Difference between revisions of "Assessing Wind Potentials"

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== Investigation of available wind velocity data for the proposed site  ==
 
  
As a first step in assessment of wind potentials available data from conducted measurements or other sources has to be gathered. In case an open access atlas for regional or national wind velocity has been prepared, it probably is available at the following websites:
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= Overview =
  
*winddata.com: [[http://130.226.17.201/side.php?nummer=11]]
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In recent years, wind energy has become one of the most economical renewable energy technology. Today, electricity generating wind turbines employ proven and tested technology, and provide a secure and sustainable energy supply. At good, windy sites, wind energy can already successfully compete with conventional energy production<ref name="GTZ (2000) Wind Energy Projects in Morocco and Namibia. Eschborn, retrieved 08.01.2013 https://www.docstoc.com/pass/22042181]">GTZ (2000) Wind Energy Projects in Morocco and Namibia. Eschborn, retrieved 08.01.2013 https://www.docstoc.com/pass/22042181]</ref>. Many countries have considerable wind resources, which are still untapped.
*UNEP Solar and Wind Energy Resource Assessment (SWERA): [[http://swera.unep.net/]]
 
  
Other possibilities for wind data enquiry:
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► [[Wind_Energy_-_Introduction|Wind Energy - Introduction]]
  
*airports  
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► [[Portal:Wind|Wind Portal on energypedia]]
*Meteorological institutes  
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= Investigation of Available Wind Velocity Data for the Proposed Site<br/> =
 +
 
 +
As a first step in assessment of wind potentials available data from conducted measurements or other sources has to be gathered.
 +
 
 +
<u>In case an open access atlas for regional or national wind velocity has been prepared, it probably is available at the following websites:</u>
 +
*[http://130.226.17.201/side.php?nummer=11 winddata.com]
 +
*[http://en.openei.org/apps/SWERA/ UNEP Solar and Wind Energy Resource Assessment (SWERA)]
 +
 
 +
<br/>
 +
 
 +
<u>Other possibilities for wind data enquiry:</u>
 +
*airports
 +
*Meteorological institutes
 
*Universities dedicated to wind energy research
 
*Universities dedicated to wind energy research
  
his ''Guide to Small and Micro Wind Systems<ref>Gipe, P. (1999) Wind Energ Basics - A Guide to Small and Micro Wind Systems, Chelsea Green Publishing</ref>,'' that in case of micro wind systems is often better to install a small wind turbine and to monitor the output during the first year, than to conduct an own measurement:&nbsp;If the wind turbine output does not suitable values, the turbine could be resold easily as there is a large market for used small and micro wind turbines<ref>Gipe, P. (1999) Wind Energ Basics - A Guide to Small and Micro Wind Systems, Chelsea Green Publishing</ref>. Nevertheless as project size, related investments and – according to this – the responsibility of the project developer increases, wind measurement becomes a central component of wind project development.''<br>''
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<br/>
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Paul Gipe explains in his ''Guide to Small and Micro Wind Systems<ref>Gipe, P. (1999) Wind Energ Basics - A Guide to Small and Micro Wind Systems, Chelsea Green Publishing</ref>,'' that in case of micro wind systems, it is often better to install a small wind turbine and to monitor the output during the first year, than to conduct an own measurement: If the wind turbine output does not suitable values, the turbine could be resold easily as there is a large market for used small and micro wind turbines<ref>Gipe, P. (1999) Wind Energ Basics - A Guide to Small and Micro Wind Systems, Chelsea Green Publishing</ref>. Nevertheless as project size, related investments and – according to this – the responsibility of the project developer, increases, wind measurement becomes a central component of wind project development.
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[[Assessing Wind Potentials#toc|►Go to Top]]<br/>
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== Site selection and wind measurement in the height of 10 m<br>  ==
 
  
The following characteristics have to be considered for inital site selection and placement of the measurement masts:<br>  
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== Site Selection and Wind Measurement in the Height of 10m<br/> ==
  
*Indications for suitable wind conditions (As a guiding value an average wind velocity of 6 m/s in the height of 10 m is generally considered suitable). Besides the available information about wind velocities, statements of the local population or landscape characteristics (inclined trees caused by the prevailing wind direction) could be used as indicators.  
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<u>The following characteristics have to be considered for inital site selection and placement of the measurement masts<ref>European Wind Energy Association (1999) Best Practice Guidelines for Wind Energy Development, retrieved 8.7.2011 [[http://ec.europa.eu/energy/renewables/studies/doc/wind_energy/2002_best_practice.pdf]]</ref>:</u>
*Proximity to the electricity grid, especially to suitable connections points (transformer stations for larger projects)<br>
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*Indications for suitable wind conditions (As a guiding value an average wind velocity of 6 m/s in the height of 10 m is generally considered suitable). Besides the available information about wind velocities, statements of the local population or landscape characteristics (inclined trees caused by the prevailing wind direction) could be used as indicators.
*A sufficient transport-infrastructure for transport of the large and heavy parts of wind turbines to the site (Curve radii of roads, inclination of roads, carrying capacity of bridges, width and height of bridges to be passed through etc.)  
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*Proximity to the electricity grid, especially to suitable connections points (transformer stations for larger projects)
*Proximity to cities and their infrastructure to locate a center for maintainance and service of the wind park  
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*A sufficient transport-infrastructure for transport of the large and heavy parts of wind turbines to the site (Curve radii of roads, inclination of roads, carrying capacity of bridges, width and height of bridges to be passed through etc.)
*Conflicting interests of site utilization: Hill sides providing good wind conditions are usually prefered placements for telecommunication masts as well. Telecommunication processes can be disturbed by the installation of wind turbines. Airports, radar-stations and areas of environmental protection could be constraining factors, too.&nbsp;
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*Proximity to cities and their infrastructure to locate a center for maintainance and service of the wind park
 +
*Conflicting interests of site utilization: Hill sides providing good wind conditions are usually prefered placements for telecommunication masts as well. Telecommunication processes can be disturbed by the installation of wind turbines. Airports, radar-stations and areas of environmental protection could be constraining factors, too.
  
In case only scarse information about wind conditions at the site is available, wind speed measurements should be conducted at 10 m height as a pre-study. In this way costs for measurements are kept low, since the suitability of the site still has a speculative character. Wind speed is measured by anemometers, while information about wind directions is gathered by a vane. It is of essential importance to calibrate the anemometers before their application. For large wind projects calibration is often done by accredited institutes. Calibration has to be conducted according to international guidelines like the <ref>International Organization of Standardization (2008) ISO 3966:2008 Measurement of fluid flow in closed conduits -- Velocity area method using Pitot static tubes, retrieved 10.7.2011, [[http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50626]]</ref>, IEA-Guidelines for calibration<ref>International Energy Association (1999) Recommended practices for wind turbine testing and evaluation - 11. Wind speed measurement and use of cup anemometry, retrieved 10.7.2011 [[http://www.ieawind.org/Task_11/RecommendedPract/11%20Anemometry_secondPrint.pdf]]</ref> or the standardized methods of the MEASNET-Group<ref>MEASNET Group (2008) Cup anemometer calibration procedure - Version 1, retrieved 10.7.2011 [[http://www.measnet.org/anocalib_updated2008.pdf]]</ref>.&nbsp;
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<br/>
  
For the storage of the measured wind data a data-logger is necessary. This device is installed in a case at the lower part of the measurement mast. The data-logger is supplied with electricity by a battery or a PV-module combined with a small battery storage. Supply of the data-logger has to be very reliable, because loss of data will result, if the data-logger is out of electricity. To prevent thievery of the PV-Module it should be fixed at a higher point of the measurement mast.  
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In case only scarse information about wind conditions at the site is available, wind speed measurements should be conducted at 10 m height as a pre-study. In this way costs for measurements are kept low, since the suitability of the site still has a speculative character. Wind speed is measured by anemometers, while information about wind directions is gathered by a vane. It is of essential importance to calibrate the anemometers before their application. For large wind projects calibration is often done by accredited institutes. Calibration has to be conducted according to international guidelines like the ISO 3966<ref>International Organization of Standardization (2008) ISO 3966:2008 Measurement of fluid flow in closed conduits -- Velocity area method using Pitot static tubes, retrieved 10.7.2011, [[http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=50626]]</ref>, IEA-Guidelines for calibration<ref>International Energy Association (1999) Recommended practices for wind turbine testing and evaluation - 11. Wind speed measurement and use of cup anemometry, retrieved 10.7.2011 [[http://www.ieawind.org/Task_11/RecommendedPract/11%20Anemometry_secondPrint.pdf]]</ref> or the standardized methods of the MEASNET-Group<ref>MEASNET Group (2008) Cup anemometer calibration procedure - Version 1, retrieved 10.7.2011 [[http://www.measnet.org/anocalib_updated2008.pdf]]</ref>.
  
Collected wind data should be read out regularly: The most comfortable read-out-method is realized by installing a mobile communication device to read out data from afar. Remote connection to the data-logger also allows observation of the measurement devices. However it is necessary to visit the site in periodically to inspect the mast and the measurement devices on-site.<br>
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For the storage of the measured wind data a data-logger is necessary. This device is installed in a case at the lower part of the measurement mast. The data-logger is supplied with electricity by a battery or a PV-module combined with a small battery storage. Supply of the data-logger has to be very reliable, because loss of data will result, if the data-logger is out of electricity. To prevent thievery of the PV-Module it should be fixed at a higher point of the measurement mast.
  
Costs of all described tools for wind measurement are listet in the following. The given prices are examples from two manufacturers of anemometers, vanes and data loggers, Ammonit and Thies. Good experiences have been gathered with measurement devices of these providers.&nbsp; <br>
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Collected wind data should be read out regularly: The most comfortable read-out-method is realized by installing a mobile communication device to read out data from afar. Remote connection to the data-logger also allows observation of the measurement devices. However it is necessary to visit the site in periodically to inspect the mast and the measurement devices on-site.
  
*Anemometer 550 €  
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Costs of all described tools for wind measurement are listet in the following. The given prices are examples from two manufacturers of anemometers, vanes and data loggers, Ammonit and Thies.
*Calibration of one Anemometer 300 €  
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*Vane 450 €  
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*Data-logger 1.200 €  
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 +
<u>Good experiences have been gathered with measurement devices of these providers:</u>
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*Anemometer 550 €
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*Calibration of one Anemometer 300 €
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*Vane 450 €
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*Data-logger 1.200 €
 
*Additional equipment (cabel, etc.) 500 €
 
*Additional equipment (cabel, etc.) 500 €
  
The measurement masts have to be equipped with appropriate consoles to fix measurement tools. A lightning conductor as well as anchored guy cables are standard parts for the erection of a measurement mast. For site evaluation in developing countries the measurement devices often have to be imported, while the mast for measurement could be acquired or constructed in the country. For example project developers used telephone masts of 10 m height to conduct peliminary wind measurement in Ethiopia.  
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<br/>
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The measurement masts have to be equipped with appropriate consoles to fix measurement tools. A lightning conductor as well as anchored guy cables are standard parts for the erection of a measurement mast. For site evaluation in developing countries the measurement devices often have to be imported, while the mast for measurement could be acquired or constructed in the country. For example project developers used telephone masts of 10 m height to conduct peliminary wind measurement in Ethiopia.
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A minimal measurement period of one year is needed to generate a complete survey of the local wind conditions. Seasonal variations can be captured only by such relatively long-term measurements.
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Based on the analysis of wind conditions in the height of 10 m, a first reliable estimation of the economical feasibility of the wind park at the proposed site can be worked out.
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An average wind velocity of 6 m/s at a height of 10 m is generally considered as a guiding value for a suitable wind project. The necessary wind conditions for a specific wind project can deviate from this: If the costs of alternative electricity sources is comparatively high, a wind project could be economically viable at average wind speeds below 6 m/s.
  
A minimal measurement period of one year is needed to generate a complete survey of the local wind conditions. Seasonal variations can be captured only by such relatively long-term measurements.
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<u>A wind regime with an average wind speed higher than 6 m/s can not be considered as a guaranty for economical feasibility as well:</u>
  
Based on the analysis of wind conditions in the height of 10 m, a first reliable estimation of the economical feasibility of the wind&nbsp;&nbsp; park at the proposed site can be worked out.  
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The returns of a wind project as well as financing conditions are heavily influenced by national, regional and even local [[Political Framework Conditions - Wind Energy|political framework conditions]]. Investigation and monitoring of the political framework conditions is a central task to prepare reliable statements about economical feasibility of the project.
  
An average wind velocity of 6 m/s at a height of 10 m is generally considered as a guiding value for a suitable wind project. The necessary wind conditions for a specific wind project can deviate from this: If the costs of alternative electricity sources is comparatively high, a wind project could be economically viable at average wind speeds below 6 m/s. A wind regime with an average wind speed higher than 6 m/s can not be considered as a guaranty for economical feasibility as well:
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Including these informations and taking into account the analysis of the collected wind data at the height of 10 m the developers may decide, whether the project should be continued or not. If the measurement has revealed a suitable outcome the next measurement campaign has to be planned. In any other case the project will be ceased at this point. Speaking generally the outcome of measurement at 10 m height is a conceptional 'rated break point' applied in every large wind project.
  
The returns of a wind project as well as financing conditions are heavily influenced by national, regional and even local [[Political Framework Conditions - Wind Energy|political framework conditions]]. Investigation and monitoring of the political framework conditions is a central task to prepare reliable statements about economical feasibility of the project.
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[[Assessing Wind Potentials#toc|►Go to Top]]
  
Including these informations and taking into account the analysis of the collected wind data at the height of 10 m the developers may decide, whether the project should be continued or not. If the measurement has revealed a suitable outcome the next measurement campaign has to be planned. In any other case the project will be ceased at this point. Speaking generally the outcome of measurement at 10 m height is a conceptional 'rated break point' applied in every large wind project. <br>
 
  
=== Specification of measurement devices and calibrated sensors  ===
 
  
The necessary devices include<br>  
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=== Specification of Measurement Devices and Calibrated Sensors<br/> ===
  
*Wind vane (accuracy ≤ 5°, definition ≤ 5°)  
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<u>The necessary devices include:</u>
*Anemometer (Impuls-output with a minimal definition of 1 Puls per 0.1m wind-track, measurement characteristics in inclined flow and accuracy have to be chosen accordingly the IEA-guidelines)  
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*Wind vane (accuracy ≤ 5°, definition ≤ 5°)
*Data-logger for capturing time series (Storage of 10-Minute values of: the average value of wind velocity, the standard deviation of wind velocity as well as minimum and maximum velocities during the interval; sampling rate should be for minimum 0,5Hz) Data transfer via storage card or chip  
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*Anemometer (Impuls-output with a minimal definition of 1 Puls per 0.1m wind-track, measurement characteristics in inclined flow and accuracy have to be chosen accordingly the IEA-guidelines)
*Battery or combined PV-Panel-storage system  
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*Data-logger for capturing time series (Storage of 10-Minute values of: the average value of wind velocity, the standard deviation of wind velocity as well as minimum and maximum velocities during the interval; sampling rate should be for minimum 0,5Hz) Data transfer via storage card or chip
*additional equipment like cables  
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*Battery or combined PV-Panel-storage system
*Notebook Computer<br>
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*additional equipment like cables
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*Notebook Computer
  
=== Installation of measurement masts and equipment<br> ===
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[[Assessing Wind Potentials#toc|►Go to Top]]
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<br/>
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=== Installation of Measurement Masts and Equipment<br/> ===
  
 
*Transport of masts for 10m-measurement to the site; planning of the steps for installation of the equipment.
 
*Transport of masts for 10m-measurement to the site; planning of the steps for installation of the equipment.
*Positioning of measurement masts; adjustment of anemometer to avoid inclined flow<br>
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*Positioning of measurement masts; adjustment of anemometer to avoid inclined flow
*Inspection of the installation of the measurement masts, including anemometer and vane adjustment as well as functioning of the data logger and reliability of its electricity supply. Safety risks and potential sources for failures have to be identified and removed.<br>
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*Inspection of the installation of the measurement masts, including anemometer and vane adjustment as well as functioning of the data logger and reliability of its electricity supply. Safety risks and potential sources for failures have to be identified and removed.
*Einhaltung nationaler und international gültiger Sicherheitsbestimmungen für die mit der Installation befassten Personen.  
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*Compiance with national and international safety regulations for all persons involved in the installation process.
*Funktionstest und Testmessungen zur Inbetriebnahme.<br>  
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*Testing of operability and test-measurements for commissioning
*Korrekte Installation und Funktion der Messgeräte durch ein Abnahmeprotokoll dokumentieren.
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*Documentation of installation of measurement system by a protocol for approval
*Geographische Position der Masten durch eine GPS-Messung ermitteln.  
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*Determination of geographic positions of measurement masts via GPS.
*Die unmittelbare Umgebung der Messmasten wird hinsichtlich eventueller Hindernisse in der Anströmung und der Rauhigkeit der Oberfläche dokumentiert und charakterisiert.<br>
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*Description of the direct surrounding of the measurement masts concerning potential obstacles for wind flow and estimation of roughness parameters.
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[[Assessing Wind Potentials#toc|►Go to Top]]
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<br/>
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=== Measurement and Periodical Data Analysis to Assess Wind Energy Potential<br/> ===
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<u>Wind measurement contains the following tasks:</u>
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*Read-out of wind data after periods of 1, 3, 6, 9 und 12 Months
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*Checking data for completeness or failures
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*Data analysis includes consistency, plausibility and identification of missing values. In case the measurement reveals significant shortcomings, possible methods to enhance data quality have to be considered.
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*Wind measurement should result in a time series, which can be easily processed with the planning project WA<sup>S</sup>P. According to this an appropriate data format has to be chosen.
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[[Assessing Wind Potentials#toc|►Go to Top]]
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=== Rating of the Wind Eata concerning the Quality of Wind Potential at the Site<br/> ===
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The developer works out a report about wind energy potential, based on the first wind measurement at the height of 10 m.
  
=== Windmessungen und regelmäßige Datenanalyse zur Windpotentialbestimmung über einen Zeitraum von 12 Monaten <br> ===
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<u>This report contains information concerning the following aspects:</u>
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*Analysis and rating of data quality and its impacts of the outcome of the measurement;
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*Annual average value, Histogram, seasonal variations in the monthly averages of wind speed, typical variations of wind speed during a day
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*Distribution of wind potentials sorted by wind directions (wind rose);
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*Weibull-parameters sorted by wind-directions;
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*roughness-parameter and obstacles in the surrounding sorted by wind direction or visualized in a map;
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*Degree of turbulence wind speed maximum at the site
  
Bei der Windmessung gilt folgendes zu beachten:
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<br/>
  
*Auslesung der Daten nach 1, 3, 6, 9 und 12 Monaten <br>
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The report recommends whether the project development should continued. Additionally recommendations for additional measurements at a height of 40 m is given.
*Daten auf Vollständigkeit Fehler überprüfen
 
*Bei der Auswertung ist die Konsistenz, Plausibilität und Datenausfall der erhobenen Daten zu beachten. Im Fall von Unzulänglichkeiten der Daten sind mögliche Abhilfemaßnahmen zu erörtern.
 
*Messdaten sollen so erhoben und aufbereitet werden, dass sie ohne weitere Bearbeitungsschritte in WASP eingegeben werden können und die für WASP erforderlichen Charakteristika aufweisen.
 
  
=== Bewertung der Windmessdaten hinsichtlich der Qualität des Windpotentials am Messstandort  ===
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[[Assessing Wind Potentials#toc|►Go to Top]]
  
Auf der Basis der gewonnenen Daten wird nach 12 Monaten ein Gutachten zur Bewertung des Windenergiepotentials der X Standorte erstellt. Dieses Gutachten soll wesentlich ausführlicher sein als die zwischenzeitlichen Kurzberichte und insbesondere folgende Informationen enthalten:<br>
 
  
*Analyse und Bewertung der Datenqualität und deren Auswirkung auf die Ergebnisse;
 
*Jahresmittelwert, Histogramm, jahreszeitlicher Verlauf der Monatsmittelwerte, typische Tagesgänge der gemessenen Windgeschwindigkeiten;
 
*Verteilung des Windpotentials nach Windrichtungen (Windrose);
 
*Weibullparameter nach Windrichtungen;
 
*Rauhigkeitsparameter und Hindernisse der Umgebung nach Windrichtung oder in Kar-tenform;
 
*Turbulenzgrad und Extrema der Windgeschwindigkeiten;
 
  
Ferner enthält das Gutachten eine Empfehlung über eine Fortsetzung des Vorhabens mit einer Empfehlung, an welchen Standorten zusätzliche Messungen in 40m Höhe durchgeführt werden sollen.
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== Wind Measurement in Major Heights<br/> ==
  
== <br>Windmessungen in größerer Höhe  ==
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As wind velocity normally increases with height the wind 10 m - measurement allows only estimation of wind velocity at hub height. In case the report of the first measurement has recommended to continue project development, a second measurement at major heights is implemented.
  
Da die Windgeschwindigkeit mit der Höhe über dem Boden in der Regel zunimmt, kann eine Messung auf 10 m Höhe lediglich einen Schätzung der Windbedingungen auf Nabenhöhe ermöglichen. An Standorten, die auf 10 m Höhe vielversprechende Windverhältnisse aufweisen, wird in einem zweiten Schritt in größerer Höhe gemessen. Am besten wäre es auf Nabenhöhe selbst zu messen. Es ist heutzutage möglich, Messmasten mit über 100 m Höhe zu errichten, allerdings sind solche Messungen mit entsprechend höheren Kosten verbunden. Es ist in der Regel ausreichend, zusätzlich zur Messung auf 10 m Höhe ein weiteres Anemometer auf 40 m Höhe anzubringen, daraus lässt sich mit ausreichender Genauigkeit die Zunahme der Windgeschwindigkeit auch in größeren Höhen extrapolieren. Wichtig ist dabei, dass die Messungen auf 10 m und 40 m Höhe tatsächlich am gleichen Standort (am gleichen Mast) durchgeführt werden. Die Zunahme der Windgeschwindigkeit mit der Höhe ist Abhängigkeit von der Umgebung des Standortes. Grundsätzlich lässt sich sagen, dass eine Flache und „glatte“ Umgebung einen geringeren Anstieg der Windgeschwindigkeit mit der Höhe mit sich bringt, als ein hügeliger und „rauer“ Standort. Somit lässt sich keine allgemeine Aussage zur Zunahme der Windgeschwindigkeit mit der Höhe machen. An manchen Standorten kann zwischen 10 m und 40 m Höhe ein Unterschied in der Windgeschwindigkeit von über 2 m/s liegen. An anderen Standorten ist es sogar möglich, dass auf Grund besonderer Strömungen in 40 m Höhe geringere Windgeschwindigkeiten gemessen werden als in 10 m Höhe. All dies unterstreicht die Wichtigkeit, Messungen auf zwei Höhen durchzuführen. Auch Messmasten mit 40 m Höhe können in der Regel in den Partnerländern selbst gefertigt werden, wobei Konstruktionszeichnungen gestellt werden sollten. Bei Beschaffung ist mit Kosten von ca. 10.000 € für den Messmast als grobem Richtwert zu rechnen. Gittermasten sind stabiler als Rohrmasten, dafür aber auch teurer. Auch hier sei zur korrekten Durchführung der Windmessung auf die Richtlinie von Ammonit in Anhang A verwiesen.  
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Measurement at hub height would reveal the most reliable outcome. It is technical feasible to install measurement masts with heights of 100 m, but the related costs of measurement are very high. It is generally considered sufficient to conduct additional measurements at the height of 40 m. The gathered data of this measurement may be used for extrapolation of wind speeds at hub height with an appropriate reliability. The measurements at the height of 10 and 40 m have to be conducted at the same placements, because the increase of wind speed with height depends on the specific placement of the mast: within flat ground conditions without major obstacles the wind speed increase with height is less than at a placement with high roughness values. The difference in wind velocity at the heights of 10 and 40 m can amount 2 m/s at several sites. On the other hand a lower wind speed is measured at 40 m than at 10 m. Thus applying additional measurements at 40 m height is fundamental for generating reliable wind data.
  
Um einen vollständigen Überblick über die Windverhältnisse am Messstandort zu erhalten, muss erneut über einen Zeitraum von mindesten einem Jahr gemessen werden. Nun ist es jedoch klar, dass es auch unter den Jahren erhebliche Schwankungen der Windverhältnisse geben kann und die innerhalb eines Jahres gemessenen Daten nicht repräsentativ für den langjährigen Mittelwert sein müssen, welcher zur Ertragsprognose sinnvollerweise herangezogen wird. Um sich dem langjährig zu erwartenden Mittelwert anzunähern, wird nun ein sogenannter Langzeitabgleich durchgeführt, bei dem die eigenen Messdaten mit Daten von anderen Standorten, für die über einen längeren Zeitraum Daten vorliegen, verglichen werden. Im Falle einer ausreichenden Korrelation im Messzeitraum lässt sich auf diesem Wege ableiten, ob und um welchen Betrag der langjährige Mittelwert der Windgeschwindigkeit vom Mittelwert des Messzeitraumes nach oben oder unten abweicht. Sollten keine Messdaten für den Abgleich vorhanden sein, kann zur groben Annäherung auch die sogenannte „reanalysis wind-data“ vom US National Center for Atmospheric Research und National Center for Environmental Prediction (NCEP/NCAR)<ref>http://www.ncep.noaa.gov/ (accessed: July 2011)</ref> verwendet werden. Diese Daten sind das Ergebnis eines globalen Klima-Berechnungsmodells, welches anhand weltweiter Messdaten (von Land, Schiffen, Satelliten und anderen Quellen) diese Daten rechnerisch reproduziert und dabei auch Werte für andere Standorte errechnet.  
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Measurement masts of 40 m height cost approximately 10000 €. Lattice towers have a better stability than masts consisting of tubes, but their price is significantly higher.
  
Natürlich ist es grundsätzlich möglich, den ersten Schritt der Messungen auf 10 m Höhe auszulassen und somit Zeit zu sparen. Allerdings sollte dies nur gemacht werden, wenn die Windbedingungen am Messstandort bereits ausreichend bekannt sind, um sicher zu sein, dass nicht unnötig auf 40 m Höhe gemessen wird. Dies wird in Ländern, die in Sachen Windenergie noch jungfräulich sind, nur selten der Fall sein, so dass sich in der Regel eine Messkampagne in zwei Phasen empfiehlt. Sollten die Messergebnisse auf 40 m Höhe schließlich unzureichend erscheinen, so kann die Planung an dieser zweiten Sollbruchstelle beendet werden.  
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Measurement is conducted for minimum for one year again. As it is known, that wind energy yield can vary significantly between years and measurement of one year does not provide enough information to determine the representative average value for the site, which is necessary for reliable further calculations. To approximate this long-time average value for wind velocity, outcome of measurements are compared with wind data available for other sites. If the correlation of the different data sets is sufficient, it will be possible to deduct the amount of deviation between the long-time average value and the outcome of the measurements. In case no data is available for comparison, a rough approximation can be calculated using so-called „reanalysis wind-data“ from US National Center for Atmospheric Research and National Center for Environmental Prediction (NCEP/NCAR)<ref>US National Center for Atmospheric Research and National Center for Environmental Prediction (NCEP/NCAR)[[http://www.ncep.noaa.gov/ (accessed: July 2011)]]</ref>. These data sets are generated by global climate-models, which include global measurement data to compute wind velocity data for different sites.
  
<br>
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It is possible to skip measurement at 10 m to safe time in project development. As measurement in 40 m causes high costs, the 10 m measurement should only be skipped, if initial data collection has revealed the general suitability of the site. As the availability of wind data for developing countries is rather low, a measurement campaign containing the two phases is recommended. After the measurement at 40 m is finished and data is analysed, developers decide again, whether the project should be continued or ceased.
  
=== Identifikation von X Standorten  ===
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[[Assessing Wind Potentials#toc|►Go to Top]]
  
Auf der Basis der Ergebnisse der [[Assessing wind potentials#Standortselektion_und_Windmessungen_auf_10_m_H.C3.B6he|1. Messphase&nbsp;]][[Assessing wind potentials#Standortselektion_und_Windmessungen_auf_10_m_H.C3.B6he|]] werden Vorschläge zur Fortsetzung der Messungen (insbes. Auswahl von X Standorten aus der 1. Messphase) erarbeitet und folgende Aspekte vorbereitet:<br>
 
  
*Mögliche Partner sind mit der Standortauswahl einverstanden;
 
*die 40m-Messmasten mit Zubehör (insbes. Messgeräten) liegen bereit;
 
*ggf. erforderliche Genehmigungen für die Installation der Messmasten und Durchführung der Messungen liegen vor.
 
  
=== <br>Messmasten und Messausrüstung installieren und in Betrieb nehmen  ===
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=== Identification of Measurement Placements<br/> ===
  
Die Installation und Inbetriebnahme der Messgeräte beinhaltet folgendes:<br>
+
Based on the outcome of the first measurement, proposals for continuing the measurements are worked out.
  
*Bereitstellung der 40m Masten, Koordinaierung der notwendigen Schritte für die Installation der Messausrüstung (Demontage der Messinstrumente von nicht mehr benötigten Messstandorten aus der [[Assessing wind potentials#Standortselektion_und_Windmessungen_auf_10_m_H.C3.B6he|1. Messphase]]. Diese Instrumente werden für die 2. Messphase benötigt).
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<u>Beside choosing the placements for the 40 m measurement, the following aspects have to be considered:</u>
*Die Positionierung der Messmasten sowie der Sensoren wird so vorgenommen, dass Messfehler durch Schräganströmung, Abschattung, etc. minimiert werden.
+
*All partners and project developers agree to the choice of placements
*Die Konstruktion der Messmasten und die Installation der Messgeräte sowie der Datenerfassung und der Stromversorgung auf Sicherheitsrisiken und mögliche Störungen des zuverlässigen Messbetriebes überprüfen. Behebung festgestellter Mängel.
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*40m-masts and equipment are available;
*Naitonale und international gültige Sicherheitsbestimmungen für die mit der Installation befassten Personen einhalten.
 
*Ein Funktionstest und Testmessungen werden zur Inbetriebnahme durchgeführt.
 
*Die korrekte Installation und Funktion der Messgeräte wird durch ein Abnahmeprotokoll dokumentiert.
 
*Die geographische Position der Masten wird durch eine GPS-Messung ermittelt.
 
*Die unmittelbare Umgebung der Messmasten wird hinsichtlich eventueller Hindernisse in der Anströmung und der Rauhigkeit der Oberfläche dokumentiert und charakterisiert.
 
  
=== Windmessungen und regelmäßige Datenanalyse zur Windpotentialbestimmung über einen Zeitraum von 12 Monaten  ===
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permissions for the installation of the masts and the conduction of the measurement has been granted by local authorities.
  
Bei der Datenanalyse zu beachten:
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The installation of masts and equipment and the conduction of wind measurement and data analysis is conform to the implementation of the first measurement phase.
  
<br>
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[[Assessing Wind Potentials#toc|►Go to Top]]
  
*Überprüfung der Daten auf Vollständigkeit, Fehler
 
*Beachtung der Konsistenz, Plausibilität und Datenausfall der erhobenen Daten. Im Fall von Unzulänglichkeiten der Daten werden mögliche Abhilfemaßnahmen erörtert.
 
*Messdaten werden so erhoben und aufbereitet, dass sie ohne weitere Bearbeitungsschritte in WASP eingegeben werden können und die für WASP erforderlichen Charakteristika aufweisen. Nach 3, 6 und 9 Monaten sind Kurzberichte über den Verlauf und die Messergebnisse zu erstellen (max. 5 Seiten).
 
  
=== <br>Datenauswertung und Ertragsprognose  ===
 
  
Auf Basis der Daten der erhobenen Messungen sowie geeigneter Langzeitdaten wird nach 12 Monaten eine Bewertung des Windenergiepotentials der X Standorte erstellt und Modellrechnungen zur Windverteilung vorgenommen.
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=== Data Analysis and Forecasting of Wind Energy Yield<br/> ===
  
<br>Ein solches Gutachen liefert folgende Informationen für die X Standorte:<br>
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Measurement data and additional long-time data from comparable sites is used as input for model-calculations.
  
*Analyse und Bewertung der Datenqualität und deren Auswirkung auf die Ergebnisse;  
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<u>The resulting report contains the following information:</u>
*Jahresmittelwert, Histogramm, jahreszeitlicher Verlauf der Monatsmittelwerte, typische Tagesgänge der gemessenen Windgeschwindigkeiten;
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*Analysis and rating of data quality and its impacts of the outcome of the measurement;
*Verteilung des Windpotentials nach Windrichtungen (Windrose);  
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*Annual average value, Histogram, seasonal variations in the monthly averages of wind speed, typical variations of wind speed during a day
*Weibullparameter nach Windrichtungen;  
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*Distribution of wind potentials sorted by wind directions (wind rose);
*Rauhigkeitsparameter und Hindernisse der Umgebung nach Windrichtung oder in Kartenform;  
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*Weibull-parameters sorted by wind-directions;
*Turbulenzgrad und Extrema der Windgeschwindigkeiten;  
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*roughness-parameter and obstacles in the surrounding sorted by wind direction or visualized in a map;
*Korrelation mit Langzeitdaten;  
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*Degree of turbulence wind speed maximum at the siten;
*Jährliche Energieerträge für verschiedene Windkraftanlagen in Abhängigkeit der Nabenhöhe für die Messzeiträume an den X Standorten;
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*Correlation to long-time data;
*Jährliche Energieerträge und deren Variation auf der Basis der Korrelationsrech-nungen mit Langzeitdaten;  
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*annual energy yield for different types of wind turbines depending on hub height and placement
*Bewertung der Unsicherheiten des prognostizierten Ertrags und daraus resultierend Angabe der Überschreitungswahrscheinlichkeit des Ergebnisses.
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*annual energy yield based on adjustments by correlation analysis with long-time data;
 +
*Rating of uncertainty and potential deviations of energy yield from the forecasted values. Calculation of the probability by which the forecasted outcome will be exceeded.
  
<br> '''Mikrostandorte'''  
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<br/>'''Micro-siting''':
  
Für eine Abschätzung der direkt an den in Frage kommenden Standorten erzielbaren Jahreserträge wird jeweils eine Windparkkonfiguration entwickelt und die durch Abschattung bedingten Mindererträge abgeschätzt.  
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To evaluate the energy yield of the specific turbines within a wind park a project layout is generated: The potential decrease of annual energy yield for specific turbines is calculated considering the effects of shading between the turbines. This model calculations are used to generate proposals for the conduction of a feasibility study. The final report of the measurement campaign contains the outcome of the model calculations as well as a recommendation, whether the project should be continued or ceased.
  
&nbsp;Aus diesen Modellrechnungen werden Vorschläge für die Durchführung einer [[Feasibility Study - Wind Energy|Machbarkeitsstudie]] ermittelt.
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[[Assessing Wind Potentials#toc|►Go to Top]]
  
Die endgültigen Modellrechnungen werden in dem Gutachten (s.o.) dokumentiert. <br>Ferner enthält das Gutachten eine Empfehlung über eine Fortsetzung des Vorhabens (Machbarkeitsstudien) mit einer Priorisierung der Standorte nach verschiedenen Kriterien (Windgeschwindigkeit, verfügbare Fläche, Netzanbindung, transportinfrastrukturelle Anbin-dung, etc.).
 
  
<br>
 
  
<br>
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= Further Information =
  
<references /><br><br>  
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*[[Portal:Wind|Wind Portal on energypedia]]<br/>
 +
*[[Estimation of Wind Energy Production|Estimation of Wind Energy Production]]<br/>
  
<br>
 
  
[[Portal:Wind]]<br>
 
  
<br>  
+
= References<br/> =
  
<br>  
+
<references />
  
 
[[Category:Wind]]
 
[[Category:Wind]]

Latest revision as of 14:51, 14 October 2014

Overview

In recent years, wind energy has become one of the most economical renewable energy technology. Today, electricity generating wind turbines employ proven and tested technology, and provide a secure and sustainable energy supply. At good, windy sites, wind energy can already successfully compete with conventional energy production[1]. Many countries have considerable wind resources, which are still untapped.

Wind Energy - Introduction

Wind Portal on energypedia


Investigation of Available Wind Velocity Data for the Proposed Site

As a first step in assessment of wind potentials available data from conducted measurements or other sources has to be gathered.

In case an open access atlas for regional or national wind velocity has been prepared, it probably is available at the following websites:


Other possibilities for wind data enquiry:

  • airports
  • Meteorological institutes
  • Universities dedicated to wind energy research


Paul Gipe explains in his Guide to Small and Micro Wind Systems[2], that in case of micro wind systems, it is often better to install a small wind turbine and to monitor the output during the first year, than to conduct an own measurement: If the wind turbine output does not suitable values, the turbine could be resold easily as there is a large market for used small and micro wind turbines[3]. Nevertheless as project size, related investments and – according to this – the responsibility of the project developer, increases, wind measurement becomes a central component of wind project development.

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Site Selection and Wind Measurement in the Height of 10m

The following characteristics have to be considered for inital site selection and placement of the measurement masts[4]:

  • Indications for suitable wind conditions (As a guiding value an average wind velocity of 6 m/s in the height of 10 m is generally considered suitable). Besides the available information about wind velocities, statements of the local population or landscape characteristics (inclined trees caused by the prevailing wind direction) could be used as indicators.
  • Proximity to the electricity grid, especially to suitable connections points (transformer stations for larger projects)
  • A sufficient transport-infrastructure for transport of the large and heavy parts of wind turbines to the site (Curve radii of roads, inclination of roads, carrying capacity of bridges, width and height of bridges to be passed through etc.)
  • Proximity to cities and their infrastructure to locate a center for maintainance and service of the wind park
  • Conflicting interests of site utilization: Hill sides providing good wind conditions are usually prefered placements for telecommunication masts as well. Telecommunication processes can be disturbed by the installation of wind turbines. Airports, radar-stations and areas of environmental protection could be constraining factors, too.


In case only scarse information about wind conditions at the site is available, wind speed measurements should be conducted at 10 m height as a pre-study. In this way costs for measurements are kept low, since the suitability of the site still has a speculative character. Wind speed is measured by anemometers, while information about wind directions is gathered by a vane. It is of essential importance to calibrate the anemometers before their application. For large wind projects calibration is often done by accredited institutes. Calibration has to be conducted according to international guidelines like the ISO 3966[5], IEA-Guidelines for calibration[6] or the standardized methods of the MEASNET-Group[7].

For the storage of the measured wind data a data-logger is necessary. This device is installed in a case at the lower part of the measurement mast. The data-logger is supplied with electricity by a battery or a PV-module combined with a small battery storage. Supply of the data-logger has to be very reliable, because loss of data will result, if the data-logger is out of electricity. To prevent thievery of the PV-Module it should be fixed at a higher point of the measurement mast.

Collected wind data should be read out regularly: The most comfortable read-out-method is realized by installing a mobile communication device to read out data from afar. Remote connection to the data-logger also allows observation of the measurement devices. However it is necessary to visit the site in periodically to inspect the mast and the measurement devices on-site.

Costs of all described tools for wind measurement are listet in the following. The given prices are examples from two manufacturers of anemometers, vanes and data loggers, Ammonit and Thies.


Good experiences have been gathered with measurement devices of these providers:

  • Anemometer 550 €
  • Calibration of one Anemometer 300 €
  • Vane 450 €
  • Data-logger 1.200 €
  • Additional equipment (cabel, etc.) 500 €


The measurement masts have to be equipped with appropriate consoles to fix measurement tools. A lightning conductor as well as anchored guy cables are standard parts for the erection of a measurement mast. For site evaluation in developing countries the measurement devices often have to be imported, while the mast for measurement could be acquired or constructed in the country. For example project developers used telephone masts of 10 m height to conduct peliminary wind measurement in Ethiopia.

A minimal measurement period of one year is needed to generate a complete survey of the local wind conditions. Seasonal variations can be captured only by such relatively long-term measurements.

Based on the analysis of wind conditions in the height of 10 m, a first reliable estimation of the economical feasibility of the wind park at the proposed site can be worked out.

An average wind velocity of 6 m/s at a height of 10 m is generally considered as a guiding value for a suitable wind project. The necessary wind conditions for a specific wind project can deviate from this: If the costs of alternative electricity sources is comparatively high, a wind project could be economically viable at average wind speeds below 6 m/s.

A wind regime with an average wind speed higher than 6 m/s can not be considered as a guaranty for economical feasibility as well:

The returns of a wind project as well as financing conditions are heavily influenced by national, regional and even local political framework conditions. Investigation and monitoring of the political framework conditions is a central task to prepare reliable statements about economical feasibility of the project.

Including these informations and taking into account the analysis of the collected wind data at the height of 10 m the developers may decide, whether the project should be continued or not. If the measurement has revealed a suitable outcome the next measurement campaign has to be planned. In any other case the project will be ceased at this point. Speaking generally the outcome of measurement at 10 m height is a conceptional 'rated break point' applied in every large wind project.

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Specification of Measurement Devices and Calibrated Sensors

The necessary devices include:

  • Wind vane (accuracy ≤ 5°, definition ≤ 5°)
  • Anemometer (Impuls-output with a minimal definition of 1 Puls per 0.1m wind-track, measurement characteristics in inclined flow and accuracy have to be chosen accordingly the IEA-guidelines)
  • Data-logger for capturing time series (Storage of 10-Minute values of: the average value of wind velocity, the standard deviation of wind velocity as well as minimum and maximum velocities during the interval; sampling rate should be for minimum 0,5Hz) Data transfer via storage card or chip
  • Battery or combined PV-Panel-storage system
  • additional equipment like cables
  • Notebook Computer

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Installation of Measurement Masts and Equipment

  • Transport of masts for 10m-measurement to the site; planning of the steps for installation of the equipment.
  • Positioning of measurement masts; adjustment of anemometer to avoid inclined flow
  • Inspection of the installation of the measurement masts, including anemometer and vane adjustment as well as functioning of the data logger and reliability of its electricity supply. Safety risks and potential sources for failures have to be identified and removed.
  • Compiance with national and international safety regulations for all persons involved in the installation process.
  • Testing of operability and test-measurements for commissioning
  • Documentation of installation of measurement system by a protocol for approval
  • Determination of geographic positions of measurement masts via GPS.
  • Description of the direct surrounding of the measurement masts concerning potential obstacles for wind flow and estimation of roughness parameters.

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Measurement and Periodical Data Analysis to Assess Wind Energy Potential

Wind measurement contains the following tasks:

  • Read-out of wind data after periods of 1, 3, 6, 9 und 12 Months
  • Checking data for completeness or failures
  • Data analysis includes consistency, plausibility and identification of missing values. In case the measurement reveals significant shortcomings, possible methods to enhance data quality have to be considered.
  • Wind measurement should result in a time series, which can be easily processed with the planning project WASP. According to this an appropriate data format has to be chosen.

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Rating of the Wind Eata concerning the Quality of Wind Potential at the Site

The developer works out a report about wind energy potential, based on the first wind measurement at the height of 10 m.

This report contains information concerning the following aspects:

  • Analysis and rating of data quality and its impacts of the outcome of the measurement;
  • Annual average value, Histogram, seasonal variations in the monthly averages of wind speed, typical variations of wind speed during a day
  • Distribution of wind potentials sorted by wind directions (wind rose);
  • Weibull-parameters sorted by wind-directions;
  • roughness-parameter and obstacles in the surrounding sorted by wind direction or visualized in a map;
  • Degree of turbulence wind speed maximum at the site


The report recommends whether the project development should continued. Additionally recommendations for additional measurements at a height of 40 m is given.

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Wind Measurement in Major Heights

As wind velocity normally increases with height the wind 10 m - measurement allows only estimation of wind velocity at hub height. In case the report of the first measurement has recommended to continue project development, a second measurement at major heights is implemented.

Measurement at hub height would reveal the most reliable outcome. It is technical feasible to install measurement masts with heights of 100 m, but the related costs of measurement are very high. It is generally considered sufficient to conduct additional measurements at the height of 40 m. The gathered data of this measurement may be used for extrapolation of wind speeds at hub height with an appropriate reliability. The measurements at the height of 10 and 40 m have to be conducted at the same placements, because the increase of wind speed with height depends on the specific placement of the mast: within flat ground conditions without major obstacles the wind speed increase with height is less than at a placement with high roughness values. The difference in wind velocity at the heights of 10 and 40 m can amount 2 m/s at several sites. On the other hand a lower wind speed is measured at 40 m than at 10 m. Thus applying additional measurements at 40 m height is fundamental for generating reliable wind data.

Measurement masts of 40 m height cost approximately 10000 €. Lattice towers have a better stability than masts consisting of tubes, but their price is significantly higher.

Measurement is conducted for minimum for one year again. As it is known, that wind energy yield can vary significantly between years and measurement of one year does not provide enough information to determine the representative average value for the site, which is necessary for reliable further calculations. To approximate this long-time average value for wind velocity, outcome of measurements are compared with wind data available for other sites. If the correlation of the different data sets is sufficient, it will be possible to deduct the amount of deviation between the long-time average value and the outcome of the measurements. In case no data is available for comparison, a rough approximation can be calculated using so-called „reanalysis wind-data“ from US National Center for Atmospheric Research and National Center for Environmental Prediction (NCEP/NCAR)[8]. These data sets are generated by global climate-models, which include global measurement data to compute wind velocity data for different sites.

It is possible to skip measurement at 10 m to safe time in project development. As measurement in 40 m causes high costs, the 10 m measurement should only be skipped, if initial data collection has revealed the general suitability of the site. As the availability of wind data for developing countries is rather low, a measurement campaign containing the two phases is recommended. After the measurement at 40 m is finished and data is analysed, developers decide again, whether the project should be continued or ceased.

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Identification of Measurement Placements

Based on the outcome of the first measurement, proposals for continuing the measurements are worked out.

Beside choosing the placements for the 40 m measurement, the following aspects have to be considered:

  • All partners and project developers agree to the choice of placements
  • 40m-masts and equipment are available;

permissions for the installation of the masts and the conduction of the measurement has been granted by local authorities.

The installation of masts and equipment and the conduction of wind measurement and data analysis is conform to the implementation of the first measurement phase.

►Go to Top


Data Analysis and Forecasting of Wind Energy Yield

Measurement data and additional long-time data from comparable sites is used as input for model-calculations.

The resulting report contains the following information:

  • Analysis and rating of data quality and its impacts of the outcome of the measurement;
  • Annual average value, Histogram, seasonal variations in the monthly averages of wind speed, typical variations of wind speed during a day
  • Distribution of wind potentials sorted by wind directions (wind rose);
  • Weibull-parameters sorted by wind-directions;
  • roughness-parameter and obstacles in the surrounding sorted by wind direction or visualized in a map;
  • Degree of turbulence wind speed maximum at the siten;
  • Correlation to long-time data;
  • annual energy yield for different types of wind turbines depending on hub height and placement
  • annual energy yield based on adjustments by correlation analysis with long-time data;
  • Rating of uncertainty and potential deviations of energy yield from the forecasted values. Calculation of the probability by which the forecasted outcome will be exceeded.


Micro-siting:

To evaluate the energy yield of the specific turbines within a wind park a project layout is generated: The potential decrease of annual energy yield for specific turbines is calculated considering the effects of shading between the turbines. This model calculations are used to generate proposals for the conduction of a feasibility study. The final report of the measurement campaign contains the outcome of the model calculations as well as a recommendation, whether the project should be continued or ceased.

►Go to Top


Further Information


References

  1. GTZ (2000) Wind Energy Projects in Morocco and Namibia. Eschborn, retrieved 08.01.2013 https://www.docstoc.com/pass/22042181]
  2. Gipe, P. (1999) Wind Energ Basics - A Guide to Small and Micro Wind Systems, Chelsea Green Publishing
  3. Gipe, P. (1999) Wind Energ Basics - A Guide to Small and Micro Wind Systems, Chelsea Green Publishing
  4. European Wind Energy Association (1999) Best Practice Guidelines for Wind Energy Development, retrieved 8.7.2011 [[1]]
  5. International Organization of Standardization (2008) ISO 3966:2008 Measurement of fluid flow in closed conduits -- Velocity area method using Pitot static tubes, retrieved 10.7.2011, [[2]]
  6. International Energy Association (1999) Recommended practices for wind turbine testing and evaluation - 11. Wind speed measurement and use of cup anemometry, retrieved 10.7.2011 [[3]]
  7. MEASNET Group (2008) Cup anemometer calibration procedure - Version 1, retrieved 10.7.2011 [[4]]
  8. US National Center for Atmospheric Research and National Center for Environmental Prediction (NCEP/NCAR)[(accessed: July 2011)]