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Kombinert Wind- og Bølgekraft Rasmus Borenius Marin teknikk Innlevert: juni 2015 Hovedveileder: Dag Myrhaug, IMT Medveileder: Professor Bernt Leira, IMT Norges teknisk-naturvitenskapelige universitet Institutt

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Kombinert Wind- og Bølgekraft Rasmus Borenius Marin teknikk Innlevert: juni 2015 Hovedveileder: Dag Myrhaug, IMT Medveileder: Professor Bernt Leira, IMT Norges teknisk-naturvitenskapelige universitet Institutt for marin teknikk i ii Declaration of Authorship I, Rasmus Pontus Borenius, declare that this thesis titled, Compined Wave And Wind Power and the work presented in it are my own. I confirm that: Where any part of this thesis has previously been submitted for a degree or any other qualification at this University or any other institution, this has been clearly stated. Where I have consulted the published work of others, this is always clearly attributed. Where I have quoted from the work of others, the source is always given. With the exception of such quotations, this thesis is entirely my own work. I have acknowledged all main sources of help. Where the thesis is based on work done by myself jointly with others, I have made clear exactly what was done by others and what I have contributed myself. Signed: Date: iii You see, we should utilize natural forces and thus get all our power. Sunshine is a form of energy, and the wind and tides are manifestations thereof. Do we use them? Oh no!, we burn up wood and coal, as renters we burn up the front porch for fuel. We live like squatters, not as if we owned the property. Thomas A. Edison 1916 Abstract In this thesis the possibility of combining wind and wave power was investigated. A literature study on different concepts of wind power, wave energy converters as well as combined wind and wave power devices has been performed. A brief introduction on the origin of wind and waves are introduced. The physics of how wind and wave power is extracted will be discussed. From the obtained knowledge, a design proposal combining the two power sources with common underwater storage tank, was elaborated and analyzed. In addition, a suitable offshore site in the North Sea with a joint distribution has been proposed. The offshore site investigated has a water depth of 29[m], an average wind power density of [W/m 2 ] and an average wave power density of 14.29[kW/m] The analysis can be divided into three main parts. In the first part, a wind turbine blade was designed using optimal BEM (Blade Element Momentum) theory in MATLAB. The power output was then calculated for a three bladed wind turbine using the designed blade. The diameter of the turbine was set to 126 meters, which gave an average power output of 3.92MW at an operational wind speed of 10m/s and a TSR (Tip Speed Ratio) of 8. To analyse the performance of the designed wind turbine in a more realistic manner, the software ASHES was used, which resulted in a power output of 4.35MW. The average power output of the wind turbine was also calculated, using a Rayleigh distribution. This resulted in a average energy production of 3.22MWh. The second main part of the analysis investigated the time average power output of a WEC (Wave Energy Converter) in frequency-domain for both regular and irregular sea. In this regard, the CorPower WEC was chosen. The hydrodynamic coefficients for the WEC were obtained using the software WAMIT. In addition, the WEC was equipped with a new technology called WaveSpring. To v calculate the power output for different sea state conditions, a scatter diagram of the North Sea site was used. The calculations made in MATLAB showed that the WEC is able to produce between [kWh], depending on the sea state condition. In average the WEC is able to produce 127, 61[kWh] when placed at the aforementioned offshore site. The calculations also showed that the efficiency of the device capturing wave power increased with approximately 30% for the most occurring sea states due to the WaveSpring. In addition, a model of the WEC was established in the software SIMA. However, running and analysing this model has not been a high priority in this thesis and has, therefore, not been performed. The third main part of the analysis estimates the required size of the under water storage tanks. As expected, the WEC proved to have low energy production compared to the wind turbine. Based on this, it was decided to find out how many WECs are needed to produce the same amount of energy as one wind turbine. This resulted in 25 WECs per wind turbine. When combining the two power sources we get a total amount of [kWh]. This resulted in a total required volume of [m 3 ] at a water depth of 29[m]. Since the wave power density of the offshore site is rather low, different sites have to be investigated before deciding whether the proposed system is feasible. One should also reconsider the site with regard to water depth. The volume of the under water tank decreases exponentially when entering deeper waters. The total required volume of the tank reduced to less than half when installed at for example 80[m]. Sammendrag I denne master oppgaven ble muligheten for å kombinere vind- og bølgekraft undersøkt. Det er blitt utført et litteraturstudie på ulike konsepter av vindkraft, bølgekraft og kombinert vind- og bølgekraft. Basert på den oppnådde kunnskapen i litteraturstudiet, ble det utarbeidet og analysert et konsept som kombinerer vindog bølgekraft. Konseptet går ut på å ta i bruk undervanns tanker som lagrer potentiel energi. Det ble også foreslått et passende område med felles distribusjon i Nordsjøen. Det undersøkte offshore området har en vanndybde på 29 [m], en gjennomsnittlig vindkraft tetthet på 872,03 [W/m 2 ] og en gjennomsnittlig bølgekraft tetthet på 14,29 [kw/m] Analysen kan deles inn i tre hoveddeler. I første del, ble et vindturbinblad designet i MATLAB ved hjelp av BEM (Blade Element Momentum) teori. Utgangseffekten ble deretter beregnet for en trebladet vindturbin sammensatt av det designede bladet. Diameteren på turbinen ble satt til 126 m, noe som ga en gjennomsnittlig effekt på 3.92MW ved en operativ vindhastighet på 10 m/s og en TSR (Tip Speed Ratio) av 8. For å analysere ytelsen til vindturbinen på en mer realistisk måte, ble programmet ASCHES brukt, noe som resulterte i en effekt på 4.35MW. Den gjennomsnittlige effekten av vindturbinen ble også beregnet ved å anvende Rayleigh-fordelingen. Dette resulterte i en gjennomsnittlig energiproduksjon på 3.22MWh per time. Den andre hoveddelen av analysen undersøkte gjennomsnittseffekt over en tisperiode av en WEC (Wave Energy Converter) for både vanlig og uregelmessig sjø i frekvens-domene. I denne forbindelse ble det valgt å bruke modellen til Cor- Power. De hydrodynamiske koeffisienter for WECen ble funnet ved bruk av programmet WAMIT. I tillegg ble WECen utstyrt med en ny teknologi som kalles WaveSpring. For å beregne strømproduksjonen for forskjellige sjøtilstander, ble et vii scatter-diagram av området brukt. Beregningene som ble gjort i MATLAB viste at WEC er i stand til å produsere mellom [kwh] per time, avhengig av forholdene på. WECen er i gjennomsnitt i stand til å produsere 127,61 [kwh] per time når den plasseres på det nevnte offshore-området. Beregningene viste også at effektiviteten av å høste bølgekraft økte med ca. 30 % for de mest forekommende sjøtilstandene på grunnet av WaveSpring. I tillegg ble det laget en modell av WEC i programmet SIMA. For å avgrense omfanget til oppgaven, ble det bestemt å ikke gå videre inn i analysen av denne modellen. Dette kan være et emne for videre arbeid. Den tredje hoveddelen av analysen anslår den nødvendige størrelsen på undervanns tankene. Som ventet, viste WECen å ha lav energiproduksjon i forhold til vindturbinen. På bakgrunn av dette ble det besluttet å finne ut hvor mange WECs som er nødvendig for å produsere den samme mengden energi som en vindmølle. Dette resulterte i 25 WECs pr vindturbin. Når man kombinerer de to kraftkildene får man en total energi pruduksjon på 6407,21 [kwh] per time. Dette resulterte i et total nødvendige volum av 58901,58 [m 3 ] på en på 29 [m] vanndypde. Siden bølge energi tetthet i det undersøkte offshore-området er nokså lav, burde forskjellige områder undersøkes for å finne mest optimal plassering. Man bør også ta vanndybden i betraktning da, volumet av undervanntankene minsker raskt når en oppsøker dypere vann. For eksempel vil det totale volumet som kreves av tanken reduseres til mindre enn halvparten når tankene blir instalert på 80 meters dypde isteden. Acknowledgements This Master Thesis has been written during the 2015 spring semester at the Norwegian University of Science and Technology. The thesis has been submitted to partially fulfill the requirement for completing the degree of Master of Science, and has been performed at the Department of Marine Technology in Trondheim, Norway. The motivation behind this thesis was to determine whether it is possible to combine wind and wave power with a common energy storage underwater tank. The idea arose after investigating different already existing hybrid devices and their disadvantages. The attempt of the elaborated solution is to reduce these disadvantages, such that a combination may be possible to conduct. I suggested doing an analysis of this in my master thesis in hydrodynamics and caught my supervisors interest to the subject. To ensure the quality of this thesis many people with expertise have been asked for advice. I would, however, like to thank some of them in particular. First of all I would like to thank my supervisors Dag Myrhaug and Bernt Leira, Professors at NTNU, for their guidance and dedication throughout the work with this Master Thesis. We had many educational meetings at the institute, which kept me focused and motivated. I would also like to thank Johannes Falnes for many hours of informative conversations. I am very thankful that he gave me an impression of what he had explored during his many years of research within wave energy. I feel privileged to be able to get this kind of support. Also I would like to thank Jørgen Hals Todalshaug and Madjid Karimirad, for their prompt replies to inquiries over . In addition, I would like to thank my fellow students and family, who helped me to overcome obstacles from day to day, and kept my motivation going. In particular M.Sc. Eivind Finne Riley and M.Sc. Asgeir Hovdelien Midthaug were very helpful with the parts of the thesis dealing with wave power. A special thanks goes to my life partner Colleen, who had to endure my absence during this demanding year. Trondheim, June 2015 ix Contents Project description sheet Declaration of Authorship i iii Abstract v Sammendrag Acknowledgements vii ix List of Figures List of Tables Abbreviations Symbols xv xix xxi xxiii 1 Introduction General Background Marine Renewable Energy Offshore Wind and Wave Energy Scope and Objectives of the Thesis Wind Power Origin of Wind Wind Probability Distribution Influence of the Terrain and Altitude Offshore Wind Turbines Energy and Power Wave Power Origin of Ocean Waves Characteristics of ocean waves Wave Spectrum xi 3.2.2 Wave Statistics Energy Density in Regular and Irregular Waves Irregular Waves The Wave Energy Resource Wave Absorption The Budal Diagram Power-Take-Off It s All about the Phase Control systems of WECs Latching WaveSpring Wave Power Technologies Classification Of Devices Point Absorber Overtopping Devices Oscillating Water Column (OWC) Attenuator Combined Wind and Wave Power Why Combining Wind and Wave Power? The Floating Power Plant Poseidon W2Power Wave Treader NEMOS Design Proposal of a Combined Wind and Wave Power Device The Concept Choice of Offshore Site Evaluation of the Wind and Wave Resource Pumping Height and Total Power Requirement Choice of the Wind Turbine Generator Motor Pump Choice of the WEC Historical Investigation of Wave Driven Piston Pumps Design Criterias for the WEC List of Fundamental Requirements for a WEC The Chosen Wave Energy Converter Piston Pump The Storage Tank Wind Power Model Simplifications and Predefined Parameters Choice of Blade Choice of the Tip Speed Ratio Summary of Predefined Parameters xii Contents 6.2 Maximum Wind Turbine Power Output Betz Limit Thrust Force and Thrust Coefficient Aerodynamics of a Blade Forces on the Blade Rotational Induction Factor Blade Element Theory Design of the Blade Universal parameter table Determining the twist angle, θ Determining the Chord Length, L C Power Output of the Wind Turbine Electric Wind Pumping Results and Discussion of the Wind Power Analysis MATLAB Script MATLAB Results Testing in ASHES Power Output Strength analysis Electric Wind Pumping Wave Power Model WAMIT Simplifications and Predefined Parameters Geometry of the CorPower Point Absorber Summary of Simplifications and Predefined Parameters Hydrodynamic Coefficients Mechanical Oscillator Useful Converted Power Including the WaveSpring Wave Power Captured in Regular Waves Wave Power Captured in Irregular Waves Results of the Wave Power Model Sea State Analysis MATLAB Results for Regular Waves Wave Power in Irregular Waves Power Captured by the WEC in Irregular Waves Wave Capture Width and Efficiency Effect of the Wavespring Wave Driven Pump Modelling in SIMA SIMA Modelling in SIMA The WEC Model The Coupled WEC Model xiii 11 Combining Wind and Wave Power Proposal Simplifications and Assumptions Chamber Size Estimation Estimating the Volume of the Underwater Chamber Discussion Conclusion Further Work 113 A Wind Power 123 A.1 Blade Element Momentum Theory A.2 Forces on the Blade A.2.1 Induction Factors A.2.2 Wake Momentum A.2.3 Completing the BEM method A Prandtl Corrections for Tip Loss A Glauert s Correction for Heavy Loads A.2.4 Ideal Situation with no Drag A.2.5 Ideal BEM Theory A.2.6 Determining Twist angle ϕ and the Chord Length, L C B Wave Power 137 C Underwater Storage Tank 147 xiv List of Figures 1.1 World consumption (EIA, 2013) Global circulation of wind The Atmosphere Wind speed histogram (GreenPower, 2015) Rayleigh distribution for varying mean wind speeds Horizontal axis wind turbine (Layton, 2015) Bottom fixed wind turbines (SINTEF, 2014) Floating wind turbine concepts (NREL, 2011) Wave motion (Welland, 2011) JONSWAP vs. PM spectrum (Myrhaug, 2007) Global annual mean power (SWECO, 2007) Absorbtion of waves (Falnes, 2005) Budal diagram (Falnes and Todalshaug, 2012) Energy distribution of the seas and response of different marine structures Energy distribution of the seas and response phase controlled WEC Latching, resonance and phase control WaveSpring phase control Effect of WaveSpring Schematic of Terminator, Attenuator and Point absorber (Cruz, 2008) Concepts of Typ E (Falnes and Budal, 1978) and Wavebob (Wavebob, 2008) Illustration of the Wave Dragon (wavedragon) Illustration of an OWC (OpenEi) Illustration of the Pelamis (Falcao, 2009) Floating Power Plant Poseidon (FPP) W2Power (W2Power) Wave Treader (Treader) NEMOS (NEMOS, 2013) Sketch of the developed concept Location of potential European offshore sites Joint distribution of wind speed U w and significant wave height H s from 10 years hindcast data Mechanical and Electrical Wind Pump (Ziter, 2009) Experimental set up xv List of Figures xvi 5.6 CorPower buoy and PTO (CorPower) Sketch of the wave driven piston pump Storage power plant on the seabed (Benjaminsen, 2013) Schematic concept description Geometry of the NACA0064 airfoil Increasing Reynolds number Power vs TPR (Schubel and Crossly, 2012) TSR desgin considerations Schematic of fluid flow through a disk-shaped actuator (Quaschning, 2013) Maximum power output for wind turbine with swept area A swept =1m Pressure and velocity field around an airfoil Velocity diagram with the induced velocities Airfoil Velocity Triangle (Frøyd, 2010) Volume flow rate V m 3 /day per swept area Workflow MATLAB script sequence Chord Distribution Twist Distribution Torque and thrust distribution over the blade ASHES 2.0 simulation Caption Wing element performance (ASHES) C p vs TSR Flexible and stiff blade Pumping output of NREL 5MW Geometry of CorPower wave energy converter Added mass and damping coefficient Excitation force and RAO for heave motion Mechanical Oscillator JONSWAP wave spectrum Frequency response of absorbed power for two different values of a damping factor δ/ω 0 (Falnes, 2002) Wave probability distribution in [%] measured over 10 years Power over a period of 80s in regular waves for H=2m and T =6s JONSWAP spectrum for H S = 3 and T p = Wave power distribution in irregular waves Power captured of the WEC in irregular waves [W] Captured wave power over 2min and 2hours Wave capture width [m] Efficiency η of the device capturing wave energy in % Effect of WaveSpring List of Figures 9.11 Volume flow rate [m 3 /s] vs. head [m] The model of the WEC in SIMA The coupled model Salinity content of the ocean Volume required per unit of energy as a function of depth A.1 Blade elements of a three-bladed turbine (Frøyd, 2010) A.2 Velocities and forces on a blade element (Frøyd, 2010) A.3 Velocity Triangle (Quaschning, 2013) A.4 Rate of change of momentum A.5 Velocity triangles on a blade element(frøyd, 2010) B.1 Potential flow theory Faltinsen (1999) B.2 Scatter diagram for W and HSP from 10 years hindcast data (site No. 15)(Li, 2015) B.3 Scatter diagram (Li, 2015) B.4 Environmental conditions on the 50-year contour surfaces with maximum U w and maximum H s (Li, 2015) B.5 Wave probability distribution [%] B.6 MATLAB results for average captured wave power [W] B.7 MATLAB results for average energy produced over one year [Wh/year]143 B.8 MATLAB results for average pump rare per sec [m 3 /s] B.9 Bond graph sketch of wave driven piston pump xvii List of Tables 9.1 Wave probability distribution in [%] measured over 10 years Wave power in regular waves [kw/b W EC ] per WEC width B W EC =8m) Average captured power from the WEC [kw] Wave capture width [m] Wave power capture efficiency % Energy period T e [s] values calculated by JONSWAP spectrum Wave power in irregular waves [kw/b W EC ] per WEC width B W EC =8m) Power captured of the WEC in irregular waves [W] Wave capture width [m] Efficiency η of the device capturing wave energy in % Volume and number of underwater tanks Volume and number of underwater tanks A.1 Universal parameter table of induction factors, flow angle and B EP obtained from MATLAB A.2 Air Foil Data NACA0064 (SIMA) C.1 Volume required per unit of energy as a function of depth xix Abbreviations WEC HAWT TSR FWEC OWC PTO JONSWAP AoA RAO Wave Energy Converter Horizontal Axis Wind Turbine Tip Speed Ratio Floating Wave Energy Converter Oscillating Water Column Power Take Off Joint North Sea Wave Project Angle of Attack Response Amplitude Operator xxi Symbols v, U wind speed m/s v mean wind speed m/s p(v) Wind Weibull/Rayleigh distribution - a, k Weibull distribution shape parameters - h height over sea surface m z 0 roughness length m m mass kg ṁ mass flow rate kg/s A swept area m 2 ρ density kg/m ν kinematic viscosity m 2 /s E k energy J P power W (J/s) ω angular frequency rad/s ω p peak frequency rad/s M, A 33 Added mass coefficient in heave kg R r, B 33 Damping coefficient in heave kg/s S, C 33 Stiffness coefficient in heave kg/s 2 S(w), S(f) Wave spectrum m 2 s X Complex motion amplitude in heave m ζ a Wave amplitude m R u, B P T O Damping from the PTO system Ns/m f P T O Force from the PTO system N F e Excitation force N xxiii Symbols H s Significant wave height m H m0 Zero moment wave height m H Wave height m k Wave number m 1 P Time averaged power W W Capture width m λ Wave length m T Wave period s T P Peak period s T e Wave energy period s T z Zero crossing period s σ standard deviation - p pressure N/m 2 C p power coefficient - R total radius of blade m F T thrust force N C T thrust coefficient - a axial induction factor - a rotational induction factor - ω rotational speed rad/s U tangential velocity rad m/s φ flow angel θ twist angel α angel of attack W, U rel relative flow velocity m/s T thrust force N M torqu

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