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Comment by RIcardo HErnandez on March 26, 2012 at 10:42pm

Sure, I will send you the paper that I normally use, in the mean time you can look at the following link, http://www.egc.com/useful_info_lighting.php

I found it today when I was looking for some info for my project

Ricardo

Comment by Bob Campbell on March 26, 2012 at 11:31am

Thanks Ricardo. 

I've done a little research in order to understand the acronyms and their definitions.  I beleive...

PAR stands for Photosynthetic Active Radiation which is the light spectrum that plants use for photosynthesis.
PPF stands for Photosynthetic Photo Flux which is basically a measure of the total light energy used in or available for photosynthesis.

I appreciate that you put this analysis in the correct terminology. 

I can convert lumens to moles of light but that depends on the light type. fluorescent lamps have a different spectrum than incandescent lamps, high pressure sodium lamps. and LED lamps. So there is a way to find out the number of moles in the PAR region for each lamp but i need to do some calculations.

Would it be possible to share the calculations for converting from Lumen (LUX) to mol/sqmeter/day?  I understand this depends upon the bulb's PAR, but I'm very interested in this science, and would be willing to take the time to learn about this.

Thank you very much!

Bob

Comment by RIcardo HErnandez on March 26, 2012 at 10:49am

Hello Bob

Variety of vegetables is too broad of a definition. For example if we take lettuce (low light requirement and quantitative long day plant) you need around 17 mol/sqmeter/day of light to harvest heads of a desirable head weight of 150 g in around 5 weeks after seeding. To achieve this with CFLs of 1600 lumens in your growing area and assuming lamps are 6 inches from the plant surface you will need aprox 74 lamps with a 24 hour photoperiod. Now if we talk about tomatoes, for maximum growth you need about 35 mol/sqmeter/day (this is for maximum growth. lower DLI's will also produce fruit but less yield) using the same lamps and under the same conditions you will need 204 lamps "ON" for 18 hours (tomato needs a least 4 hours of dark to avoid damage). Now I calculated an extension coefficient based on reflectance of  70% for ceilings, 30% for walls and 10% for floor, This number will fit If you had your growing area cover with foil in the ceiling and white paint in the walls. Hope this helps

Comment by Bob Campbell on March 25, 2012 at 10:01pm

Wow Ricardo it sounds like you know a lot about grow lights.  I could use your help.

My grow bed measures 10 ft long and 30 inches wide. I just built it and don't have a crop planned.  I just put an assortment of vegetables in to see what would grow.

I have
16 - 18W 6500K 1170 Lumen CFLs

16 - 14W 5000K 800 Lumen CFLs

16 - 23W 2700K 1600 Lumen CFLs to work with.

I have placed aluminum foil on the walls for reflection, and have built one light bar as shown here.

I was about to build two more light bars, but I'd like some guidance from you before I go any further.

I'd also be interested in the math and how you figure out the light requirements.

Comment by RIcardo HErnandez on March 25, 2012 at 6:26pm

Hello Tom

I work a lot with lights and plants, I have a concern with your set up not providing enough light for your plants to grow. I see you are using 1000 watt lamps, I was wondering if you could check the number of lumens each tube provides (effective flux) it is normally listed as a spec when you buy the lights. Lummen is a measurement based on human eye perception that goes between 380 nm and 780 nm peaking in the yellow green spectrum. In contrast plants use light between 400-700 nm commonly named as Photosynthetic Active radiation (PAR) but the main difference  is that plants peak absorption is in the  blue (400-500 nm) and red (600-700 nm). So something that looks very bright to your eyes is not very bright for the plants. I can find out how many fixtures you need of your current fluorescent lamps if you send me the lummens per lamp, your square footage, and your type of plants. To give you an idea, plants have a linear response to total amount of light they receive during one day (DLI) for example for lettuce (lower light requirements) if you provide the plant with 5 moles/sqmeter/day you will only get a growth of 50 gr of fresh weight, but if you provide 20 moles/sqmeter/day you can get a up to 150 grams of lettuce growth. Now i am sure you notice I am using units in moles instead of lumens. Well when i say moles I mean moles of light in the PAR range. I can convert lumens to moles of light but that depends on the light type. fluorescent lamps have a different spectrum than incandescent lamps, high pressure sodium lamps. and LED lamps. So there is a way to find out the number of moles in the PAR region for each lamp but i need to do some calculations. Again if you send me the lumens per tube, I can find that out. Sorry for the long message I just get excited when I talk about lights/plants. Ricardo

Comment by Tom Parsons on March 14, 2012 at 5:31pm

Bob

We ordered another 600 foot of mylar 4 foot high.  I am not sure if this will work or not.  We today got two 1000 watt lights on them.  The plants that are on the south east corner of the building are doing the best.  No matter what everyone says i still try different things.  We put in lights 4 foot florucent about a foot above some tomatos and they really did well.  I will keep adding pics.

Thank you for the encourgement.

 

Tom

Comment by Bob Campbell on March 14, 2012 at 1:10pm

Tom I am very interested in what you are doing.  Your scale is much larger than my system, but I too have chosen to grow inside.  I planted lettuce, basil, peppers, cilantro and spinach from seed and have small seedling poking out of the gravel.  But my little seedlings are stretching for the light and I'm beginning to fear that one wall of  glass may not provide enough light. I'm looking forward to seeing how you resolve this and other issues.

I saw your mylar walls. It looks like a good idea, and I plan to follow your lead.  I'm documenting my project on my blog at ChicoAquaponic.Blogspot.com

Please keep us up to date with more good pictures of your very impressive effort.

Here's my small grow room with an 800 gallon fish tank and 32sf of grow bed

Comment by Tom Parsons on March 10, 2012 at 1:55pm

My plan is to cover all the walls and maybe the ceiling tiles with mylar.  Then light up 1000 watt lites.  The whole building will bounce off of the other walls. 

Comment by Elizabeth on March 9, 2012 at 10:48pm

Hi Tom,

I think the mylar is a great idea.  It creates specular reflections, but eventually the light nominally has to hit a plant.  The other way to think about this is to paint everything white (diffuse reflection).  This is how an "integrating sphere" works - it collects all of the light that enters through an orifice (window) and bounces it around inside the sphere.The sphere in your case is the entire building.  You can think of your garden (building) as a big integrating sphere.  Anything in your place that is not covered with mylar would benefit from being painted the whitest white you can find, including the floor. 

As an engineer (physicist, working in optics) I think you are doing all the right thing.  If it is not mylar coated, paint it white.

I truly wish you the best with this endeavor.  You have come up with a number of very innovative concepts.

Very impressive,

Elizabeth

Comment by Tom Parsons on March 9, 2012 at 7:59pm

Elizabeth.  I will let you know on the mylar.  I wont know until i try.  I just purchased two 1000 watt bulbs.  I think this will blast bright lite on all the plants.  I expect hyperinflation soon.  When it hits the price of food will go way up. 

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