Six Senses and Four elements
In case of the mind-sense(the stream of Bhavaangha cittas), the object received by the sense is a thought itself. There's no physical element involved. That's why Arupa beings only have the mind sense. 

'Energy' is a concept. There's no such thing according to Buddhism. Even sunlight is said to be containing the pure octad. Anything physical is Rupa and the rest is Nama.