Feasibility study of pultruded blades for wind turbine rotors

Abstract

In work performed under subcontract * to the National Renewable Energy Laboratory (NREL), a preliminary design study and proof-of-concept field test were conducted to evaluate the feasibility of using pultruded blades for wind turbine rotors. A 400 kW turbine was selected for the design study, and a scaled 80 kW rotor was fabricated and tested as a demonstration of the concept. To examine the feasibility of pultruded blades, several issues were addressed, including power performance, tower strikes, yaw stability, stall flutter, fatigue, and rotor cost. Results showed that with proper design, rotors using pultruded blades demonstrate acceptable fatigue life and stable yaw behavior without tower strikes. Furthermore, blades using this technology may be manufactured for approximately half the cost of conventional blades. Field tests of the scaled rotor provided experimental data on power performance and loads while verifying stable yaw operation.

A novel powder-epoxy towpregging line for wind and tidal turbine blades

“…out-time effects [26]), and they generally do not address the issue of high exotherms, with the exception of Hexcel's Hexply M79 resin [27]. One alternative that allows blade manufacturers to avoid infusing dry fabric and controlling large exotherms, is the use of pultruded UD-CFRP [18,20,28], which has even been considered for offshore wind turbine tower structures [29]. Pultruded sections are fully infused (usually to a relatively high fibre volume fraction) and they are typically pre-cured, so they have no exotherm, they don't require temperaturecontrolled storage, and their high degree of fibre alignment is "locked in".…”

Effect of uncertainty on the bifurcation behavior of pitching airfoil stall flutter

“…1, b is the semi-chord of the blade, C m is the aerodynamic moment coefficient, U is the nondimensional airspeed defined as U ¼V =bo a , m and r a are nondimensional structural parameters, mass ratio m ¼ m=ðprb 2 Þ, radius of gyration r a ¼ I a =ðmb 2 Þ, K nl is the nondimensional form of K nl1 . Typical data for a 1000 KW capacity wind turbine are used with a semi-chord of b ¼ 0:8 m at 0:75 blade radius and a representative resultant wind speed ofV ¼ 50 m=s (Cheney and Migliore, 2000;Stiesdal, 1999). The uncertain parameters in the structural model are the pitch natural frequency o a , the cubic structural nonlinearity parameter K nl , and the structural equilibrium angle a m .…”