Upvote:0
Tourist (B1/B2) visas can be renewed by mail in most countries, so long as your previous visa was full-validity, and it was not misused. Since you didn't travel on it, there shouldn't be any question over whether it was used properly.
Your nearest U.S. Consulate or Embassy in-country will have instructions on renewal by mail on their website.
Upvote:3
Strictly speaking, most visa "renewals" are actually fresh applications for a new visa. That is, the existing visa is not extended, but rather cancelled (if it has not already expired), and a new visa is issued.
There is nothing that requires you to have used your previous visa. It may raise some questions, of course.
When you are asked about the fact that you never used your visa, you can explain that you applied for that visa because of a "specific project," and that the project was cancelled before you used the visa. This is a perfectly plausible story, and I imagine a fairly common one. Unless the consular officer has some reason to doubt you, there should be no problem.