For centuries navies used a renewable energy form as a means of propulsion — the wind. Now the U.S. Navy is investigating another potentially limitless fuel source to produce JP-5 jet fuel — seawater.
The U.S. Naval Research Laboratory (NRL) is developing the chemistry for producing jet fuel from renewable resources in theatre. The process envisioned would catalytically convert carbon dioxide and hydrogen directly to liquid hydrocarbon fuel used as JP-5.
And how exactly would this alchemic sleight of hand be performed?
By extracting CO2 to produce H2 gas from seawater and subsequently catalytically converting it into jet fuel by a gas-to-liquids process.
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NRL research chemist Dr. Heather Willauer said, "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. 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. By modifying the surface composition of iron catalysts in fixed-bed reactors, NRL has successfully improved CO2 conversion efficiencies up to 60 percent. With such a process, the Navy could avoid the uncertainties inherent in procuring fuel from foreign sources and/or maintaining long supply lines."
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Note the comment “at sea.” The process would eliminate the time-consuming and risky process of refueling at sea, theoretically allowing each of the U.S. Navy’s 10 operational Nimitz-class carriers to produce their aircrafts’ fuel while underway.
The NRL has now successfully developed and demonstrated technologies for the recovery of CO2 and the production of H2 from seawater using an electrochemical acidification cell, and the subsequent conversion of CO2 and H2 to organic hydrocarbons that can be used to produce jet fuel.
The project, if successful, would add to the Navy’s desire for a self-sustaining carrier task force. Nimitz-class carriers are already independent of the fuel chain logistic because of their nuclear capacity — such a development would subsequently free them from the need to replenish their aircrafts’ fuel reserves as well, leaving them needing only to restock food and ammunition supplies, allowing them greater operational autonomy.
So, how far forward is this process?
In the past three years the NRL has made significant advances developing carbon capture technologies in the laboratory, having begun by utilizing a standard commercially available chlorine dioxide cell and an electro-deionization cell were modified to function as electrochemical acidification cells, whereby both “dissolved and bound CO2 were recovered from seawater by re-equilibrating carbonate and bicarbonate to CO2 gas at a seawater pH below 6. In addition to CO2, the cells produced H2 at the cathode as a by-product.”
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Again, according to the NRL website, “NRL has developed a two-step process in the laboratory to convert the CO2 and H2 gathered from the seawater to liquid hydrocarbons. In the first step, an iron-based catalyst has been developed that can achieve CO2 conversion levels up to 60 percent and decrease unwanted methane production from 97 percent to 25 percent in favor of longer-chain unsaturated hydrocarbons (olefins). In the second step these olefins can be oligomerized (a chemical process that converts monomers, molecules of low molecular weight, to a compound of higher molecular weight by a finite degree of polymerization) into a liquid containing hydrocarbon molecules in the carbon C9-C16 range, suitable for conversion to jet fuel by a nickel-supported catalyst reaction.”
The principle has been proven — can it be ramped up to provide JP-5 for task forces at sea, spread around the globe?
The NRL website is silent on the possibility of full-scale production. Most 102,000-ton Nimitz-class carriers, the largest warships ever built, mount aerial forces of 50 TACAIR air wing of up to 82 aircraft, a usual mix of: 12 F/A-18E/F Hornets, 36 F/A-18 Hornets, four E-2C Hawkeyes, four EA-6B Prowlers fixed-wing a brace of four SH-60F and two HH-60H Seahawk helicopters.
But it is one thing to prove a fuel conversion technology, another to implement it. Will Neptune permit the U.S. Navy to mine the liquid gold of his realm? Watch this space. This might be the biggest naval propulsion revolution since Britain’s Royal Navy reluctantly abandoned sail.