A picture of my greenhouse:
It has been mostly emptied due to uncontrolled fluctuations in humidity. The nursery faces North, but some early morning direct sun still overheats the greenhouse. The plants on the bottom shelves are the surviving ones.
I am planning to build an evaporative cooler, placed at the top, so that cold air naturally sinks and cools the shelves all the way down. The cooler comprises of a 12V fan, its power supply and a body of soft water which will serve as the cooling agent. I am trying to choose a model which will work with the least number of fans, water pumps and pipelines. Here are few models I'm thinking of:
1- A capillary mat: I will use the mat as the cooling radiator. The mat is mounted vertically over the body of water. Water will go up through capillary action. If necessary, the cooling mat can be sliced so that it serves as a radiator through which the fan blows air. The issue: How high capillary action may conduct the water? Does the capillary mat work when mounted vertically rather than under the planters? Would other types of cloth work just fine?
2- Fan blowing over a vase made of unglazed clay. The vase of clay transpires water which evaporates and cools the vase. The closest example from another discussion here: Matka. The issue: Depending on size and quality of the pottery, the vase may transpire too much and lose water quickly.
3- Fan blowing over a tray of water: Consider the tray as a horizontally-mounted radiator. A metallic tray holds the water. I chose metal over plastic for its better heat conductivity. The fan blows air over the surface of the water and evaporation will cool the water down. As metal conducts heat, the tray will also cool down and then it cools the air underneath it. The horizontal orientation not only holds the water but also allows a more efficient convection and heat transfer. The issue: Is the evaporative cooling from the surface of the tray as effective as that of a cooling radiator? Will it provide enough cooling?
So out of those three possibilities, which one is effective and work for me?
