Marine Renewables
Group 4
Kenneth Agbeko
Steven Fitzpatrick
Scott Love
“Growing a Scottish Marine Renewable Industry”
• Introduction & Aims of Presentation
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State project aims and objectives
Provide background to Marine Renewable Energy
Discuss methodology/ approach
Present results and conclusions
Highlight policy recommendations
Project Aims and Objectives
• Aim:
– To investigate how best to exploit the potential which
exists for Scotland to develop a successful Marine
Renewable Energy Industry
• Objectives:
– Identify marine resource potential and available
technology to harness it
– Identify supporting structures to help develop and
promote a marine industry
– Identify barriers & challenges that could affect the
development of a marine industry
– Draw conclusions & make recommendations towards
Growing a Scottish Marine Renewable Industry
Background
•
There is a growing need for renewable energy
generation options because of
– Global concerns about CO2 emissions, climate
change and dwindling fossil fuel reserves
– UK government’s obligation under the Kyoto
Protocol agreement
• To reduce CO2 emission to 12.5% of 1990 levels
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Set Targets
•
Wave and tidal resources can help meet
growing energy demands and renewable
energy targets in the UK.
•
Recent estimates put potential energy yield at
around
– Overall UK target - 20% by 2020 (DTI)
– Scotland target – by 2020 (Scottish Executive
2004)
– 50 TWh/y from wave
– 36 TWh/y from marine current
Background
• Wave/Tidal Technologies under
Development around the World
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Oscillating Water Column (Limpet) - UK
Pelamis Wave Energy Converter - UK
Seaflow Marine Current Turbine - UK
Stingray tidal generator - UK
Wave Dragon – Denmark
Pendulator – Japan
Tapchan - Norway
MCT Background
•
Marine Current Turbines (MCT’s) are
recognised as the most readily available form
of technology
– Technologically similar to wind turbines
which is a proven industry
– Expertise easily transferable from both wind
and general offshore industries
– Recognised as closest to commercialisation
compared with other technologies
(source: Wave Energy Council 2001)
•
Scotland can thus kick start a marine industry with
MCT’s and later diversify into wave technologies
with waves having a much larger resource size
towards world leadership status
•
MCT devices are generally
– Either horizontal axis or vertical axis types but
other developers are looking at a ducted type
– Blades are usually between 1 and 3 of lengths
varying from 15m to 20m.
– Turbines are coupled to a generator
– Under water cables transmit generated
electricity to land
MCT Background
• Limiting factors to the size of
marine current resource
– Conflict of interests
• Shipping, boating, coastal fishing,
MOD etc.
– Environmental
• Blocking of migratory fish/ sea
mammals,
sediment transport etc.
– Technical Issues
• Wake shadow effects
• Effects of channel
blockage from large numbers of
MCT’s
Purpose of Technical Focus
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Technical limitation investigated
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Why this direction?
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What was the investigation aimed at?
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How can these blockage issues be investigated?
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Which sites were modelled?
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Reasons
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Effects of channel blockage from large numbers of MCT’s
Literature review pointed to the fact that little work has been done on blockage effects
Technical factors determine to a large extent potential scale of market
How much blockage can be installed?
What is that saturation point?
Is there a power drop off?
A spreadsheet modelling approach was development
Pentland Firth and Kyle Rhea
for these sites choices
availability of velocity data
Close to our “idealised” channel criteria
Both previously identified by 3rd parties as suitable sites for MCT deployment
Procedure/ Methodology
• Idealised Channel Model
– Obtain sea level data from 2 “reservoirs”
by selecting 2 points on either side of
the channel with tidal heights h1 and h2
Side View
h1
h2
– The ideal (theoretical) velocity (Vth) is
therefore estimated as
Top View
Vth  2 g (h1  h2 )
– The theoretical velocity is then
compared with actual measured marine
current velocity (Vact) of the channel to
estimate an effective loss coefficient for
the channel (KL) from
Vact 
2 g (h1  h2 )
1 KL
1
2
Effects of MCT’s
• What effects will arise from placing MCT’s in this channel?
– Extract energy from stream
– Resulting in new revised value for Vact:
VACT 
2 g (h1  h2 )
, where KT  turbine loss coefficient
1  K L  KT
– As KT increases, V decreases but more turbines may mean more
power
– Performed trial and error to obtain an optimum KT value
• Power extracted from the channel was then computed
knowing KT and V
From
1
P  ghQ  K T AV 3
2
Power extracted  KT and V
Results
• Power Flux & Velocity vs. KT for both channels
• Pentland Firth
New Channel Velocity Curve Due to Blockage
4.50
4.00
3.50
45000.00
40000.00
35000.00
30000.00
25000.00
20000.00
15000.00
10000.00
5000.00
0.00
Velocity
Power Flux (W/m2)
Power Flux Versus KT Curve
0
2
4
6
8
10
3.00
2.50
2.00
1.50
1.00
0.50
0.00
12
0
2
4
KT Value
6
8
10
12
KT Value
• Kyle Rhea
Power Flux Versus KT Curve
New Channel Velocity Curve Due to Blockage
4.00
3.50
25000.00
3.00
20000.00
Velocity
Power Flux (W/m2)
30000.00
15000.00
10000.00
2.50
2.00
1.50
1.00
5000.00
0.50
0.00
0.00
0
2
4
6
KT Value
8
10
12
0
2
4
6
KT Value
8
10
12
Results Analysis
• Velocity decreased gradually with increasing KT,
as expected
• Power Flux increased steadily with increasing KT
until a “saturation” point was reached
• Diminishing returns occur after this point
• This led to an investigation into an optimum KT
value
• 40% power per KT drop off was adopted to
represent the optimum KT value
How Many Turbines?
• What does optimum KT represent in terms
of number of turbines?
• To do this,
We have defined solidity as:

MCT swept area
CSA of channel
Cross Sectional Area (CSA)
• And from Betz theorem we obtained a relationship
between KT and solidity as
9
 for max power   K T
8
How Many Turbines?
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With optimum solidity () values the number of turbines that can be
installed in a channel for a full blockage was then determined
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Do interactions occur between the MCT’s?
– Yes but channel model does not account for that hence the need for further
investigations
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How do could that be done?
– CFD modelling
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CFD Methodology
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MCT’s were modelled as porous bodies in an idealised rectangular channel
They were placed in a 2d X 10d “farm” configuration (DTI recommendation)
Model simulated to obtain pressure drop across the turbines
Pressure drop then was used to obtain a KT value from the relation
V2
P  gh  
.KT , where V  actual (new) MC velocity
2
Results
Actual Velocity
Time (mins) in P. Firth (m/s)
-320
4.895862486
-300
5.092541038
-280
5.142449422
-260
5.04407273
-240
4.800397066
-220
4.418818906
-200
3.910920587
-180
3.292118738
-160
2.58119633
-140
1.79973254
-120
0.971447743
-100
0.121483507
-80
-0.724360547
5 MCT ARRAY
Time Case
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1a
1b
2
2a
2b
3
3a
3b
4
4a
4b
5
P1
15.8
16.9
17.3
16.6
15
12.6
9.8
6.94
4.27
2.09
0.61
0.00958
-0.0236
P2
P
E
P

-1.38
17.18 0.016761
-1.68
18.58 0.0181268
-1.69
18.99 0.0185268
-1.66
18.26 0.0178146
-1.59
16.59 0.0161854
-1.45
14.05 0.0137073
-1.2
11 0.0107317
-0.855
7.795 0.0076049
-0.522
4.792 0.0046751
-2.47
4.56 0.0044488
-0.007
0.617 0.000602
7.09E-04 0.008871 8.655E-06
0.379
0.4026 0.0003928
K T for 5 MCT array
0.001398527
0.001397921
0.001401171
0.001400375
0.001404747
0.00140401
0.001403269
0.001403367
0.001403398
0.002746977
0.001275711
0.001172854
0.001497167
Results Analysis
• Calculation of Site Rated Capacity
Channel Model Estimate by Joule
KT

Estimate (GW)
Report (GW)
Estimate by Black
& Veatch (GW)
Kyle Rhea
0.74
0.83
0.12
N/A
1.35
Pentland Firth
0.63
0.71
4.70
6.1
N/A
• BV analysis used a “significant impact factor” approach
which simply applied a loss factor of 20% to the total
available resource
– This factor is not site specific and also over estimates the rated site
capacity (as conceded by Black & Veatch 2004)
– Our approach seems to provide a more site specific result taking into
account blockage effects
– Leading to a far more conservative and realistic estimate
– This is demonstrated clearly in the Comparison of values for Kyle
Rhea
Results Analysis
KT
Kyle Rhea

Channel
Model
Estimate (GW)
Estimate by
Joule Report
Estimate by Black
& Veatch (GW)
(GW)
0.74 0.83 0.12
N/A
1.35
Pentland Firth 0.63 0.71 4.70
6.1
N/A
• Pentland Firth data is slightly closer
– Compared with data from Joule Report (ref. JOU2-CT_93-1355)
– Their approach concedes that only a “fraction of this value would be
converted to useful energy”
– Again channel model estimate is more conservative
– There seems to be a trend of overestimation of site capacity
– The blockage effect in our channel model has addressed this to a degree
Economical Implications
• Will the large number of turbines obtained be financially
feasible?
• How can this be verified and investigated?
– Financial Spreadsheet Model Approach Adopted
• What were the inputs to the spreadsheet?
– Turbine data
– Tidal data
– Scheme data
• Data then processed using a costing analysis
• Outputs from the model
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Cash flow
Break even point analysis
Payment plan
Energy cost per kWh
Results
Result analysis
• Taking Vadjusted at optimum KT, it is possible to evaluate
cost per kWh at this value
• Gives costs for a particular size of MCT farm
• Crucial in determining competitiveness
• Financial model allows the user to specify number of
turbines in the farm
• The results for cost per kWh are shown below:
Pentland Firth
Kyle Rhea
£/kWh for a 30 MCT farm
0.065
0.0695
£/kWh for a 4000 MCT farm
0.0351
0.0375
Result analysis
• Conclusions & Future Work:
– To reduce the cost of energy significantly a large number of MCT’s
required.
– Economies of scale will inevitably further lower costs
– This model is primarily intended for:
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cost/ kWh analysis
basic level of cost-benefit analysis
annual cost estimates
break-even analysis for investors.
– Further development of model would include:
• depreciation on capital and equipment
• pre and post tax values and
• Influence of economies of scales
Environmental Considerations
• Possible Impacts identified include
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Loss of habitat for flora and fauna
Changes to seabed morphology and current hydrology
Changes in the sedimentation and turbidity of water
Changes to the wave regime
Increased risk of collisions from marine vessels
Objections due to visual impact
General Conclusions
• How big a limitation on MCT numbers is imposed by channel
blockage effects?
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Saturation point will be reached
This point occurs at a reasonably high level of channel blockage
This seems to be optimistic purely from a technical approach
Main limitations however will be financial and environmental
• Technical and economical feasibility are two independent issues
– Technical limits could never be reached due to unfeasibility (i.e full
channel blockage)
– Economic factors such as cost, market prices, incentives etc. will limit
farm sizes
• Environmental constraints will limit installed capacity
– Shipping & fishing activities
– Disruption to migratory fish/ sea mammal patterns
General Conclusions
• Impact on future projections for growth of the industry
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Technical limitations are not the greatest constraint
Environmental issues will be key
Uncertainty due to risk and lack of direction
Not good for investor confidence
Need clear guidance and leadership from UK/ Scottish governments
• Comparisons with the development of the Danish on-shore wind
industry from the 1970’s
– UK & Scotland is in a similar situation to Denmark in the 1970’s
– Scotland is ideally placed to mimic the Dane’s success story
– Many of the World’s leading academics and experts in wave and tidal
energy are in resident in the UK
– There is considerable potential to export technology worldwide and
become a World leader in MCT’s
– Benefits to export economy and skilled jobs market
Executive Summary/ Policy Recommendations
• There should be competitive tariff’s
• The electricity grid needs upgrading
– Redeveloped into a more decentralised
structure
– Capable of dealing with diverse generation
options
• Additional cost must not be burdened upon
the developer
• Technological learning and development will
help reduce cost
• However the industry must be nurtured and
managed
Executive Summary/ Policy Recommendations
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A long term development plan beyond 2010
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Governments must state its commitment to the
marine sector
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A closer look should be taken at the funding
mechanisms for marine project
– especially for ways to bridge the gap between the R&D
stage and the supported commercial stage.
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An intelligent funding approach should be adopted
– Those projects which perform best should then receive
further funding
Questions?