Note: This is the first article of a three-part series covering plastic in wind energy (1) trends, (2) material/process advances and (3) applications.
In wind energy, the trend is to create larger and lighter blades to capture more wind and lower rotational inertia. New technology is being developed to build enormous turbine blades, while also eliminating the need for molds and the transportation problems typical with large blades.
Intelligent blades that adapt to wind conditions will also provide a leap in energy yield. Vertical-axis wind turbines are being developed for large-scale offshore wind turbine applications.
Electrical energy storage capability will be increasingly important to grid stability as electricity production via wind gains market share. Technical innovation will make wind and marine wave and tidal more competitive with other forms of energy.
Wind developments hold much promise to help meet the growing global energy demand, with innovations in plastics playing a key role.
Wind energy designs increasingly depend on plastics materials. Plastics parts and components are extensively used in all major sectors of wind energy generation to:
- Reduce weight
- Extend service life
- Lower cost
- Advance design and provide design flexibility
- Maximize productivity and safety
The long-term growth of wind energy requires technical innovation to make wind more competitive with other forms of energy. Blade manufacturers are seeking ways to improve productivity by reducing cycle time and cutting costs.
Robotic lay-up, enhanced finishing techniques, two-piece or segmented blades and on-site manufacturing are potential tools to trim labor and logistics costs, while resin and prepreg suppliers are looking to develop materials that cure faster, at lower temperatures.
Bigger and lighter blades are also needed to improve wind generation. Larger blades will require use of more advanced materials, including carbon fiber, S-glass as well as better bonding and stronger core materials.
Greater use of carbon fiber is seen due to its higher stiffness/lighter weight than standard E-glass — despite disadvantages of cost and tight supplies. Diamond nanoparticles incorporated as a nanofiller in polymer matrices also show promise to significantly improve the strength and stiffness of glass fiber-reinforced composites without additional layers of fiber reinforcement.
Blade tests will become more sophisticated. As longer blades are developed, more data acquisition will better characterize blade performance to aid blade designers.
Let's start with composite blade design optimization, which is an emerging plastics technology trend. As wind turbine manufacturers seek additional ways to reduce costs and improve performance, attention has turned to improving modeling techniques as a way to reliably predict wind turbine behavior prior to expensive prototyping and testing.
In particular, better-designed wind-turbine blades are more effective, and they create significant savings for the tower and drive train — major components in the overall system. Variational Asymptotical Beam Sectional Analysis (VABS) software, has recently gained the attention of the wind industry for its unique capabilities in realistic modeling of wind-turbine blades.
AnalySwift LLC VABS wind turbine blade cross-section. At the top, the images present the 3-D mesh in the finite element analysis (FEA) program in its global view (white) and a close up of its edge. At the bottom, the 2-D mesh was generated in the VABS program. .
VABS is an efficient, high-fidelity, cross-sectional analysis program and a unique tool capable of realistic modeling of initially curved and twisted anisotropic beams. Like helicopter blades, blades on wind turbines have arbitrary sectional topology and materials.
The VABS program offers users a powerful analysis tool to calculate sectional properties, including structural properties such as tension center/neutral axis, centroid, elastic axis and shear center, shear correction factors, extensional, torsional, coupling, bending, shearing and stiffness, along with principal bending axes pitch angle, modulus weighted radius of gyration.
Using VABS for efficient, high-fidelity design and analysis allows saving 2-3 orders of magnitude in computing time relative to 3-D FEA analyses and without a loss of accuracy.
Next, the PIQO compact horizontal axis micro wind turbines are being marketed to industrial facilities, high-rise buildings and private homes. Dutch company EverkinetiQ International developed the PIQO Series of small turbines in collaboration with Pekago, Albis and BASF with the intent to provide locally generated energy.
BASF/EverkinetiQ International PIQO compact micro-HAWT (horizontal-axis wind turbine).
Although multimegawatt wind turbines dominate the wind-energy landscape, there is significant effort to develop smaller turbines with output well under 1 MW. The small-kilowatt-capacity turbines — both Horizontal Axis Wind Turbines (HAWT) and Vertical Axis (VAWT) — are within the economic range of small businesses, farmers and homeowners.
Cost-efficient Luran S KR 2858 G3a with 15 percent glass-fiber-reinforced acrylic ester-styrene-acrylonitrile (GFR ASA) and unfilled Luran S 797 S are supplied by BASF subsidiary Styrolution, leading to full commercialization. Pekago, the Dutch injection molding company is producing in volume the micro wind turbine parts.
Plastics component use — 15 percent GFR ASA has been specified for the turbine's rotor and unfilled ASA for the 1.5-meter diameter frame. ASA offers good resistance to weathering, UV radiation and aging. The PIQO wind turbines are rugged, compact and generate little noise.
Finally, project NOVA (Novel Offshore Vertical Axis), a public/private U.K. consortium is testing a 50-kW VAWTS demonstrator (Vertical Axis Wind Turbine System), named the Aerogenerator X and built by Wind Power Ltd. at Cranfield University. NOVA is sponsored by the U.K. Energy Technologies Institute (ETI) and the Engineering & Science Research Council (EPSRC), with financial support from the European Regional Development Fund (ERDF).
The fully-working 50 kW prototype will demonstrate Project NOVA's new concept 10 MW offshore, double-arm, VAWTS. The 50 kW prototype scaled-down demonstrator is equipped with embedded structural strain and air pressure monitoring.
Urethane acrylate structural adhesive (Crystic Crestomer 1152PA), supplied by Scott Bader Co. Ltd., provides light-weight structural bonding of the various carbon-fiber and glass-fiber epoxy composite parts for the prototype's two 10-by-1.9-meter rotor sails.
Prototype rotor sail weight was significantly reduced by using the structural adhesive, which had the added benefit of also providing lower overall manufacturing costs compared to a jointed sectional and mechanical assembly design. The structural approach used for the rotor sails is similar to a large commercial aircraft wing.
The sail central box components were manufactured from multidirectional carbon-fiber fabrics and epoxy resin using a vacuum infusion-molding process. To the central box is added glass-fiber-reinforced leading and trailing edge components.
