Tuesday, September 17, 2013

Vent Cap

Weather: Today is bright and sunny with thin clouds. The sea is slightly rougher and 10-15 mph winds.

Science Update:
Today’s Objectives: We completed three CTD deployments yesterday and a multibeam mapping survey overnight and are underway to shore.

Harvesting Energy from Hydrothermal Vents Dave Dyer is an engineer at the Applied Physics Lab at the University of Washington where he thinks a lot about renewable energy, specifically, harnessing energy from hot vent fluids to create a source of electricity on the ocean floor. With Keith Scidmore and Jeff Breedlove, Dave is part of a team of engineers who are installing two different devices that could eventually result in harvesting energy from the hydrothermal vents of Axial Volcano. The instruments are in the process
Two instruments to test feasibility of generating energy from Axial Volcano’s hydrothermal vents
of being installed at three sites on the volcano where they will collect data for a year. One device will record water temperature using thermocouples inside the titanium tubes (see photo top right), which measure the temperature of the vent fluid as it travels out of the vent, into the Energy Harvesting Devices (EHD- also known onboard as the vent caps) and out of the titanium tubes at the top. The degree to which the water temperature remains high throughout the device helps the team understand the viability of converting hot water to electricity. The second model is actually generating electricity from the thermal energy released by the vent (see photo lower right).

3. Diagram showing tall instruments on seafloor transmitting data acoustically (sound waves), received by a modem on the buoy, which then transmits data to a satellite.
Energy generated could be as much as 100kW to power a variety of instruments on the ocean floor, some of which are currently battery operated and must be serviced regularly to replace batteries. For now the energy conversion devices are experimental and still in the very early stages but Keith is already thinking into the future and envisions that one day the generators could potentially power underwater vehicles that could rove across the seafloor to recharge batteries on ocean bottom instruments.

One of each of the EHDs has now been installed and will remain at Axial Seamount for another year. But the group doesn’t want to wait a year to get data, so they launched a communications buoy early in the cruise (see blog entry on Sept 4th). The EHDs on the seafloor transmit their data acoustically (with sound waves) to the communications buoy, which sends data to a satellite that transmits the information to the team by email (see schematic diagram above left).
Science team (including Dave, Keith, and Jeff) gather around a live video feed from Jason Van (control center) to Main Lab to see the first video of the vent cap after 6 days on the seafloor in the Vixen Vent area of the Coquille Hydrothermal Vent Field shown with annotations below image.

Because two of the three vent caps were already installed, we were able to re-visit one of the sites to see how it has fared so far. On Thursday afternoon, just 6 days after installation, the crew got their first look and was riveted (below) at the sight of the vent cap which had already become partially covered with anhydrite growth (black towers and white powdery coatings). All three engineers were surprised by the extent of the anhydrite on the EHD, but were excited to be able to learn from the images too. Jeff says they knew that anhydrite would grow but they didn’t realize how fast it would grow and that the most important thing is that the hot fluids are still flowing through the tubes. Keith agrees, “It looks bad, but it’s working… it can get as ugly as it wants as long as it keeps working.” Both indicate excitement and wonder at the fast rate at which the anhydrite has formed on the tower and were happy to see how the natural system was adapting to the artificial structure placed over the vent. Dave says he thinks the experience is also good because the video shows that even though they didn’t expect to see such growth of anhydrite, they’ve learned a lot about the instrument in just the 6 days it’s been installed. Jeff says that challenges like these keep them excited about their work, “it’s very gratifying to work on really challenging problems- doing things no one has ever done, and that’s what makes me love my job.”

To learn more about the team who are here at Axial Seamount, working to install the variety of instruments involved in with the EHD, see the “Science Team” blog entry and the Axial Volcano Buoys blog entry from September 4.