Sure! Just take any ordinary heater and reverse the polarity! That is, if it
is electrical, turn the plug around and plug it in the "Wrong" way (if it is a
polarized plug, you may have some filing to do). If you are using a battery
operated heater, just put the battery in backwards.
Barry will attest to my finesse in physics, and my expertise in such matters!
:-)
No really, a heater works by sending an eletrical current through a resisitor,
and this (somehow) creates heat (and often light, usually dull red to orange).
I don't know of any way to reduce ambient heat via electrical resistance.
Most (all) "coolers" or "refrigerators" only act as heat pumps. They "transfer"
heat from inside an insulated container, and release it outside the container.
This is done by boiling and condensing freon or other ozone-eaters. Anyway,
therefore, a refrigerator heats up a room whilst it cools the inside of the
fridge. This kind of thing does not seem like a workable idea for a
terrarium, which is not well insulated to start (unless you would like to
insert the ENTIRE terrarium in a fridge, with its own light source) hmm...
this might be a plan, if you've got a spare horizontal deep-freeze unit, but
I'd save it for frozen dinners bought bulk on sale...
Anyway, your best bet would be to try to reduce heat sources in the room
where your terrarium's at. You could start by re-routing your balasts
away from the tank. Or you could do what I do, just cut down on the
amount of light you give the plants, and this reduces heat! Also I
run the lights at night, and have them off during the day.
Michael