User blog comment:Tsubori/Ren no-sells a snake/@comment-11109699-20130824202453/@comment-4773581-20130825001503

So he used his Aura to convert the kinetic energy into...what, Aura? Given how much Aura that would take in the first place (just as much, if not more than, the amount he'd gain), what would even be the point of that? Plus I don't think you can convert physical energy into soul energy. That's just silly. Like, turning-a-cannonball-into-a-soul level silly.

Moreover, you're ignoring Jaune's remarking that it's like a forcefield, which Pyrrha even agrees with. Forcefields do not convert energy A into energy B, store energy B for X amount of time, and then turn energy B back into energy A so that it can be used offensively. It'd be faster to just use the forcefield itself as a weapon.