I wasn't really responding to you. I was responding to Shubi's comment that a Sun was needed on day 1 for light.
I thought your physical vs spiritual light comment was interesting. But I believe God was talking about physical light on Day 1.
My view on the type of energy involved in "let there be light" is it is some type of primordial energy. The Hebrew language would have no other terms for energy other than heat or light. No writer in Hebrew thousands of years ago, given a picture from God of cosmic rays or some such, would ever be able to find a word to describe it.
So, I think it might be a good bet that light in the passage could be any one of a number of different types of energy. It might even be a type of energy we no longer are able to observe.