I have a lot of loud, fast, server fans kicking around. So my thinking would be to mount a bunch of those up, and have them blow the air. a 15K RPM 80mm fan moves quite a lot of air. I think I could build something cool with them
I do have a pool actually, how would you suggest I get the water through? Divert pipes or just dump something in the pool?
Might still need a few of those ridiculusly fast fans to cool it, id guess one of those is about the blowing power of a hair drier. The suggestion of using electric oven heating elements is a good one, those should be able to pull 2kW each, So you could make a box with an array of these and a fan to blow air trough it. Not sure how good ones from a junkyard might be since these heaters do die with age. Perhaps you can find a cheep crappy electric grill at your local hardware store, buy a bunch of those and rip the elements out.
As for the pool idea you could just dip some of those big water heater replacement elements directly into the pool. Tho you will want to mount them to a protective board to let you submerge them whole without the water getting to the electrical connections on the back of them. Or i suppose a hacky redneck solution could be to dip the connections in some of that "liquid electrical tape" stuff to protect them from water and just dunk the heater completely. The use of the pool pump is a more permanent type of option that you could leave hooked up. Get something along the lines of a large metal can (some chemicals and bulk paint come in them), mount 5 to 10 of those water heaters all around it (likely on the lid and bottom sides) and put two water ports on opposite sides. Then just put it inline with the pool pump to push water trough the metal can. However you probably want to add some safety cutoff to this (like temperature or flowrate) since if the pump is not pushing water this thing will quickly start to boil and push all the water out due to steam, meaning the heaters are no longer submersed and you get a 'meltdown'