Navy ships could convert seawater into fuel on the go

The U.S. Navy has started work on a project it hopes could have its ships refueling at sea, using nothing but the seawater they float in. Despite common misperceptions, few organizations have put more efforts into going green than the…

The U.S. Navy has started work on a project it hopes could have its ships refueling at sea, using nothing but the seawater they float in.

Despite common misperceptions, few organizations have put more efforts into going green than the U.S military. Initiatives in each of the branches have been started with the express purpose of reducing their reliance on sometimes unreliable fossil fuels.

Security at stake

The problem is hardly just academic either. Resources like the Strategic Petroleum Reserve and regional alliances can help protect the Navy from an absolute dearth of oil. However, both still require either that the ship come to port or that the Navy maintain an expensive fleet of tankers to refuel ships at sea.

Already the country has suffered the consequences of this vulnerability.

In 2000, 17 crewmembers were killed and 39 were injured when the USS Cole was damaged in a bombing at the Yemeni port of Aden. The Cole was in Aden for a regular refueling when a suicide bomber attacked the craft.

Making use of carbon dioxide

A new engineering research project at the U.S. Naval Research Laboratory in Washington, D.C., hopes to limit the need for these kinds of refueling stops and the dangers inherent in them.

The research actually combines three different advances from the past few years. Scientists developed means of more efficiently extracting carbon dioxide from sea water, splitting that water to create hydrogen and combine the hydrogen with the carbon dioxide to create more complex hydrocarbons.

While most people think first about carbon dioxide in the air, particularly from fossil fuel emissions, there is dramatically more of the gas trapped in the ocean. With the water itself providing the hydrogen with which to produce hydrocarbons, the only requirement is power for the process.
The researchers made use of an electrochemical acidification chamber, running electricity through the seawater. The electricity breaks the bonds between the oxygen and hydrogen. At the same time it could produce hydrogen ions, which would be encouraged to swap with sodium in the seawater to create acidified water.
Fuel from nothing
This water can then be recombined with other byproducts of the electrolysis to produce normal seawater. However, using a process of repeatedly recombining the simple carbon structures produced in this approach, carbon dioxide can successfully be converted over time into hydrocarbons with between nine and 16 carbon atoms, ideal for the production of jet fuel.
“The reduction and hydrogenation of CO2 to form hydrocarbons is accomplished using a catalyst that is similar to those used for Fischer-Tropsch reduction and hydrogenation of carbon monoxide,” Dr. Heather Willauer explained in a statement. “By modifying the surface composition of iron catalysts in fixed-bed reactors, NRL has successfully improved CO2 conversion efficiencies up to 60 percent.”
The only requirement is for large amounts of electricity, which are far less difficult to come by on the open sea. Many American naval ships are powered by nuclear reactors, providing them large power supplies when necessary. However, renewable energy sources such as wind and solar energy can also be used to power these processes, in particular since the timeline of the conversion is not critical.
Ultimately, the researchers at the NRL Center for Corrosion Science & Engineering in Key West, Florida, project that the combined process could be able to produce jet fuel at a cost of around $3 to $6 per gallon.
“The potential payoff is the ability to produce JP-5 fuel stock at sea reducing the logistics tail on fuel delivery with no environmental burden and increasing the Navy’s energy security and independence,” Willauer noted.