Integrated Overtopping Wave Energy Converter in a Hybrid Offshore Wind Turbine Power Generation System

2014 ◽  
Author(s):  
Artemis Ioannou ◽  
Anestis I. Kalfas ◽  
Theofanis V. Karambas
Keyword(s):  
Power Generation ◽  
Wind Turbine ◽  
Power Output ◽  
Fossil Fuel ◽  
Integrated Design ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Generation System ◽  
Micro Gas Turbine ◽  
Generation Unit

Marine construction technologies could be designed to offer power generation in addition to their sea defence and coastal erosion prevention function. This paper aims to evaluate and optimize the performance of an Overtopping Wave Energy Converter (OWEC) as part of a hybrid generation system integrated into an offshore wind turbine. For that purpose, two configurations have been investigated. A 100kW OWEC was combined with a micro-gas turbine of 80kW at the first configuration and the same OWEC with a wind turbine (WT) of 200kW at the second. The preliminary design of an integrated offshore OWEC/WT is presented. The findings of the present investigation have been applied to a specific test case of a small, off–grid island, in the Aegean archipelago. Regarding its power requirement, Donoussa island currently relies exclusively on fossil fuel. At the same time, a high wave and wind power potential is available. A representative set of wind data have been obtained and numerically analyzed. A wave simulation, overtopping prediction and power output has been carried out. Moreover, a techno-economic and environmental assessment of the proposed offshore integrated design is presented. The stand alone coastal OWEC, and a single offshore wind turbine have been evaluated versus the proposed offshore hybrid power generation scheme. The OWEC is expected to generate 320MWh per year, thus covering half of the island’s estimated power demand. Using both wave and wind power generation, energy autonomy of the island could be achieved. In order to cover the requirements of extreme cases, a micro gas-turbine power generation unit has been considered, in parallel to the existing fossil fuel power generation unit. From the techno-economic assessment point of view, the coastal OWEC construction has a shorter return on investment time of 11 years as compared to 13 years of the proposed integrated design but lower profitable investment. Besides providing sufficient electrical power for the island, the additional environmental benefit of the proposed system is that it can be used to counter coastal erosion. The integrated offshore OWEC/WT design could potentially double the power output of each and every offshore wind turbine installation. This result could therefore be interpreted either as halving of the required number of offshore wind turbines erections or as doubling of the power output of an offshore wind park.

Dynamic Response of a Spar-Type Floating Wind Turbine at Power Generation

2014 ◽  
Author(s):  
Tomoaki Utsunomiya ◽  
Shigeo Yoshida ◽  
Soichiro Kiyoki ◽  
Iku Sato ◽  
Shigesuke Ishida
Keyword(s):  
Numerical Simulation ◽  
Power Generation ◽  
Dynamic Response ◽  
Wind Turbine ◽  
Prestressed Concrete ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Foundation ◽  
Mooring Dynamics ◽  
Nagasaki Prefecture

In this paper, dynamic response of a Floating Offshore Wind Turbine (FOWT) with spar-type floating foundation at power generation is presented. The FOWT mounts a 100kW wind turbine of down-wind type, with the rotor’s diameter of 22m and a hub-height of 23.3m. The floating foundation consists of PC-steel hybrid spar. The upper part is made of steel whereas the lower part made of prestressed concrete segments. The FOWT was installed at the site about 1km offshore from Kabashima Island, Goto city, Nagasaki prefecture on June 11th, 2012. Since then, the field measurement had been made until its removal in June 2013. In this paper, the dynamic behavior during the power generation is presented, where the comparison with the numerical simulation by aero-hydro-servo-mooring dynamics coupled program is made.

Characterization of a Wind Generation System for Use in Offshore Wind Turbine Development

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Raul Urbina ◽  
James M. Newton ◽  
Matthew P. Cameron ◽  
Richard W. Kimball ◽  
Andrew J. Goupee ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Wind Tunnels ◽  
Wind Generation ◽  
Offshore Wind Turbine ◽  
Generation System ◽  
Wave Basin ◽  
Wide Range ◽  
Wind Generation System ◽  
The Waves

Environmental conditions created by winds blowing oblique to the direction of the waves are necessary to conduct some survivability tests of offshore wind turbines. However, some facilities lack the capability to generate quality waves at a wide range of angles. Thus, having a wind generation system that can be rotated makes generating winds that blow oblique to the waves possible during survivability tests. Rotating the wind generation system may disrupt the flow generated by the fans because of the effect of adjacent walls. Closed or semiclosed wind tunnels may eliminate the issue of wall effects, but these types of wind tunnels could be difficult to position within a wave basin. In this work, a prototype wind generation system that can be adapted for offshore wind turbine testing is investigated. The wind generation system presented in this work has a return that minimizes the effect that the walls could potentially have on the fans. This study characterizes the configuration of a wind generation system using measurements of the velocity field, detailing mean velocities, flow directionality, and turbulence intensities. Measurements were taken downstream to evaluate the expected area of turbine operation and the shear zone. The dataset has aided in the identification of conditions that could potentially prevent the production of the desired flows. Therefore, this work provides a useful dataset that could be used in the design of wind generation systems and in the evaluation of the benefits of recirculating wind generation systems for offshore wind turbine research.

Motion Characteristics of TLP Type Offshore Wind Turbine in Waves and Wind

2010 ◽  
Author(s):  
Yasunori Nihei ◽  
Hiroyuki Fujioka
Keyword(s):  
Wind Turbine ◽  
Reduction Rate ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wind Effect ◽  
Generation System ◽  
Mooring Lines ◽  
Wind Energy Generation ◽  
Motion Characteristics ◽  
Generation Power

In this research, we propose a new offshore wind energy generation system that uses a Tension Leg Platform (TLP) and performed the experimental test of the TLP type wind turbine both in waves and in wind. The authors used a 1/100 scale wind turbine. Not only the motion characteristics, but also the loads of the tension legs and the bending moments of the tower were revealed in this paper. From the research, the following conclusions were mainly obtained. 1) In the case of waves-wind coexisting condition, the wind effect stabilizes the pitch motion compared with in only waves. 2) The wind effect is decreasing the vibration of the mooring lines in waves and wind coexisting field. Especially, the springing (2nd order or 3rd order force) is also decreasing in this field. 3) It can be estimated that the amount of reduction rate of electricity generation power is up to about 6% from the results of the heel angle.

Application of a Speed Exclusion Zone Algorithm on a Large 10MW Offshore Wind Turbine

2016 ◽  
Author(s):  
Emil Smilden ◽  
Asgeir J. Sørensen
Keyword(s):  
Wind Turbine ◽  
Power Output ◽  
Natural Frequencies ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Rotor Speed ◽  
Exclusion Zone ◽  
Rotor Aerodynamics ◽  
Speed Controller ◽  
Tower Vibration

To optimize tower design it is desirable to relax the constraint of having to place natural frequencies outside the rotor and blade passing frequency-bands. A speed exclusion zone algorithm is tested to assess its effectiveness on preventing tower resonance caused by 3p thrust oscillations. The effect of the speed exclusion zone algorithm on power output is also considered. A simulation model adequate for qualitative testing of the algorithm is developed and implemented in the simulation tool Simulink by MathWorks. The model is based on a 10MW offshore wind turbine and includes a simplified representation of rotor aerodynamics, drive-train and generator dynamics and a two-dimesional finite element representation of the tower and support structure. To support simulations a rotor speed controller is implemented together with wind models accounting for wind shear, tower shadow, turbulence and rotational sampling. A significant reduction in tower vibration is seen with a ±10% speed exclusion zone. A exclusion zone width of ±5% is shown to increase tower vibrations in some cases. The speed exclusion zone algorithm will lead to a reduction in power output for a ±10% and ±15% speed exclusion zone. For the ±5% speed exclusion zone no significant change in power output is observed.

Experimental Investigation of Negative Damping Effects for a TLP Type Offshore Wind Turbine

2018 ◽  
Author(s):  
Masaaki Aoki ◽  
Sharath Srinivasamurthy ◽  
Kazuhiro Iijima ◽  
Naoyuki Hara ◽  
Tomoki Ikoma ◽  
...  
Keyword(s):  
Power Generation ◽  
Wind Turbine ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbine ◽  
Primary Control ◽  
Floating Platform ◽  
Scaled Model ◽  
Negative Damping ◽  
Motion Characteristics

Wind power generation has been paid much attention over the years as a countermeasure against global warming. Especially in recent years, researches and developments have also been made on Floating Offshore Wind Turbine (FOWT) in relatively deep offshore. Unlike Bottom-mounted Offshore Wind Turbine (BOWT), the motion characteristics of FOWT is complicated owing to coupled response of wind turbine and floating platform motions since the FOWT system is not fixed to the seabed. Due to these complexities, negative damping is one of the major problems reported for SPAR type FOWT moored by catenary chains. Negative Damping, in which the natural periodic motion is excited by blade pitch control employed for keeping the power generation constant, has to be addressed. In this paper, we discuss the negative damping of TLP type FOWT with a series of dedicated experiments. We manufactured a 1/100th-scale model TLP type FOWT model with a primary control system of the blade pitch angle for a geometrically scaled model of the 5MW wind turbine based on the NREL. At first, we formulated the mechanism for occurrence of Negative Damping and derived the conditions under which unstable fluctuations of the floating platform occurs using the motion equation. After that, we conducted scale model tank tests in wind alone and confirmed the phenomenon wherein the fluctuation of the floating platform does not converge. Finally, how dangerous such coupled motion of wind turbine and floating platform would be for real-scale FOWT is discussed.

scholarly journals A simplified model for the dynamic analysis and power generation of a floating offshore wind turbine

2018 ◽  
Vol 61 ◽  
pp. 00001
Author(s):  
Markus Lerch ◽  
Mikel De-Prada-Gil ◽  
Climent Molins
Keyword(s):  
Power Generation ◽  
Dynamic Analysis ◽  
Wind Turbine ◽  
Complete System ◽  
Complex Model ◽  
Offshore Wind ◽  
Simplified Model ◽  
Offshore Wind Turbine ◽  
Aerodynamic Loads ◽  
Acceptable Accuracy

This paper presents a simplified model for the dynamic analysis of a floating off-shore wind turbine (FOWT), which can be suitable for early feasibility and pre-engineering studies, where the complete system has to modeled in order to predict its behavior and to assess the performance. The model solves the equation of motion in time domain and considers Morison equation for computing the hydrodynamic loads. The aerodynamic loads are included by considering the wind thrust at hub height and the loads from the mooring system have been computed as a non-linear model. A methodology is also presented for calculating the structural properties of the system. The model is tested for two load cases and compared to results obtained with the more complex model FAST. The comparison between the response of the models is satisfactory. The simplified model allows to capture the main motions of the FOWT with an acceptable accuracy. A further feature of the model is to calculate the power generation of the floating wind turbine. The results show that the losses in comparison with a bottom-fixed off-shore wind turbine are below 1% or 1.1% according to the load case, which confirms the good performance of the studied FOWT.

Load control and unsteady aerodynamics for floating wind turbines

2021 ◽  
pp. 095765092199325
Author(s):  
Xin Shen ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Wind Turbine ◽  
Power Output ◽  
Aerodynamic Performance ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Pitch Control ◽  
Unsteady Aerodynamic ◽  
Floating Wind Turbine ◽  
Fixed Base

Unlike fixed-base offshore wind turbine, the soft floating platform introduces 6 more degrees of freedom of motions to the floating offshore wind turbine. This may cause much more complex inflow environment to the wind turbine rotors compared with fixed-base wind turbine. The wind seen locally on the blade changes due to the motions of the floating wind turbine platform which has a direct impact on the aerodynamic condition on the blade such as the angle of attack and the inflow velocity. Such unsteady aerodynamic effects may lead to high fluctuation of the loads and power output. The present work aims to study the high unsteady aerodynamic performance of the floating wind turbine under platform surge motion. The unsteady aerodynamic loads are predicted with a lifting surface method with a free wake model. A preview predict control algorithm is used as the pitch control strategy. A full scale U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) 5 MW floating wind turbine is chosen as the subject of the present study. The unsteady aerodynamic performance and instabilities have been discussed in detail under prescribed platform surge motions with different control targets. Both minimizing the power output and rotor thrust fluctuation are set as the control objectives respectively. The theory analysis and the simulation results indicate that the blade pitch control can effectively alleviate the variation of the rotor thrust under platform surge motions. Larger amplitude of the variation of blade pitch is needed to alleviate the variation of the wind turbine power and this leads to high rotor thrust fluctuation. It is also shown that negative damping can be achieved during the blade pitch control process and may lead the floating platform wind turbine system into unstable condition.

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