Science in Context database is an excellent place to start. This link will take you directly to the section of the database on Alternative and Rewable Energy. As you research, be sure you are reading specifically about renewable energy. Use the search box to look for more information about the particular types of energy you are reasearching.
Interactive Renewable Energy book
This is an interactive ebook that has a lot of good information about renewable energy sources. After clicking on the link, click the "Open Lightbox" button and then scroll through the book using the left and right arrows on the sides of the screen.
eBooks from ORHS Library