Your topic needs to be narrow so that you can focus your thesis and so you don't have to write a whole book!
For example, instead of searching just "wind energy," you would want to think about a subtopic in that larger topic. Some examples might be "advantages of wind energy" or "costs of wind energy."
In your search, you would put "advantages AND wind energy" or "costs AND wind energy." You would also want to think of some alternate words to search, like "wind power" instead of "wind energy."
The following databases can help you determine research topics that you might find interesting!