My latest cooling design is on the next page.
So I recently received a terrarium from a friend. I have become interested in cost-effective setups, and a couple weeks ago I set up a 75 gallon lowland terrarium with only a sunny windowsill to heat/light it (it's exactly the same thing shown here without the cooling system). My plants love it. With my new terrarium, I decided to try my hand at highland nepenthes, which I have never really considered due to the extensive, power-sucking setups used by most growers. Here is my version, and my sole N. ventricosa (I'm starting with nothing fancy, so I can experiment without worrying about pricey plants) seems to like it.
Here's a picture of inside the terrarium. Gravel sits on the bottom, with water up to the tips of the rocks. Sunlight from the window evaporates the water and keeps it humid, about 75%. I don't want to resort to supplemental lighting, so I chose light-colored gravel to reflect light. I used some velcro to attach very reflective insulation to the back of the terrarium, as seen on the right. The pitchers on the ventricosa are showing some coloration, so I assume this is quite effective.
Now the most important part of a highland setup is the cooling system. I have read lots of different threads, and evaporative cooling seems to be the cheapest way to go. Although other kinds of setups are very effective, I didn't like the priciness of ones with water coolers pumping frigid liquid through radiators. Often times evaporative cooling systems involve fans blowing around mist from a humidifier, but I didn't want to spend the money on one, or pay for its electricity. I devised a simpler, albeit less-effective system. However, my ventricosa seems to like it.
Essentially, the cooling system is a cardboard box sitting on top of the terrarium with two holes for the exhaust ends of two computer fans. Plastic wrap surrounds the inside so the moisture doesn't destroy the box.
The fans suck air over piece of thin cloth with long slits cut into it. I secured the cloth onto the box with thumbtacks around the perimeter.
This cloth is kept evenly wet by having one end submerged in a long tray of water.
The basic concept is that water evaporates from the wet cloth when it passes through the slits. The evaporation chills the air, and it is blown inside to lower the temperatures within the terrarium. Remember to include an exhaust vent at the other end so it runs through the whole tank. Because it is evaporating water, it doesn't have much of an effect on the humidity at night.
I have the cooling system timed to go on for a few hours at night. Unfortunately, I haven't been able to get an accurate reading of the temperature of the cooled air. I doubt that it is any better than the more complex systems. It may not even be close! However, my ventricosa was putting out deformed leaves and refused to pitcher before I installed all of this. It now looks great, so I'm certain it works well enough.
The only problem I have run into is the wicking system. I have to place the cloth in the tray before the fans kick on, but if I do it too early, the water drips off the saturated fabric. This isn't really annoying, but it does waste some water. Also, if all the water in the tray is not used when the fans are on, it continues to wick and eventually drip. Either way, I have to fill the tray the next evening. Even if I were to have an upside-down bottle keeping the water level constant for a few nights, I can't stop the dripping until I pull the cloth out in the morning. I could avoid this by turning the fans on all night, from before I go to bed to after I wake up.
Anyway, I hope you like this system. It's appearing to work well. Any comments or questions are welcomed. I think if we all work together, we can make a very easy, cheap way to enjoy these marvelous plants. I will post updates as I refine the terrarium.