COmpatak. pretty easy dude. Take the shell off of a dehu unit and CAREFULLY CAREFULLY CAREFULLY bend the cold radiator into a bucket, cooler, whatever. Then put a small pump in that cooler and have it pump water through a SS wort chiller than you can get on e-bay for about $50. You can not use copper pipe nor bend the (copper) cooling radiator directly into your rez. Copper will kill your plants deader than shit.
Now just plug (or directly wire) the Dehu into a temperature control switch. I use the ranco ETC-111000 baby! LOL, it is pretty slick. You can set it to turn on something for heating nor cooling, set the desired temperature and the deadband. Super easy.
http://www.amazon.com/RANCO-ETC-111000-Digital-Temperature-Control/dp/B0015NV5BE
BUT, and this is a huge but, your dehumidifier has to have an auto start feature. meaning that after the power is off and you plug it in, it automatically starts. Otherwise the controller would not work.
ok? ok.