Transcript An Overview of the Technology and Economics of Offshore Wind Farms

Renewable Energy Research Laboratory
An Overview of the Technology
and Economics of
Offshore Wind Farms
James F. Manwell, Ph.D.
University of Massachusetts
Renewable Energy Research Laboratory
Typical Offshore Windfarm
20, 2 MW Turbines
Middelgrunden Wind Farm (off Copenhagen, Denmark)
University of Massachusetts
Photo: J. Manwell
Renewable Energy Research Laboratory
Winds off Massachusetts
• Excellent wind
resource off the
coast
• Wind speeds highest
furthest from shore
Map: True Wind Solutions, with support from Mass. Tech.
Collaborative, Northeast Utilities, CT Innovations
University of Massachusetts
Renewable Energy Research Laboratory
Typical Week of Wind in
Nantucket Sound
Wind Speed, B&C, Nov 8-15, 2002
40
35
30
Speed, Mph
25
20
15
10
5
0
11/8
11/9
11/10
11/11
11/12
11/13
11/14
11/15
11/16
Date
Primary Anemometer
Redundant Anemometer
Average
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Renewable Energy Research Laboratory
Water Depth
• Moderate
depths (less
than 100’)
presently
required
• Shallow
water (less
than 50’)
preferred
< 120 ft
< 90 ft
< 60 ft
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Renewable Energy Research Laboratory
Typical Wind Turbine
• Converts energy in wind to electricity
• Major components
– Rotor
Rotor
Gearbox
Generator
• Hub
• Blades
– Gearbox
– Generator
– Tower
Constant Speed
System
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Offshore Wind Farms
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Multiple wind turbines
Bottom mounted foundation
Electrical grid between turbines
Power cable to shore
Infrastructure for operation & maintenance
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Conceptual Design of Typical
Offshore Wind Plant
•Foundation
–Bottom mounted up to ~ 60 ft.
depth
–Floating structure in deep water
Wind Turbine
Grid
Connection
Onshore Staging Area
and
Control Room
Installation
Crane
Maintenance
Vessel
Submarine Cable
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Renewable Energy Research Laboratory
Conceptual Design of Typical
Offshore Wind Plant
•Submarine cable to mainland for
power and communication
Wind Turbine
Grid
Connection
Onshore Staging Area
and
Control Room
Installation
Crane
Maintenance
Vessel
Submarine Cable
University of Massachusetts
Renewable Energy Research Laboratory
Conceptual Design of Typical
Offshore Wind Plant
•Barge with crane for installation
Wind Turbine
Grid
Connection
Onshore Staging Area
and
Control Room
Installation
Crane
Maintenance
Vessel
Submarine Cable
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Renewable Energy Research Laboratory
Support Options for Offshore
Wind Turbines
Spar
bou y
Gravity
ca isss on
Stee l
pil ing
Trus s
Arti ficial
isl and
Pontoon
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Renewable Energy Research Laboratory
Electrical Cables
Cable cross section
Cable laying ship
Illustrations from www.hornsrev.dk
Typical cable layout
Cable trencher
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Installation
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Photos: Courtesy GE Wind
Renewable Energy Research Laboratory
Determinants of Cost of Energy
• Total installed costs
– Turbines, Foundations, Electrical System
– Installation
• Energy produced
– Wind resource
– Turbine operating characteristics
– Turbine spacing
• Operation and Maintenance (O & M)
– Scheduled maintenance and repairs
• Financial considerations (interest rates, etc.)
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Renewable Energy Research Laboratory
Factors Affecting Cost of Energy
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•
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Number of turbines
Size of turbines
Distance from shore
Water depth
Mean wind speed
Turbine reliability and maintainability
Site accessibility
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Renewable Energy Research Laboratory
Typical Offshore Capital Costs
• Turbine costs (inc. tower): $800-1000/kW
• Cable costs: $500k-$1,000,000/mile
• Foundation costs:
– Costs depend on soil and depth
– North Sea: $300-350/kW
– Price increases ~15%-100% when depth
doubles (from 25 ft to 50 ft)
• Total installed costs: $1200-$2000/kW
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Renewable Energy Research Laboratory
Offshore Capital Cost
Breakdown
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Turbine (w/out tower): 17-40%
Tower and foundation: 28-34%
Electrical grid: 9-36%
Other: 6-17%
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Renewable Energy Research Laboratory
Energy Production
1600
Power, kW
• Wind resource
• Turbine power curve
• Capacity factor
1200
800
400
0
0
5
10
15
Wind Speed, m/s
20
25
– Actual energy/maximum energy
– Typical values offshore: 35-45%
• Availability
– Fraction of time turbine can run
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Renewable Energy Research Laboratory
Typical O & M Costs
• 1.0 – 2.0 US cents/kWh
• O & M increases with
– Increased distance from shore
– Increased occurrence of bad weather
• O & M decreases with
– More reliable turbine design
– Greater number of turbines
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Renewable Energy Research Laboratory
Cost of Energy
• Cost of energy (COE), $/kWh, depends on:
– Installed costs, C
– Fixed charge rate, FCR – fraction of installed
costs paid each year for financing
–O&M
– Annual energy production, E
• COE = (C*FCR+O&M)/E
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Renewable Energy Research Laboratory
Simple Payback
• Simple alternative economic measure
• Simple payback period (SP), years, depends
on:
– Installed costs, C
– Annual energy production, E
– Net price obtained for electricity, P
• SP = C/(E*P)
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Renewable Energy Research Laboratory
Value of Energy
• Bulk energy sold at wholesale
• Internalized social benefits
– Wind energy production tax credit (PTC)
– Renewable energy portfolio standards (RPS)
certificates (RECS)
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Renewable Energy Research Laboratory
Social (External) Costs of
Electricity Production
• Costs not accounted for directly in fuel
price or production costs
• Examples:
– Air pollution health affects
– Damage due to global warming
• Typical estimates:
– Coal: 2-15 cents/kWh
– Gas: 1-4 cents/kWh
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Renewable Energy Research Laboratory
Actual Costs of Energy,
Existing European Projects - 2001
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Turbine size: 450 kW-2000 kW
Number of turbines: 2-28
Wind speeds: ~7.5 m/s
Water depth: 2-10 m
Distance from shore: 250 m-3 km
Cost of Energy: 5.3- 11.2 cent (EC) /kWh
( ≈ 5.3 – 11.2 US cent/kWh)
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Renewable Energy Research Laboratory
Costs as a Function of
Distance and Total Size
• 1997 European study:
• 7.5 MW wind farm, 1.5 MW turbines,
– 5 km from coast – 4.9 US cent/kWh
– 30 km from coast – 6.9 US cent/kWh
• 200 MW wind farm, 1.5 MW turbines,
– 5 km from coast – 4.1 US cent/kWh
– 30 km from coast – 4.4 US cent/kWh
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Renewable Energy Research Laboratory
Sample Economic Assessment
• Assume
–
–
–
–
Installed cost: $1500/kW
Capacity factor: 40%
Availability: 95%
Value of Energy: 8.3 cents/kWh, based on:
• Wholesale: 4 cents/kWh
• PTC: 1.8 cents/kWh
• RPS: 2.5 cents/kWh
– Operation & Maintenance: 1.5 cents/kWh
– Fixed charge rate: 14%
• Simple payback = 6.6 years
• COE= 7.8 cents/kWh
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Renewable Energy Research Laboratory
Technical Considerations with
Sites Further from Shore
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Greater energy production
More extreme environment
Greater cable length
Deeper water, larger foundation costs
– Technology development useful to reduce costs
– Floating supports for deep water
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Renewable Energy Research Laboratory
Deep Water Possibilities
Delft University, 2001
UMass, 1974
University of Massachusetts
Renewable Energy Research Laboratory
Summary
• Offshore wind energy is a reality in shallow
water, close to shore
• Cost of energy higher than from
conventional sources, ignoring externalities
• COE competitive, including RECS and PTC
• Technology for moderately deep water still
expensive
• Technology for deep water, far from shore
remains to be developed
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