Change the narration: The teacher said, "The wind is a renewable energy source."

The teacher tells that the wind was a renewable energy source.

The teacher said that the wind was a renewable energy source.

The teacher said that the wind is a renewable energy source.

None of these

This is a universal truth (wind as a renewable energy source), so the present tense "is" remains unchanged in indirect speech.

The reporting verb "said" does not require "told" unless followed by an object.

So the correct narration: The teacher said that the wind is a renewable energy source.