Can I replace my fluorescent tube with LED tube?

[hafezzahruddin]

Greetings,
Currently, i am using fluorescent tube to light my cacti and seedlings. As my seedlings are growing in number, I am wondering if I can replace fluorescent tubes with LED, because I believe that LED tubes are cheaper in long run. Currently, I am using 10 fluorescent bulbs, and will have to install more if my seedlings keep growing. FYI, I grow cacti indoor because I don't have compound around my house anymore... Thank you.

[CactusFanDan]

Which LEDs are you thinking of using? If it's one of those red and blue systems which are often used by narcotic growers and claim to be best for plant growth, then I suggest thinking otherwise. Cool white or ideally full spectrum LEDs would be better. They have higher setup costs though, which might be worth thinking about. Fluorescent tubes are good, but ballasts severely reduce their efficiency. Is your growing space fully enclosed with reflective material, such as white paper or shiny metal? If not you could do that to make sure the light output from your tubes is put to as much use as possible.

[iann]

Whether it is cheaper in the long run will depend how long you use it for, how much it costs you, and how expensive your electricity is. Also how efficient it is. Most of the LED tubes I have seen on the market area actually no more efficient than a good quality fluorescent tube. Assuming you can find one that is more efficient than a fluorescent, then the initial cost should be offset by savings on electricity after a few thousand hours.

This example of what I believe to be pretty much the latest top-of-the-line spec is actually significantly less efficient than a good quality fluorescent tube of the same size, as well as having about half the total light output. You can perhaps find something a little better, and the more directional light output is convenient, but don't fall for hype and expect miracles from these rather expensive gadgets. Another aspect of the hype, although not especially relevant for use on plants, is the declared "high colour rendering index", again actually a little lower than even the worst modern triphosphor tube and far below specialist tubes.

[Heather]

I have been wanting buy a light and have no idea what I am looking for. Could somebody give me some specs please? Do I need those hooded things or will I want to fit overhead fluorescents?
Many thanks.

[iann]

I have been wanting buy a light and have no idea what I am looking for. Could somebody give me some specs please? Do I need those hooded things or will I want to fit overhead fluorescents?
Many thanks.

What do you want to use the light on?

[Heather]

I have been wanting buy a light and have no idea what I am looking for. Could somebody give me some specs please? Do I need those hooded things or will I want to fit overhead fluorescents?
Many thanks.

What do you want to use the light on?

Seedlings and growing Cacti. I don't have a greenhouse so I have them in an empty room under a window. I don't think they are getting enough natural light in there so I want to supplement it in any way I can.

[hafezzahruddin]

At the moment I am using white tiered racks to put my seedlings. They are as young as 3 weeks old and as old as 2 years old. Each tier has 2 long 'super bright' fluorescent tubes. I turn on the light 14 hours a day (they grow indoors and not etiolated with this set up). They tubes not only give them bright light but also the warmth emittted from the set up. (Malaysia is warm though, at night 30 degrees celcius)
Last week I stumbled upon LED tubes with the same size and brightness at a mall. They use waaay less electricity than the fluorescent tubes. This what i mean by saving on the long run. I have operated the cacti set up for almost 2 years and the tubes will add up as i collect more cacti. Yeah, 2 years now, 14 hours a day.
However, the LED produces very little heat than the fluorescent, so I am concerned that changing the type of tubes will affect my plants drastically... (Eg: soil will not dry up as quick as before, etc)
Advice, anybody?

[teo]

LEDs still use power and will produce heat that has to be handled. The power LEDs used today seem to consume 1W each (and also produce 1W heat). If you pack 12 of these in one bulb (a common size) it will produce 12W of heat. Since the LEDs will deteriorate faster and be less efficient with high temperatures the heat need to be dissipated either by built-in fans (with limited life span) or a big heatsink. I have a grow-box setup with these (with blue and red LEDs) with a noisy small PC-fan for cooling and it seems to work OK. I also have a grow-box with 6 fluorescent tubes (6x23W) that also have a fan for cooling but the temp still is around 30C in the box, a bit lower at night when the lights are off. I try to convince myself that the warm temps are good for germination of the seeds

[iann]

Last week I stumbled upon LED tubes with the same size and brightness at a mall. They use waaay less electricity than the fluorescent tubes.

They either don't produce the same amount of light as the equivalent tube, or they use a similar amount of electricity. The absolute best available LEDs are modestly more efficient than the best fluorescent tubes (although you may have obsolete inefficient tubes). The "less heat" claim may simply be more hype, but it generally indicates a low power product making false claims about the light it emits. LEDs are tiny little things with very directional light output that can appear immensely bright to the naked eye in comparison with a large smoothly luminous conventional light, but expect them to light a room (or a plant) and the low total light output becomes a problem.

The directional light output of LEDs can be helpful for getting 100% of the light onto a small area of plants. It is generally only possibly to get about 80% of a conventional fluorescent tube output onto and many of the setups I see, possibly including yours, get less than half the light to the plants. This can lead to some exaggerated claims for the effectiveness of LEDs when the real problem is a sloppy fluorescent installation. Also note that many LED lamps for conventional use are deliberately designed to spread out the light rather than send it in a single direction, for example by sticking LEDs onto a base at different angles, so consider the design of the lamp you are looking at.

Although it is now possible to buy ambient LED lighting that is slightly more efficient than a good (4-5', 1200-1500mm) straight tube (which works out to about twice as efficient as the energy saving CFLs now in widespread use), 90% of the ones I've seen for sale, even from Hong Kong and China (UK approved LED lights are technically way behind and extremely expensive) are less efficient than a good fluorescent tube, hence the example I showed. I will say it again: don't be caught out by the hype. Look very carefully at what you intend to buy and check the specifications or you could end up with an expensive white elephant. There, I've said it, you've had your warning. I'll comment further if you want to post a link to the lamp you are looking at (or the ones you currently have), but I'm not going to argue further. Buy what you want, but I warned you and my conscience is clear.

[hafezzahruddin]

Ian, Teo,
I have not made any decision yet on which one is the best. My knowledge on this is very limited and that is why I am posting this in the forum. I am just a simple guy who loves cacti very much and I love to collect them. However, sadly, i reside in a building which doesnt have ample place for me to expose my cacti to natural light. I am using fluoroscent light for past few years to light my cacti, and it goes well. But there are times when I sit down and think if there's a better way to make my cacti grow well inside a building. (I live on 17th floor, the only natural light access is the window in the bathroom and my bedroom.) i cannot simply put them at the public verandah, my neighbours will go beserk. My mom denied them because she hated thorns.
I am trying to find a way to optimise the life of my cacti within the building for at least a year, before I move to a landed property.
I am very concerned that the lighting set up that I am using at the moment is torturing the cacti. I am open to any suggestion on how to set up the shelves efficiently.

[teo]

I think that to grow full-size desert-type cacti you need much more light than you can produce using LED/fluoroscent tubes. I was talking about seed-growing. I have seen big HPS lights using 400W (and making a lot of noise) that can be used but I don't think you want these in a home.

[hafezzahruddin]

i guess i need to move some of my cacti to my brother's place until i move to a landed house February 2014.
For time being. They will get enough light there.

[iann]

I have been wanting buy a light and have no idea what I am looking for. Could somebody give me some specs please? Do I need those hooded things or will I want to fit overhead fluorescents?
Many thanks.

What do you want to use the light on?

Seedlings and growing Cacti. I don't have a greenhouse so I have them in an empty room under a window. I don't think they are getting enough natural light in there so I want to supplement it in any way I can.

Seedlings you can easily grow under fluorescent tubes, or even individual energy saving bulbs for just a handful of pots. You should aim to get as much of the light as possible onto your seedlings, which could be a spotlight for a single bulb or a more advanced reflector system for fluorescent tubes. Since seedlings will often want to be in a heated enclosed environment, just sticking your lights inside a white box is a simple and effective approach. Plan on around 20W of fluorescent light per square foot of seedlings.

Lighting adult cacti is an ambitious project. The required light levels are much higher than for seedlings, just about possible with something like high output T5 tubes, but easier with a metal halide lamp. Not for the faint-hearted, it would be expensive to buy and expensive to run.

[Heather]

Thank you.

[nimich]

I hope I’m not too late to join the discussions here, and to disagree with some of the comments above.
I would like to first remind you some facts about luminescent lamps construction and SPECTRA. Whatever the content of the phosphors coating of the tube is, a fluorescent light source (mercury vapor filled tube with phosphorus coated inner side) generates a series of wavelengths that are often concentrated into narrow bands, termed line spectra. Phosphors mainly emit yellow and blue lines, and relatively little green and red. This mixture appears white to the eye, but the light has an incomplete structured spectrum, quite different from the spectrum of the natural light. See the illustration bellow and various fluorescent lamp type spectra - http://en.wikipedia.org/wiki/Fluorescen ... omposition

Sources of visible light.jpg (24.24 KiB) Viewed 3709 times

Next, let’s talk about Luminous efficacy

Roughly speaking, it is a measure of how well a light source produces visible light. Mathematically, it is a correlation between the spectrum of the light source and the human eye response to light. The human eye sensitivity is peaked at around 550 nm (yellow-green).

The plants however, doesn’t “care” much about the human eye sensitivity and hence, to some extent, to luminous efficacy. Important for the plants is so called “photosynthetic efficiency” which is a correlation between the spectrum of the light source and the plants “photosynthetic response” to light. The difference between the two efficiencies is illustrated bellow for sunlight, together with the photosynthetic response of the green leaf.

Efficiencies and responce.jpg (130.91 KiB) Viewed 3709 times

What we see, is that the plants respond better to light sources which deliver more light in the blue and red regions, than to light spectra giving high luminous efficacy.

Thus, when we talk about cacti or other plants growing under artificial light, the luminous efficacy is not an adequate measure of the light source, and we should always think about the specific spectrum of the source.

The fluorescent tubes, depending on the type of the ballast, have indeed high luminous efficacy, ranging typically from 60 lumens per watt with an ordinary magnetic ballast, to over 100 lm/W with a modern electronic ballast, because they are designed to reproduce the colors of the objects, as seen by the human eye (high color rendering index – CRI). But the plants don’t “see” much of this light as illustrated above.

So, hafezzahruddin, one simple thing you can do to improve the indoor illumination of your seedlings, is to replace the usual fluorescent tubes with specialized ones. I would combine tubes with near-natural light, broadband spectrum, close to daylight, like HAGEN Sun-Glo, with tubes having the red and the blue part of the spectrum reinforced, like NARVA “Lumoflor” , “Oceanic light”, NARVA Oceanic Flora, or similar e.g. SILVANIA Grolux. These tubes, in addition to “better” light (in terms of an appropriate spectrum), delver more flux at the same consumption and have extended life (up to 20 000 h). The prices are quite reasonable. The cost of Sylvania GroLux T8 36W 120cm in Bulgaria is 6.00 Euro.

Now about your question regarding LEDs.
T8-LED tubes which directly replace the usual fluorescent, are stacks of low power (~ 0.3 W) “white” LEDs . Few years ago, low power LEDs indeed had low luminous efficacy (of the order of 40 lm/W), but the modern diodes already have an efficacy of over 100 lm/W. See e.g. http://www.sinostarled.com/18W-LED-Tube ... 8W-61.html

An important thing is that although LEDs are not designed for plants illumination, they have spectrum which resembles the photosynthetic response curve of the plants.

LC 5630 white LED.png (20.96 KiB) Viewed 3709 times

I haven’t seen the photosynthetic efficiency calculated for these diodes, but looking at the spectra, if calculated, the efficiency will be much higher than the luminous efficacy of the best quality fluorescent lamp even if the LED tubes you “stumbled upon” are not compiled with the best quality diodes. In simple words, this means that, in addition to an appropriate spectrum, with LEDs the plants will effectively “see” more light, for the same overall light flux as rated by the manufacturers. Moreover, as mentioned by iann, you have more directional light (~120 deg, full angle), and you don’t need reflectors neither you need ballasts or other hardware.

So, if you are prepared to invest, I would encourage you to replace by LED tubes, for sure it will be cost effective in long run, as the LED’s lifetime is up to 50 000 h. T8-LED, 120 cm here costs 18 Euro. There are numerous companies in Honk Kong, Europe and N. America.

You must be careful not to buy LED tubes with inner surface coated with a fluorescent ! Such exist. In this case you will have the same spectrum as of an usual tube, or some mixed spectrum.

I’m using a LED “lamp” produced for street lighting and containing 4 high power – 10 W white LEDs in a line. The lamp length is only 55 cm, but it is good for my 60 cm – grow box.

LED Lamp.jpg (31.25 KiB) Viewed 3709 times

The diodes have a spectrum as the one shown above and deliver 4000 lm total on a growing area of about 1 sq. foot at an intensity level of 60 % from the maximum (divergence angle of 125 deg), with the majority of the light going onto the plants. This flux intensity is too much for seedlings, so I attenuate by ground glass. My “lamp” is outside the grow-box enclosure, so I don’t have heat dissipation problems.