Experiment study of a seawater hydrostatic energy conversion rig

Abstract The seawater's hydrostatic energy is an alternative power source for seafloor operation apparatus, such as the sediment sampler, cone penetration test rig and long-term platform for underwater sensors. A seawater hydrostatic energy conversion rig which is proposed to harness the seawater hydrostatic energy to drive the seafloor sediment sampler and seabed cone penetration test rig was built and tested in lab. The test system of the energy conversion rig in lab can properly simulate the seawater hydrostatic energy and the fluctuating sediment resistance. Under the great influence of the fluctuating resistance, the rig can hold stable speed and attain high energy efficiency at different depth of water. The speed error is very small during the test and is within ±10% of the stable speed. The feature makes the conversion rig qualified to drive the seabed cone penetration test rig and high-quality sediment sampler. The hydrostatic energy conversion efficiency of the conversion rig in different cases are all higher than 80%, which enables the sediment sampler to obtain longer sediment sample and make cone penetration test rig obtain deeper sediment's geotechnical data. The experiment results demonstrate the feasibility of the seawater hydrostatic energy conversion rig and show its excellent performance.