Green Options » ocean energy

Mining Hydrothermal Vents For Renewable Electricity, Drinking Water + Valuable Minerals

Susan Kraemer — Fri, 04 Sep 2009 20:55:02 +0000

Only after I snoozed my way through high school science class did science become more compelling than science fiction.

Back then, there was just no compelling reason to pay attention. Just a browzy fly buzzing in a smelly boring lab full of long agreed-upon dull principles that were really neither here nor there. In those days there were no colliding continents or hydrothermal vents or extremophile lifeforms. We looked to sci-fi for that.

Who knew that our planet would soon be busting at the seams with 7 billion of us. That our fossil fuel use would threaten our survival with climate changes — on a level unseen on the planet since Cyanobacteria made it safe it for oxygen-breathers 4 billion years ago.

Or that we would not only discover vast strange heat sources under the ocean but that we’d actually consider mining these hydrothermal vents for renewable energy: That was the sort of story you’d only find in science fiction back then.

But yet, here we are. This is not science fiction:

Ocean Heat Powers Underwater Glider

Shirley Siluk Gregory — Tue, 12 Feb 2008 22:10:55 +0000

A green-energy ocean glider has cruised back and forth between the islands of St. Thomas and St. Croix more than 20 times since its launch in December. Being tested by researchers from the Woods Hole Oceanographic Institution and Webb Research Corporation, the robotic glider uses ocean heat to warm wax-filled tubes that then expand to generate mechanical energy that drives the vehicle.

Photo courtesy of the Woods Hole Oceanographic Institution, taken by John Lund.
Marshall Hydrothermal is pretty frank about the horrible ecological consequences: The company says that there is no way to sugar-coat the fact that these organisms will die so that we humans can live our much more exciting lives though electricity.

The company “plans” to relocate the local flora and fauna to another vent nearby. But can people work 7,000 feet down to carefully pull these limpet-like creatures off the sides of volcanic vents? I’m not quite sure how that would happen.

Or, perhaps a closed loop system would be safer? Marshall offers this alternative method:

Closed Loop Version

This looks a little less invasive: a closed loop system.

Rather than bringing up the hydrothermal fluid itself with bits and pieces of sea creatures as well, a simple heat exchange is effected within a closed loop: all the fluid is contained in the pipe and heated at the vent and circulated up for use to drive the turbines on the surface.

The cooled fluid is then sent back to be reheated by the vent again and again, but the hydrothermal fluid itself is never actually brought to the surface. More than just a huge renewable energy supply is at stake here.

We could also be making desalinated water from the ocean vents:
At least 264 million gallons of fresh water daily.

20 million gallons of hot fluid would flash to steam at the surface and that could be distilled back into fresh water. Further purification would be needed, but the natural heat from the process itself provides the most important part of the energy needed for the process. Fresh water is the new oil.

If even only 50% of the total volume could be recovered, that would still provide about 264 million gallons of fresh water daily.

Catch 22

Unfortunately, desalination apparently requires the (more ecologically disruptive) open loop system, to work. (See first diagram) But, if that could be solved, there is another argument for mining the actual fluid (open loop); not just the heat (closed loop) system.

The materials in these geologically ancient vent fluids include iron, gold, silver, copper, zinc, cadmium, manganese, and sulfur. Halides, sulphates, chromates, molybdates and tungstates are also abundant.

When the fluid is trapped, the slurry left over after the heat is extracted can be loaded aboard ships for processing elsewhere, or processed on-site.

Cap and Trade would also help fund this completely new form of renewable energy extraction. Who better to carry it out than the oil industry. They already have the expertize with ocean drilling extraction.

Turns out there is also significant amounts of methane gas mixed into the fluid. Maybe there is a way to cap that for remediation-cum-fossil energy at the same time, as well as selling the renewable electricity, fresh water and minerals produced by the vents.

For the oil industry, with all these inducements, surely switching to mining renewable energy would be more cost effective than having to keep on paying media outlets and school districts and think-tanksfull of talking heads to keep enough people ignorant enough about climate change to slow the legislation needed to stop it; decade after decade.

Let’s hope.

Images from Flikr users aakova and thomitheos
Via Marshall Hydrothermal

Tapping Undersea Energy, Wind-Style

Shirley Siluk Gregory — Sat, 22 Dec 2007 18:53:13 +0000

Imagine a vast source of energy as clean as wind power but without the NIMBY factor of wind farm projects like the one in Cape Cod. The source? South Florida’s Gulf Stream.

Researchers at Florida Atlantic University’s (FAU) recently established Florida Center of Excellence in Ocean Energy Technology are working on a pilot project that would plant test turbines on the ocean floor about 50 meters underwater. The turbines will be placed in the path of the Gulf Stream, a powerful current that flows through the Florida Straits. That current promises to be a massive source of potential energy to Florida residents and businesses: it surges through the ocean at a rate of more than eight billion gallons per minute. That’s more than 30 times the total flow of all the world’s freshwater rivers.

This isn’t the first time anyone’s tried to tap the power of the Gulf Stream, but it is the most realistic and ambitious test yet. Past experiments have depended on simulations, lab tests or short-term turbine deployments that lasted only a few hours. That leaves a lot of unknowns to sort out yet, like how well the turbines will actually perform or what impacts the project might have on the underwater environment. Researchers at Nova Southeastern University’s Oceanographic Center plan to study the effects on marine life, although the turbines are expected to move too slowly to harm any creatures.

Slow, though, doesn’t mean wimpy. The power of the Gulf Stream is expected to generate as much energy as a wind turbine would produce in a 55 mile-per-hour gale. That means each undersea turbine could produce up to three megawatts of power: enough to supply the energy needs of 500 homes.

Another plus for Gulf Stream energy comes from the current’s lower regions, which are made up of cold water flowing from the Arctic. FAU researchers say that chilly flow could be tapped to drive air-conditioning, which currently accounts for up to 45 percent of Florida’s residential electricity consumption.

Rick Driscoll, who directs the Florida Center of Excellence in Ocean Energy Technology, says Gulf Stream energy could supply all of Florida’s energy needs … without aggravating global warming or creating any pollution. It could also create thousands of jobs for the state and provide the power needed to produce potable water, a much-needed resource for the fast-growing, drought-plagued state.

Clean energy, energy independence, jobs and no negative environmental impact? It all sounds almost too good to be true. I’m hoping that Driscoll and his colleagues at FAU can prove that’s not the case.
Marshall Hydrothermal is pretty frank about the horrible ecological consequences: The company says that there is no way to sugar-coat the fact that these organisms will die so that we humans can live our much more exciting lives though electricity.