Ok, Since this topic has not received any replies, well, I will state my opinion on the subject, if you think otherwise, I welcome your opinion.
I have decided through my research that unless you have a free source of heat ( I don't) then trying to heat the air is a waste of resources. The air is a terrible heat sink because it has no mass. Yes, I can dig a bunch of holes and put pipe in to hold some hot air during the day, but then I still must use electricity in the way of fans to move it down there and get it back out. I am planning a DWR system, so I will have lots of water. Lots of water means i have lots of MASS. I think I will spend my money on a pump instead of a fan and I will move my water to a place it can get heat in the sun the pump it back to my FT and DWR to store it. If I have us some kind of stove etc. then I will also move water via. a pump to the heat source and back to the DWR and FT. The mass of the water should do a fine job of giving off a bit of heat to the air in the green house. If it does not and all I do is keep my water warm, well, I think my plants will be just fine as they will be basically sitting in a hot tub with their roots. That's my opinion anyway, what is yours???