The first thing that one wishes to do in preparing for an informative speech is gather information--of course! Yours is a delightful topic as it should interest your audience of college students who often suffer from sleep deprivation.
Dependant upon the tenor of your professor and the course for which you are doing this speech, you can take different approaches. But, employing humor is usually a great way to "hook" the audience and entertain them at the same time. If, for example, you can use visuals, take photos of students who have dozed off in the library or student union or other areas on campus--especially watch for humorous positions (if you can capture someone in your class, this will be funny). With them displayed, open with a clever or sarcastic question as "Do these people look productive?" followed by "Acutually they are!", or just something like, "Do any of these shots look familiar? Don't let people poke fun of you next time you fall asleep. Tell them you were taking a power nap."
Then launch into your speech on how power naps are beneficial and actually increase productivity. In Spain, for instance, workers often celebrate until late in the evening; however, it is permissible at work for them to nap after lunch at their desks as employers believe it increases productivity. And, studies show that taking a power nap is, indeed, a way to increase productivity. (There was an article on this years ago in one of the news magazines such as Newsweek or Time.)
Taking a survey on campus, asking students if they take such naps and how they feel afterwards will also provide you with some statistics. At any rate, you should not have any trouble finding information. Do not forget to ask any doctors or others in the medical field their opinions as this information qualifies as statements from authorities. As a second part of your speech, you can also provide information on high to take a power nap.
Good luck and have fun with this topic.