Where are some good places to find different types of sources for a research paper on solar energy?

I’m writing a research paper for English and I need 5 different types of sources to use, like a book, documentary/film. scholarly article, etc. My topic is solar energy, specifically research/development, funding, and policy issues on it. Where would be a good place to look for credible sources of different forms?
I found a handful of possible sources from our library, but hardly any that aren’t incredibly focused on even smaller areas than what I’m writing about.

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