Marine Renewables

Group 4Kenneth Agbeko

Steven FitzpatrickScott Love

• Introduction & Aims of Presentation

– State project aims and objectives– Provide background to Marine Renewable Energy– Discuss methodology/ approach– Present results and conclusions– Highlight policy recommendations

“Growing a Scottish Marine Renewable Industry”“Growing a Scottish Marine Renewable Industry”

• 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

Project Aims and ObjectivesProject Aims and Objectives

• 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

• Set Targets – Overall UK target - 20% by 2020 (DTI)– Scotland target – by 2020 (Scottish Executive

2004)

• 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

– 50 TWh/y from wave– 36 TWh/y from marine current

BackgroundBackground

• Wave/Tidal Technologies under Development around the World

– 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

BackgroundBackground

• Marine Current Turbines (MCT’s) are recognised as the most readily available form of technology

– Technologically similar to wind turbineswhich 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 BackgroundMCT 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

MCT BackgroundMCT Background

• Technical limitation investigated– Effects of channel blockage from large numbers of MCT’s

• Why this direction?– 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

• What was the investigation aimed at?– How much blockage can be installed? – What is that saturation point?– Is there a power drop off?

• How can these blockage issues be investigated?– A spreadsheet modelling approach was development

• Which sites were modelled?– Pentland Firth and Kyle Rhea

• Reasons 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

Purpose of Technical FocusPurpose of Technical Focus

• 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

– The ideal (theoretical) velocity (Vth) is therefore estimated as

– 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

)(2 21 hhgVth

Procedure/ MethodologyProcedure/ Methodology

Side View

Top View

h1

h2

1 2

Lact K

hhgV

1

)(2 21

• What effects will arise from placing MCT’s in this channel?– Extract energy from stream– Resulting in new revised value for Vact:

– 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

tcoefficienturbineKwhereKK

hhgV T

TLACT loss ,

1

)(2 21

Effects of MCT’sEffects of MCT’s

V and extractedPower TK

3

2

1AVKhQgP T

Power Flux Versus KT Curve

0.005000.00

10000.0015000.0020000.0025000.0030000.0035000.0040000.0045000.00

0 2 4 6 8 10 12

KT Value

Po

wer

Flu

x (W

/m2)

ResultsResults

New Channel Velocity Curve Due to Blockage

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0.50

1.00

1.50

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2.50

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3.50

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4.50

0 2 4 6 8 10 12

KT Value

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y

• Power Flux & Velocity vs. KT for both channels

• Pentland Firth

• Kyle RheaPower Flux Versus KT Curve

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5000.00

10000.00

15000.00

20000.00

25000.00

30000.00

0 2 4 6 8 10 12

KT Value

Po

we

r F

lux

(W

/m2

)

New Channel Velocity Curve Due to Blockage

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0.50

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KT Value

Vel

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ty

Results AnalysisResults 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

• What does optimum KT represent in terms of number of turbines?

• To do this, We have defined solidity as:

• And from Betz theorem we obtained a relationship between KT and solidity as

channel ofCSA

areaswept MCT

How Many Turbines?How Many Turbines?

Cross Sectional Area (CSA)

TK8

9power max for

• With optimum solidity () values the number of turbines that can be installed in a channel for a full blockage was then determined

• Do interactions occur between the MCT’s?– Yes but channel model does not account for that hence the need for further

investigations

• How do could that be done? – CFD modelling

• CFD Methodology– 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

How Many Turbines?How Many Turbines?

velocityMC (new) actual V where,.2

2

TKV

hgP

ResultsResults

5 MCT ARRAY

Time (mins) Time Case P1 P2-320 4.895862486 1 15.8 -1.38 17.18 0.016761 0.001398527-300 5.092541038 1a 16.9 -1.68 18.58 0.0181268 0.001397921-280 5.142449422 1b 17.3 -1.69 18.99 0.0185268 0.001401171-260 5.04407273 2 16.6 -1.66 18.26 0.0178146 0.001400375-240 4.800397066 2a 15 -1.59 16.59 0.0161854 0.001404747-220 4.418818906 2b 12.6 -1.45 14.05 0.0137073 0.00140401-200 3.910920587 3 9.8 -1.2 11 0.0107317 0.001403269-180 3.292118738 3a 6.94 -0.855 7.795 0.0076049 0.001403367-160 2.58119633 3b 4.27 -0.522 4.792 0.0046751 0.001403398-140 1.79973254 4 2.09 -2.47 4.56 0.0044488 0.002746977-120 0.971447743 4a 0.61 -0.007 0.617 0.000602 0.001275711-100 0.121483507 4b 0.00958 7.09E-04 0.008871 8.655E-06 0.001172854

-80 -0.724360547 5 -0.0236 0.379 0.4026 0.0003928 0.001497167

Actual Velocity in P. Firth (m/s)

PE

array MCT 5for TKP

Results AnalysisResults Analysis

• Calculation of Site Rated Capacity

• 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

KTChannel Model Estimate (GW)

Estimate by Joule 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

Results AnalysisResults Analysis

• 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

KT

Channel Model Estimate (GW)

Estimate by Joule 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

Economical ImplicationsEconomical 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

– Cash flow– Break even point analysis– Payment plan– Energy cost per kWh

ResultsResults

Result analysisResult 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: £/kWh for a 30 MCT farm £/kWh for a 4000 MCT farm Pentland Firth 0.065 0.0351 Kyle Rhea 0.0695 0.0375

Result analysisResult 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:• 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 ConsiderationsEnvironmental Considerations

• Possible Impacts identified include

– 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

• How big a limitation on MCT numbers is imposed by channel blockage effects?– 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 ConclusionsGeneral Conclusions

• Impact on future projections for growth of the industry

– 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

General ConclusionsGeneral Conclusions

• 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 RecommendationsExecutive Summary/ Policy Recommendations

• A long term development plan beyond 2010

• Governments must state its commitment to the marine sector

• 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.

• An intelligent funding approach should be adopted

– Those projects which perform best should then receive further funding

Executive Summary/ Policy RecommendationsExecutive Summary/ Policy Recommendations

Questions?Questions?