I have cards in 3 library systems. They all work this way:

Each system requires a yearly card renewal, you have to physically go into a branch to renew, although they do have accommodations for disabilities and stuff. If you have not returned a book or have way overdue books, you will be unable to renew your card unless you return the overdue ones. The only fees I have are if I were to lose a book and it needs to be replaced.