SeaGen Shatters Tidal Power Generation Record

Written by Timothy B. Hurst

Since its inception, we have been keeping a close eye on Marine Current Turbine’s SeaGen project in the UK, the world’s first commercial scale tidal stream turbine. Well, today there is more big news to report from the strong tidal flows of Strangford Lough as SeaGen has generated at its maximum capacity of 1.2MW for the first time. Thus far, this is the highest power produced by a tidal stream system anywhere in the world and exceeds the previous highest output of 300kW produced in 2004 by the company’s earlier SeaFlow system, off the north Devon coast.
“Generating at full power is an important milestone for the company, and in particular our in-house engineering team. We are very pleased with SeaGen’s performance during commissioning,” said Martin Wright, Managing Director of Marine Current Turbines (MCT). “It demonstrates, for the first time, the commercial potential of tidal energy as a viable alternative source of renewable energy.”

According to company officials, now that SeaGen has reached full power it will move towards full-operating mode for periods of up to 22 hours a day, with regular inspections and performance testing undertaken as part of the project’s development program.

“Marine Current Turbines has pioneered the development of tidal current turbines. As the first mover in tidal stream turbine development, we have a significant technical lead over all rival tidal technologies that are under development,” rightfully boasted Wright. “There are no other tidal turbines of truly commercial scale; all the competitive systems so far tested at sea are quite small, most being less than 10% the rotor area of SeaGen.”

Drawing on its experience at Strangford Lough, MCT’s next project is a joint initiative with npower renewables to build a 10.5MW project using seven SeaGen turbines off the coast of north Wales. That project is scheduled to come online in late 2011/early 2012.

The company is also investigating the potential for tidal energy schemes in other parts of the UK and Ireland, and in North America.

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Global Warming Impacts On U.S. Coming Sooner Than Expected, Report Predicts

The American West is likely to become more arid in the future due to global warming. (Credit: iStockphoto/Tobias Helbig)

A report released at the annual meeting of the American Geophysical Union on December 16 provides new insights on the potential for abrupt climate change and the effects it could have on the United States, identifying key concerns that include faster-than-expected loss of sea ice, rising sea levels and a possibly permanent state of drought in the American Southwest.

The analysis is one of 21 of its type developed by a number of academic and government agency researchers for the U.S. Climate Change Science Program. The work incorporates the latest scientific data more than any previous reports, experts say, including the 2007 Intergovernmental Panel on Climate Change.

While concluding that some projections of the impact of climate change have actually been too conservative – as in the case of glacier and ice sheets that are moving and decaying faster than predicted – others may not pose as immediate a threat as some scenarios had projected, such as the rapid releases of methane or dramatic shifts in the ocean current patterns that help keep Europe warm.

"We simulate the future changes with our climate models, but those models have not always incorporated some of our latest data and observations," said Peter Clark, a professor of geosciences at Oregon State University and a lead author on the report. "We now have data on glaciers moving faster, ice shelves collapsing and other climate trends emerging that allow us to improve the accuracy of some of our future projections."

Some of the changes that now appear both more immediate and more certain, the report concludes, are rapid changes at the edges of the Greenland and West Antarctic ice sheets, loss of sea ice that exceeds projections by earlier models, and hydroclimatic changes over North America and the global subtropics that will likely intensify and persist due to future greenhouse warming.

"Our report finds that drying is likely to extend poleward into the American West, increasing the likelihood of severe and persistent drought there in the future," Clark said. "If the models are accurate, it appears this has already begun. The possibility that the Southwest may be entering a permanent drought state is not yet widely appreciated."

Climate change, experts say, has happened repeatedly in Earth's history and is generally believed to be very slow and take place over hundreds or thousands of years. However, at times in the past, climate has also changed surprisingly quickly, on the order of decades.

"Abrupt climate change presents potential risks for society that are poorly understood," researchers wrote in the report.

This study, in particular, looked at four mechanisms for abrupt climate change that have taken place prehistorically, and evaluated the level of risks they pose today. These mechanisms are rapid changes in glaciers, ice sheets and sea level; widespread changes to the hydrologic cycle; abrupt changes in the "Atlantic Meridional Overturning Circulation," or AMOC, an ocean current pattern; and rapid release to the atmosphere of methane trapped in permafrost or on continental margins.

Considering those mechanisms, the report concluded:

• Recent rapid changes at the edges of the Greenland and West Antarctic ice sheets show acceleration of flow and thinning, with the speed of some glaciers more than doubling. These "changes in ice dynamics can occur far more rapidly than previously suspected," the report said, and are not reflected in current climate models.
• Inclusion of these changes in models will cause sea level rises that "substantially exceed" levels now projected for the end of this century, which are about two feet – but data are still inadequate to specify an exact level of rise.
• Subtropical areas around the world, including the American West, are likely to become more arid in the future due to global warming, with an increasing likelihood of severe and persistent drought. These are "among the greatest natural hazards facing the United States and the globe today," the report stated, and if models are correct, this has already begun.
• The strength of "AMOC" ocean circulation patterns that help give Europe a much warmer climate than it would otherwise have may weaken by about 25-30 percent during this century due to greenhouse gas increases, but will probably not collapse altogether – although that possibility cannot be entirely excluded.
• Climate change will accelerate the emissions of methane, a potent greenhouse gas, from both hydrate sources and wetlands, and they quite likely will double within a century – but a dramatic, potentially catastrophic release is very unlikely.

The "overarching" recommendation of the report is the need for committed and sustained monitoring of these climatic forces that could trigger abrupt climate change, the researchers concluded.

Better observing systems are needed, better forecasting of droughts should be developed, a more comprehensive understanding of the AMOC system is needed, and monitoring of methane levels should be maintained, among other needs.

The findings of this report will be used to inform federal agencies and policy makers, the researchers said. Another lead author on the report was Andrew Weaver at the University of Victoria in British Columbia, and the contributing authors included scientists from Columbia University, NOAA, the University of Colorado, and Edward Brook, a professor of geosciences at OSU.

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Did Early Global Warming Divert A New Glacial Age?

Glacier and mountain peaks in East Greenland. Using three different climate models and removing the amount of greenhouse gases humans have injected into the atmosphere during the past 5,000 to 8,000 years, scientists observed more permanent snow and ice cover in regions of Canada, Siberia, Greenland and the Rocky Mountains, all known to be seed regions for glaciers from previous ice ages. (Credit: iStockphoto/Rob Broek)

The common wisdom is that the invention of the steam engine and the advent of the coal-fueled industrial age marked the beginning of human influence on global climate.

But gathering physical evidence, backed by powerful simulations on the world's most advanced computer climate models, is reshaping that view and lending strong support to the radical idea that human-induced climate change began not 200 years ago, but thousands of years ago with the onset of large-scale agriculture in Asia and extensive deforestation in Europe.

What's more, according to the same computer simulations, the cumulative effect of thousands of years of human influence on climate is preventing the world from entering a new glacial age, altering a clockwork rhythm of periodic cooling of the planet that extends back more than a million years.

"This challenges the paradigm that things began changing with the Industrial Revolution," says Stephen Vavrus, a climatologist at the University of Wisconsin-Madison's Center for Climatic Research and the Nelson Institute for Environmental Studies. "If you think about even a small rate of increase over a long period of time, it becomes important."

Addressing scientists on Dec 17 at a meeting of the American Geophysical Union, Vavrus and colleagues John Kutzbach and Gwenaëlle Philippon provided detailed evidence in support of a controversial idea first put forward by climatologist William F. Ruddiman of the University of Virginia. That idea, debated for the past several years by climate scientists, holds that the introduction of large-scale rice agriculture in Asia, coupled with extensive deforestation in Europe began to alter world climate by pumping significant amounts of greenhouse gases — methane from terraced rice paddies and carbon dioxide from burning forests — into the atmosphere. In turn, a warmer atmosphere heated the oceans making them much less efficient storehouses of carbon dioxide and reinforcing global warming.

That one-two punch, say Kutzbach and Vavrus, was enough to set human-induced climate change in motion.

"No one disputes the large rate of increase in greenhouse gases with the Industrial Revolution," Kutzbach notes. "The large-scale burning of coal for industry has swamped everything else" in the record.

But looking farther back in time, using climatic archives such as 850,000-year-old ice core records from Antarctica, scientists are teasing out evidence of past greenhouse gases in the form of fossil air trapped in the ice. That ancient air, say Vavrus and Kutzbach, contains the unmistakable signature of increased levels of atmospheric methane and carbon dioxide beginning thousands of years before the industrial age.

"Between 5,000 and 8,000 years ago, both methane and carbon dioxide started an upward trend, unlike during previous interglacial periods," explains Kutzbach. Indeed, Ruddiman has shown that during the latter stages of six previous interglacials, greenhouse gases trended downward, not upward. Thus, the accumulation of greenhouse gases over the past few thousands of years, the Wisconsin-Virginia team argue, is very likely forestalling the onset of a new glacial cycle, such as have occurred at regular 100,000-year intervals during the last million years. Each glacial period has been paced by regular and predictable changes in the orbit of the Earth known as Milankovitch cycles, a mechanism thought to kick start glacial cycles.

"We're at a very favorable state right now for increased glaciation," says Kutzbach. "Nature is favoring it at this time in orbital cycles, and if humans weren't in the picture it would probably be happening today."

Importantly, the new research underscores the key role of greenhouse gases in influencing Earth's climate. Whereas decreasing greenhouse gases in the past helped initiate glaciations, the early agricultural and recent industrial increases in greenhouse gases may be forestalling them, say Kutzbach and Vavrus.

Using three different climate models and removing the amount of greenhouse gases humans have injected into the atmosphere during the past 5,000 to 8,000 years, Vavrus and Kutzbach observed more permanent snow and ice cover in regions of Canada, Siberia, Greenland and the Rocky Mountains, all known to be seed regions for glaciers from previous ice ages. Vavrus notes: "With every feedback we've included, it seems to support the hypothesis (of a forestalled ice age) even more. We keep getting the same answer."

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