Contemplating excess wind

Contemplating excess wind

June 16th, 2009

How much usable energy do wind turbines produce? It is a question that perplexes engineers and frustrates potential users, especially on windless days. A study published this month in the International Journal of Energy provides a formula for answering this vexing question.

Abolfazl Ahmadi and Mehdi Ali Ehyaei of the Department of Mechanical Engineering, at Iran University of Science and Technology-Arak Branch, in Arak, have investigated the "exergy" of wind power. Exergy is a term from thermodynamics that measures that the energy a system that is available to do work.

Wind is one of the oldest renewable energy resources. Fan blades atop a tall capture the wind's energy and convert it to useful power at ground level. Modern turbines, of course, take this notion of wind power one stage further and produce electricity to drive equipment elsewhere. A single wind turbine can vary in size from a few kilowatts for small residential applications to more than 5 megawatts for industrial scale electricity generation.

Ahmadi and Ehyaei point out that wind turbines have to compete with many other energy sources, primarily fossil fuels but also other renewable energy sources such as solar and biomass technology. As such, a wind turbine has to be cost effective in order to be environmentally effective.

Turbine design must meet load requirements and produce energy at a minimal per dollar cost. In order to address this cost issue, performance characteristics such as power output versus wind speed or versus rotor angular velocity must be optimized. Exergy analysis looks at the "quality" of the energy produced by a system. To be viable, there is little point in producing intermittent power at wildly varying levels, as this feeds only low-quality energy into the power supply system.

Usually, wind speeds of above 9 meters per second are considered irrelevant in exergy calculations of wind turbines and previous research has not taken all factors that are required for a holistic analysis into account, the Iranian team believes.

They have now developed an improved exergy analysis for wind turbines, which considers the kinetic exergy of the wind in much greater detail. Their approach gives them a model of how the turbine's potential for work can be lost. This then offers a way to optimize a wind turbine's three main parameters, cut-in, rated, and furling wind speeds, so that usable energy is maximized at any given wind speed from the gentlest breeze to a roaring gale; within the safe working parameters of the turbine.

They have carried out an exergy analysis of turbines sited in two cities in Iran, Tehran and Manjil, where wind speeds are very different. Tehran has low average wind, whereas Manjil is a windy city. Their formula offers optimized values for wind turbine rotation speed, which can be altered depending on wind speed. The results are a theoretical boost of 20% efficiency at both sites and a decrease in "wasted" energy of 80%.

Source: Inderscience Publishers (news : web)

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Obama calls for new era of energy exploration

Obama calls for new era of energy exploration: "Obama calls for new era of energy exploration
April 23rd, 2009 By PHILIP ELLIOTT and MIKE GLOVER , Associated Press Writers Obama calls for new era of energy exploration (AP)


(AP) -- President Barack Obama, standing Wednesday in the shell of a once-giant Maytag appliance factory that now houses a wind energy company, declared that a 'new era of energy exploration in America' would be a crucial to leading the nation out of an economic crisis.


With pieces of wind turbine towers as a backdrop, Obama touted the small manufacturing firm as a success and as a step toward reducing the United States' reliance on polluting fuels. But as the president on Earth Day set a goal for wind to generate as much as 20 percent of the U.S. electricity demand by 2030, legislation to make that a reality faced a challenge back in Washington in the Democratic-led Congress.

"The nation that leads the world in creating new energy sources will be the nation that leads the 21st century global economy," Obama said in a state that launched him on the road to the White House with a surprise upset over one-time rival Hillary Rodham Clinton.

"America can be that nation. America must be that nation. And while we seek new forms of fuel to power our homes and cars and businesses, we will rely on the same ingenuity - the same American spirit - that has always been a part of our American story."

It's an American spirit, though, that has been damped with economic downturn and financial crisis.

The president left Washington for a few hours Wednesday to visit this small Iowa town, which took a huge economic hit when Maytag Corp. shut its doors in 2007. The Maytag plant employed some 4,000 in a town of 16,000 residents in jobs that paid about $30,000 to $40,000 a year.

In its place is Trinity Structural Towers, a 90-person manufacturing firm that makes parts of wind turbines the president hopes to expand on land and at sea through the government's first plan to harness ocean currents to produce energy.

"Now, the choice we face is not between saving our environment and saving our economy," Obama said. "The choice we face is between prosperity and decline. We can remain the world's leading importer of oil, or we can become the world's leading exporter of clean energy."

In Washington, the president's plan to increase alternative energy sources and create environmentally friendly jobs hit some snags despite Obama's fellow Democrats controlling both chambers of Congress. Energy Secretary Steven Chu, EPA Administrator Lisa Jackson and Transportation Secretary Ray LaHood reinforced Obama's message in testimony to a House Energy and Commerce subcommittee on Wednesday.

The administration's draft bill is designed to help stem the pollution blamed for climate change by capping greenhouse gas emissions and reducing the nation's reliance on fossil fuels. The goal is to reduce greenhouse gases by 20 percent from 2005 levels by 2020, and by 83 percent by mid-century.

The White House wants to see movement on the legislation by Memorial Day. To help that along, aides said the president plans to personally make his case that the costs of dealing with climate change can be reduced dramatically by adopting programs that will spur energy efficiency and wider use of non-fossil energy such as wind, solar and biofuels.

In Newton, Obama proclaimed that "once-shuttered factories are whirring back to life," although the facility he toured is a shadow of what it replaced here about 30 miles east of Des Moines.

"Today this facility is alive again with new industry," Obama said, while noting that "this community continues to struggle and not everyone has been so fortunate as to be rehired."

Trinity now employs about 90 people - hardly the replacement Newton so desperately needs.

"We'll never have another Maytag," said Paul Bell, a Newton police officer who also serves in the state legislature. "Maybe we shouldn't have had a company here that the majority of people worked for. We put all of our eggs in one basket."

Recognizing the challenges remaining in Newton and scores of towns like it coast-to-coast, Obama quickly added: "Obviously things aren't exactly the same as they were with Maytag."

With the same root in realism, Obama acknowledged the United States' energy policy will not change instantly, given the country's reliance on oil and natural gas.

"But the bulk of our efforts must focus on unleashing a new, clean-energy economy that will begin to reduce our dependence on foreign oil, will cut our carbon pollution by about 80 percent by 2050 and create millions of new jobs right here in America, right here in Newton," he said.

But it won't come quickly. The United States imports almost 4.9 billion barrels of oil and refined products annually. That is raw energy that cannot be replaced, one windmill at a time.

Instead, Obama urged bold thinking - and spending - to address climate change and energy supplies.

"So on this Earth Day, it is time for us to lay a new foundation for economic growth by beginning a new era of energy exploration in America," he said to applause.

Obama also pushed personal responsibility, calling on every American to replace one incandescent light bulb with a compact fluorescent. The president also said the leaders of the world's major economies will meet next week to discuss the energy crisis.

In Landover, Md., on Monday, Vice President Joe Biden marked Earth Day by announcing that $300 million in federal stimulus money will go to cities and towns to purchase more fuel-efficient vehicles.

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Associated Press writer Brian Westley in Landover, Md., contributed to this report.
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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