I would go with SSIS as well, but if you want to do it with Powershell, there are plenty of examples in the web.
A search on google for "powershell export sql server csv" gave several posts.
Here are some examples.
http://poshcode.org/1662
http://www.sqlteam.com/article/fast-csv-import-in-powershell-to-sql-server
http://beyondrelational.com/modules/2/blogs/908/posts/18005/exporting-from-sql-server-to-csv-file-using-powershell.aspx
Luis C.
General Disclaimer:
Are you seriously taking the advice and code from someone from the internet without testing it? Do you at least understand it? Or can it easily kill your server?
How to post data/code on a forum to get the best help: Option 1 / Option 2