Desktop hibernate then wake on lan

I'm trying to come up with some sort of solution to help with power savings (greening our labs) for our Windows 7 labs. These systems are part of a large Windows Domain. Currently we run a 'sysctl' task at night (written in Perl) that does various things like archiving Event logs, random nightly reboots (a random period between 0 and 4 hours so not all the thousands of systems are rebooting at the same time), etc. What I'd like to have happen once all that has run and the system boots up is to put the system into hibernate mode until some prescribed time in the am (before classes start, etc.). It seems like a doable thing but I'm not sure how to approach it.

I've downloaded and will give it a shot, thanks!