STEP-WEC: STEP CHANGE FOR WAVE ENERGY CONVERSION THROUGH FLOATING MULTI-BODY MULTI-MODE SYSTEMS.

Transcription

1 UKCMER SuperGen Marine Energy Grand Challenge Assembly 216 STEP-WEC: STEP CHANGE FOR WAVE ENERGY CONVERSION THROUGH FLOATING MULTI-BODY MULTI-MODE SYSTEMS.

2 People Manchester Bath Oxford Peter Stansby Jun Zang Paul Taylor Tim Stallard RA RA Consultant Efrain Carpintero Moreno Hanbin Gu Liang Sun Rodney Eatock Taylor

3 M4WavePower M4 Moored MultiMode Multibody Multi body (3) for variable resonance Multi-mode (heave, surge, pitch) for large capture width Broad band across typical range of wave periods Moored for ease of deployment PTO above deck for maintenance at one hinge point Stansby.P., Carpintero Moreno, E., Stallard, T. & Maggi, A. (215a) Three-float broad-band resonant line absorber with surge for wave energy conversion. Renewable Energy 78,

4 How it works

5 Efficient frequency domain analysis using DIFFRACT Multi body analysis with 6 modes Forcing, radiation damping, added mass from DIFFRACT (Oxford/Bath research code) Output relative pitch, average power and beam bending moment Regular waves, irregular waves, multidirectional waves Sun,L., Stansby,P., Zang,J., Carpintero Moreno, E., Taylor,P. 216 Linear diffraction analysis and optimisation of the three-float multi-mode wave energy converter M4 in regular waves including small arrays, J. Ocean Engineering and Marine Energy, 2(4), Sun,L., Zang,J., Stansby,P., Carpintero Moreno, E., Taylor,P., Eatock taylor,r. 216 Linear diffraction analysis of the three-float multi-mode wave energy converter M4 for power capture and structural analysis in irregular waves with experimental validation, accepted for J. Ocean Engineering and Marine Energy.

6 Regular waves H.3 m 12 1 H.5 m Experimental Numerical H.5m Relative rotation θr (deg) Experimental Numerical T s H.3m Experimental Numerical T s H.5m T (s) Power average Pc REG (W) T (s) Pc REG (W) T (s) Sun et al JOEME 216 Bending moment

7 Irregular waves (uni-directional) Relative rotation Power average Bending moment

8 Irregular waves s=5 Relative rotation Power average Bending moment

9 Conclusion Linear diffraction analysis accurate for operational wave conditions Effective tool for fatigue analysis Optimisation of energy capture by mechanical damping and hinge height gains extra 2+% power Lab experiments appear less reliable for regular waves than irregular or spread waves when reflections are expected to be minimal due to frequency averaging

10 Geometry optimisation Determine how length of bow beam affects average power and float diameter Assess how constant force damper (simple hydraulic damper) and rectified freewheel clutch affects power compared with linear damper Time domain linear diffraction model (Cummins) with nonlinear damper Stansby, P.K., Carpintero Moreno, E. & Stallard, T Modelling of the 3-float WEC M4 with nonlinear PTO options and longer bow beam, Proc. 2nd Int. Conf. on Renewable Energies Offshore, Lisbon (RENEW 216.

11 Sketch of freewheel clutch Clutch Gearbox Flywheel Induction generator output input

12 schematic pneumatic damper

13 Capture width ratio CWR = average power absorbed/wave power/metre/wavelength of energy period NB NOT normalised by body width and Max CWR possible for single body in heave and pitch or surge is 3/2π.48 CWR Pmax = average power absorbed/ wave power at max power/metre/wavelength of energy period at max power (basically power normalised by max power conditions)

14 validation CWR T p [s] CWR variation with T p : h 12 = h 23 =.8 m ; model ; expt (Beams of equal length)

15 Effect of longer bow beam.4.35 linear damper: CWR and CWR Pmax CWR variations with T p ; spacings.8-.8 m ( ), m ( ), T p [s] m ( ) CWR P max T p [s]

16 variation of CWR with T p.4.3 Spacing.8/ /.8 CWR / T [s] p

17 variation of CWR Pmax with T p.15 Spacing.8/ CWR P max / / T [s] p

18 Experiment and model 1.33/.8 m linear damper H s.4 m.4 3 CWR mod rms mod.35 CWR exp 2.5 rms exp CWR.2 rms T p [s] T p [s]

19 Plots of CWR and relative rotation: beams 1.33/.8 m CWR θrms CWR mod CWR exp 2.5 rms mod rms exp CWR Hs.4 m.15 (2m full scale) rms T p [s] T p [s].35 CWR mod CWR exp 4 rms mod rms exp Hs.6 m (3m full scale) CWR rms T p [s] T p [s].45 CWR mod 7.4 CWR exp rms mod 6 rms exp.35 Hs.8 m (4m full scale) CWR rms T p [s] T p [s]

20 Conclusions Longer bow beam by 5% improves power capture Linear damper performs better than constant force damper Rectifying clutch performs almost as well as linear damper for larger periods and induction generator potentially inexpensive Linear theory gives reasonable predictions in quite large waves H s ~ 4 m Linear analysis also works very well in extreme focussed waves in Paul Taylor presentation

21 LCOE estimates Based on CWR for beams 1.33 /.8 m Steel design 5x lab scale : mass 2.2 tonnes (engineering design by Cammell Laird) 13% 15% 11% 23% 38% Structure & prime mover PTO & control Foundation and mooring Installation Grid connection Carbon Trust 212

22 Relative CWR (Belmullet) M4 x4,5,6,7 lab scale.4.35 Capture width ratio Seapower Pelamis T [s] p

23 Sites with scatter diagrams Belmullet The WaveHub The FabTest Longitude 4 3 California Nova Scotia Leixoes Death Coast Sardinia Latitude

24 LCOE for different sites, pre optimisation of structure and control 2/tonne steel x4 x6 Optimum scale P_ave [kw] LCOE [ ] P_ave [kw] LCOE [ ] P_ave [kw] LCOE [ ] Scale WaveHub, UK FabTest, UK Belmullet, IRL Death Coast, Spain Leixoes, PRT Sardinia, ITA Nova Scotia, CAN California, USA

25 Thanks and questions Stansby,P., Carpintero Moreno,E., Stallard,T.,Maggi,A. 215 Three-float broad-band resonant line absorber with surge for wave energy conversion, Renewable Energy, 78, DOI 1.116/j.renene Stansby,P., Carpintero Moreno,E., Stallard,T. 215 Capture width of the three-float multi-mode multi-resonance broad-band wave energy line absorber M4 from laboratory studies with irregular waves of different spectral shape and directional spread, J. Ocean Engineering and Marine Energy, 1(3), , DOI 1.17/s Santo,H., Taylor,P.H., Eatock Taylor,R., Stansby, P. 216 Decadal variability of wave power production in the North-East Atlantic and North Sea for the M4 machine, Renewable Energy 91, DOI 1.116/j.renene Eatock Taylor,R., Taylor,P.H. and Stansby, P.K. 216 A coupled hydrodynamic-structural model of the M4 wave energy converter, J. Fluids and Struct. 63, DOI 1.116/j.jfluidstructs Stansby, P. K., Gu, H., Carpintero Moreno, E. and Stallard, T. 215 Drag minimisation for high capture width with three float wave energy converter M4, Proc EWTEC Nantes 215. Sun,L., Stansby,P., Zang,J., Carpintero Moreno, E., Taylor,P. 216 Linear diffraction analysis and optimisation of the three-float multi-mode wave energy converter M4 in regular waves including small arrays, J. Ocean Engineering and Marine Energy, 2(4), DOI 1.17/s Stansby, P.K., Carpintero Moreno, E. & Stallard, T Modelling of the 3-float WEC M4 with nonlinear PTO options and longer bow beam, Proc. 2nd Int. Conf. on Renewable Energies Offshore, Lisbon (RENEW 216. Sun,L., Zang,J., Stansby,P., Carpintero Moreno, E., Taylor,P., Eatock taylor,r. 216 Linear diffraction analysis of the three-float multi-mode wave energy converter M4 for power capture and structural analysis in irregular waves with experimental validation, accepted for J. Ocean Engineering and Marine Energy.