Re: 420 Consumer Reports Competition - GrowLEDHydro's 600W LED vs. 600W HPS by Be Iri
do you think that leds might end up having a separate ballast the way that hids do? in order to keep the heat down in a grow space. would this be possible for leds?
Yo, Falcore- great question. LED's do not have 'ballasts', they have 'drivers'. For the average user this is a matter of semantics- both LED's and HID require some form of power control/ conversion provided by a device external to the light producing element itself. The LED ad's you see that say 'requires no ballast' (or something to that effect) are misleading.
The LED driver could in fact be remotely mounted and there would be several advantages to this, including the reduction on grow space thermal load as you so correctly point out, as well as a few disadvantages- I can summarize below-
Advantages-
1. The heat produced as a result of AC power conversion to what the LED likes (typically a voltage clamped constant current DC source- the LED driver) could be totally external to the grow space all together.
1.1 The energy consumed in then trying to remove this heat with either air con or ventillation, 12 or 18 hours a day worth, could be forgotten, along with the electrical bill.
1.1.1 This may not be much heat- but it all adds up, particularily in the summer months, and your plants will like you for it.
2. One of the large advantages of LED's, one that is not particularily hyped by the current batch of LED vendors, is the inherent safety advantages available with a properly designed LED fixture for horticultural use. I think this is probably beause a lot of the current LED iterations are not designed with this in mind, just low cost.
2.1 If the drivers were remotely mounted from the fixture, you would be feeding isolated, low voltage DC to the LED fixture.
2.1.1 Wall AC would, of course, have to be provided to the drivers- but the dangers of electrical shock by the User and/ or fire if the fixture should, for whatever reason, fall from its mounting into, say, hydroponic or bubbler solution, would be GREATLY reduced.
2.1.2 Nobody thinks about these issues until they return home from the ball game to find the fire department and the police at their house- I guess if you are growing tomatoes you get good wishes from local law enforcement and they move on, if you are growing something else, maybe not so much.
2.2 The point here would be that there would be a number of advantages to a remotely mounted driver- besides the thermal issue, the fact is that LED systems can be designed which are orders of magnitude safer for the User and the property than current HID technology.
Disadvantages
1. Cost- it would cost more to design the system this way, for a number of reasons which would make this post longer and it is already longer than I intended.
2. There are constraints related to DC resistive losses in the power feed cable from the driver to the LED fixture which would limit the practical distance to which the driver and fixture could be separated.
2.1 If your looking at 20 feet or something to run the cable thru a small hole drilled in the wall so that the driver and grow space are in separate rooms- this should be no problem in a properly designed system with compensation for these losses.
Your very clever observation about separating the driver from the LED leads to a whole host of thermal issues related to LED technology that are not being well served by the current class of LED fixtures I have seen advertised. Another day perhaps.