The browse menu provides access to the documents within the collection. The tags used within the menu are collected from a variety of sources. The tags used in the areas of geography, animal, and technology present a particular challenge. To the best of our ability NREL has selected tags that will offer a good level of specificity while still giving the casual user (without any subject matter expertise) the ability to easily access the collection. We are also well aware of the fact that there may be omissions and/or mistakes, particularly for the tags used in the animal category. NREL welcomes any and all feedback.
Tags will only appear in the browse menu if a document within the collection has been tagged with it. In other words, the tag "penguin" does not appear in the list because none of the documents in the collection have been tagged with that term.