Patent attributes
Example embodiments may facilitate altitude control by a balloon in a balloon network. An example method involves: (a) operating a balloon in a first mode, wherein the balloon includes an envelope and a fuel cell, (b) while the balloon is operating in the first mode: (i) drawing ambient air from outside the envelope into the envelope through a first opening, (ii) using solar energy to heat the air in the envelope such that a buoyancy of the balloon is increased, and (iii) releasing air from inside the envelope to outside the envelope through a second opening such that the buoyancy of the balloon is decreased; (c) transitioning to operating the balloon in a second mode; and while operating the balloon in the second mode, using a portion of power generated by the fuel cell to heat the air in the envelope such that the buoyancy of the balloon is increased.
