Accumulation

Ac·cu·mu·la·tion

Accumulation

n.
  1. The act of accumulating, the state of being accumulated, or that which is accumulated; as, an accumulation of earth, of sand, of evils, of wealth, of honors.
  2. The concurrence of several titles to the same proof. (Law)

Phrases & Compounds
Accumulation of energy [or] power
the storing of energy by means of weights lifted or masses put in motion; electricity stored.
An accumulation of degrees
the taking of several together, or at smaller intervals than usual or than is allowed by the rules.