hydrodynamic analysis and optimal design of floating wind turbine and ocean wave energy systems paul...
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Hydrodynamic Analysis and Optimal Design of Floating Wind Turbine and Ocean Wave Energy Systems
Paul D. SclavounosProfessor of Mechanical Engineering and Naval Architecture
Department of Mechanical Engineering
LSPF Laboratory for Ships and Platform Flows
Advantages of Floating Offshore Wind Farms
Wind a Rapidly Growing, Free, Inexhaustible, Environmentally Friendly, Utility Scale and Cost Effective Energy Source
Vast Offshore Wind Resources with Higher and Steadier Wind Speeds in Deeper Waters
Over 75% of Worldwide Power Demand From Coastal Areas
Wind Power Output Increases with Cube of Wind Speed
Lower Offshore Wind Turbulence – Longer Farm Life ~ 25-30 Years
Connection to Electric Grid by Sub Sea AC or HVDC Cables
Experience of Oil Industry Essential for the Development of Safe and Cost Effective Spar and TLP Wind Turbine Floaters
Floating Wind Turbines Provide Infrastructure for Arrays of Wave Energy Converters in Waters Depths over ~ 40m with Significant Wave Power Density
Courtesy: NREL
Horns Rev Wind Farm (Denmark) - Rated Power 160 MW – Water Depth 10-15m
Expensive Installation Process for Seafloor Mounted Turbines
Floating Wind Turbine Attributes
Water Depths of 30 – 1000 m
5-MW Wind turbine: 1 GW Floating Wind Farm (200 Units)
Flexible Installation process:
Full Assembly at a Coastal Facility Ballasted TLP or Spar Buoy Tow Stable Floating Wind Turbine at Offshore Wind Farm Site Tow In of Floating Wind Turbine for Major Maintenance Gravity Anchors for TLP Tethers Conventional or Synthetic Catenaries for Spar Buoy
Attractive Economic and Financial Attributes
Coastal Zone of Visual Influence (ZVI)
L Distance from Shore for Turbine to be Invisible H Max Height of Turbine Blade Tip (90 + 65=155 m) R Earth Radius (~ 6,370,000 m)
L = 28 miles (45 Km) (H=155m - Blade Tip) L = 21 miles (34 Km) (H=90m - Hub)
2L H R
New Jersey Offshore Wind Farm
Courtesy: NY Times
Deep Water Offshore Platforms for Oil and Gas Exploration
Spar and TLP SML Simulation Modelsof MIT Laboratory for Ship and Platform Flows
5 MW Wind TurbineRotor Orientation UpwindControl Variable Speed, Collective PitchRotor Diameter/Hub Diameter 126 m/3 mHub Height 90 mMax Rotor/Generator Speed 12.1 rpm/1,173.7 rpmMaximum Tip Speed 80 m/sOverhang/Shaft Tilt/Precone 5 m/ 5°/ -2.5°Rotor Mass 110,000 kgNacelle Mass 240,000 kgTower Mass 347,460 kg
Overall c.g. location:
(x,y,z)t = (-.2,0,64)m
Coupled Dynamic Analysis
Wind Turbine Floater Analysis & Design
Design Studies Sea States Design Models
Tension Leg PlatformSpar Buoy in SLC (Single-Layer Catenary)Spar Buoy in DLC (Double-Layer Catenary)
Pareto Optimization Analysis
Sea Spectra
41
244.0
5
11
2
22
11.0)(
wT
s ewT
THwS
ITTC (International Towing Tank Conference) Standard
TLP; Water depth = 200 m; Seastate H=10m
TLP Water depth = 200 m; Seastate H=10mPareto Fronts
Design Models: Spar Buoy in SLC (Single-Layer Catenary)
Design Models: Spar Buoy in SLC
=
Fairlead Position
DraftPlatform
DepthFairlead
Design Models: Spar Buoy in SLC
Platform Diameter, 2R [m] 18
Draft, T [m] 40
Displacement [metric tons] 10453.586
Concrete Concrete Mass [metric tons] 9036.997
Concrete Height [m] 13.858
Center of Gravity [m] -25.522
Center of Buoyancy [m] -20
Seacondition
Water depth [m] 200
Mooring Catenary angle, [degree] 10 ~ 70
k [m/m] 0.995
Fairlead Location, [m/m] 1.0
* EA [N] 400E6
MBL [N] 20E6
Design Models: Spar Buoy in DLC (Double-Layered Catenary)
Spar Buoy OptimizationPareto Fronts
Offshore Wind Capacity Factor
Assessment of Offshore Wind Resource – Wind Velocity Probability Distribution
Ideal Efficiency of Wind Turbine in Steady Wind – Betz Limit : η=16/27=0.59
Reported Efficiencies of Large Scale Wind Turbines ~ 50%
Advanced Control Systems to Enhance Power Absorption from High Wind Gusts
Height of Tower, Size of Rotor and Electric Generator – Cost Benefit Analysis
Capacity Factor: Percentage of Time Wind Turbine Generates Power at its Rated Capacity
Offshore Wind Capacity Factors (CP) ~ 40-45%
Available Wind Power per 1 GW Offshore Wind Farm at 40% CP ~ 400 MW
Wave Energy Converters ~ 100 MW / Square Parcel
Hybrid Offshore Wind & Wave Energy Plant
Wave Energy Capacity Factor
Wave Power in Storm with 3m Height / 8 sec Period / 100 m Wavelength ~ 36 kW / meter
Wave Power in Storm with 10m Height / 12 sec Period / 200m Wavelength ~ 500 kW / meter
More Wave Power Encountered in Water Depths Over 40 m (Waves do not feel seafloor)
Maximum Wave Power Captured by Point Wave Energy Absorber ~ Wavelength/ 2π (m)
In 3m Seastate ~ 573 kW / Absorber; In 10m Seastate ~ 15 MW / Absorber
Spacing of Point Absorbers ½ a Wavelength – Wave Power Output Increases by 50%
Use of 100 Absorbers Rated at 1 MW Between 4 Wind Turbines – Power Output ~ 150 MW
Maximum Utilization of 1 GW “Offshore Wind Farm Real Estate” – 150x13x13 MW ~ 25 GW
Capacity Factor of Ocean Wave Energy ~ 30%
Available Wave Power per 1 GW Rated (400 MW Available) Offshore Wind Farm ~ 7.5 GW
Floating Wind Farm Financial Attributes
Annual Revenues of 1 GW Farm (200 5 MW Units) @ 40% Capacity Factor and @10 cents/KWh: ~ $400 Million
Breakeven Cost vs CCGT ~ $ 3 M/MW: Based on Natural Gas Price Projections $9-15/MMBtu from 2010-2027
Breakeven Cost per Floating 5 MW Unit: $15 M; 1GW Wind Farm: $3 B
Onshore 5 MW Unit Cost ~ $10 M; Breakeven Cost of Floater & Mooring System ~ $5 M
O&M: Unit Ballasted & Towed to Shore – On Site Routine Maintenance
Interconnection Costs ~ 15-20% of Capital Costs ~ $ 450-600 M for 1 GW Farm
AC Sub Sea Cables up to ~ 100-130 km. HVDC Light Technology over 100-130 km
Coal Plant Emits ~ 1 ton CO2/MWh; Combined Cycle Gas Turbine Emits ~ 300 Kg CO2/MWh
At $10/ton of CO2 – Emissions Credit ~ 1 cents/KWh; 10% Increase in Revenue
Floating Wind Farms vs. Oil & Gas Reservoirs
1 Barrel of Oil ~ 130 kg ~ 1.5 MWh of Energy (~ 12 kWh / kg)
1 MW of Rated Wind Turbine Power @ 40% Capacity Factor ~ 9.6 MWh / Day ~ 6.4 Barrels of Oil / Day
Conversion Efficiency of Oil & Gas Engines / Turbines, Wind Turbines ~ 40-50%
1 GW Wind Farm (30 year life) ~ 70 M Barrel Oil Field ~ 6,400 Barrels / Day
Breakeven Cost of Wind Turbines $3M / Rated MW = $3 B / Rated GW
Equivalent Cost per Barrel of Oil ~ $43 / Barrel
Investment Risk in Oil & Gas: Exploration Costs & Volatility of Oil & Gas Prices
Investment Risk in Wind: Volatility of Wind Speed & Electricity Prices
Summary
Optimized Spar Buoy and TLP Wind Turbine Floaters
Low Responses – Use of Onshore Wind Turbines
Hybrid Offshore Wind & Wave Farms
Optimal Control to Enhance Wind and Wave Power Output
Design of Offshore Electric Grids
Attractive Economic Attributes
Project Finance for Utility Scale Offshore Wind & Wave Farms