Refrigeration based units (as most are) shift roughly 3 times more than they consume. Meaning a 1000w unit, can move 3000w of heat out. While thermoelectric units, such as the useless $50 wardrobe units, Are about watt for watt.
The 3rd type of drier doesn't rely on cold surfaces at all. The desiccant based units. These are what you would use to get below 40% RH at any meaningful flow rate.
If a 600w LED is 33% efficient, then 400w is directly turned to heat. If moving that uses 150w, then we find ourselves struggling to get a small enough aircon. It's about 1300btu. Such a tiny unit as 150w, is like a 12L dehu, which at 50% RH is more like a 3L so there is no hope of it drying the 10L out that a 600w LED grow produces. 66% of which is in the 12 hours of light.
A freezer evaporator differs from a room based one, it that it's fins are wider spaced. The freezer one is working with much colder air, and as such dries it more and must resist ice from blocking it up. It would be a good choice for over chilling the air, which could then be desiccant dried and warmed up a bit before entering a tent. This becomes possible using an actual freezer, and some sort of defrost cycle at night. So the freezer is a small cooler/drier and then another drier finishes the job. The larger aircon is only needed where outside air is too hot, so more cooling than the light is required.
As yet, I have seen only evidence that UV doesn't work. When it does, we will see it added to larger opps. I have seen many people try, but it's just not catching on. A few positive experiences will always come through the placebo effect, but in labs, the lighting guys can't prove we should be buying them.
Your highest transpiration rate times (hot/wet) grew the most resinous flowers, and cooler/wet, slower transpiration did not. (Edit: have you had the opportunity to grow in <70F, 20% RH??)
