raschemmel:
a way to keep the temperature of a small atmosphere of air at a constant 30 C (probe, PID, and some kind of heat source insensitive to elements, as there will be dripping water and 100% humidity).
A way to keep the temperature of a reservoir of water at 30 C (waterproof probe, aquarium heater)
These two may be problematic unless you can guarantee the temp for BOTH will NOT INCREASE, eliminating the need for the ability to cool either one. If not, you may need to design a cooling system that circulates air slowly through PVC pipes to an ice
bath where the air enters the bottom , rises to the top of the ice bath and out the exhaust vent above the sealed chiller enclosure
(lexan) and back to the CAVE via a small PWM speed controlled computer cooling fan that turns off an on by a PID running the chiller based on feedback from the CAVE. Conversely, the heating of the cave would need a similar PID and possibly heating coils.
The reservoir and the chamber atmosphere will be too completely different modules. The reservoir contains the CO2 reactor for dissolving limestone and providing soil water pCO2 end members for the water going to the "cave" chamber. The only thing the reservoir provides to the cave chamber is a drip of water.
Also, just for more info, the setup will be indoors, so no need to worrying about cooling below ambient, as this is meant to simulate tropical caves.