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mattie

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Reply with quote  #11 
Thanks Keith.
I was looking on that website today actually.I was also looking at some clips on how to put together your own fixtures running full spectrum CFLs.This could be a better decision for me initially allthough I am back to building again.
Ive also looked at lumigrow LED bars, the common problem for me is the small area they cover vs cost.I know there are many advantages to using them however and tbh in an ideal situation i would choose this route,this is based what ive seen so far anyway.Ive also seen some diy clips online on how to build LED fixtures too.I cant imagine they could match the performance of the pro versions, but do wonder how near you could get or what the percentage difference may be.

What are your thoughts on greenhouse lighting? Is there a better approach that i may not have mentioned? What is your opinion on the CFL route? Would they provide a sizeable proportion of the light requirements in a greenhouse when the sky conditions are not ideal and at times of the year when sunlight hours are lowered.
Regards Mattie

kcl1s

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Reply with quote  #12 
Mattie,
We do spring annuals in our one acre greenhouse. We do not need supplemental lighting. There is a commercial grower in our area that does hydroponic tomatoes and lettuce. They use HPS (high pressure sodium) lamps. The cost of running the lights cuts deeply into their profit in the winter but they justify the extra cost because they need an uninterrupted supply to serve their restaurant customer base.

One neat thing they did on their large recent expansion is that the electric for the lighting is supplied by a large diesel generator. 180 kw if I recall. They use the lights in the morning for several hours before dawn. They reclaim the engine heat and the exhaust stack heat from the generator to help heat the greenhouse. The process is called combined heat and power (CHP). They say they are making use of 97+% of the potential energy in the diesel fuel.

Now for a backyard greenhouse I would not recommend year round growing. It is just too expensive. You need two things to keep plants like tomatoes producing. Heat (60 deg nights minimum) and light (14 hr optimum). A better plan would be season extending. Use light in a small area to start plants a month or two early. A lot of plants will finish started fruit in the fall if you keep the temperature up. Doing this would give you tomatoes from May to November and lettuces year round (but expect slower growth in the winter).

Hope this helps
Keith
gbwillson

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Reply with quote  #13 
Kevin-

800 seedlings was by far the most I ever grew. That was the year I learned a new way to give me almost 100% germination of my seeds. I wasn't expecting so many viable seeds, but what was I to do, toss them out? But what the heck, I either planted, swapped, or gave away literally 100's of flowers and plants. I live on the corner of the block across the street from a park so I get lots of people walking by. If anyone sees something they like, I usually have a baby or plant for them the next time I see them. Each spring I attend the worlds largest plant sale which supports a local school. Over 1,000,000 plants and flowers are sold in only 3 days! Thank goodness I have a wonderful dark rich sandy loam to dig in. I can't imagine gardening in hard clay like my neighbors only 2 blocks away.

Greg in MN[wave]

PS:I'm selling my 6'x8' greenhouse. I have an extra set of front and back panels I'd toss in too. I only used it two growing seasons so it is in great shape.
mattie

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Reply with quote  #14 

Thanks Keith.
Ive seen Dutch greenhouses that use CHP here's a short clip for anyone interested in general overview of how CHP works with a greenhouse.



Initially i had planned for a 200 m^2 floor space but using the ratios on Missouri U passive solar design and adding 10 degrees to my latitude i ended up with more than a 60 degree incline and a roof structure that was much too high and a danger of becoming a sail in high wind conditions.
My idea now is to keep roughly the same size as the Missouri U floor area and just add consecutive units or greenhouses to make up the floor space and keep the roof peak height lower.

I would be growing lettuce and leafy greens due to their resilience and have seen a commercial aquaponics grower quote 50 degree f or 10 c night temperatures which is more feasible from an energy saving standpoint.

I can understand that over a growing season lighting would add up to be another considerable bill which eats into profit margins.I really like the idea of a small area that could be used to boost growth rates early and extend the growing season this makes a lot of sense. I'm not looking to jump in feet first and naively and think huge scale initially , i just want to make sure what i have works first and is sustainable before i make any more decisions.

It also seems that large scale growers can run on really small margins and it can be difficult for a small greenhouse business to establish a customer base.Aquaponics has the USP but in an honest world theres a large percentage of people here who have probably never heard of it and some that could care less and will allways go for the cheapest option.Cost as allways is a driving force in decision making, which points back to margins and pricing once more.

This is all a long way of the original heading of this thread so i better stop here.
Regards Mattie

kcl1s

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Reply with quote  #15 
Mattie,
Yes. Leafy greens will require lower heat and light than tomatoes. Lettuce likes the blue end of the spectrum so cfls or 4 ft tubes will be economical and give good results. Little to no benefit in using the grow light bulbs for lettuce. Keep the light close to the plants for max candle power.

Keith 
KenD

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Reply with quote  #16 
This help?
http://lowpowergreen.com/product-catalog/2-x-4-led-replacement-panel-2.html
I don't know much about growing and the color temperature required for different plants and such. I am an electrical engineer however and if you give me the requirements I can try to design a lighting system that uses low power with the lowest initial cost and longest life if you want.
mattie

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Reply with quote  #17 
Hello KenD.
That is a great offer for sure and would be useful to others who might be looking at greenhouse options. My current issue is much like you described in how to judge whether a greenhouse LED and an LED for a commercial building have the same light spectrum that’s suited to growing lettuce. I can’t seem to see any costs on that link you’ve posted i presume its contact for details.

As Keith stated earlier that CFL and fluorescent would provide good results and that there would be no advantage to using a light that’s sold for plant growth? I’m a bit confused here as i thought there was a difference just need to do more research.

This vid seems to point to LED being the better option for lettuce. Although the initial cost is much higher, you gain on electrical costs, bulb replacement along with the other points that are made in the clip


The LED fixtures used here are shared in the info tab.
A set up like the one shown there allthough costly would be ideal from the point if view of saving floor space even the t5 would work and wouldnt be as expensive.
Perhaps it would be useful to show how to spec the lighting arrays for the greenhouse using the LEDs, fluorescent or CFL. The Missouri U greenhouse could be a used as a template here as it has all the plans already shared and is available to others, here is the link that’s shows all the dimensions http://aes.missouri.edu/bradford/education/solar-greenhouse/solar-greenhouse.php

I would be interesting to see what you  come up with here but only if its an easy task for you to do and you have the time.Time is a precious commodity and i don’t wish to waste any of yours. In fairness the setup shown in the clip above used in a small section of the greenhouse seems to be the best route for me to take.

Regards Mattie
KenD

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Reply with quote  #18 
Ok it seems that from a quality standpoint LED is better than T5. This paper:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1087990/ seems to indicate that a small amount of red light around 3000K mixed with blue light around 5-6000K stimulated plant growth. Do you want to use PV or run off grid power? How many hours a day on average to run the lights? The average temperature during the winter of the inside of the greenhouse would be nice as well since some LED controllers have a minimum starting temperature like CFL's do, but not many of them. I have to do my taxes today so I might not have any time to work on it but this shouldn't be to hard to solve.
gbwillson

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Reply with quote  #19 
I've spoken to many master gardeners and only one insisted that florescent lights specifically designed for growing plants were worth the cost. A full spectrum bulb, like the sun, has everything plants require for healthy growth, but at a fraction of the price for grow bulbs. I haven't used LED's yet, since I still have life in my florescent bulbs. The cost for LED bulbs are high, and selection is still limited. But the market is catching up fast. 
Greg in MN[comp]
KevinH

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Reply with quote  #20 
Interesting video.  The LED grow lights shown are mostly in the red and blue spectrum needed for photosynthesis.  Regular lights will also include other parts of the spectrum so you are paying to create light the plants don't need.

The reason the lettuce in the video is not turning red is the lack of UV light.

Kevin H
MN
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