Archive for the ‘Wind Power’ Category

Sodar: Operation and Limitations (1/2)

February 18, 2012

On last post I explained briefly some features related to this Remote Sensing (RS) apparatus, but I consider that it should be explained further. Therefore, I am going to detail other considerations related to Sodar’s technology through two posts based on the academic paper of S. Bradley, I. Antoniou et al. (2005). By now, physical principles and uncertainties will be described. Next post will focus on its calibration methods.

Sodar is a Remote Sensing apparatus that measures 3D wind speeds at high altitudes. By emitting vertical sound beams of sound, it is possible to interpreter the backscattering frequencies due to the Doppler Effect and thus, wind components can be decoded (See Fig. 1). Usually, three or five beams are necessary to obtain reliable raw data measurements. Each of them is usually tilted 15-20º (ϕ) to the vertical (See Fig. 2). Though the emitted signal produces a continuous backscattering echo after crossing the infinite turbulent layers in the atmosphere, the echo generated at the studied altitude (Z) can be recognized according to the following formula. This means that among the continuous echo signal received, the specific signal generated at the Scattering Volume at Z height is generated at t (time) moment. The same principle is used by pulsed lidars.

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Sodar’s Overview

January 3, 2012

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Sodar (Sonic Detection And Ranging) is device for measuring remotely wind profiles from the ground by projecting sound waves. By sending an acoustic pulse away at sound velocity, it interacts with density fluctuations in the air and the frequency of backscattered signal is interpreted. This is possible due to the Doppler Effect that means frequencies between the sent signal and the backscattered one are different. Hence, wind speed can be interpreted.  Hence, wind profiles (wind speed and wind directions in function of height) at that place can be obtained.

Reliable Sodar ranges are typically around several hundred meters and basically, it depends on ambient noises and atmospheric humidity. First Sodars were developed in late 1950’s, but the first commercial ones appeared in 70’s in California (AeroVironment, Inc). Prizes are around 50.000 USD per unit.

Advantages:

– Higher altitudes than met masts.

– Cheap and easy-to-install.

– Accurate at appropriated atmospheric conditions.

Disadvantages:

– Not accurate under rainy, noisy, and low humidity conditions (sound is attenuated more rapidly in dry air).

– Data are obtained by averaging the received data. Hence, wind speed and wind direction standards are not reliable.

– Not appropriate when high obstacles are nearby (buildings, trees, towers).

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Spain Wind Power Development

September 6, 2010

Today Monday, we had another presentation. This time we had to speak about the Wind Power industry in our countries. As you can guess, Spain holds a privileged position in the world with our fourth place.

Again, here is the presentation I have just shown to teachers and the rest of students. Now we need to write the reports and they must contain further information. So, let’s start as soon as possible. :-)

The World’s largest wind power farm.

July 30, 2010


Alta Wind Energy Center (AWEC) will be the world’s largest wind power farm with its 1.550 MW. It will be located in the Tehachapi-Mojavi region (about 100 miles north of urban Los Angeles, U.S.) The wind farm is being developed by Terra-Gen Power and will consist of 300 turbines manufactured by Vestas. This Mega-project will replace the current “largest wind farm” which is in Texas (Roscoe Wind Farm).

The company in charge of this project is Terra-Gen Power, which primarily sells the output of the renewable energy projects to load serving entities under long-term power purchase agreements. In this case, Southern California Edison has agreed to a 25-year power purchase agreement for the power producer. The project is planned to finish in 2011.

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Nuclear against Wind Power

July 26, 2010

TED (Technology Entertainment and Design) is a small Californian nonprofit organization devoted to “Ideas Worth Spreading”. It was founded in 1984 and now their events are in Long Beach and Palm Spring as well in Europe and Asia offering live streaming of the talks. They address a wide range of topics within the research and practice of science and culture. Past presenters include Bill Clinton, Al Gore, Bill Gates, Google’s founders and many Nobel Prize winners. A website I really recommend to you if you like Science and Culture.

This time, I would like to pay attention on the video that is about Wind and Nuclear Energy. Firstly, we have the nuclear supporter, Stewart Brand, who shows to us actual data about the disadvantages of each energy source, from solar to coal energy. On the other hand, Mark Jacobson, focus his speech on the nuclear problems and then, on the advantages of the Wind power.

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Opponents to Wind Farms.

July 16, 2010

In preview posts, we described some benefits about the Wind Power. We usually hear wind power is a renewable, clean and a safe energy source. However, this kind of power has got disadvantages as well. Noise, visual impact, weather changes, birds mortality are just examples. This video is the trailer of a documentary film that shows us those problems. Spectacular and painful the image of a vulture bird brought down by a wind turbine blade.

The video is just one piece of the work from associations, organizations and people who think wind farms bring more problems than advantages. Maybe, the most famous organization is Country Guardian created in 1991 in the UK and although they are not opposed to wind energy as such, they condemn the abusive construction of wind farms nearby population centres and natural landscapes. It is not the only, they are more in Europe and America.

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Adopt a Wind Turbine.

July 13, 2010

The EWEA (European Wind Energy Association) started a campaign to promote the wind energy, called Fresh Air. On this website is possible to choose an installed European wind turbine and “adopt” it. It is FREE cost, and the goal is to make people more conscious on Wind Power’s benefits. You can adopt just one wind turbine for each email, so I suggest you to be sure which one you select. Are you interested to adopt a wind turbine? What are you waiting for?

According to this campaign, the video show us interesting facts on Wind Power sector and the potential of wind energy to satisfy the energy market demand without CO2 emissions. Today, Wind Power represents the 4% in the EU electricity, and in 2030 it is expected to increase that proportion to 35%. Strategic investment for a continent as Europe which is so shortfall of conventional energy resources.

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Power Electronic Concepts in Wind Turbines.

July 10, 2010

In recently years, we have lived big discoveries on the Power Electronic field that unveil new opportunities to improve the performance in the electric circuits and therefore, in Wind Power industry. Power Electronic can be defined as the brand of the electrical engineering which studies the control and conversion of electric power. Therefore, the power conversion systems can be classified according to the type of the imput and output power:

Here we are the basic components in the Wind Power industry.

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Types of Commercial Wind Turbines.

July 8, 2010


We already saw the different wind turbines we can find nowadays, from the HAWT to VAWT. However, the most commercial at this moment are the High Tip Speed Ratio HAWT. In this post, we are going to describe the different models of wind turbines and what kind of technology they use to convert the mechanical energy to electric energy.

If we pay attention at the above table, we can see there are two wind turbines models according to their Speed Control and Power Control. Thereby, we can find four models: Type A, Type B, Type C, and Type D (see the below diagram). There are three variants for the Type A (A1,A2 and A3). Although it would be possible to manufacture the same variations for the B, C and D Types, it would be not worthy (from the commercial point of view) because these models lack the capability for a fast reduction of power (see the grey-colored boxes in the first diagram). Let´s start describing the possibilities to control the power the aerodynamic forces on the turbine rotor.

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What’s inside a wind turbine?

July 7, 2010

This video posted on Youtube.com has sparked my attention. Firstly, because there are not so many videos like this that explains the main parts of a wind turbine, and second because it is worthy and is well-structured. The video is made by UVSAR, a British company which provides technical services for all those involve in work at height.

The video shows us the layout of two typical wind turbine generators, from the transformer at the floor level, ladders (or elevators), to the electrical cables attached to the walls of the tower.

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