Fluid Structure Interactions
Research Group
Adaptive Composite Blades for Horizontal Axis Tidal Turbines
R.F. Nicholls-Lee, S.R. Turnock and S.W. Boyd
Fluid Structure Interactions Research Group, Faculty of Engineering and the Environment
rnl@soton.ac.uk
Background
Project Breakdown
Recently the world has seen a resurgence in the development of the
renewables industry, essentially to reduce the environmental impact of
energy generation such as that produced from fossil fuels, and create energy
security for countries using renewable energy, decreasing reliance on energy
imports.
The oceans are an untapped resource, capable of making a major contribution
to our future energy needs. They have the potential to equal or exceed wind
energy in the make-up of our future electricity demands. In the search for a
non polluting renewable energy source, there is a push to find an economical
way to harness energy from the ocean. There are several different forms of
ocean energy that are being investigated as potential sources for power
generation. These include thermal energy, wave energy, offshore wind
energy, tidal energy and ocean current energy, but these can only be applied if
the technology can be successfully developed to exploit such resources
reliably and cost effectively.
TIDES – DYNAMICS,
RESOURCES
TIDAL ENERGY
EXTRACTION
BLADE DESIGN
COMPOSITE BLADES – PASSIVELY ADAPTIVE
PASSIVELY ADAPTIVE BLADE DESIGN TOOL
Aim
This work aims to increase the efficiency
of horizontal axis tidal turbines through
optimisation of the blade design
Blade Design
Composite Blades
• Considerations:
• An adaptive textile composite = a
structure tailored to exhibit desirable
elastic deformation behaviour which is
not necessarily proportional to the
imposed load. E.g. bend-twist coupled beam
•
Cavitation,
Yaw,
Structural
loading,
Efficiency, Cost, Maintenance
Design tools – BEMT, CFD,
FEA, FSI
• Variable pitch blades vs
wholly bi-directional blades.
Figure 3 illustrates gains in
power capture from differing
blades
Figure 1: Tidal stream energy
density around the UK[1]
(mirror layup, Figure 4).
• Preliminary analysis indicated potential
improvements of:
•
•
•
2.5% increase in annual energy capture
10% decrease in thrust loading
Half as likely to cavitate
Figure 2: CFD of a horizontal axis tidal turbine
Experimental and Numerical Structural Analysis
• Basis central blade spar - carbon, bend-twist coupled, uniform planform,
double box beam
•Laser based experimental setup – Figure 5
•Finite Element Analysis
•Results:
- Generally good correlation between experiments and FEA, especially at low loads (Figure 6)
- FEA sensitive to manufacturing accuracy
- FEA does not model progressive plywise failure or matrix cracking observed in experiments
Figure 3: Fixed pitch, variable pitch
and bi-directional blade comparison
Figure 4: Preliminary analysis of adaptive blades
Adaptive Blade Design Tool
•
•
•
•
•
•
Blade input geometry developed and manipulated
CFD run – pressure loading and performance data obtained
Pressures applied to geometry in FEA – structural deflections noted
Deformed structure remodelled in CFD
Iterated until max bend is <10mm
Results concur with preliminary analysis:
- >5% increase in Cpow – Figure 7
- >12% decrease in CT – Figure 8
Figure 5: Experimental setup
Figure 6: Comparison of FEA and
Experimental bend
Conclusions and Further Work
• Tidal energy is an immature industry with great potential, but to further it
requires efficient and economic devices to be developed - blade design of
HATTs is a key area for optimisation.
•Different blade types have been compared, and it was found that adaptive
composite turbine blades could improve device performance with preliminary
results suggesting that a 10% reduction in thrust loading and 2.5% increase in
annual energy capture is achievable with bend-twist coupled blades.
•A design tool has been created for the development of passively adaptive
bend-twist coupled HATT blades and further validation will be carried out
Figure 7: Comparison of fixed pitch, preliminary
adaptive and design tool adaptive blades - Cpow
Figure 8: Comparison of fixed pitch, preliminary
adaptive and design tool adaptive blades - CT
References:
[1] BERR, Atals of UK Marine Renewable Energy Resources: A Strategic Environmental
Assessment Report, BERR, Editor. 2008.
FSI Away Day 2012