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Scaling Up to
Reduce Costs:
The Way Forward for
Tidal Turbines?
Peter Fraenkel
Fraenkel-Wright Ltd
Typical unit-cost breakdown (£/kW):
different sizes of single rotor turbines note: rated velocity 2.5m/s
Economies of Scale:
fixed and variable overhead costs
Power (MW)
capital
cost
£millions
0
2
4
6
8
10
12
14
16
1 1.5 2 2.5 3 3.5 4 4.5 5
Fixed o/h £M variable costs £M
Economies of Scale:
fixed and variable overhead costs
Power
(MW)
cost-effectiveness
£millions/MW
installed
0
1
2
3
4
5
6
1 1.5 2 2.5 3 3.5 4 4.5 5
Cost-effectiveness (£M/MW) fixed o/h (£M/MW)
Economies of Scale:
fixed and variable overhead costs
What are fixed overhead costs? Any and all marine renewable energy projects have similar fixed overhead
costs, i.e., costs that are independent of scale and power of the systems.
The additional variable costs will be proportional to power. Most budget
heads contain a varying mixture of fixed and variable costs. E.g.:-
System
size
Fixed
costs
Variable
costs
Total cost Unit cost
£k/MW
Financial &
consents
1MW
4MW
£360,000
£360,000
£20,000
£50,000
£380,000
£410,000
380
102
Infrastructure &
installation
1MW
4MW
£1,200,000
£1,200,000
£330,000
£800,000
£1,530,000
£2,000,000
1,530
500
Machine costs 1MW
4MW
£450,000
£450,000
£2,350,000
£7,200,000
£2,800,000
£7,650,000
2,800
1,912
Total 1MW
4MW
£2,010,000
£2,010,000
£2,700,000
£8,050,000
£4,710,000
£10,060,000
4,710
2,515
DECC levelised cost estimates for CfD:
different electricity generation technologies Projects commissioning in
2014 (£/MWh)
Projects commissioning in
2020 (£/MWh)
Offshore wind Round 2
CfD strike price
131-168
155
105-135
<135
Offshore wind Round 3
CfD strike price
144-189
155
115-152
<135
Large scale solar PV
CfD strike price
114-131
120
83-94
<100
CCGT (gas) 73-76 79-83
Nuclear new build n.a. 79-102
Tidal Stream 305 (for 1st 30MW) 105
7
wind - the big one over 3GW operational offshore
(approx 300GW onshore)
75GW planned offshore by 2020
28% p.a. growth last 5 years
Wind turbine development
1980-2005
double the energy per MW installed
and at the same time halve the costs
....economies of scale
2010
7500kW
130m
100m
20,000,000kWh
1980 - 2010
16m dia
640kW
430kNm
24m dia
1440kW
1450kNm
Increasing Rotor Size to get more Energy torque & thrust increase faster than energy capture
Rotor Diameter (m)
Example:
f or 16m to 24m increase:-
• 50% increase in rotor diameter
• 125% more power (and energy)
• 237% more torque (and thrust)
Experience ... the word we use to
describe our mistakes
river current
turbine on the Nile
1978 - 1982
world’s first tidal
turbine, Loch
Linnhe - 1994-5
5 kW
20 kW
300 kW
1200 kW
MCT Seaflow,
Lynmouth,
2003-2009
MCT SeaGen,
Strangford
Narrows
2008- ?
SuperTideGen (TM) : 4MW @ 2.4m/s 2018? Fraenkel-Wright Ltd
4000 kW
Super-TideGen: four rotors
4MW at only 2.4m/s – true economies of scale
4 rotors – 762 sq.m. – twice the power of any known competitor
Rotors near surface – 20% more energy than for submerged system
Rapid and low cost installation and retrieval
Rotors can be raised above the surface in a few minutes
Super-TideGen: two rotors raised for maintenance
SuperTidegen 4MW @ 2.4m/s – cost projection Key ref
Description No. off
Dimensions (m) Unit Mass (est)
(tonne)
Total mass (tonne)
Cost (£ 000s)
1 Catamaran hull 2 6 x 6 x 80 300 600 £1,500,000
2 Superstructure 1 50 x 30 x 5 340 342 £855,400
3 Powertrain wings 4 15 x 6 x 0.5 30 120 £360,000
4 Power trains 4 10 x 4 x 4 (20m rotor) 100 400 £4,000,000
5 Mooring and pile 2 10 x 2 + 200m cable 200 400 £800,000
6 systems (hydraulic/electronic) £100,000
totals 1862 £7,615,400
£/ MW £1,903,850
Installation will be ~£2Million giving an installed cost of ~£10million
i.e. Installed cost circa £2.5million per MW
15
tidal turbine revenue earning capacity importance of rotor swept area
Present day systems Annual Energy with 45% LF *
1 x 18m rotor (254m2) 0.86 MW GWh/yr
1 x 20m rotor (314m2) 1.06 MW GWh/yr
2 x 18m rotors (508m2) 1.72 MW GWh/yr
2 x 20m rotors (628m2) 2.12 MW GWh/yr
Super Tide-Gen
(Fraenkel-Wright design)
Annual Energy with 45% LF *
4 x 16m rotors (804m2) 2.72 MW GWh/yr
4 x 20m rotors (762m2) 4.24 MW GWh/yr
4 x 22m rotors (942m2) 5.14 MW GWh/yr
** assumes 42% system efficiency and 95% availability
in 2 yrs
in 3 yrs
in 4 yrs
now
in 1 yr
in 1 yr
in 1 yr
future
3.2
4.0
6.4
7.9
10.2
15.9
19.2
£0.00
£50.00
£100.00
£150.00
£200.00
£250.00
£300.00
£350.00
£400.00
£450.00
£500.00
0 1 2 3 4 5 6 7
£/MWh
Tidal Cost of Generation v Rated Power Assuming 10%discount rate, 15 year life and 40% Capacity Factor
Rated Power at 2.5m/s MW
DECC strike price
tidal stream 1st 30MW @ £305
probable DECC strike price
for offshore wind £135/MWh
SuperTideGen: tidal stream energy comes of age
Fraenkel-Wright Ltd
Economies of scale: 4MW @ 2.4m/s at potential cost of <£M 2.5/MW
