When I recommend LED technology to people, the often say: its still too expensive! Its not. This article explains it why: >>>>LED lights have very specific emission spectrum, so these grow lights avoid the areas that the plants cannot use - this is why the pictures look so oddly colored. So consider that most LEDs and HPS bulbs both have lumens/watt efficacy of about 150. The PAR lumens will be much less than that for HPS, but pretty much identical for LED because you select the LEDs that are within the PAR range. Furthermore just like how PAR is more meaningful than lumens/watt, the useful energy/watt is even more specific, and thats where LED will really shine (pardon the pun). This means massive increase in efficacy in terms of usable light per watt despite the lumens/watt being roughly the same. To put this into some non-technical numbers anecdotal evidence suggests that 300W of LED is about the same as 800W of HPS (yes, there are debates still on this, but lets assume that this is correct for the moment). So thats 500W of additional wasted energy, plus 150W cost to remove that energy, or 650W of additional energy cost. At $0.13/kWh at an average of 16h/day over the entire 3-month grow cycle is $123 in extra electricity. So if your LED setup costs $250 more than an HPS setup it will pay for itself after only 6 months. This isnt even addressing the issue of being able to place the lights closer to the plants, but thats a complicated topic for another thread. To address your second question about the efficiency of higher wattage LED bulbs: Fewer bulbs does not mean more efficiency. Bigger is not always better. Looking at the specifications of lower wattage bulbs they tend to be in the 150 lumens/watt range. Higher power bulbs are usually in the 120 lumens/watt range - meaning youre spending more overall energy per unit of light. This is the same as the 600W HPS vs 1000W HPS debate. 600W HPS is roughly 150 lumens/watt - 90,000 per bulb (give or take). 1000W HPS is only about 140 lumens/watt - 140,000 per bulb. If you scaled the 600W to 1000W youd have 150,000 lumens instead for 1000W power draw. In other words you spend 7% more energy to get the same light output with the larger bulb. Three 600W bulbs will put out 270,000 lumens, whereas two 1000W bulbs put out 280,000 lumens. Only 10,000 lumens more, but 200W extra power required. Sometimes smaller bulbs are more efficient; Same goes for LED. Its more convenient and cheaper to use the bulbs with the higher output (which is why manufacturers use them), but the energy cost is higher. The people who build the LEDs arent concerned with power draw, so the less efficient draw doesnt really matter that much. Third point about inverse square law. Again this is a complicated topic, as it is not as simple as it is typically made out to be, but for our purposes we can assume that it is. Yes it does still apply here. Double the distance, half the energy per unit area. However HPS bulbs emit light in 360 degrees, and this is really what is more important than (and the source of) the inverse square rule. You need reflectors and white/mylar walls to try to get as much of that light to your plants as possible. At a distance of 24 above the canopy (and assuming a 2ft diameter canopy) only 53 degrees of that light is directly hitting your canopy (again, this is a simplification). So the other 307 degrees (or 85%!) of emitted light has to reflect in order to get to the plant. Assuming a very generous 25% overall loss before that light hits your plant (due to multiple reflection surfaces, bouncing back into the bulb, not hitting the plant at all, etc) and 22% of your usable HPS light is being lost, again ultimately to heat (which requires energy to remove). So, in a very large nutshell, this is why LED can be significantly better than any other source. LED emits light in a very tight beam - as tight as 15 degrees. These LED grow lights mix bulbs of varying focus from 120 to 15 degrees in order to get as much light directly to the plant without reflecting. All of these factors combine to why 300W of LED can be considered equal to an 800W HPS light, and the energy costs will allow it to pay for itself within 6 months. Reduced energy consumption also has additional benefits for the guerrilla grower as that means less overall household consumption. Even for the legitimate growers it means 2.5X the number of plants for the same household draw. Proper growing is limited by 5 factors, one of which is light. A house with 100A 240V service can realistically only provide about 80A 120V to grow lights, which if using HPS is only about 8000W or about 20 plants at 0.5lb/plant and 0.5g/W of yield. Using LED you can grow 50 plants (assuming the other 4 factors are attended to!) with the same yield per plant.
Posted on: Fri, 07 Mar 2014 09:04:17 +0000
Trending Topics
Recently Viewed Topics
© 2015