JEC COMPOSITES MAGAZINE - Issue #79 - March 2013 - 26

wind energy

A 50kW vertical axis offshore
wind turbine prototype with V-sails
A key milestone has been achieved by the UK
APP project team with the successful construction of the sails for a fully working 50kW prototype demonstrator of their new 10MW “double
arm” offshore vertical axis wind turbine concept.

By

Andrew Mills, Composites Design & Manufacturing Leader,
Cranfield University Composites Centre
Jonathan Stowell, Global Business Manager - Adhesives,
Scott Bader Advanced Composites Business

T

his is a two-year renewable energy feasibility
project supported by the
UK Energy Technologies Institute (ETI) and the Engineering
& Physical Sciences Research
Council (EPSRC), with financial support from the European
Regional Development Fund
(ERDF). The project aims to
investigate the affordability
and feasibility of manufacturing a vertical axis wind turbine
system (VAWTS) of this design
and scale. The APP project’s
50kW VAWTS demonstrator is
located on the Cranfield campus. The 50kW prototype was
manufactured at the Cranfield
University Composites Centre,
with extensive design and

manufacturing advice and support provided by key material
suppliers. These included Scott
Bader Company Ltd., whose
Crystic® Crestomer® 1152PA
urethane acrylate structural
adhesive was specified for the
lightweight structural bonding
of the various carbon and glass
fibre-reinforced epoxy composite parts which make up the
two 10 metre by 1.9 metre rotor
sails. To be viable, the planned
massive scale-up in offshore
wind turbine manufacture
will require the rotor blades to
sustain at least 20 years’ service
without maintenance. As such,
the structural design and selection of suitable high-quality
materials with these long-term
performance capabilities are
critical success factors for this
project.

26 jec composites magazine / No79 March 2013

Fig. 1: An artist’s impression of the final vertical-design 10MW offshore wind
turbine - Courtesy Wind Power Limited

Scaled down
prototype demonstrator
By first developing a 50kW
scaled down prototype
demonstrator with embedded structural strain and air
pressure monitoring, the APP
project team will be able to
gain an understanding of the
engineering performance and
aerodynamic behaviour of the
design in use and extensively
test the composite materials
selected in offshore operational
conditions.
The fabrication stage has
already helped them to address,
on a much smaller scale, any
processing challenges to costeffectively manufacture and
assemble the composite components; these can then be applied to the full-sized version to
help ensure its affordability and
commercial viability. This novel
vertical axis turbine design, if

ever fully commercialized as a
10MW offshore wind turbine,
would have two 160 metre
length arms supporting two 80
metre long V shaped sails and
be the heaviest composite construction in the world, weighing
around 160T.

Design, weight and
manufacturing considerations
The overall wind turbine
assembly was designed and
constructed to have the best
long-term structural reliability in order to meet the key
criteria of being “maintenance
free” during its expected 20
years’ service period. The two
prototype rotor sails each
have dimensions of 10 metre
long by 1.9 metre wide, with a
maximum depth of 180mm at
the mid-section. The structural
approach used for the rotor
sails is similar to a large com-
JEC COMPOSITES MAGAZINE - Issue #79 - March 2013

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