lets use a good example to figure lighting out instead of your shelf unit we will go with a 4 foot x 4 foot growing area and use your 2 bulb fixture with the t-5 light bulbs
Fluorescent: Since we are trying to be educated gardeners, we will have sought out the extra high output tubes for our garden. These Fluorescent tube generate 2750 lumens per 40 watt tube. That's 68 lumens per watt - now we are getting somewhere. Let's use enough fixtures to cover our 4x4 garden. The fixtures are 4 feet long by six inches wide. This allows us to cram 8 fixtures over our garden - using a total of 640 watts. Each fixture hold 2 tubes, so we have a total of 16 tubes generating 2750 lumens each - that's a total of 44,000 lumens. Subtracting for the loss due to reflectance, we now have 33,000 lumens to cover our garden with. 33,000 divided by 16 square feet equals 2062 foot candles of light intensity, ASSUMING the lights are right on top of the plants. When you raise the lights to accommodate for the plants the light intensity drops rapidly. When you double the distance, you cut the light intensity by four times - OUCH. Using an array of 16 - 40 watt tubes you can expect to achieve about 500 foot candles at a distance of 12 inches. With this setup we can grow low to medium light plants without burning them. much is said about foot candles on growing plants what you really need to look at is light intensity over the foot candles
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