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0. WIND ENERGY DATA
• Statistics: In 2009, in the E.U., more than 10GW of power were produced by new installed wind turbines, with almost zero
decommissioned power. The corresponding value for the natural gas (the immediately next more productive energy source) is
6,63GW, while for coal the decommissioned power is greater than the produced one (3,2GW compared to 2,4GW).
• Stock: Each power source has a specific stock globally, and more specifically in the E.U. It is estimated that the oil stock in
the E.U. is sufficient for 7 more years, the gas stock for 14 years, the coal stock for 50 years, while the uranium stock is
unknown. Of course, wind is never running out!
• Goal of EWEA: EWEA’s goal is for the installed wind power to be 230GW (40GW offshore) until 2020, and 400GW (150GW
offshore) until 2030, by covering increasing percentage of needs in electric power. The exploitation of the offshore wind energy
(around European coasts) will increase, with the expansion of the offshore European electrical network, by uniting the offshore
production sites with the consumption sites.
• Electrical network. The electrical networks market must become more agile. The existing companies must separate the
energy production from its distribution, by allowing to new companies to enter as well. Moreover the electrical network
(offshore and in land) must be expanded, for more effective and economical distribution of the produced energy.
• Protection of nature. Wind energy, opposed to fossil fuels, does not burden the environment with CO2 transmission
(greenhouse effect) or of other infective gases. This way, the nature’s pollution and the climatic changes are reduced.
Copyright© 2010, Symmetron Electronic Applications. With all rights reserved.
1. MEASUREMENTS
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To assess the capability of a site to produce wind energy, the following measurements are required:
- Wind speed, in various heights.
- Wind direction, in various heights.
- Barometric pressure and temperature. The air density derives from these measurements.
The power produced by the wind turbine is proportional to air density, to the square of the radius of the turbine’s wings and to the
cube of wind speed. Furthermore, the main wind direction is required, for the proper direction of the wind turbine.
Measurements for 1-3 years must be available.
The data are preferred to be received by measuring in the site itself. Alternatively, the assessment can be made via existing data, which
occur from reference stations, with data correlation. However, In order for this to be accurate, it must be done under conditions, as it is
mentioned in the next slide.
There are two main measurement methods:
- By using one anemometer and one wind vane per measuring height. The method’s advantage is its low cost, especially if low-medium
cost sensors are used, such as NRG ones, instead of higher cost ones (better accuracy, more resistant in greater wind speeds, more
sensitive in low speeds, smaller dead band), such as the Thies First Class ones. In each case, the cost of the mast-datalogger-sensorsaccessories system is of about a few thousand euros plus the installation cost. Moreover, the high accuracy of the measurements is a
plus. The only disadvantage is the difficulty in the installation of the measuring system.
- By using LIDAR and SODAR. These instruments are put on the ground and assess wind speed and direction via the transmission of
sound and light pulses in the atmosphere respectively. A portion of the pulses returns in the instrument and the speed, the direction
and the turbulence are assessed via the Doppler effect. The advantage of the method is that these instruments do not require
installation. However, the measurements are not that accurate, while the instruments’ cost is of about 100000 euros.
2. MEASUREMENTS METHODOLOGY
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The methodology of receiving the measurements must be specific and in line with the international standard ISO 17025. The lab which
realizes them must be accredited to ISO 17025. Lab accreditation is the official recognition by a recognized competent body (ESYD in
Greece), that a test or calibration lab is technically capable of conducting specific types of tests or calibrations respectively.
The requirements that such a lab must meet are concisely:
- Organization and staffing: The organizing structure of the lab must be documented in writing and each member of the staff must
know exactly the field of their responsibilities.
- Facilities: The lab’s facilities must immunize the required environmental conditions (dust, noise, vibrations, etc), so that the reliability
of the measurements/tests conducted is ensured.
- Equipment: All the lab’s equipment which is used for conducting various measurements/tests must firstly be able to offer the desired
accuracy, and secondly, it must be maintained and calibrated properly anytime, according to a respective schedule.
- Documentation: For any measurement/test performed by the lab, or for the total equipment (along with any software) which is used
during the tests/measurements, documented guides, standards, technical specifications, manuals, etc must be available, which will be
updated and accessible to the responsible personnel.
- Quality Management System: The lab must apply a documented Quality Management System. Within this system, one of the lab’s
members must take the general responsibility of the system’s operation and supervising, while in parallel, the writing of a Quality
Manual is required, which must be accessible to all the lab’s members.
-Management reports of measurements or tests: Each measurement/test report must be unique and all the data regarding the
identification of the lab and the client, all the data regarding the conditions and the methodology of the measurement’s/test’s
conducting, along with their uncertainty margin, must be included in it.
- Cooperation with subcontractors: In case of cooperation with subcontractors, the technical competence of the subcontractor to
execute any tests/measurements they are assigned, must be proven.
- Cooperation with other labs and bodies: The lab must develop the appropriate cooperation so with its customers, as with the
cooperative accreditation body, along with other labs and bodies conducting standards and regulations.
- Independency, uncertainty of measurements and confidentiality: By all means, the reliability and the impartiality of the conducted
measurements/tests must be ensured.
3. DATA CORRELATION
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Data may be missing from a station, because of a sensor’s malfunctioning for a time period. However, an early diagnosis and
repair/replacement of the sensor is recommended, for as little data loss as possible. These missing data, along with all data can be
calculated via data correlation from existing data of a reference station.
This can be done via the appropriate software, which take into account site parameters which affect the wind measurements, such as
height, topography and the exaggeration (the peaks and dips of the earth’s surface).
In order for the measurements of the reference station to be reliable long term, it must be ensured that the station is sufficiently
exposed, that is no natural obstacles exist near the measurement system, such as trees, buildings or other measuring systems.
These data will be calculated via certain values in a known site and they usually derive
from local meteorological measurements or other data regarding the weather, which
were recorded or occurred from arithmetic prediction models, such as the ones used by
the national meteorological services.
This wind mapping software, will export typically a graph of the average wind speed for
απεικόνιση της μέσης ταχύτητας του a
specific height in a location. This may have the form of a wind atlas, which reenacts the
wind speed over a flat homogeneous area. In some locations, wind maps which take into
account the location’s exaggeration and topography are available. Such a map is shown
in the picture on the right for Europe for 50m height. The different wind speed zones are
represented with different colors. Of course, this map shows the speed distribution in a
large area. There are more detailed maps for each country.
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4.RESULTS (MEASUREMENT ANALYSIS)
The final step in order to decide if a site is suitable to become a wind park is the assessment of wind resources locally, in terms of a
wind park. The wind map is a step to search for sites but does not justify by itself a development investment.
Therefore, an appropriate software is required, which will take the measurement results and will analyze them, in order to provide a
reliable prediction about the expected energy production of the future park, during its entire lifetime, which must also take into
account the uncertainties and errors in the main assessment of the wind speed.
The data that must have been recorded for analysis in a specific height is the average wind speed, the main wind direction, the
temperature, the barometric pressure, the wind speed’s standard deviation and the maximum speed (gust), in a period of 3 seconds
maximum.
This way, the following will be calculated:
-The main wind direction, for the proper orientation of the wind turbine’s wings.
-The air density, from the temperature and the barometric pressure.
-The turbulence, that is the fluctuations and gusts of the wind, along with their frequency. If the turbulence is maintained in relatively
low levels, the site is suitable for installation of wind turbines with minimum material damage.
-The level of wind speed, along with the distribution of the different wind speeds (see the figure on the left).
-A Windrose graph, which shows the wind speed’s
distribution per wind direction (see the figure on the
right).
From these results, the wind turbine’s type will be
decided, that is:
- the height of the rotor, which rotates the wings, which
will be the height with the optimum measurements,
which came from the corresponding anemometer and wind vane.
-the radius of the wings, which must be great enough for greater energy production, but as great as
to withstand the measured turbulence.
- the wind turbine’s orientation and the wings’ slope, in order to exploit the wind’s main direction.
5. EVALUATION OF THE RESULTS
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The last step for the creation of the wind park is the submission of the results, in the form of an application, to E.R. (Energy Regulator),
which will evaluate them and will authorize the park’s construction, typically after 5-7 years.
The E.R. are an independent administrative authority and their responsibilities are mainly advisory and precursory in the energy field.
Its role is not auditing or judicial, but its purpose is to facilitate the free and healthy competition in the energy market.
Furthermore, purpose of the E.R. is to ensure the long-term strategic targets of the energy policy and the service of the public interest,
such as the sufficient, reliable and equal supply of all consumers, the safety of the country’s supply, the environment, the development
of the renewables, the new technologies, the efficient usage and supply of energy and the ensuring of sufficient structure for energy.
The application submitted to E.R. and to the Ministry of Development for Production License includes: the results of wind
measurements, the energy study, the techno-economical study, along with the Preliminary Environmental Impact (PEI) of the project.
The E.R. evaluate the application and, if the energy and economical standards which the Regulation Permits set are satisfied, they
forward the folder to the competent environmental authority for the conduct of the PEAE (Preliminary Environmental Assessment and
Evaluation). In this phase, all the competent services are questioned and finally after the granting of the PEAE, the investor will receive
the Production License, within 1-4 years.
After receiving the Production License, the investor proceeds to the next step, which includes serially the application to GOSO (Greek
Operator System Operator) for the formulation of conditions of connection with the Electrical System and next the preparation of the
analytical Environmental Impact Study of the project and its submission for approval to the competent bodies and services, in the
context of the application for installation license.
In the Environmental Impact Study, the investor has to examine all the special observations made until that moment by the competent
services and probably to prepare additional and specialized studies, where appropriate. Indicatively, studies that have been requested
at times are ornithological studies (for sites which have special importance for the birdlife), studies of flora and of rare plants.
Howsoever, a noise study, a photorealism study of the wind park, a study for routing the power lines, analytical road construction
studies and studies for rehabilitation of the natural environment from the interferences that are about to take place during the
project’s construction are required.
6. TYPICAL MEASURING SYSTEMS
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A simple system (with a 10m mast), includes:
- An anemometer at 10m (for measuring wind speed at 10m)
- A wind vane at 10m (for measuring wind direction at 10m)
- A thermometer and a barometer, to measure temperature and barometric pressure to assess the air density.
- A datalogger with at least one counter channel (for the anemometer) and at least 3 analog channels for the remaining sensors.
- Optionally, depending on the datalogger’s model, this may include an internal modem or an external one can be added (with an
antenna in each case), for remote communication, via GSM/GPRS.
- Lead acid battery 12V, with a charger and a photovoltaic module, for the system’s power supply.
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A more complex system (with a 40m mast), includes:
- 4 anemometers: 1 for measuring at 10m, 1 for measuring at 30m and 2 at the top (40m). The second top anemometer is used to
confirm the measurement and in case one of them is destroyed.
- 3 wind vanes for measuring wind direction at 10m, at 30m and at 40m.
- A thermometer and a barometer, to measure temperature and barometric pressure to assess the air density.
- A datalogger with at least 4 counter channels (for the anemometers) and at least 5 analog channels for the remaining sensors..
- Optionally, depending on the datalogger’s model, this may include an internal modem or an external one can be added (with an
antenna in each case), for remote communication, via GSM/GPRS.
- Lead acid battery 12V, with a charger and a photovoltaic module, for the system’s power supply.
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7. METEOROLOGICAL MASTS
The meteorological masts are divided in two main categories:
-Tubular, which are heavy duty, of relatively small height (10-40m usually),
which tube diameter is 130-150mm. They are suitable for relatively low
altitudes (up to about 1000m), where no ice of great width is produced,
which will add hazardous weight to the mast and the guy wires. Moreover,
they are less resistant to the high wind speeds which occur in high altitudes.
Because of their weight many levels of guy wires are required (about 2 per
10m), while they must be attached to the ground via the appropriate
anchors, according to its morphology.
-Lattice, which are light duty, are more resistant to higher altitudes, where
more ice is produced and high wind speeds appear (over 50m/sec), which
rarely appear in Greece. The guy wire levels required for a typical mast
height of 50m are 4. Of course, lattice masts are more expensive than
tubular masts.
In the diagram on the right, a simple example of installation of a 10m
tubular mast is shown. The mast is based and grounded electrically via its
base, to which grounding rods are nailed, which are caved about 2m in the
ground.
The datalogger is installed at a low height to be accessible by man, in a
sealed IP65 box, suitable for all weather conditions.
The sensors are installed on horizontal booms or on a vertical rod, as it is
shown in the figure, with regulations imposed by the standard
IEC 61400-12-1, which will be discussed below.
The cables connecting the sensors to the datalogger are flexible cables
LiYCY double stranded to 5 fold stranded, 0.25mm thick, with ground.
8. IEC 61400-12-1 STANDARD
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The IEC 61400-12-1 standard, concerning sensors of wind measuring systems,
provides the following:
Wind speed.
- The anemometers must be installed in height of ±2.5% of the height of the
rotor of the future wind turbine, preferred on the top of a vertical rod, which
stands without obstacles on the mast’s top. The cups’ distance from the top
must be at least 15cm.
- Moreover, anemometers can also be installed in lower heights on
horizontal booms, attached on the mast’s edge and directed to the main wind
direction. To reduce the effect of possible obstacles to the wind flow the
vertical distance from any other boom must be at least 7 times the boom’s
diameter, while the horizontal distance from the mast must be at least 7
times the maximum diameter of the mast (either it is a tubular or a lattice
one).
Wind direction.
- The wind vanes will be installed in a height of ±10% of the height of the
rotor of the future wind turbine. Attention must be paid so that their position
does not cause distortion of the wind flow between anemometers and wind
vanes.
- The absolute accuracy of the measured wind direction must be better than 5 degrees.
Air density. The density is calculated from the air’s temperature (inversely proportional) and pressure (proportional)
- The temperature sensor must be installed at least 10m above the ground’s surface and near the height of the rotor of the future wind
turbine.
- The same apply for the barometric pressure sensor , but in case it is installed in a different height, the measurements can be corrected
and reduced to the right height, according to ISO 2533.
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9. SENSOR TYPES
The wind measurement sensors which will be used are divided in certain categories.
The anemometer types are:
- Sine signal (of low AC output voltage). The rotation of the cups’ axis, via a magnet, induces an sinusoidal ac output voltage in a spool, the
frequency of which is proportional to the wind speed. Typical sensor examples are: NRG’s #40 and YOUNG’s 05103.
- REED type, which use a reed switch which is activated magnetically, which is placed in an iron oxide package, to provide an indication of
the wind speed, by maintaining the sensor’s boot speed low. The reed switch’s output is an on-off switch and the frequency of its state
change is recorded. Typical sensor examples are Vector’s A100R and RISO’s P2546A.
- Optical disk. The low inertia 3-cup rotor is rotated by the wind and the rotation is read opto-electronically and is converted to a square
wave. The signal’s frequency is proportional to the number of the rotations. Typical sensor examples are Thies’s First Class and Vector’s
A100-K, -L, -M, -LM.
- Propeller type (tachogenerator type), which, opposed to the previous ones, do not use rotating cups, but a helical propeller. They use a
high quality tachogenerator, which converts the rotation to dc voltage which is proportional to the wind speed. The propeller responds
only to the wind’s component which is parallel to its rotation axis, which can be set. Other components have a cosinusoidal curve response.
They are usually used to measure the wind’s vertical component. Typical sensor example is Young’s 27106.
Concerning the 3 first categories (cup anemometers), the first ones have the greatest recording start speed (0.7-0.8 m/sec) while their
accuracy and resolution is clearly worse. For instance, #40’s resolution is 76cm, while the one of Thies’s First Class is 5cm. Of course, the
difference in cost is proportional.
The wind vane types are:
- Potentiometric, which is the most commonly used type. The wind’s direction is read via a potentiometer. With the exact voltage
stimulation from the datalogger, which is applied to the potentiometer, the output signal is an analog voltage which is proportional to the
azimuth angle of the wind direction. Typical sensor examples are NRG’s 200P, Vector’s W200, and Thies’s First Class.
- Grey code disk. The vane’s rotation is read opto-electronically and the output consists of 6 bits, the possible values of which (64) divide
the circle in 5.6 degree areas. Therefore, every possible value corresponds to an angle zone. Typical sensor example is VAISALA’s WAV151.
Regarding the specifications of the potentiometric vanes, there is a difference in accuracy and resolution which is better at Vector’s W200,
and even better at Thies’s First Class. Moreover, there is a difference in the dead band, ie in the area of degrees (around the 0 reference
point) where the output cannot be read. At the 200P it is typically 4°, at the W200 2.3° while Thies’s First Class practically has no dead
band. Of course, the difference in cost is proportional.
10. DATALOGGERS
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The used dataloggers of Symmetron company cover many needs in different types of meteorological measurements.
Stylitis-10, the simplest low cost and small size datalogger, more suitable for solar measurements, features 8 channels in total, 1-2
counter channels (for anemometers, rain gauges, etc) and 6-7 analog channels (for wind vanes, thermometers, hygrometers,
barometers, pyranometers, etc). It records average, maximum and minimum data values in a selectable interval (from 1 second to 1
hour) with sampling rate 1 sec. It features a serial port (PERIPHERAL) for local communication with the PC and downloading data, via
Opton software. Optionally, it features an internal GSM/GPRS modem for remote connections, via the same software. To the
COMMUNICATION port, you can connect an external modem. Finally, optionally, it features a wired or wireless (WiFi) Ethernet port,
fro communication via a LAN, via the same software.
Stylitis-41, more suitable for wind measurements, which features 3 counter channels and 4 analog channels. It records average,
maximum and minimum data values in a selectable interval (from 1 minute to 1 hour) with sampling rate 1 sec. It features a serial port
for local communication with the PC and downloading data, via Stylitis Explorer software. Moreover, via a NULL MODEM cable, you can
connect to it an external GSM modem or Symmetron’s Sym-o-net for remote GSM/GPRS connections, via the same software, and
automatic data emailing. Furthermore, via the appropriate Serial-to-Ethernet adaptor, it can also be connected to a LAN. The
communication is achieved via the same software.
Stylitis-101, which features: 6 counter channels, 18 analog channels, of which 12 are differential inputs, in which the appropriate
sensors can also be connected, such as the PT-100/PT-1000 sensors, and 3 digital inputs, which comprehend measurements near 5V as
digital 1, and measurements near 0V as digital 0. It can record data in two ways: with statistic calculations, within a selectable interval,
as Stylitis-41 does, and with time series, ie it is capable of recording at frequencies 1-32Hz, independently selectable for each channel.
The communication methods with the PC are the same with the ones of Stylitis-41.
Stylitis-50, which combines the features of Stylitis-41 and Sym-o-net. It features 9 counter channels and 10 analog ones. . It records
average, maximum and minimum data values in a selectable interval (from 1 minute to 1 hour) with sampling rate 1 sec. It features a
serial port for local communication with the PC and downloading data, via Opton software. Furthermore, it features an internal
GSM/GPRS modem for remote connections and automatic data emailing. Moreover, it features an internal Ethernet port, for
communication via a LAN.
11. OPTON- STYLITIS EXPLORER
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As mentioned in the previous slide, Opton (figure on the top) and
Stylitis Εxplorer (on the bottom) are operating software of the
dataloggers of Symmetron company and are available for free.
Some of their features are management of data files, connections and
site folders, while they contain graphs and statistics related to the
data files.
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12. AUTOCONNECT-CAPTUM
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Moreover, the AutoConnect software is available for free, which in cooperation with Opton and Stylitis Εxplorer, accomplishes
automatic connections with the dataloggers and data downloading, once or more times a day. Moreover AutoConnect can update a
website with real time data, related to the selected channels, via the Captum application, which does not require additional software,
but simply a web browser.
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13. WINDROSE
Windrose is a wind data analysis software, developed by C.R.E.S. It is not an
independent software, but an add-on to Microsoft Excel.
In order for it to operate, it needs data files as inputs, which include, in
of data columns: wind speed, wind direction, standard deviation of wind
speed, date and time.
The analysis is in line with the requirements imposed by IEC and MEASNET
standards.
Its results are stored in Excel worksheets and they are:
-Wind speed distributions per direction
-The main wind direction
-The turbulence, that is the wind’s variances and gusts, along with their
frequency.
-Via the comparison of two sites and the appropriate parameters,
calculation of the missing data.
-Correction of systematic measurement errors
14. EMMETRON
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Finally, the Emmetron software is available, which organizes measuring resources in MySQL databases, that is locations, data per
location, equipment, personnel, documents and tasks. Besides organizing data, it provides statistics and graphs, while it produces
reports and queries.
REFERENCES
BOOKS
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Wind Energy Factsheets, by EWEA-2010
IEC 61400 Standard
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WEBSITES
http://www.wind-energy-the-facts.org/en/part-i-technology/
http://155.207.46.127:8080/roadmaps/roadmaps/quality/page.html?page_id=2058
http://www.rae.gr/about/main.htm
http://www.scribd.com/doc/19999834/http://www.2en.gr/
http://www.symmetron.gr/
http://www.symmetron.gr/uploads/Catalog.pdf
http://adsabs.harvard.edu/abs/1972JApMe..11..742F
http://www.windspeed.co.uk/ws/index.php?option=displaypage&op=page&Itemid=67
http://meteocentre.com/StationUqam/instruments/Girouette/WAV151QuickReferenceGuide.pdf
http://www.directindustry.com/prod/dp-measurement/tachometer-12594-410767.html
http://67.199.19.247/gp/wind09/exhibitors/dateien/05_Ammonit_Thies_FirstClassAdvanced.pdf
http://www.campbellsci.com/documents/product-brochures/b_03002.pdf
http://www.proviento.com/NRG40.pdf
http://www.campbellsci.com/documents/manuals/llac4.pdf