Eltra PSO 2001/no MEASUREMENTS AT THE HORNS REV OFFSHORE WIND FARM Establishment of Meteorology Measuring Stations in the Horns Rev Wind Farm

Transcription

1 REPORT May 30, 2002 Phone: Fax: Our ref.: PBS/hdp Project no.: Pages: 22 + Enclosures Verified: Approved: Eltra PSO 2001/no MEASUREMENTS AT THE HORNS REV OFFSHORE WIND FARM Establishment of Meteorology Measuring Stations in the Horns Rev Wind Farm

2 energy. environment. knowledge. Page i Table of Contents 0. Edition Project Background Basic Points Objectives Options Overall Measuring System Measuring Systems Meteorological System Placement of Sensors Boom Layout System Specifications Main System Specifications Specifications of Statistical Met Data Specifications of Met Back-up System Specifications of Computers Spare Sensors Data Type of Data Records Data Acquisition for Met Statistics Data Acquisition for Met Back-up System Synchronisation of Data Programs for Data Handling Data Quality Power Supply Power Supply for Statistical Met Data Power Supply for Met Back-up System Lattice Tower and Hut Lattice Tower Warning Systems Lightning Protection Equipment Hut Buoyage System Operation and Maintenance System Operation System Maintenance Experiences from the Horns Rev and Læsø Met Station Conceptual Descriptions Pre-assembly and Transport Assembly and Test at Sub-supplier Tower Erection Installation of Equipment Implementation Proposed Implementation Procedure Enclosures References...22

3 energy. environment. knowledge. Page 1 of Edition Edition: Edition No Version Date Changes Working copy is not subjected to QA control May be changed without any notice Distribution list: Edition No Elsam-PF TW-PBS TW-JPE TW-JOP TW-SNE TW-UKJ 01 X - - X NB: Only ticked off members of the latest edition will automatically be updated.

4 energy. environment. knowledge. Page 2 of Project Background The overall project goal is to provide wind data for the Horns Rev demonstration project which serves to support the measurements according to the Danish Power Supply act. The project establishes and initiates measuring stations (Met. Stations), by which it will be possible: To investigate the relation between the atmosphere and offshore wind farm for verification and enhancing the design basis; specially with focus on the turbulence down the park In co-operation with an other project to measure the big scale effect from the park (e.g. shadow) To do measuring of load response on the turbines placed close to the met stations The project takes advantage of the large amount of experiences gained during design, planning, installation, O&M of the Met. Stations on the Horns Rev and south of Læsø in Denmark. 1.1 Basic Points The system should be very reliable. Therefore, it has been decided to base the design (sensors, data acquisition and communication, tower and supporting structure) on the proven technology of the existing offshore met station M2 at Horns Rev. The measurements have to be carried out according to best practices and current standards.

5 energy. environment. knowledge. Page 3 of Objectives The objective of the present report is to describe the design specifications for the proposed offshore met station. The object of the measurements is to improve the understanding of: The relation between the atmosphere and offshore wind farm for verification and enhancing the design basis; specially with focus on the turbulence down the park. The objectives of this report are: To provide a general description of the measurement system; To provide the technical specifications of the required sensors (meteorological), data acquisition, power supply, lattice tower and hut; and To provide conceptual descriptions of pre-assembly, transport, erection and installation of tower and equipment, and implementation aspects.

6 energy. environment. knowledge. Page 4 of Options Option 1: 2-year operation & maintenance agreement.

7 energy. environment. knowledge. Page 5 of Overall Measuring System The purpose of recording data is among others: To investigate the relation between the atmosphere and offshore wind farm for verification and enhancing the design basis; specially with focus on the turbulence down the park. The met station comprises two in principle different measuring systems whose data can be combined in different ways. The systems are described below. 4.1 Measuring Systems Sys. 1. Statistical Met Data The system continuously collects meteorological data at 2 Hz. The data are recorded at 5 levels, including the top of the mast. The system uses cup anemometers for measuring wind speed; 3D-sonic anemometers for recording wind speed/direction; and thermometers for recording air and water temperature. Furthermore charging of batteries and battery voltage are measured. Sys. 2. Met Back-up System The meteorological back-up system continuously collects meteorological data at 2Hz. The data are recorded at one level, near the top of the mast. The system uses a cup anemometer for measuring wind speed and a wind vane for wind direction. The system is completely independent of Sys. 1 and acts as a back up of that system. 4.2 Meteorological System This section describes the overall meteorological measuring system. The system is placed on a lattice mast and in the hut onto the platform Placement of Sensors At the met station most of the sensors will be placed on different booms (horizontal beam or tube bolted to the tower). The boom reference levels are shown in the table below.

8 energy. environment. knowledge. Page 6 of 24 Level Measurement parameter System Unit 70 m Wind speed Sys. 1 m/s Wind speed Sys. 1 m/s 68 m Wind direction/ 3D-sonic Sys. 1 m/s, X,Y,Z Wind speed Sys. 2 m/s 66 m Wind direction Sys. 2 Deg. 64 m Air temperature Sys. 1 C 50 m Wind speed Sys. 1 m/s Wind speed Sys. 1 m/s 40 m Wind speed Sys. 1 m/s 30 m Wind speed Sys. 1 m/s Wind speed Sys. 1 m/s 28 m Wind direction/ 3D-sonic Sys. 1 m/s, X,Y,Z 20 m Wind speed Sys. 1 m/s 16m Air temperature Sys. 1 C Air pressure Sys. 1 hpa TABLE 1. Parameters measured at different levels relative to Mean Sea Level (MSL). The mast layout is shown in Encl. 1 and Encl Boom Layout Booms (tubes or beams) are used for mounting of sensors, cables etc. At each level one or two booms will be used for mounting of anemometers or direction sensors (except of top boom). Each boom is mounted on a corner of the rectangular lattice tower to cover the largest possible wind sector and minimise the influence of the tower disturbance, see Encl. 2.

9 energy. environment. knowledge. Page 7 of System Specifications The system is designed on basis of the first Horns Rev met station concept. 5.1 Main System Specifications The general system specifications are: The measuring systems comply with: Wind speeds from 1 to 75 m/s; All measuring systems are capable of automatic restart after stop or power failure etc.; The demands to anemometers, calibration and minimum distance to tower etc. fulfil the IEA recommendations and the IEC Annex G (Ref. 1); Sensors, fittings, cables etc. are resistant against solar radiation and protected against corrosion corresponding to class IM2, according to SD/EN ISO ; All pressure and temperature sensors are housed in aspirated shields; All sensors are galvanically insulated from other adjoining electrical parts. 5.2 Specifications of Statistical Met Data System requirements: Parameter Unit Range Accuracy Wind speed m/s [0;75] +/- 0.5 Win-d direction, 3D-sonic m/s [X,Y,Z] +/- 2.5 Air temperature C [-20;40] +/-0.5 Air pressure HPa [850;1100] +/-2.5 TABLE 2. Specifications of Statistical Met Data. Sampling rate 2Hz. The system measures 10-min. period data. After each period the statistical data (min, max, standard deviation and mean, 3-s gust) are stored by datalogger. A 3-s gust is defined as the max running 3-s mean value for a 10-min. period. The data are recorded by a data logger, which collects data in a circular buffer. The data logger is designed to the sensors used and can store more than 6 month of statistical data. The cup anemometers are of the "RISØ type" and comply with the demands of accuracy, tolerances to inclined airflow etc. The Data Logger DT800 has been chosen to accomplish the demands to the systems. Measurements of 3 dimensional wind speeds will be don with sonic anemometers from Metsupport, the Danish agent for Metek sonic anemometers (Appendix 10.8).

10 energy. environment. knowledge. Page 8 of 24 Some Specifications of the Data Logger DT Bit resolution. Input signals: +/-2.5 VDC resolution 1µV, +/-25mA resolution 10µA. Temporary data storage for up to 10-min. Data manipulation: Statistical data - min, max, standard deviation and gust calculation. Programmable: Period length, date-time, re-boot etc. Storing of data for up to 12 months of statistical data. Internal power supply (batteries) for at least 6 months of operation. 5.3 Specifications of Met Back-up System A complete set of AANDERAA system placed near the top anemometer. (Named Sys. 2). System specifications: Parameter Unit Range Accuracy Wind speed m/s [0;75] +/-0.5 Wind direction Deg [0;360] +/-5.0 TABLE 3. Specifications of Met Back-up System Sampling rate: 2 Hz. Recording wind speed and direction in one level. Is completely independent of Sys. 1, both electrically and physically. Is able to store data for at least 12 months. Internal power supply (batteries) for at least 9 months of operation. 5.4 Specifications of Computers A personal computer (PC) is used for retrieving, converting and storing data to a database and for back up. No Name Type Data Notes 1 Onshore Data PC#1 Stationary Scaled data TABLE 4. Requirements to computer The PC data are: IBM compatible PC; CPU speed more than 500 MHz; Windows 2000 or Windows NT Build 3 or newer; Retrieving data through a communication line Generating data to SQL database Server for other parties

11 energy. environment. knowledge. Page 9 of 24 More than 128 MB Ram and 10 GB Hard disc; K56Flex modem or better. The computer is not included in the delivery. 5.5 Spare Sensors The spare parts are suggested to be as follows: 9 cup anemometers 1 Converter for cup anemometer 1 wind vanes 1 Converter for wind vane 0 DT800 loggers 0 Memory card for data logger 1 Temperature sensor 2 Data Storing Unit 262 Kb, sys. 2 2 Battery box, sys. 2 2 Battery pack, sys. 2 This spare part list ensures that it is possible to make calibration of sensors ahead of the ½-year exchange of sensors and thereby reduces O&M costs significantly. Furthermore, this list assures availability of components, which have a long delivery time.

12 energy. environment. knowledge. Page 10 of Data This section describes the type of data, data acquisition, their handling and quality. 6.1 Type of Data Records TABLE 5 to table 6 gives a brief demonstration of which records are delivered to the database. Furthermore, the tables show the number of sensors and where data is retrieved. The data type (typ.) is marked by H (data in Header), or S (statistical data). Description Typ. No Records: Met statistical data Origin Identification H 1 Date and time in file header PC clock Sensor no H 1 No. in file header Wind speed S 8*5 10-min. Statistic: Max, min, mean, standard deviation, 3-s gust (max of running 3-s mean) Wind direction S 2*6 10-min. statistic: Mean, standard deviation Air temperature S 2*3 10-min. statistic: Max, min, mean Water temperature S 1*3 10-min. statistic: Max, min, mean Air pressure S 1*3 10-min. statistic: Max, min, mean Battery charge S 1*1 10-min. statistic: Mean Battery discharge S 1*1 10-min. statistic: Mean Battery voltage S 1*1 10-min. statistic: Mean Total H/S 2/67 No. of sensors: 16 (Sys. 1+3) TABLE 5. Data record types for met statistical data. Appended before transferring to SQL database Sys.1: Circular buffer in data logger Sys.3: Circular buffer in PC Sys.1: Circular buffer in data logger Sys.1: Circular buffer in data logger Sys.1: Circular buffer in data logger Sys.1: Circular buffer in data logger Sys.1: Circular buffer in data logger Sys.1: Circular buffer in data logger

13 energy. environment. knowledge. Page 11 of 24 Description Typ. No Records: Met statistical back-up data Origin Identification H 1 Date and time in file header Data logger clock Sensor no H 1 No. in file header Appended before transferring to database Wind speed S 1*2 Wind direction S 1*1 10-min. statistic: Mean, 2 sec gust (max of running 2s mean) 10-min. statistic: Mean Total no. of data H/S 2/3 No. of sensors: 2 (Sys. 2) TABLE 6. Data record types for met statistical back-up data - Option 2. Sys. 2: Circular buffer in data logger Sys. 2: Circular buffer in data logger 6.2 Data Acquisition for Met Statistics To generate a measurement record 10-min. statistics, data are extracted from Sys. 1 and 3. Data from the systems are stored in the database. Handling Met Statistics (Record in TABLE 5) min. measuring values are stored on a changeable PCMCIA Memory card installed in a DT-800 data logger with a storage capacity of at least 6 months. After this period old data are overwritten by the latest measuring data. The PCMCIA card contains station ID (M3, M4 or M5), date/time of stored 10-min. values as well as a program for Data logger specifying sensor channel, sensor type, span ranges (scaling factors) as well as scan frequency of the individual schedules, including statistical scan, alarms etc. 2. As arranged GSM 900/1800 has been chosen as transmission system for transfer of data between the measuring systems on M3, M4 and M5 masts and the Owner s PC at Tech-wise A/S in Fredericia. Data are transferred as ASCII characters in a text string, comprising all calculated numerical values from the measured channels. Further data validation is not included in the supply, as the Owner manages supply of the data collecting program and PC at Tech-wise A/S. 3. The onshore PC shall scale the ASCII data using calibration information. 4. The onshore PC shall store scaled ASCII data into the database. 5. The data shall be checked manually by plotting wind speed, wind direction, air temperature, barometric pressure, battery voltage, battery charge and discharge etc.

14 energy. environment. knowledge. Page 12 of Quality check shall be made. If errors are found the database is adjusted accordingly (removal, fault mark). All 10-min. statistical raw and scaled data shall be stored as back up on tape or CD- Rom by the onshore computer. 6.3 Data Acquisition for Met Back-up System Handling Met Back-up System The data are handled as for Sys. 1 except that fewer data is available. Only wind speed and direction is available for a single level. Furthermore the data handling is different from 2 and 3 in section During a visit to the met station the full data logger is exchanged with an empty data logger. 3. The data logger is connected to a special interface card in the onshore PC and data are extracted to the PC. 6.4 Synchronisation of Data The data are synchronised as follows: The system clock from which the data is retrieved and defined as Logged Time identifies the data. When the data are put into the onshore database a small program adjusts the data to the Database Time by rounding down to a 10-min. time logged by Sys Programs for Data Handling It is suggested to develop the tools briefly mentioned here. Purpose Program Notes Generating calibration files Excel Macro All calibration data are stored in one file Converting raw data from Sys. 1 to scaled Integrated in Appending sensor no. and common time ASCII data supplier s software. Retrieving data from Sys. 1 via a Made by supplier Stores data on onshore PC#1 communication line Extracting data from data logger in Sys. 2 Data Reading Program Made by supplier (AANDERAA Instruments) Extracting data from database to report Any program with ODBC/SQL interface Chosen by time, sensor numbers TABLE 7. Programs for data handling

15 energy. environment. knowledge. Page 13 of 24 More programs may have to be made to analyse the recorded data. 6.6 Data Quality A quality system will be established to ensure a high quality of the measurements. To accommodate this, the following methodology will be used: Before Installation and during Commissioning 1. The sensors and the system will be calibrated on shore by recognised methods and institutes. 2. Measurement chains (from sensor to data received onshore) will be calibrated during the onshore test. 3. The separate back up of the wind speed and direction measurement system ensures that the main data will be available even if the primary system fails. This has been proven to work at the Horns Rev station. During Semi-Industrial Operation period 1. The sensor outputs must be checked by visual inspection, looking for discrepancies between min/max/mean values and between the different sensors. 2. All measured data wills be stored and a back up made to ensure traceability. These data must be stored in a place physically separated from that of the onshore PC.

16 energy. environment. knowledge. Page 14 of Power Supply This section describes the main specifications for the different power supplies. 7.1 Power Supply for Statistical Met Data The power supply for the Statistical Met Data system is based on a cable connection from a wind turbine combined with batteries. The figures below are derived from the data from the Horns Rev met station. The demands to the power supply for the Statistical Met Data are: Main System Power supply system from wind turbine : 400 V Continuous consumption over a day : 16 W System voltage : 24 V DC Current needed per hour : 16 Ah Battery Package for the Buoyage System Battery type : BAE Solar Block No. of batteries/capacity : 1 x 12 V / 102Ah, C10 Minimum voltage : 11 V DC Nominal voltage : 13.7 V DC = 100% capacity The solution gives a possibility of 30 days autonomous operation that is power is supplied only by the batteries. 7.2 Power Supply for Met Back-up System The power supply for the Met Back-up System is a separate power battery system lasting for at least 6 months.

17 energy. environment. knowledge. Page 15 of Lattice Tower and Hut This section describes the tower, lightning protection and hut. 8.1 Lattice Tower The main specifications of the tower are: The tower is a lattice tower structure build by steel lattice square sections. It is possible to climb up inside the mast for maintenance of the sensors etc. Resting platforms inside the mast are installed for every m. The lattice sections are assembled by means of bolts. The base lattice section is via an "anchor plate" bolted onto the platform. It is possible to correct the inclination of the mast by up to +/-0.5 (in case the platform is not in horizontal position). A hut with measurement equipment is placed inside the lattice frame on the base/platform. No measures for protection against lightning strikes for the mast itself are taken. The mast is provided with personal safety equipment, ladders and cable trays etc. The mast is protected against corrosion corresponding to class IM2, according to SD/EN ISO The mast is hot-dip galvanised. The bolt connections fulfil DS412 for bolted connections. The mast is designed for loads according to wind loads described in the tender. The mast has the following main data (level: Level above MSL): Level of top anemometer : 70 m Length of stay for top anemometer : 2 m Level of top of lattice tower : 68 m Length of mast sections : 59 m Level of platform for bolting of lattice tower : 9 m Necessary hoisting height : 63 m Weight (incl. Booms and equipment on mast) : 18 t (approx.) The complete tower and the base section of lattice mast are shown in Encl. 1 and Encl Warning Systems The Contractor will mount the met station with warning systems according to the Clients instructions. This work is assumed to be limited to 10 hours.

18 energy. environment. knowledge. Page 16 of Lightning Protection The Horns Rev mast M2 is not equipped with lightning protection because the risk of being struck by lightning was found to be low for the site. The mean density of lightning strikes in the period of in Denmark was 0.23 annual strikes per km². It has been assumed that the risk of being struck by lightning is approx. the same for the chosen position and hence this met station need not be equipped with lightning protection for the mast itself. 8.4 Equipment Hut Inside the base of the mast there will be a small room (a hut) to contain and protect the data acquisition systems and batteries and some spare parts. Specifications of the hut: The hut protects the equipment against sun, rain and spray from the waves. The hut contains batteries, data acquisition, switchboards, a table and a chair, manuals etc. The hut contains survival kid for two persons for 14 days. The hut is without insulation, air conditioning or heating. The hut will be squared inside approx. 1.9x1.9x2.2 m The hut has a low powered lighting to allow working in there. There are a few bookcases for manuals, logs etc. The hut is placed on the platform at the base of the mast. It has been chosen to place the platform 9 m above MSL in order to keep it above the expected maximum wave crests. 8.5 Buoyage Mast M3 is equipped with two lanterns with lighthouse character for the letter U (danger ahead). Two short and one long light signals are given at intervals of 15 sec.

19 energy. environment. knowledge. Page 17 of System Operation and Maintenance This section describes how the measuring system must be operated and maintenance performed. 9.1 System Operation Meteorological Data 1. On a regular basis data must be collected from the primary system, transferred to the database and their quality checked. 2. During service visits, data from the back-up measurement system must be collected. 9.2 System Maintenance The measuring systems are designed in co-operation with their suppliers and in a way that minimises maintenance of mechanical and electrical parts and secures power supply equipment. The supplier of anemometers, data loggers etc. maintains a sufficient stock for scheduled and unscheduled service visits, in such a way that a service visit not will be obstructed because of long delivery time of components. These parts will be provided as the spare parts procured within this order - if the option for the spare part list is agreed upon. The batteries in the back-up system have to be changed on a regular basis (approx. to times a year). 9.3 Experiences from the Horns Rev and Læsø Met Station The Horns Rev met station (M2) has been in operation from May 1999 until now. In summary the experiences from the met station are as follows: 1. The availability of the measurement system has been % for meteorological measurements and 60 90% for marine measurements. 2. During the hurricane a small vertical axis wind turbine broke down (a blade came off). The turbine supplies the fifth system (ultrasonic sensors for research purposes) which was not in operation at the time of the event. 3. Data have been presented at various seminars and conferences (e.g. OWEMES in Sicily) showing the fine behaviour of the measuring system and some unexpected situations, such as the December hurricane.

20 energy. environment. knowledge. Page 18 of Conceptual Descriptions This section describes in a conceptual way assembly, transport and installation of components and equipment. The descriptions below are just indicative suggestions Pre-assembly and Transport Before shipping the equipment, the pre-assembly is suggested to be grouped as follows: The lattice tower is assembled in one suitable section, complete with ladders (cable trays), platforms and safety equipment. The cables (with both ends plugged) are mounted in the cable trays. The fittings for all booms for the different sensors are placed at the correct levels on the tower. The booms are fastened in a vertical position inside the tower (prepositioned). The hut and the lowest section of the tower are assembled together in a vertical position. All equipment (sensors, beacons etc.) is safely stored in the hut for transportation. Encl. 3 shows some photos from the Horns Rev installation Assembly and Test at Sub-supplier The complete meteorological measuring system is assembled and tested at one of the sub-supplier workshop. Test reports are made for the complete system Tower Erection The tower is erected as follows (assuming a mono pile is used): 1. The mono pile, platform, boat-landing arrangement, hut and lattice tower are placed on a barge. 2. When the weather condition allows it, the barge and a jack-up or another suitable vessel with a sufficient crane and piling unit are towed to the site. 3. The exact spot is found, e.g. by means of GPS. 4. The mono pile is driven into the right depth. 5. The top of the mono pile is prepared for the platform. 6. The boat landing arrangement is fitted to the mono pile. 7. The platform is put on top of the mono pile. 8. The exact orientation of the platform is found, e.g. by means of GPS. 9. The platform is welded to the mono pile.

21 energy. environment. knowledge. Page 19 of The integrated hut and lowest section of the tower are placed on the platform. 11. The upper section of the tower is erected. 12. Other works, such as paintwork, are carried out Installation of Equipment The equipment is installed as follows: 1. The pre-positioned booms are mounted in the fittings. 2. The sensors are fitted to the booms. 3. The booms are pushed into the right position and bolted. 4. The pre-laid cables are connected to the sensors and to the equipment in the hut. 5. The PV panels are fitted to the tower and connected to the battery charge etc. 6. The data loggers are connected to the power supply. 7. The communication systems are connected. 8. All remaining equipment and systems are thoroughly tested.

22 energy. environment. knowledge. Page 20 of Implementation 11.1 Proposed Implementation Procedure The implementation procedure could be as follows: 1. Procurement of measurement equipment. 2. Installation of system at the developer site nearby onshore site or workshop. 3. Testing all systems in workshop. 4. Obtaining permissions for the offshore installation. 5. Signing contracts with contractors. 6. Installation of offshore foundation. 7. Installation of local PC system (recording data via communication line). 8. Pre-assembly onshore. 9. Loading barge with equipment. 10. Transport of equipment to offshore site. 11. Installation of equipment on offshore site. 12. Testing all systems on offshore site.

23 energy. environment. knowledge. Page 21 of Enclosures Encl. 1. Offshore Met Station. Lattice mast. May, 2002, Tech-wise A/S Encl. 2. Offshore Met Station. Boom and base section of lattice mast. May, 2002, Tech-wise A/S Encl. 3. Photos of part of lattice mast for the Horns Rev installation. 1999, Tech-wise A/S

24 energy. environment. knowledge. Page 22 of References Ref. 1. IEC , Annex G. Ref. 2. DS412, Code of Practice for Structural use of Steel. Dansk Standard, 3. Udg/1.oplag, Approved:

25 energy. environment. knowledge. Page 1 of 1 Encl. 1 Encl. 1 Offshore Met Station. Lattice mast. May 2002, Tech-wise A/S

26 energy. environment. knowledge. Page 1 of 1 Encl. 2 Encl. 2 Offshore Met Station. Boom and base section of lattice mast. May 2002, Tech-wise A/S

27 energy. environment. knowledge. Page 1 of 1 Encl. 3 Encl. 3 Photos of part of lattice mast for the Horns Rev installation 1999, Tech-wise A/S