Apparatus and methods of generating electricity using buoyancy principles, a buoyancy-driven power generation system comprising a closed-loop passage defined by a surrounding structure, the closed-loop passage arranged vertically to extend longitudinally along a closed-loop path, the passage configured to retain a liquid, a plurality of rotor-vessels slidingly arranged within the closed-loop passage and configured to translate along the closed-loop path within the closed-loop passage, each of the plurality of rotor-vessels including a fluid-retention cavity formed in a body of the rotor-vessel and having a density greater than a liquid in which the plurality of rotor-vessels will be submerged for power generation operations.