Recent Research Results Important to Nordics

15 March, 2018, 09:30-16:00 CET

Location: Umeå Universitet, MIT Huset, room 15/16e
includes questions and answers session
For webinar access: https://connect.sunet.se/windcoe/

Topical schedule:

• Introducing the Nordic Forum for Wind Energy Research.
• Wind Turbine Icing – Progress and Challenges.
• The Logic of Information & Process in Systems-of-Systems.
• How weather is affecting acoustic propagation in cold climate regions OR Our microphones can hear it now.
• Statistical learning in wind power production and weather prediction.
• Atmospheric modeling and weather forecasting for cold climate regions.
• Wind turbine noise characteristics – Infrasound and amplitude modulation.
• Nordic Wind Forum Research going Forward.

Presentation descriptions

Target Audience:

• Municipality staff concerned with wind park development.
• Government agencies involved with wind energy regolatory issues.
• Wind industry participants currently owning unaddressed research issues.

Interest:

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If attending in person, please email Kendall Rutledge to receive logistics details.

Nordic Wind Energy Center is planning three different surveys to these three groups to come closer to understanding their current positions and opinions in different questions concerning wind power. Our primary goal is to produce a more efficient debate between the three groups. With better knowledge of what the groups see as a fair deal for developing wind parks and which questions that need to be addressed, the debate is easier to follow out.

The first questionnaire, the society questionnaire, is now sent out to residents in Finland. The center would like to study four different groups in society, each with a different relationship to wind power. The questionnaire is distributed to four different areas:

1. Area where a wind park is newly built
2. Area where a wind park already has existed a few years
3. Area with existing plans for building a wind park
4. Area that is untouched and no existing plans for wind parks

It is also possible to answer this questionnaire (in Finnish or Swedish) on the internet if you follow this link: in Swedish or in Finnish

The questionnaire consist of assertion responses scaled 1-7 and its´ head topics are

Place attachment – how does the personal attachment to the respondant´s home and area affect their opinions? Can people feel a loss of authority over their area if wind turbines are built there?
Environmental effects – concerns about landscape, wildlife and noise from turbines.
Health concerns – do people worry about turbines affecting their health?
Economic effects – for the region and the whole nation
Objective information – is neutral information easy to find?
Sustainability and renewable energy – is it easier to accept a wind park in the area if it contributes to renewable energy goals?

The questionnaires to governments and wind industry will have other head topics. The society questionnaire also contains questions regarding how you perceive yourself. These questions belongs to a method called Ten-Item Personality Inventory-(TIPI).

The results from the society questionnaire will be analyzed in the autumn of 2017 and presented at the centers homepage.

If you want to participate in the questionnaire and also have a chance to win a 100 euro S-market gift card, follow this link:  in Swedish or in Finnish.

Please answer all questions. The questionnaire will take you about ten minutes.

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On the theme; Popular and Participatory Wind Power, the conference will focus on how to contribute to the development of wind power with a mix of players working for the energy transformation.

Visit the page here.

The conferences last 4 days and are packed with presentations, poster presentations, workshops exhibits and informal discussion.

For more information, visit INCE/Europe

University of Tromsø have special research facilities for studying wind energy in cold climate. Except for the low speed wind tunnels they also have cold climate chambers.

The project meeting started with a visit to the UiT Wind Tunnel Lab.

The wind tunnel is used for measuring in aerodynamic studies; how the air moves around solid objects, turbulence and pressure.

Participants had both presentations of their own project activities as well as discussions about future plans for the project.

The same questions were sent to two groups;
1. To residents in three areas where wind power was establishing in an early stage
2. To residents in two areas where wind parks were already built.

The survey showed a healthy skepticism towards establishing wind parks in people´s own neighborhood. People were mostly worried if wind turbines would disturb the landscape and also if the sound of them would be disturbing. Another fear was if building them would affect the nature and in particular, if it would affect birds. Despite these fears, most residents were positively set to establishing wind energy.

This short summary only shows some of the statements and answers from the survey. If you want to read more about the survey and also about some facts in these topics, you can find it here: http://www.tuulivoimaopas.fi/files/28/tuulen_voimalla_suomessa.pdf

The survey had different statements, with answers to them from 1-5:

1. Completely disagree
2. Somewhat disagree
3. I can´t say
4. Somewhat agree
5. Completely agree.

The brown staple shows group 1 (before wind park) and
the green shows group 2 (after wind park)

The statement to the left: “Wind turbines are causing damage for animals”.

This question had a much higher rating than other questions on number 3,
(I can´t say), which indicates that the residents lacks information about this topic.

Brown staple  before wind park,  green staple after wind park

The statement to the left: “Blinking air craft warning lights from wind turbines are disturbing”.

1. Completely disagree
2. Somewhat disagree
3. I can´t say
4. Somewhat agree
5. Completely agree.

Brown staple  before wind park,  green staple after wind park

The statement to the left: “Wind turbines do not disturb the landscape”.

1. Completely disagree
2. Somewhat disagree
3. I can´t say
4. Somewhat agree
5. Completely agree.

Brown staple  before wind park,  green staple after wind park

The statement to the left: “I did get enough information about the wind park establishing in beforehand”.

1. Completely disagree
2. Somewhat disagree
3. I can´t say
4. Somewhat agree
5. Completely agree.

Brown staple  before wind park,  green staple after wind park

The statement to the left: “The residents´ well-being have weakened while the wind park is being built”.

1. Completely disagree
2. Somewhat disagree
3. I can´t say
4. Somewhat agree
5. Completely agree.

Brown staple  before wind park,  green staple after wind park

The statement to the left: “Wind turbines are causing a high noise”.

1. Completely disagree
2. Somewhat disagree
3. I can´t say
4. Somewhat agree
5. Completely agree.

In the surveys´ results, not much difference was shown between women´s and men´s opinions. Even if the survey was done at different areas, the opinions in the areas were also surprisingly similar. It is very common when a wind park is planned in a new area, that the resistance towards it is high. The survey showed that even in these areas, a majority of the residents were positive to wind energy. The survey also showed that the society needs more information about wind energy and how building it affects us and our surroundings.

You can read the whole article here (in Finnish) or a short summary below in English.

In Finland, wind energy has partly been met with scepticism and criticism, regarding the environmental effects. A possible explanation to negative attitudes, could depend on lack of new information based on empirical studies. Without reliable information available, people are more likely to rely on hearsaying and theories that are not backed up by studies.

The WindSoMe-project wants to do research to provide more updated information, which will hopefully reduce preconceptions regarding wind industry. Except for the compensations for the land meant for wind park areas, most of the criticism is concerning the noise from the wind turbines.

Within the project, research is being done about noise propagation, the strength of the noise and its´ special traits and in particular; how noise behave at different weather conditions and seasons. Except for sound- and weather measurements and weather models, surveys about noise from the wind turbines are also being performed. Feedback from the surveys is received in real time by a smartphone app and also by questionnaires.

This forms a new kind of versatile combination, containing weather information and clients´ opinions with measurements of the sound propagation from wind turbines. Based on the research it is possible to describe how the noise is experienced, when, why and under which circumstances the noise can be disturbing and to realize which parameters that makes varieties in the sound propagation. Differences in the terrain will also be one factor to affect the sound.

The project aims to find best practice amongst the individual, the community and the industry when building wind energy parks. The research will help to understand how wind energy parks are approved both generally and locally and which factors that affect these attitudes. The project ends in 2017.

Participants in the project WindSoMe are a program called Innovatiiviset Kaupungit (Innovative Cities), the University of Vaasa, Novia University of Applied Sciences, Lappeenranta University of Technology, VTT Technical Research Centre of Finland Ltd, Merinova Ltd. Companies involved in the project are: Nordex Energy GmbH, ABB Ltd, VindIn Ltd, Cleanhub Ltd, Taaleri Plc, EPV Tuulivoima Ltd, the City of Lappeenranta and National Instruments Finland Ltd.

Click here to read the whole article.

A microwave radiometer has been installed at a WindCoE-project site for measuring the atmosphere to help understand why distantly propagated sound has so much variability. Especially wind turbine sound. The radiometer scans the atmosphere and measures temperatures up to 1000 meters at time intervals of five minutes. We intend to average these data to coincide with the temporal resolution of other data taken at the site.

Other equipment at the site taking data at 10 minute intervals include a sodar measuring wind speed and wind direction at heights from 50-200 m. Meteorology stations on the top of wind turbine nacelles are measuring at a height of 120 m. A mast mounted met station is measuring basic meteorological parameters also at a height of 10 m. Acoustic data measured at ground level is also being recorded at an interval of 25,600 times per second (we have a way to summarize it into 10-minute intervals).

Some of these observations are being used for estimating effective speed of sound fields in the atmosphere. The speed of sound is also called celerity and it primarily depends upon temperature plus wind profiles through the atmosphere. We will use this information to determine if we can qualify the Weather Research and Forecasting model (WRF) to be helpful in estimating the details of the atmosphere as we work to understand sound traveling in the environment.

The Finnish weather and temperature inversions

Finland’s climate has characteristics of both a maritime and a continental climate, depending on the direction that frontal passes. The mean temperature in Finland is several degrees higher than many other areas at the same latitudes because of the influence of the heat distribution from the oceans. Weather can also change quite rapidly, particularly in winter. (1)

With the radiometer, we have already observed surface based temperature inversions with a strength of 8 degrees spanning the 0 to 200m altitude range. This means the temperature increased 8 degrees from 0 to 200m and this condition is not so common except in cold climate areas. This is called a surface based inversion and it is indicative of an extremely stable atmosphere.

When high pressure is dominant across Finland in winter, the atmosphere is characterized by a near permanent temperature inversion, meaning warmer air can be found over a cooler air. The low sun angle and the short days in winter do not allow enough heat to erode the inversions in the high latitudes. The ordinarily occurring stratus clouds (low level clouds) also play an important role in vertical transfer of heat and moisture. Numerical models quite often experience difficulties in forecasting inversions and low clouds during winter. (1) The image below shows differences in atmosphere temperature at different heights during a 24 h period from the radiometer.

Temperature inversions and their effect on sound propagation

The Nordic weather, with high proportions of ground based temperature inversions can have effects on environmental noise propagation. Inversion means that layers of air have temperature increasing in as elevation increases. In cold climate areas, layers of colder air usually form near the earth´s surface during winter time.  The inversion layer can de-couple the surface winds from the stronger upper layer winds. For this reason, surface wind speeds tend to be lower than upper wind speeds in winter than one might expect. (1) 

Since the speed of sound is higher with warmer temperatures, these changing temperature layers lead to sound moving in curved paths near the ground as shown in the picture. (2) Since the temperature structure can be complicated, so can be the sound propagation bending.

In dry air at 20 °C, the speed of sound is 343.2 m/s. The picture below shows an example of speed of sound in dry air at two different times the same day, from a WRF-model performed by members of the the Nordic Wind Energy Center, Drs Fonseca and MartinTorres of Luleå University. In the side by side plots of speed of sound, two very different scenarios are observed at different times on the same day. In one of the images the atmosphere is warmer near the ground and colder above. In the other image it is opposite. It is expected that when the sound goes through these two types of scenarios, on one of them, a distant observer would not hear the wind turbine noise and in the other, the distant observer would hear the wind turbine noise.

The way that the sound moves through the atmosphere can be estimated by acoustic ray tracing methods. As the temperature in the atmosphere varies, it affects the sounds propagation directions according to Snell’s law of refraction. The picture below shows an example of acoustic ray tracing from a hypothetical wind turbine, using one (10 minute) instance of the WRF results. It is to be remembered that the process described here is changing in time. In this way, you can see how the diurnal and seasonal weather effects actually modulate the sound propagation. In the ray tracing diagram, the rays “bend” according to the temperature and wind fields observed at the moment. So the plot represents a single 10 minute summary of how the sound travels through the atmosphere.

In the display, we have ignored relections and interactions for the ground.  Also here, the frequency in undefined, so these are generic results. In the example, the rays are released at a height appropriate for large modern day wind turbines, approximately 75% of the altitude associated with the rotor plane top height is used. The rays initially are directed every few degrees but as they travel through the atmosphere, the environmental factors cause them to bend. In this exmple there is a strong gradient near the height of the wind turbine acoustic source location and some rays are bent downward and some are bent upward.

The rays can be thought of as paths of which the acoustic energy (sound) is transferred. In this case, a microphone or person listening at the location (on the ground) 1.1 km away from the wind turbine would not hear the wind turbine (as no rays come close to this point on the ground). At other times, the wind turbine acoustics can be observable.  A goal of the project is to understand the proportions of time that the wind turbines can and can’t be detected (and use the weather data to explain why).

By understanding the atmospheric effects on sound propagation, the Nordic wind energy industry is developing a clearer understanding of their operational environment.

Sources
1. Pelkonen Antti, FMI. The boundary layer in Finland during winter. The European Forecaster Newsletter 5/2006. http://www.euroforecaster.org/newsletter11/full_2006.pdf
2. O’Connor Michael. Temperature Inversions & Sound Propagation. MO’C Physics Applied. Webpage. http://mocpa.com/inversion.html