They run about 20-30 bucks, with about another 50 - 100 you could pick up the other components you need (relays, microchips, other hardware, wifi if you want). Program in c++, counts time in seconds, so id essentially program a calendar to match what you want to do, personally instead of 3 eight hour cycles i think 2 with a 4 hr offset would be a bit easier to manage, and mught allow for one in veg while the other is flowering (traditional non gas light method).
Torontoke, take a look at what vegaswinner (go green led?) has done also look into the garduino. Also check youtube vids by aquaporn (now how dirty you feel?)
TT, happy to work with you and happy to share, i almost think you could eliminate the need for your chiller if things were scaled properly and maybe fewer watts in summer, more in winter so excess can heat house.