Maritime hybrid electricity: Abundant power at sea

Petroleum price spikes, like the one that collapsed the global economic house of cards in the summer of 2008, will probably recur as we venture farther into the era beyond the global maximum peak of oil production. The recession produced a temporary respite from high oil prices by destroying demand and freeing up some supply. I expect this reprieve to expire before the recession does. For that reason, we must continue to earnestly seek ways to replace petroleum as the primary fuel for the global economy.

Global markets and travel will increasingly rely on maritime routes as air transport becomes more expensive. Maritime transportation relies heavily on the concentrated energy in fossil fuels. On land, trains can run on electric grid power generated by sources other than fossil fuels. Ocean-faring craft cannot stay connected to any grid on the high seas but must carry their fuel with them. That fact might change if they could generate their power en route. Ships powered by the sun and kinetic energy might become feasible with recently-developed technology.

The fossil fuel era accustomed us to relying on a single source for all power required by any given endeavor. In the case of ships, the fuel that powers the engines powers everything else on board – except maybe cooking fuel. The post-fossil fuel era will teach us to combine and hybridize technologies in order to garner the requisite kilovolts. Already, kites – instead of sails –attached with tethers, pull ships across the ocean and reduce – but do not eliminate – the need for liquid hydrocarbon fuel (http://www.kiteship.com/). Thin-film solar photo-voltaic (PV) panels can already turn office building window walls into electricity generators (http://www.heliovolt.net/). Sufficiently thin and lightweight solar films could turn sails into PV solar arrays. Carbon nanotubes might play a role in making solar sails feasible or practical, utilizing their exceptional tensile strength and electrical conductive properties.

Placing the solar arrays more than 100 feet above the waves might expose them to more powerful ultra-violet light and therefore more effective power generating potential. A parasail-dirigible hybrid might provide some protection against capsizing in addition to a platform for thin-film PV arrays.

Light-intensifying sheet acrylic (LISA) can increase the quantity of light striking the PV collection surface (see Marc Baldo, MIT, Technology Review), thus decreasing the quantity of expensive PV arrays required. Either LISA panels, fiber optics, or solar guides could channel sunlight into compartments below deck to eliminate the need for electric lights during daytime.

On the open ocean, a ship finds itself surrounded by space and open water, unlike the tight confines found in ports and harbors. This begs the question: Does a ship on the open ocean need to occupy the same amount of water surface as it does while in port? Of course, it does not. Retractable pontoons or outriggers could provide broad surface areas on which to mount solar arrays. Maneuverability in port would require retracting the outriggers. Inflated outriggers could enhance buoyancy and resistance to sinking or capsizing.

Extending and retracting would require energy of some sort. The automatically-opening umbrella and the Hoberman sphere give me ideas here. The actions of opening and closing should not require the same amount of power if doing one sets it up for doing the other. Compressed air released from storage canisters could open and inflate the outriggers. Recompressing the air into storage canisters would take energy but would store energy for subsequent re-inflation. Releasing compressed air takes less energy than compressing it. The Hoberman sphere’s scissor-like armatures could provide a model for extension and retraction of the internal structure of the outriggers.

Outriggers deployed at sea provide yet another opportunity to generate power. Ocean waves oscillate, causing articulated outriggers to buck, flex, and bend. This kinetic energy could provide an important power supplement to the ship. Piezoelectric effect converts mechanical strain into electrical current or voltage. Dr. George A. Lesieutre, professor of aerospace engineering and associate director of the Penn State Center for Acoustics and Vibration, claims that when vibrated so that they bend or flex, piezo-electric materials produce an alternating or AC current and voltage (http://www.sciencedaily.com/releases/2002/09/020924071946.htm).

Thermal solar power often gets short shrift compared to PV, but when gathering small contributions of power from a variety of sources in order to make the entire system work, every little bit counts. In some applications, heat might work better than electricity. Pontoons with transparent tops would cause air inside to heat up (greenhouse effect). This provides yet another source of energy for the ship.

As we sail into the uncharted waters of the post-petroleum era, we must consider a wide variety of options for reducing power demands as well as accumulating power generated in a variety of ways in order to meet the sum of our needs. Hybridization will become the watch word for meeting power needs from now on.

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