Some information I found off the web:

First type:

cat /sys/power/state

If the result line contains “mem”, you can use this to suspend to RAM: sudo pm-suspend

If the result line contains “disk”, you can also use this to suspend to disk (hibernate): sudo pm-hibernate

If you have both results, you can use this to suspend with a hibernate backup. In other words, your system will prepare for hibernation, but only suspend, not turn off. This will use a bit of power, but means that it’s faster to resume, and if your battery runs out, it’ll use the hibernate image as backup. sudo pm-suspend-hybrid

You can pipe the hibernation into a timed job using the at command. This will hibernate in one hour from now echo ‘pm-hibernate’ | sudo at now + 60 minutes

And you can confirm the job is present: sudo at -l 10 Wed Jan 1 12:38:00 2014 a root

Suspend/Hibernate requires root access, hence the reason I did sudo before the at command