posted on 2023-02-22, 14:05authored byYu Du, Ping Li, Yumei Wen, Zhibin Guan
The buoyancy potential energy contained in bubbles released
by
subsea geological and biological activities represents a possible
in situ energy source for underwater sensing and detection equipment.
However, the low gas flux of the bubble seepages that exist widely
on the seabed introduces severe challenges. Herein, a passive automatic
switch relying on Laplace pressure is proposed for efficient energy
harvesting from low-gas-flux bubbles. This switch has no moving mechanical
parts; it uses the Laplace-pressure difference across a curved gas–liquid
interface in a biconical channel as an invisible “microvalve”.
If there is mechanical equilibrium between the Laplace-pressure difference
and the liquid-pressure difference, the microvalve will remain closed
and prevent the release of bubbles as they continue to accumulate.
After the accumulated gas reaches a threshold value, the microvalve
will open automatically, and the gas will be released rapidly, relying
on the positive feedback of interface mechanics. Using this device,
the gas buoyancy potential energy entering the energy harvesting system
per unit time can be increased by a factor of more than 30. Compared
with a traditional bubble energy harvesting system without a switch,
this system achieves a 19.55-fold increase in output power and a 5.16-fold
enhancement in electrical energy production. The potential energy
of ultralow flow rate bubbles (as low as 3.97 mL/min) is effectively
collected. This work provides a new design philosophy for passive
automatic-switching control of gas–liquid two-phase fluids,
presenting an effective approach for harvesting of buoyancy potential
energy from low-gas-flux bubble seepages. This opens a promising avenue
for in situ energy supply for subsea scientific observation networks.