What is a substance that supplies energy cushions vital organs and is a solid at room temperature?

I believe lipids is what you are going for. A lipid is a macromolecule (monomer of fatty acids) that cushions organs, stores energy, and a version of it is solid at room temperature. The version of it that is solid at room temperature is called a saturated fat. Saturated fat may also be a correct answer.

It allows water to resist freezing and thawing cycle.