Contemplating excess wind

June 16, 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 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" of 80%.

Source: Inderscience Publishers (news : web)

Explore further: Global wind map identifies wind power potential

Related Stories

Global wind map identifies wind power potential

May 16, 2005

A new global wind power map has quantified global wind power and may help planners place turbines in locations that can maximize power from the winds and provide widely available low-cost energy. After analyzing more than ...

Recycling wind turbines

September 21, 2007

The development of wind power promises much in terms of providing us with renewable energy for the future and wind turbines could be the most effective way to harness that power. Danish researchers now suggest that in order ...

Engineer aims to regulate varying wind power

October 19, 2007

As Texas' electric grid operator prepares to add power lines for carrying future wind-generated energy, an electrical engineer at The University of Texas at Austin is developing improved methods for determining the extent ...

Tilting at wind farms

January 7, 2009

A way to make wind power smoother and more efficient that exploits the inertia of a wind turbine rotor could help solve the problem of wind speed variation, according to research published in the International Journal of ...

Recommended for you

Netherlands bank customers can get vocal on payments

August 1, 2015

Are some people fed up with remembering and using passwords and PINs to make it though the day? Those who have had enough would prefer to do without them. For mobile tasks that involve banking, though, it is obvious that ...

Power grid forecasting tool reduces costly errors

July 30, 2015

Accurately forecasting future electricity needs is tricky, with sudden weather changes and other variables impacting projections minute by minute. Errors can have grave repercussions, from blackouts to high market costs. ...

Microsoft describes hard-to-mimic authentication gesture

August 1, 2015

Photos. Messages. Bank account codes. And so much more—sit on a person's mobile device, and the question is, how to secure them without having to depend on lengthy password codes of letters and numbers. Vendors promoting ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.