Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Antonios Peppas (1) F P Theodore Papatheodorou (3) Dimitris Tsakalomatis (2)
(1) FLOATMAST LTD, London, United Kingdom (2) ETME LTD, Athens, Greece (3) Streamlined Naval Architects LTD, Athens, Greece
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Founder and Director of FloatMast Ltd, UK.
Antonios as a fluid dynamics civil engineer, with a MSc degree in Hydrology in Imperial College, comes from the Hydro industry. As Head of fluid dynamics department in ETME Ltd in Greece, he is in close cooperation with the Naval and Shipping industry. He is also involved as consultant engineer in major environmental infrastructure projects and in renewable energy projects for more than 14 years. His knowledge of hydro, wind and ocean engineering coupled with hydrometeorology led to the creation of the FloatMast concept and company.
An innovative TLP platform for combined reliable and bankable offshore Cup anemometer - Lidar wind measurements
Reliable and Bankable Wind Resource Assessment in offshore wind farms, presents a huge challenge, as only fixed met-masts are, at the moment, IEC compliant measuring devices. Furthermore, as offshore wind parks are getting into deeper waters, further from the shore and bigger in size, the costs are scaling up too and need better wind resource assessment to mitigate this and drive down the costs per kWh. Finally, financial competition between potential offshore wind parks raises up the question of reliability of the data measurements, in order to lower the income risks for lenders.
The solution to the above issues can be provided by the FloatMast innovative combination of three industries: Onshore Wind, Naval and Oil & Gas. On the deck of a small Tension Leg Platform (TLP), which is a standard and proven technology in the Oil & Gas Industry, a met mast and a Lidar are fixed. This provides the ability to apply offshore, the widely accepted reliable and bankable onshore methodology, consisting of a short met mast and a Lidar to produce IEC 61400-12-1 compliant wind measurements. Therefore, the offshore wind industry can gain an important benefit, without reinventing the wheel.
Main body of abstract
The accuracy of the provided wind speed measurements is assured by the use of three different state-of-the-art devices (cup anemometers, ultrasonics and a lidar) at the height of 40m asl, which is inside the today’s offshore WT’s rotor. Cup anemometers assure the highest data availability (no matter the weather conditions) and the conformity to the today’s IEC/MEASNET standards. A 3D-ultrasonic anemometer provides fast measurements for turbulence and other meteorological quantities (Reynolds stresses, etc). Finally, the lidar provides the wind shear by measuring the wind speed at several heights within the WT’s rotor.
The verification of cup-lidar data is performed according to the IEA Recommended Practices RP15 for two 2 heights (40m and a lower one), by an accredited organization for such measurements and member of the MEASNET network. The verification will comprise also turbulence intensity and wind gust speed correlations, two quantities that play an important role in the classification and the design of the wind turbines.
The small (unavoidable) motion of the TLP platform is monitored by high-precision marine motion and orientation sensors. CFD simulations and model tank tests of a 1:25 prototype showed practically no heave motion, very low translations (<0.1Hz) and tilt angles below 5deg, even in storm conditions thus, excluding the need for motion compensation. A full scale prototype will serve as demonstration project off the coast of Makronisos island, in the Aegean sea, known also for its severe sea state conditions and with an annual average wind speed of 9m/s.
The project demonstrates that TLP platforms are very well suited to wind energy applications and practically no motion compensation is required for the wind speed measuring devices.
Lidars are known to have lower data availabilities than cup anemometers, mainly due to atmospheric conditions, but also because they are sophisticated opticoelectronic devices, requiring also power autonomy. In this solution, lidar unavoidable data losses are recovered from cup anemometers, with much lower uncertainties than correlating with faraway met masts. The high data availability assured by the reliable cup anemometers, lowers the results uncertainties and therefore, the investment cost of the offshore wind farm.
Wind Resource Assessment Specialists can provide better assessments by the knowledge and use of the FloatMast innovative platform and concept. The use of the platform provides: i) IEC compliant wind measurements, ii) low-cost alternative compared to fixed met masts, iii) a unique solution for deeper waters where fixed mast installations is (financially) not an option, iv) a reliable reference measuring site for a pack of floating Lidars.