SuperGen UK Centre for Marine Energy Research

Annual Assembly 2013

STEP-WEC: STEP CHANGE FOR WAVE

ENERGY CONVERSION THROUGH

FLOATING MULTI-BODY MULTI-MODE

SYSTEMS IN SWELL

.

UKCMER

UKCMER Step-WEC:Consortium of the Universities of Manchester, Oxford and Bath

led by Professor Peter Stansby of University of Manchester

Proposal statement

AIM

To design, analyse and optimise floating systems for wave energy conversion of

approximately 10 MW capacity in swell and mixed swell/wind waves based on

two or more dynamically connected bodies with multi-mode response and to

assess their interaction, particularly power generation, within an array.

UKCMER

Proposal statement

OBJECTIVES

1. To explore wave energy concepts with multi-mode and multi-body response using

simplified nonlinear time stepping modelling, small scale (1:100) wide flume

experiments (Manchester), and 1:20 scale basin testing (Plymouth)

2. To develop power/response prediction methods for multi-mode systems in swell and

random (wind) waves with 1st and 2nd order diffraction theories (using codes

WAMIT and DIFFRACT) providing input into nonlinear time stepping

formulations. Oxford using DIFFRACT.

3. To analyse interaction of swell and random (wind) waves for a wide range of

conditions using DIFFRACT. This analysis is relevant to any form of wave

energy conversion.

4. To measure interaction of directional random waves, swell and currents in the

Edinburgh FloWave wave/current tank, comparing with DIFFRACT.

5. To assess performance of arrays in intermediate-to-deep water (20-100 m). Up to 4

systems will be analysed in a group and periodic boundaries will be used to

analyse infinite rows.

UKCMER

PROGRESS with PhD student Efrain Carpintero Moreno

Proposal 2012

2013 January H=0.02m T=0.85s

Shapes optimised using WAMIT in 2 body heave

UKCMER

3.5 4 4.5 5 5.5 6 6.5 7 7.5 80

0.1

0.2

0.3

0.4

0.5

0.6

0.7

[rad/s]

Po

wer

[W

]

Hs=0.02m

Hs=0.03m

Hs=0.04m

Hs=0.05m

4 4.5 5 5.5 6 6.5 7 7.5 80

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

[rad/s]

Po

wer

[W

]

H = 0.01m

H = 0.015m

H = 0.02m

H = 0.025m

H = 0.03m

H = 0.04m

H = 0.05mregular

random

AVERAGE POWERS

Scale 1:50

Hs=2m

Pav = 180kW

Scale 1:100

H=1m

Pav = 250 kW

SCOPE FOR OPTIMISATION

UKCMER

Next 1:10 scale tests at Plymouth ocean basin

Device built by Cammell Laird

Hydraulic actuator donated by Rexroth Bosch

UKCMER

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18-50

0

50

100

150

200

250

H [m]

Po

ut [

W]

2.2

2.4

2.5

2.6

2.8

3.0

3.2

Regular wavesT [s]

Note:-Solid lines means theesperimental results.

-Dashed lines meansthe Quadratic fitting.

-Valve setting at 1

0 0.05 0.1 0.15 0.2 0.25 0.3-20

0

20

40

60

80

100

120

140

160

Hs [m]

Po

ut [

W]

2.2

2.4

2.6

2.8

3.2

3.6

2.4

2.8

Note:-Solid lines means theesperimental results.

-Dashed lines meansthe Quadratic fitting.

- The square mark means15mins test length.

-Valve setting at 1

Ramdom waves Tp [s]

Regular

Random

JONSWAP

1:16 scale

H=1m T=10s

Pav= 320kW

1:8 scale

Hs=2m Tp=7s

Pav = 150kW

AVERAGE POWERS

UKCMER

But scope for improvement:

• Pivot point was not optimum – known from lab tests

• PTO is simple linear damper – scope for optimisation

• Body motions are large and drag significant – may be reduced

with bigger radius on base – tests planned in lab

FURTHER TESTS AT PLYMOUTH 2013 – 10th -16th December

•Optimising PTO location

•Testing in directional waves

•Testing sea keeping in extreme waves and measuring mooring

loads

Mathematical model of 3 body system has been set up and is being tested

Time stepping with WAMIT coefficients (fully interactive) – method for

handling pivot point incorporated – demonstrates effect of drag coefficient

on power

UKCMER

M4M wave energy conversion

Multi-body Moored Megawatts Multi-Mode

CRITERIA

1. M4M electricity generation cost competitive or less than offshore wind energy

2. Moored floating device for easy deployment and long-term maintenance in port

3. Hydrodynamic design with 3 bodies responding in anti-phase to heave, pitch and surge

modes of motion with variable resonance

4. Broad band frequency response through the different modes to cover offshore wave

conditions

5. Hydraulic power take off on one hinge, accessible from deck for maintenance

6. Power take off automatically adapts to wave conditions

7. Survivable in extreme waves with no power generation

MACE Wave Ltd

Peter Stansby