When they start the expansion/interview process they start fresh. They may review resumes from a previous round of interviews, but a year is a very long time to hang on to that kind of administrative "weight". It is most likely that they'll start entirely fresh. You may have a slight leg up if the same people will be interviewing you who had a positive impression of you before. You will also have the benefit of being within the company and almost certainly will have a managerial endorsement from your current manager.
You should consider if the position has been posted to an internal company job board. Consult with the HR team to see what listing they have for it and how they prefer to handle it. I would initiate this verbally, I'm assuming you know at least one person in the HR department who would help with this. If they want you to resubmit an official resume have it prepared and ready to submit immediately.
Speak to your current manager, and let him/her know of your intentions to pursue the position. Things will go better for you if you can get them to "cheer" for you. Once you have all of your ducks in a row, and you're ready to pursue it officially, send a brief, to-the-point email to the manager of that team. State your previous candidacy, your understanding of the new position and that you'd like to be considered. Ask for guidance on properly submitting your new candidacy. They might like you to go through proper HR channels, they might just want you to walk your resume over and have a chat. It depends on how the company culture is.
It's come to my attention that your team will be expanding in the near
future, and a position is being created for senior widget
smack-packager. Approximately a year ago, I was considered for an
identical position, and I would like to pursue this opportunity again.
I feel my qualifications and experience within the company over this
last year will make me a great candidate for your team.
I have discussed this with my current manager, Ms. Jazzlescamper, and
she has given her support. Please let me know what I need to do to
submit my candidacy officially, and if there is anything I can do to
help streamline the process don't hesitate to call on me.
If your company has a very formal culture, they'll expect you to submit your resume to HR, listing references, etc. If it's a less formal culture, the manager might just stop by your workstation and chat you up about it, maybe collect your resume. So make sure you have everything in a row before you make the first contact.
Chance favors only the prepared mind. - Louis Pasteur