The Edge of Wind
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|Neal Rauhauser||November 10th 2008|
Cutting Edge Sci-Tech Writer
The last three years have seen a mad scramble in the Arctic with undersea mapping of continental surface features and a Russian submarine placing a flag on the ocean floor at the North Pole—all efforts to claim potential fossil fuel resources beneath the sea bed.
But another vision, by independent researcher Dr. Homer Wang, is far different, allowing not only the production of energy but also the simultaneous correction of arctic ice loss.
Wind speeds of 7.5 meters per second in the continental United States can be promptly developed for the four hundred to five hundred watts per square meter available. But Arctic winds are twice as fast. Because wind energy increases with the cube of speed, harnessing winds in a Arctic meter can yield three to four thousand watts. The question is how?
Today's largest wind turbines, built by Enercon, offer hubs that stand a hundred and forty meters above the landscape and sweep an area of twelve thousand square meters. Such a device would not work on an oceangoing plantship facing arctic winds. Instead, it would act as a gigantic lever, capsizing even a large vessel. Arctic wind must be harvested with vertical axis wind turbines.
Many experts feel that vertical axis wind turbines make little sense in the typical conditions found on land or temperate offshore conditions. The wind for the first thirty meters from the earth is a messy, turbulent flow that loses much of its energy to interference from whatever is on the ground. Climb to fifty meters and smooth, powerful parcels of air are the norm, providing power without beating up wind turbine blades and rotors.
The arctic winds are so fast at the surface they carry fantastic energy density, so much so that maintaining the efficiency becomes the key operating issue. The cranes used to repair troubled components at the hub level in a land-based system would be extremely dangerous even in the rolling seas of calm weather. Yet the Arctic seldom sees calm conditions. Vertical axis turbines have their drive train and generating equipment—the parts that most commonly need attention—safely below deck on a shipboard installation. A return to port would be required for serious work on the vertical axis turbine blades themselves, but heavy construction and heating elements, easily powered by onboard energy storage, will make conditions such as ice buildup merely a nuisance rather than a serious operational problem.
The electricity generated from this sea-based turbine system cannot be transmitted directly, so an oceangoing plantship has to make something with the power. The operating environment would be similar to that of a tropical based ocean thermal energy conversion (OTEC) plantship, and several issues make ammonia the product of choice.
Ammonia can be created from atmospheric nitrogen and hydrogen taken from water, so no initial raw material would need to be transported to the ship for the processing to begin. But, although ammonia is a fine fuel for diesel engines, it doesn't compression ignite, so some amount of diesel would need to be carried and mixed with the ammonia as a starter fuel. An alternative strategy for powering the ships might be to use diesel/electric drive, permitting the wind energy for the bulk of the propulsion work. The diesel conversion is simple for existing ships being refitted while the diesel/electric method is how submarines were powered before we used nuclear reactors.
Today's ammonia synthesis uses a century old process known as Haber Bosch. Powering this method with electricity turns about 40 percent of the total power into waste heat and requires expensive electrolyzers. The entire renewable ammonia industry is holding its breath, waiting for a current pilot of a solid state ammonia synthesis system to be completed. This technology promises to produce ammonia without expensive, inefficient electrolyzers and without the high pressures used by Haber-Bosch. Once mature enough for deployment, it is expected to be a game changer in the renewable energy realm.
The solid state synthesis system requires only two thirds of the energy used in a Haber Bosch-based system and it is much kinder to the Arctic, producing only a fraction of the waste heat. Operation and durability are expected to be greatly improved over the old method as the solid state method involves nothing more than bundles of sturdy ceramic tubes.
The heat issue is important. Dr. Wang believes “creating a renewable fuel and removing excess heat energy from the areas in the process…[is the answer]…because we can correct the effects of global warming at the same time we harvest a renewable fuel from the endless winds of the arctic.”
How does this all fit together? Ammonia is a gas at room temperature and pressure. Cool it to -33 Celsius and you get a stable liquid that is easily stored. Herein lies the genius of Dr. Wang's proposal. Not only would a plantship produce clean, renewable ammonia, but given that cryogenic storage is required, water ice would be easily produced as well.
The Arctic melting season ending in 2008 saw a bit more physical area for the ice pack than the record low set in 2007. But the ice is still thin. Scientists believe we reached a record low ice volume despite the slightly larger pack. The total ice volume produced by the plantships would not be large but it would be very valuable in reducing the effects of global warming
Neal Rauhauser is a member of the Stranded Wind Initiative and can be found at www.strandedwind.org.