Answer:
it is entirely possible, as new experimental forms are still being discovered. However these can't currently be used as the technology needed to harness this energy does not exist, rendering them useless now, but still leaving them a possible source in the future. A possible energy source would be nuclear fusion: the reaction that takes place in the sun to provide the massive amounts of energy from the sun. It is currently unusable as it demands massive pressure and temperature that we can't achieve yet
