Offshore Wind Turbine Blade Structures The engineering challenges in creating the world’s largest rotating structures
[Date Month 20XX, Name, Department, etc.]
Contents 1. Business drivers 2. Market growth 3. Direction 4. Challenges 5. New Directions 6. Developing Trends
7. The future
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Business Drivers What are we working to achieve?
Cost per kwh being driven down over the years • Technology developments sought to achieve further reduction in Cost of Energy
Business case certainty • Reliability
Wind as an energy source on par with oil and gas
Market Growth The recent past
A lot of change with the recent markets – but there is still growth
Source: Global Wind Energy Council
Market Growth Offshore specific
• Offshore wind is gaining as a percentage of the wind market – but it’s still a small share of the global wind market
Vestas are managing to maintain their status at No.1 Source: Global Wind Energy Council
Market Growth Offshore specific
• However this isn’t indicative of the total potential market size • Installed and under construction is still at less than 8% of the planned for Europe alone • This is considering current technology
Note: Installation figures in MW Source: Global Wind Energy Council - 2011
Direction Turbine trends
There is a move towards dedicated ―onshore‖ and ―offshore‖ turbine SYSTEMS This is due to the differing operation constraints / drivers experienced at sea • • •
Maintenance Reliability Installation cost
But from a rotor systems perspective the trend is still increasing diameter both on and offshore offshore wind turbines
Onshore wind turbines
Source: Global Wind Energy Council
Direction Rotor system trends
With the increase in size there are some obvious implications:
•
Beating the length weight cubic relationship ᅳ Good design mass ~ length2.2-2.5 ᅳ Step changes - carbon fibre
Currently 2000 Kg/hour deposition rate – NEED to go faster!
Source: Tom Ashwill, Sandia National Laboratories
Challenges Defining the envelope The envelope for the design of a WTG blade is defined from one driver:
COST THIS dictates the materials and processes used within a WTG With the aim of:
• • •
Driving down the Cost of Energy (CoE) increasing Business Case Certainty Public Acceptance
High impact drivers are: • Forecast → efficiency of annual energy production, serviceability, maintenance, reliability • Weight → CoE • Wind capture → CoE • Conversion → reduced losses Cost of Energy embraces all aspects in wind power performance
Annualized CAPEX + Annualized OPEX CoE =
Annual Energy Production
Challenges Structural
The primary design cases affecting the definition of the structure of a WTG blade are driven by Fatigue: • Gusts and turbulence / Self weight • Light-weight Composites - ideal material for WTG Blades • Lower loads due to low weight • Higher fatigue resistance than metals
Challenges Manufacturing
Main drivers within manufacturing processes: High Speed Manufacture • Needed for industry growth expectations • V90 = 7 tonnes composite per blade • Currently 1000+ blades produced per line per year
Process Control • Six Sigma Production objective • Greater automation utility
Precision – shape • Allow advanced aerodynamics
Scale: • Vestas planned offshore blade – 80m • Off shore = single piece (reliability)
Challenges The ―unseen‖ challenges
Tip speed: ᅳ Generator loads/efficiency
ᅳ Blade efficiency – relative vector axis
Damping: ᅳ Buffeting in high wind stopped conditions
Wind shear: ᅳ Fatigue loads from differential wind speeds ᅳ Blade efficiency – average pitch angle
New Directions Near term – what’s next in turbine design
Increasingly it is apparent that there are 2 diverging drivers for turbines of the near term future: • Greater flexibility within onshore turbines: ᅳ The ability to utilise VERY low wind environments ᅳ Greater site ―specific‖ designs within the aero structures • Higher individual power output for offshore: ᅳ Fewer, higher power turbines ᅳ Installation and maintenance costs are significant business case drivers ᅳ Deep water positioning
This is leading to specific offshore turbine blade designs
New Trends Near term
Larger rotor system machines for higher power output unit:
Floating turbines (using technology from the Oil and Gas industries) for deep sea installations
The Future Longer term – when bigger just isn’t the answer
Technologies under investigation: • LIDAR gust prediction • Bend-twist coupling for passive load reduction
LIDAR wind speed measurement
The Future Longer term – when bigger just isn’t the answer
Leading to alternative developments: • Twin blade machines – lower cost, potential for structural efficiency gain • Non-linear bend-twist coupling to eliminate the need for pitch bearings (being developed here at the UoB) • Incorporating control surfaces within the blades for active gust load reduction and precision control
Example of a ―morphing‖ trailing edge being developed at the UoB
Any questions?
Thank you for your attention
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