Hey Chris,
I am so happy that you are also looking for Cleantech. Welcome to the club buddy
The best way to get in touch with Alumns is through admissions office and the respective clubs( ex: Energy club, Cleantech club).
Drop them an email and wait patiently

for them to reply. The best schools will reply with contacts. Then you can ask for a skype meeting.
Also search for websites and you will get a lot of them.
Hey man, when are you applying? I am applying for 2014 start class. Mostly US schools. I am looking for Consulting in Cleantech, mainly Green Energy.