Design a model of OWC plant for Sri

Sea wave powered power plant for Sri

Lanka and some aspects of modeling

Presented ByA.M.P. Jayamanne

Why sea wave power for Sri Lanka ?

Sri Lanka has huge potential of wave power

Small frequency variations

Plenty of sites

Can use as a break water

Less environmental impact

Medium rough sea conditions

The technic and why?Propose Oscillating Water Column (OWC)

wave extractor.Promising and proven technology

Simple structure

Less links from wave to turbine which causes the loses minimum

Total concrete collector

An OWC plant…Turbine

ChamberOscillating

water columnIncoming

Water waves

Available Plant..

The 400 kW Oceanlinx wave powered generator off the coast at Port Kembla NSW Australia

Wells - TurbineUse wells turbines because it generates torque in one direction even air flow is bidirectional.A low pressure air turbine

Hub

Generator

Rotor

Stator

Pilot valve

Wave dinamicsPartial Moving

path

Water surface

Sallow water

Zero Crossing

time

Wave height

Deep water

Total energy (P)= Kinetic energy + potential energy

P = [ρg2 /64π]*H2 T ≈ 0.5 H2 T (kw/m)

H = significant wave height = 4* standard deviation of water surface elevation

T = Zero crossing wave time period

Sri Lankan wave potential..

1 2 3 4 5 6

0

20

40

60

80

Bundala

Month

PK

W/m

)

1 2 3 4 5 6 7 8 9 10 11 12

0

2

4

6

8

10

12

14

16

Dodandoova

Month

P k

W/m

1 2 3 4 5 6 7 8 9 10 11 12

020406080

100

Godayaya

Month

P (

kW/m

)

1 2 3 4 5 6

0

20

40

60

80

100

Palatupana

Month

P(K

W/m

)

Best Site – GodayayaMean significant wave height

–2.8mZero crossing time – 11.05 -

13.34Mean zero crossing time –

12.23

Mathematical model

Air way

Added damping/turbin

e

Applied damper/friction

Floating water mass

Wave force

Wave entrance

Buoyancy spring

Applied spring/viscosity

Displacement

Collector

Model Equation.. Applied wave force due to the traveling of wave in to the cession =

F e(t).

Water column displacement for an instant time = y Instant time = t Applied damping coefficient due to friction = f

Applied damping coefficient due to turbine = t

Added water mass = m a

Floating water mss = m f

Applied spring coefficient due to water mass = ks

Buoyancy spring coefficient = kb

d = 1/2( ma + mf ) x [(4 ma2 g2 - t

2) / 4 ] ½

( ma + mf ) d2y/dt2 + t dy/dt + kb y = F e(t).

Modeling..Procedure

Match actual frequency to model frequency and wave forcers

Compare available plants for Sri Lankan conditions Select best plant Scale it to model willing to build Structural and turbine design.

Results

Best plant – NEL ( Developed by Lanchester University and Polytechnic)

Scale Factor - 9.5

Collector..

Turbine..

Conclution of OWC plant performance..

Wells turbines have low efficient ratesEffective energy can captured from waves

to generator is around 12%Reduces performance due to high

frequency changersCollector profile or volume has to change

due to incoming wave frequency and amplitude changers

Sri Lankan wave climates are giving positive behavior to OWC plants.

Need to do more involvement to success

Thank You