Aerodynamic Structural Noise - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 205

Sound Pressure Level Correlation with Increase of Frequencies

120

Column A
Column B
Column C

100

80

60

40

20

0

1 2 3 4 5

Frequencies, Hz

6 7 8 9

FIGURE 7.6
Sound.emissions.reduce.when.frequencies.increase..(From.Wind.turbine.acoustic.noise..2006..
Online.at:.www.ceere.org..With.permission.)

regulatory.perspective.as.the.market.is.driving.product.design.to.larger.tur-
bines.with.higher.blade.tip.speed..Here,.aerodynamic.noise.becomes.a.cru-
cial.constraint.on.eficiency.and.yield.of.a.design..As.such,.there.is.a.need.for.
concepts.for.noise.reduction.
Gupta.and.Maeder's 3 .invention.deines.a.concept.wherein.materials.technol-
ogy.is.used.as.a.means.of.noise.reduction,.targeting.blade.self-noise.and.tip-
noise,.the.two.primary.components.of.wind.turbine.aerodynamic.noise..In.the.
past,. aerodynamic. shaping. has. been. the. primary. means. of. achieving. lower.
noise.levels,.e.g.,.the.use.of.a.large.chord,.higher.solidity.blades,.low-noise.air-
foil.design,.plan-form,.and.tip/winglets.geometry..Noise.reduction.concepts.
that.use.add-ons.like.trailing.edge.serrations,.sharp.trailing.edge.inserts,.and.
the.like,.have.also.been.investigated.and,.in.some.cases,.put.into.production.
The.invention.proposes.to.incorporate.composite.material.in.wind.turbine.
blades.to.reduce.noise,.via.noise.source.reduction.and/or.noise.attenuation.
and.absorption.
The. invention. may. be. embodied. in. a. wind. turbine. blade. having. a. pres-
sure.side.and.a.suction.side,.a.leading.edge,.a.trailing.edge,.and.a.tip.region,.
at. least. a. portion. of. the. blade. being. formed. from. a. cellular. material,. and.
the.cellular.material.portion.deining.a.portion.of.an.exposed.surface.of.the.
blade,. whereby. aerodynamic. noise. is. reduced. via. noise. source. reduction.
and/or.noise.attenuation.and.absorption.by.the.cellular.material.
The.invention.also.may.be.embodied.in.a.method.of.reducing.noise.in.a.
wind.turbine.via.at.least.one.of.a.noise.source.reduction.and.noise.attenu-
ation. and. absorption. by. a. wind. turbine. blade;. the. method. comprising:.
providing. a. wind. turbine. blade. for. the. wind. turbine,. the. blade. having. a.
pressure. side. and. a. suction. side,. a. leading. edge,. a. trailing. edge,. and. a. tip.