of the pudding is in the eating and you can find out the right distance an and power by trial and error. However my calculations to deem fairly reasonable to me.

Yes I doubt the cost of lights and electricity make it cost effective, if they did you would have a form of perpetual energy where you could grow a bio fuel cost effectively

[veggiechicken]

Hi Esbo, I'm not doubting your calculations as I don't have any knowledge of the subject. In fact I'm full of admiration as I haven't a clue about all the variables involved. But my caveat still stands! I don't mind using a heated propagator and I can see some merit in a small grolight setup but there is no way on earth that I would contemplate converting a garage into a growing place for out of season tomatoes or strawberries. For one thing, forced fruits lose a lot of flavour when not allowed to ripen naturally.
But each to their own, its none of my business.

[esbo]

Hi Esbo, I'm not doubting your calculations as I don't have any knowledge of the subject. In fact I'm full of admiration as I haven't a clue about all the variables involved. But my caveat still stands! I don't mind using a heated propagator and I can see some merit in a small grolight setup but there is no way on earth that I would contemplate converting a garage into a growing place for out of season tomatoes or strawberries. For one thing, forced fruits lose a lot of flavour when not allowed to ripen naturally.
But each to their own, its none of my business.

Fair enough, I am not advocating it, I have never grown anything with artificial lights and probably never will, it's not cost effective.

But then cost is not everything it's nice to be able to grow our own stuff and have fresh produce on hand, and there are certainly more expensive hobbies!!

I suppose I might consider a grow light at some stage if I wanted to get stuff off to an early start, you might not need much at all really just something to add to the daylight you get, maybe a couple of hours a day?

I am gonna try and figure out how much light my supposedly 100w equivalent light bulb gives out, I think it is about 20Watts, so basically that woudl need to be 5 times closer than a 100W bulb.

[veggiechicken]

Here are some other threads on the subject for anyone interested!
http://www.growfruitandveg.co.uk/gra...den_54882.html
http://www.growfruitandveg.co.uk/gra...mps_56352.html
http://www.growfruitandveg.co.uk/gra...hts_51038.html
http://www.growfruitandveg.co.uk/gra...ion_63491.html
http://www.growfruitandveg.co.uk/gra...ors_62765.html

[kazborn]

its not a matter forcing its just finding the best balance between natural and enhanced growing. you can guarentee sunny days at a strength you choose, attach it to solar battery storage to keep the sun as your carbon free power source and guarentee yout families source of vegatables even if the british summer decides to go on holiday itself.

the more you understand a particular plants sunlight needs the closer to nature you can make its enviroment. just as an example, the simple addition of an osclating fan can counter the spindley stems one can get from indoor growing. knowing the right colour lights to feed it can mean the difference between poor fruit and something better than you have brought in a shop.

at the moment we use the sun when its avaliable and make up the difference with cfls to produce full length days so the plants think its the correct time of year for its development stage

[RedC16]

Veggiechicken, it is your business because it's a public forum, anyone can jump in with an opinion. Although converting a garage is not on anyone's agenda....

Growing in this way isn't cos effective. Never was I under the illusion that this was going to be a money saver. On the other hand I will know where the food is coming from and what's been put in it. I know how fresh it is, will have it close to hand and I will always have the enjoyment aspect of the whole process that is growing you're on fruit and veggies. All plus points, the only down side will be electricity which leads me on to my next point.


As for more expensive hobbies... look no further than running a saltwater reef tank. I've had 430 watts of lighting running 10 hours a day on the tank before I switched over to LEDs. 2x 300 watt heaters switched on 24/7 and another 12 plugs running essentials an array of pumps/different apparatus. Add that to the smaller reef I have running and a 450 litre tropical tank as well. A few extra lights won't make much of a difference in the grand scale of things! Infact changing my T5 units on my main tank to LEDs saves me about 330 watts over a 10 hour period everyday.... in comes the Gro Lux in it's place lol.

[Dead Dogs]

Hi All,

Wow, what a thread.

Fist off on expense. Gardening can be as cheap or as expensive as we choose it to be. Whether it is just the cost of a packet of seed or an expensive greenhouse, it's up to us as indiviuals to decide. For me I have a greenhouse, polytunnel and yes grow lights.

RedC16, your ex-saltwater tank lights will be OK for growing fruit and veg. The spectra is good with both the blue and red needed by the plants. Light intensity may not be, just get the lights as close to the plants as you can without scorching them.

I use LEDs, as my resreach via the net sugessted that fluoresent lights were better than high pressure Sodium, because more of the energy input goes into producing the light. Same with the LEDs compared to fluorescent. Also with LEDs you can target those wavelength (colours) required by the plants.
I started with an all blue, 144 LEDs, 300mm x 300mm, light panle. Uses about 14 watts and only cost �34. This is ok for seedling and lettuce, but too week for large plants. Now have two 300 watt, 7 spectrum lights on timers.

Why do I use grow lights? Well the Toms in the poly have only just rippened and those from the greenhouse only last month. Where as I have been picking Toms from my spare room since early April. Same gose for the chilli and sweet peppers.