Personally, I don't think energies need to make sense. It's the constituents of matter that have symbolic value, not the "things that can hurt people". As far as I'm concerned, they can just stay as loosely grouped attack modes--some clearly energetic (fire, lightning), some chemical (acid), some anti-energetic (cold), some wierd (force), etc.
Having said that, I did fiddle around last year with a way of integrating the elements and energies into a single system that kind of made sense, at least from a magical point of view. My idea was that the energies represented interactions between adjacent elements. So it looked like this (imagine it arranged in a circle). The carats represent the "natural evolution" towards higher elements.
Spirit
^ Heat (the invisible "fire" that passes from a flame to us)
Fire
^ Lightning (fire coming from the sky, natch)
Air
^ Cold (water can comes from air when it's cold--consider hail, snow, condensation)
Water
^ Acid (water can dissolve solids, acid promotes this)
Earth
^ Force (acts solid, but it isn't there!)
Spirit
Make of it what you will. In this system, an elemental specialist should have access to two energies, not one. Fire specialists get both fireball and lightning bolt, water specialists get both cold and acid, and so on.