Group 4 – Marine Energy Marine Current Modelling For Energy Production James Glynn Kirsten Hamilton Tom McCombes Malcolm MacDonald James Glynn Kirsten.

Group 4 – Marine EnergyGroup 4 – Marine EnergyGroup 4 – Marine EnergyGroup 4 – Marine Energy

Marine Current Modelling For Energy Production Marine Current Modelling For Energy Production

James Glynn Kirsten HamiltonTom McCombes

Malcolm MacDonald

James Glynn Kirsten HamiltonTom McCombes

Malcolm MacDonald

Project DefinitionProject Definition

• Investigate the characteristics of the tidal resources in Scotland and demonstrate how to match those resources with the appropriate Marine current technology

• Investigate the characteristics of the tidal resources in Scotland and demonstrate how to match those resources with the appropriate Marine current technology

Project FlowchartProject FlowchartSTAGE 1

A. Resource Investigation B. Technology Investigation

ii) Vertical axis turbine

iii) Oscillating Hydrofoil

i) Horizontal

axis turbine TOMS software

A. Matching Methodology

STAGE 2

Environmental Impact & Planning

Assessment

B. Case study

Mapping Tidal Data

STAGE 3

Expert system

A. Conclusion of Resource AnalysisA. Conclusion of Resource Analysis

• Tidal Flow Model Resultant Phase & Tidal Flow

• UKHO EasyTide port & Chart surface flow data Cyclic Bulk Flow Velocity Corrected Flow, Meander, Surface Friction,

Venturi effects Energy Loss. Manning Vs Bernoulli

• Velocity Shear Model - TOM’s Detail Bathymetry Vs Approx Geometry Shear Effects Boundary Layer Thickness Manning No. Cf & Drag Correlation

• Vertical & Horizontal Vel Distribution

• Tidal Flow Model Resultant Phase & Tidal Flow

• UKHO EasyTide port & Chart surface flow data Cyclic Bulk Flow Velocity Corrected Flow, Meander, Surface Friction,

Venturi effects Energy Loss. Manning Vs Bernoulli

• Velocity Shear Model - TOM’s Detail Bathymetry Vs Approx Geometry Shear Effects Boundary Layer Thickness Manning No. Cf & Drag Correlation

• Vertical & Horizontal Vel Distribution

Model ValidationModel Validation

The Strait of MessinaThe Strait of Messina

The Strait of MessinaThe Strait of MessinaModel ValidationModel Validation

• Map Strait of Messina Bathymetry•

• Seabed Geology Surface roughness Cf wall

• Map Strait of Messina Bathymetry•

• Seabed Geology Surface roughness Cf wall

Model ValidationModel Validation

Model ValidationModel Validation

• Map Strait of Messina Bathymetry

Seabed Geology Surface roughness Cf wall

• Map Strait of Messina Bathymetry

Seabed Geology Surface roughness Cf wall

Model ValidationModel Validation

Seabed equivalent diameter

10km 100m 10m 1m 10cm 1cm 1mm

Seabed equivalent diameter

10km 100m 10m 1m 10cm 1cm 1mm

Seabed equivalent diameter

10km 100m 10m 1m 10cm 1cm 1mm

Seabed equivalent diameter

10km 100m 10m 1m 10cm 1cm 1mm

100 200 300 400 500 600 700 800 900 1000 1100

10

20

30

40

50

60

70

80

0.5

1

1.5

2

100 200 300 400 500 600 700 800 900 1000 11001.5

2

2.5Velocity at non-dimensional depth 1

Cross-streamw ise ordinate

Vel

ocity

[m/s

]

Model ValidationModel Validation

Model ValidationModel Validation

100 200 300 400 500 600 700 800 900 1000 11001.5

2

2.5Velocity at non-dimensional depth 1

Cross-streamw ise ordinate

Vel

ocity

[m/s

]

Model ValidationModel Validation

• Velocity profile from Coles law assumes turbulent BL & similitude. May not be the case

• Algorithm computationally expensive: savings if power law is adopted

• Need other profiles to compare with: USGS use 7th power law

• Is just a curve fit

• Velocity profile from Coles law assumes turbulent BL & similitude. May not be the case

• Algorithm computationally expensive: savings if power law is adopted

• Need other profiles to compare with: USGS use 7th power law

• Is just a curve fit

B. Conclusion of Technology Investigation

B. Conclusion of Technology Investigation

• 3 Main Generic Technology Types Horizontal Axis Turbine,

Oscillating Hydrofoil. Quasi-Dynamic Modelling,

BEM, Yaw Correction, Time Step

Flow conditions & Model Geometry

System Loads Torque Power

• 3 Main Generic Technology Types Horizontal Axis Turbine,

Oscillating Hydrofoil. Quasi-Dynamic Modelling,

BEM, Yaw Correction, Time Step

Flow conditions & Model Geometry

System Loads Torque Power

Vertical Turbine ModelVertical Turbine Model

• Multi-Streamtube BEMS model for Darrieus type turbine is in production. Nothing really to show for it. Yet. Except:

• Multi-Streamtube BEMS model for Darrieus type turbine is in production. Nothing really to show for it. Yet. Except:

SIF & Blockage effectsSIF & Blockage effects• Significant Impact Factor> what exactly is it?

The recognition and quantification of the fact that placing energy extraction devices in a tidal stream must vary the characteristics of that resource

If the average flow in a stream is 2.0 m/s, and one was to place 5 turbines in that stream, the average flow rate will experience a net decrease, with localised increases, causing turbulence and potentially affecting the actual topography of the site through sediment transport, scouring and so forth

Chow and Manning have to agree, that placing obstructions in a tidal stream reduces the net flow rate, due to blockage and energy losses.

If the kinetic energy flux in a stream is a function of velocity cubed and c.s.a, this energy comes from the gravitational effects of the sun and moon. If one extracts a portion of this energy from the stream, which has had work done on it by gravity, mass continuity tells us therefore that the velocity must decrease, inversely with energy extraction.

It would be very handy to be able to model this, as some kind of optimal deployment ratio must be achievable

Since work is being done, on the body of water, it will continue to be done after exiting the turbine, thus we may expect the flow to rejuvenate at some point.

The ability of flow recovery (turbulent, slow) is an approximation of free stream

• Significant Impact Factor> what exactly is it? The recognition and quantification of the fact that placing energy extraction

devices in a tidal stream must vary the characteristics of that resource If the average flow in a stream is 2.0 m/s, and one was to place 5 turbines in that

stream, the average flow rate will experience a net decrease, with localised increases, causing turbulence and potentially affecting the actual topography of the site through sediment transport, scouring and so forth

Chow and Manning have to agree, that placing obstructions in a tidal stream reduces the net flow rate, due to blockage and energy losses.

If the kinetic energy flux in a stream is a function of velocity cubed and c.s.a, this energy comes from the gravitational effects of the sun and moon. If one extracts a portion of this energy from the stream, which has had work done on it by gravity, mass continuity tells us therefore that the velocity must decrease, inversely with energy extraction.

It would be very handy to be able to model this, as some kind of optimal deployment ratio must be achievable

Since work is being done, on the body of water, it will continue to be done after exiting the turbine, thus we may expect the flow to rejuvenate at some point.

The ability of flow recovery (turbulent, slow) is an approximation of free stream

SIFSIF• ..investigators have also noted that for any site, only a finite proportion of the

total energy can be extracted without significantly altering the site’s general flow speed, which could have economic and environmental consequences..

• The SIF is unique to particular sites and may vary between 10% and 50% of the energy in the flow Carbon Trust 2005

• RGU’s envir impact suggest 10% max flow reduction ~ could be more• Packing densities suggested at 60m lateral and 250m longitudinal • Based on Chow’s Open Channel Hydraulics obstruction correction factors

can be applied to a case study, with sensitivity analysis, to see effects• Flow velocity is not constant, but varies with the sine of the period, at the

specified instant, as does time-step acceleration, work done and force, if desired

• Further, flow passes through the swept area in a quantity depending on efficiency and pitch angle (axial predominantly).

• Using these parameters, Chow’s correction factors and sensitivity SIF can be calculated, and related back to previous work, Couch, Bryden.

• ..investigators have also noted that for any site, only a finite proportion of the total energy can be extracted without significantly altering the site’s general flow speed, which could have economic and environmental consequences..

• The SIF is unique to particular sites and may vary between 10% and 50% of the energy in the flow Carbon Trust 2005

• RGU’s envir impact suggest 10% max flow reduction ~ could be more• Packing densities suggested at 60m lateral and 250m longitudinal • Based on Chow’s Open Channel Hydraulics obstruction correction factors

can be applied to a case study, with sensitivity analysis, to see effects• Flow velocity is not constant, but varies with the sine of the period, at the

specified instant, as does time-step acceleration, work done and force, if desired

• Further, flow passes through the swept area in a quantity depending on efficiency and pitch angle (axial predominantly).

• Using these parameters, Chow’s correction factors and sensitivity SIF can be calculated, and related back to previous work, Couch, Bryden.

Results analysisResults analysis

• Study undertaken on two distinct sites• Some interesting relationships…

Further model input information perhaps Suggested: “..analysis suggests a non-linear

relationship between energy extracted and velocity deficit.” C&B

10% extraction = 5 k rejuvenation/recovery distance

• Results: Channel used displays venturi effects, RGU have square cross-section, and uniform length, but general accord with findings

• Study undertaken on two distinct sites• Some interesting relationships…

Further model input information perhaps Suggested: “..analysis suggests a non-linear

relationship between energy extracted and velocity deficit.” C&B

10% extraction = 5 k rejuvenation/recovery distance

• Results: Channel used displays venturi effects, RGU have square cross-section, and uniform length, but general accord with findings

AnalysisAnalysis

Energy capture vs deployment

0

1E+13

2E+13

3E+13

4E+13

5E+13

6E+13

7E+13

8E+13

9E+13

1E+14

3.64297707 7.28595414 10.92893121

Number of turbines

kW

h p

er year

.

Energy capture

Suggested optimum

Technology ComparisonsTechnology Comparisons

• Efficiency-Velocity-Area 3D Curve Optimal site specific device characteristics Extractable energy

• For each technology compare: Size of inflow AREA Flow VELOCITY POWER output or EFFICIENCY

• Allow tidal developer to immediately identify how the different technologies perform in respect to their size and the relationship to velocity and efficiency

• Efficiency-Velocity-Area 3D Curve Optimal site specific device characteristics Extractable energy

• For each technology compare: Size of inflow AREA Flow VELOCITY POWER output or EFFICIENCY

• Allow tidal developer to immediately identify how the different technologies perform in respect to their size and the relationship to velocity and efficiency

Proposed MethodologyProposed Methodology

• Objective : To define rules to match the most appropriate technology to a particular resource site

• A number of tools have been developed throughout the project for this purpose: Surface Tidal Current Spreadsheet The influence of shear on the Velocity distribution for

a profile 3 generic technology models

• Performing analysis between different technologies and their power output and efficiency for varying flow

• Objective : To define rules to match the most appropriate technology to a particular resource site

• A number of tools have been developed throughout the project for this purpose: Surface Tidal Current Spreadsheet The influence of shear on the Velocity distribution for

a profile 3 generic technology models

• Performing analysis between different technologies and their power output and efficiency for varying flow

Proposed Methodology Proposed Methodology

• 2 parts Analysing resource Matching the resource with a particular technology for

the most suitable power output

• Resource Methodology: Manual, step by step process Essentially complete

• Technology Methodology Preliminary stages and defining logic for the process Hopefully automated process with a series of inputs

and programmed outputs

• 2 parts Analysing resource Matching the resource with a particular technology for

the most suitable power output

• Resource Methodology: Manual, step by step process Essentially complete

• Technology Methodology Preliminary stages and defining logic for the process Hopefully automated process with a series of inputs

and programmed outputs

Reso

urce M

etho

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Technology MethodologyTechnology Methodology

• Use the velocity distribution of the profile to answer the following questions: What type of technology to use? What size of the machine? How many machines? Where to locate the machines? What is the combined power output of the machines? What is the efficiency of the machines? What is the appropriate distance that the next set of

machines should be spaced along the length the channel?

• Use the velocity distribution of the profile to answer the following questions: What type of technology to use? What size of the machine? How many machines? Where to locate the machines? What is the combined power output of the machines? What is the efficiency of the machines? What is the appropriate distance that the next set of

machines should be spaced along the length the channel?

Technology MethodologyTechnology Methodology

• Calculate the most appropriate range of velocity for various modular sizes of each technology type

• e.g. for arbitrary values …

• Calculate the most appropriate range of velocity for various modular sizes of each technology type

• e.g. for arbitrary values …

Type of Technology and most Appropriate Size for Velocity Range

Flow velocity Velocity RangeHorizontal

TurbineVertical Turbine

Oscillating Hydrofoil

v1 2.0 - 2.2

size 1

size 1

size 1v2 2.3 - 2.5

v3 2.6 - 2.9

size 2

v4 3.0 - 3.2

size 2

v5 3.3 - 3.5

v6 3.6 - 3.9

size 2v7 4.0 - 4.2

v8 4.3 - 4.5

size 3

v9 4.6 - 4.9

size 3v10 5.0 - 5.2

size 3v11 5.3 - 5.5

v12 5.6 - 5.9

Tech

no

log

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Tech

no

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WIP: WebsiteWIP: Website

Next Steps:Next Steps:

• Finish programming and calculations for the resource methodology & (quasi-rigorous) validation of all models

• Complete case study on the Sound of Jura to prove robustness of work and further quantify methodology

• Examine economic and cost issues for different technology types and resource characteristics

• Complete website

• Finish programming and calculations for the resource methodology & (quasi-rigorous) validation of all models

• Complete case study on the Sound of Jura to prove robustness of work and further quantify methodology

• Examine economic and cost issues for different technology types and resource characteristics

• Complete website