Raduz is right.
You can sink ships anywhere and gain the same amount of renown.
You get extra renown for.....
Reaching your Patrol Grid
Completing 24hrs in the Grid
Returning to base (manually) i.e within 30-25km and chosing 'Dock at......'
FYI - returning to base manually is only worth 100 renown points so it's up to you whether your decide to take the trouble.