Marine Energy - iea-etsap

© IEA ETSAP - Technology Brief E13 – May 2010 - www.etsap.org
Marine Energy
Highlights
• PROCESS AND TECHNOLOGY STATUS – Ocean energy consists of various – somewhat very different –
technologies to exploit diverse types of marine energy that include: • Wind-driven marine waves; • Gravitationinduced
marine tidal (tidal-range barrage); • Tidal stream (marine currents); • Marine salinity gradients; and
• Thermal gradients between warm surface water and deep (> 1000 m) cold water (also called ocean thermal energy
conversion, OTEC)
• COSTS – Most marine energy technologies are in early stage of development, under demonstration, or have a limited
number of applications and commercial installations. As a consequence, their performance and costs may vary
significantly, depending on technology options, sites and local resource conditions. The investment cost of tidal stream
power is currently between $5000 and $6500/k We (US$ 2008), and is projected to decline to $ 4500/k We by 2020, and to
$3900/kWe by 2030 as a result of technology learning and larger deployment. The investment cost of wave power is
between $5700 and $7500/k We and it is expected to reduce to $4750/k We by 2020 and to $3900/k We by 2030.
• POTENTIAL & BARRIERS – In principle, the potential of marine energy is huge, but the economic potential is much
more modest. Because of insufficient experience and demonstration, there is a lack of information and understanding
regarding performance, lifetime, operation and maintenance of technologies and power plants. For example, the impact
of the aggressive marine environment on materials and components, and the consequence on plant lifetime must be
established. Significant research investment are still needed as well as government support for market deployment.
Policy incentives such as feed-in tariff may help initial deployment and cost reductions of these technologies
________________________________________________________________________
PROCESS AND TECHNOLOGY STATUS – Ocean
(Marine) energy includes diverse types of energy
resources and a number of technologies. The energy
resources include: • Gravitational tidal ranges (tidalrange
barrage); • Wind-driven marine waves; • Tidal
stream (marine currents); • Ocean Thermal Energy
Conversion, OTEC; • Salinity gradients. Technologies
to exploit OTEC and salinity gradients are not
addressed in this overview. Most ocean energy
technologies consist of new concepts under
demonstration. Power generation from tidal-range
barrage is the most known and proven marine
technology that has been working for years in a few
(three) power plants with a combined capacity of about
260 MW e . Marine wave and tidal stream power
technologies are currently in a stage of development
similar to that of the wind industry in the 1980s, and
commercial systems could become available between
2015 and 2025 (SEI, 2005).
• Wave power - Wave power generation is based on
the exploitation of the wind-driven wave energy. The
best wave conditions for wave power are a deepwater
power density of 60–70 kW/m of wave crest length
declining to 20 kW/m near the shore (Figure 1). About
2% of the world’s 800,000 km of coastline exceeds a
power density of 30 kW/m, with a technical potential of
about 500 GW e based on an efficiency of 40%. The
United States alone holds a technical potential of
approximately 100 GW e (PG&E, 2009), the United
Kingdom has an estimated 60 GW e , Ireland
approximately 6 GW e , and Portugal 2–3 GW e (Cato
and Falcão, 2007). For the United States, the total
resources have also been estimated by EPRI, but
much work is still needed (Musial, 2008) to get a
comprehensive and reliable assessment. Moreover,
the economic potential may be well below the technical
potential (IPCC, 2007). Approximately 50 wave power
systems have been developed or proposed, so far
Fig 1 - Global Wave Energy Flux Distribution
(Hagerman, 2005)
(AEA, 2006). Some of them are briefly illustrated as
follows. • The 315 kW e Oyster® power plant of
Aquamarine Power (UK) is being tested at the
European Marine Energy Centre (EMEC) in Orkney,
UK. Aquamarine and the Scottish Airtricity are involved
in the development of a 1000-MW e capacity to be
completed by 2020 (Internet Source 1). • AWS Ocean
Energy Ltd (UK) has developed the Archimedes
Waveswing, a fully submerged wave converter with
a linear generator, which has been demonstrated in
2004 in Northern Portugal (Internet Source 2).
• Columbia Power Technologies (US) has designed
and developed a 250 kW e Permanent Magnet Linear
Generator Buoy to be anchored to the sea floor. Figure
2 shows the scheme of a point absorber wave
generator developed by AWS Ocean Energy Ltd,
Columbia Power Technologies and Ocean Power
Technologies Inc. (Szabó et al, 2007; Internet
Sources 3–5), also called Wavebob in the Vattenfall
1
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© IEA ETSAP - Technology Brief E13 – May 2010 - www.etsap.org
version. • Ocean Energy Ltd (Ireland) developed a
floating platform with a turbine (OE Buoy for use in
water depths of 30–50 m (Internet Sources 6–7).
Figure 3 shows the so-called oscillating water column
(Mueller et al, 2007), a principle used by Ocean
Energy Ltd and the so-called Limpet by Voith Hydro
Wavegen Ltd. • Ocean Power Technologies Inc.
(OPT, US) designed the PowerBuoy®. Tests of the
device started in December 2009 at Kaneohe Bay
(Hawaii). It will also be deployed at EMEC in Orkney,
(UK). Nine PowerBuoys of 150 kW e each, with a total
capacity 1.39 MW e , will be installed at 5 km off the
Santoña coast, Spain (Internet Sources 8–9). •
Pelamis Wave Power Ltd (PWP, UK) developed a
750 kW e Pelamis module, consisting of three units of
250 kW e each, for mooring in 50–70 m deep water at
5–10 km from the shore. In 2008, a three-module
Pelamis project of 2.25 MW e was commissioned for
installation off the coast of Portugal (Figure 4). PWP
has also announced an order from E.On for a 2 nd
generation module to be installed in Orkney, followed
by four modules with a capacity of 3 MW e (Wise, 2008;
Internet Sources 10–13). • Voith Hydro Wavegen
Ltd (UK) developed the Limpet, an overtopping device
optimised for near-shore applications, with a 7-m wave
depth at the entrance of an Oscillating Water Column
(OWC). The OWC feeds a pair of counter-rotating
turbines driving a 250 kW e generator, with a total
capacity of 500 kW e (Heath, 2007; Internet Source 14).
• Vattenfall provides financial support for the
demonstration of three wave energy technologies
including Pelamis (PWP Ltd), Wavebob (Wavebob
Ltd), and a device developed by Seabased (Sweden)
(Internet Sources 15–16). The Wavebob is an axisymmetric,
self-reacting point absorber (primarily
operating in heave mode) to produce power from
ocean wave energy. According to Rodrigues (2005),
wave power could become commercial at a cumulative
capacity of about 7000 MW e . If issues such as
corrosion, materials, connection to the shore, possible
conflict with fishing, and environmental impacts are
solved, then wave power might become commercial
around 2020.
• Tidal power - Tidal power is based on two
technologies, namely tidal barrage power and tidal
stream power (marine currents). • Tidal barrage is
based on capturing seawater by a barrage when the
tidal is high, and let the water flow through hydroturbines
when tidal is low. There are only three plants in
operation worldwide, with a combined capacity of 260
MW e . A tidal barrage at Severn (UK) would have a
maximum capacity of 8.6 GW e and an average capacity
of 2.0 GW e (SDC, 2007). According to the Internet
Source 18, environmental concerns make it socially
unacceptable the Severn tidal barrage. Unfortunately,
the number of coastal sites where tidal barrages are
economically and environmentally feasible is very
limited. Costly large barrages projects are under
consideration to take into account the conservation of
marine habitats. An indicator of the cost effectiveness of
a tidal barrage power plant is the so-called Gibrat ratio
that is the length of the barrage (in meters) to the
Fig 2 - Scheme of point absorber used by AWS,
Columbia Power Technologies and Ocean Power
Technologies (Internet Source 5)
Fig 3 - Scheme of oscillating water column used by OE
Buoy and Limpet (Mueller et al, 2007)
Fig 4 - One of three sections of the 750 kWe Pelamis,
Aguçadura, Portugal (Internet Source 11)
annual energy production (in KWh) ratio. Of course,
smaller Gibrat ratios are desirable. For example, the
Gibrat ratio for the current tidal power plant at la Rance
(France) is 0.36, whereas the Gibrat ratio of the
planned tidal power plant at the Severn (UK) would be
0.87 (Soriano, 2008). Based on the Gibrat ratio and
other indicators and considerations, the global potential
of tidal barrage power plants is estimated to amount to
2
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Giorgio.Simbolotti@enea.it and Giancarlo Tosato (gct@etsap.org) (Project Coordinators)

© IEA ETSAP - Technology Brief E13 – May 2010 - www.etsap.org
approximately 60 GW e , with an electricity generation of
about 150 TWh/year (Gorlov, 2001). • Tidal stream
power can be considered as a demonstrated
technology on the basis of the existing installations and
technology advances (see Figure 5). In 2003,
Hammerfest Strøm installed the world’s first-of-thekind
300-kWe tidal turbine prototype in Kvalsundet, off
Hammerfest. In 2007, they also signed a contract with
Scottish Power for further technology development
(Internet Sources 18–19). In 2006, Verdant Power (US
and Canada) started the Roosevelt Island Tidal Energy
(RITE) project in New York City’s East River. Phases 1
and 2 involved testing and demonstrating a 35-kW e
Kinetic Hydro Power System (KHPS) prototype (Figure
6). In the phase 3 of the project, the prototype is to be
scaled up to MW-size (Internet Source 20). In 2008,
OpenHydro (Ireland) installed a 250-kW e prototype at
EMEC (Internet Source 25); Tocardo (Netherlands)
demonstrated a 45-kW e turbine, with a direct drive, 2-
bladed rotor at Afsluitdijk (Internet Source 22); and
Marine Current Turbines Ltd (UK) moored a 1.2-MW e
SeaGen tidal stream unit at Strangford Lough (UK). The
next phase of this project includes the installation of
seven 1.5-MW e SeaGen turbines with a total capacity of
10.5 MW e near the island of Anglesey, also known as
The Skerries (Figure 7; Internet Sources 23–24). In
2009, Fri-El Green Power started the tests of a 500-
kW e tidal stream pilot plant called Fri-El Sea Power in
the Strait of Messina between Sicily and the mainland
of Italy. Sea Power has been developed for either
power generation from tides, oceanic circulations or for
exploiting natural flow water streams (Figure 8; Internet
Source 25). Also in 2009, Lunar Energy Co (UK) has
started the tests of a 1 MW e submersible turbine placed
on the seabed (i.e. the Rotech Tidal Turbine, RTT –
Figure 9). Lunar Energy will supply 300 turbines, with a
combined capacity of 300 MW e to the Korean Midland
Power Co (KOMIPO) for installation off the South
Korean coast by 2015. Another unit is due for EMEC
(Internet Source 26). If major estuaries with large tidal
fluctuations can be tapped, it is estimated that tidal
stream power could yield about 100 TWh/year (4
EJ/year) or more (Internet Source 27).
COSTS – All investment, operation and maintenance
costs quoted below are intended in 2008 US dollars.
The current (2008) investment costs of tidal stream
power is between $ 5000 and $6500/kW e . This cost is
expected to decline to $4500/kWe in 2020, and to
$3900/kW e in 2030. The investment costs of wave
power is currently between $5700 and $7500/kW e ,
while it is projected to reduce to about $4750/kW e in
2020 and to $3900/kW e in 2030. Currently, because of
the harsh marine environment, the investment and the
operation and maintenance costs of the marine
technologies are high and uncertain. Governmental
incentives and fiscal policies are therefore needed for
the technology to take off. Since 2008, the 2.25 MW e
wave power plant at Aguçadoura (Portugal), consisting
of three Pelamis modules, is supported by a feed-in
tariff incentive of €230/MWh (roughly $340/MWh).
Fig 5 - Transferable design and installation experience
of renewable offshore options (IME, 2008)
Fig 6 - Scheme of free-flow power unit of Verdant
Power, USA/Canada (Internet Source 27)
Fig 7 - OeanGen tidal power (artist impression), Marine
Current Turbines Ltd (Internet Sources 21)
3
Please send comments to Paul Lako, Author (lako@ecn.nl), and to
Giorgio.Simbolotti@enea.it and Giancarlo Tosato (gct@etsap.org) (Project Coordinators)

© IEA ETSAP - Technology Brief E13 – May 2010 - www.etsap.org
POTENTIAL & BARRIERS – The potential of ocean
energy technologies is huge, but the economic
potential is more modest. Accelerated staged trials are
needed to establish whether solutions under
development are feasible and cost-effective. Because
of insufficient experience from demonstration projects,
there is a lack of understanding regarding the
technology impacts on the environment. Also, the
impact of the marine environment on components,
equipment and lifetime must be understood (AEA,
2006). In order for ocean energy technologies to enter
the market, sustained government support is needed.
Under favourable conditions, it is estimated that a
country like the United Kingdom could realistically
install between 1000 and 2000 MW e based on wave
and tidal stream power by 2020 (BWEA, 2009). The
marine (ocean) energy technologies potential is
provide in Table 1 (AEA, 2006; Internet Source 1)
Tab. 1 - Ocean Energy Technologies and Potential
(AEA, 2006; Internet Source 1)
Energy
Resource
Ocean
Wave
Tidal
Stream
Salinity
Gradient
OTEC
Technology
• Attenuators,
• Collectors,
• Overtopping,
• OWC, • OWSC,
• Point absorbers,
• Submerged
pressure differential,
• Terminators,
• Rotors
• Horizontal/Verticalturbines,
• Oscillating
hydrofoils, • Venturi
• Semi-permeable
osmotic membranes
• Thermo-dynamic
ranking cycle
Energy Potential,
TWh/yr
Economic
Global World Europe
45,000 500+ 142
2200 100+ 36
2000 N/A 28
10,000 N/A
Fig 8 - Scheme of tidal stream converter Fri-El Sea
Power (Fri-El Green Power) (Internet Source 19)
Fig 9 - Scheme of tidal stream power unit Lunar Energy,
UK (Internet Source 24)
4
Please send comments to Paul Lako, Author (lako@ecn.nl), and to
Giorgio.Simbolotti@enea.it and Giancarlo Tosato (gct@etsap.org) (Project Coordinators)

© IEA ETSAP - Technology Brief E13 – May 2010 - www.etsap.org
Table 2 – Summary Table: Key Data and Figures for Marine Energy Technologies
Technical Performance
Typical current international values and ranges
Energy input
Ocean energy
Output
Electricity
Technologies
Wave power
(Wave)
Tidal-range Barrage
(TB)
Tidal Stream
(TS)
Efficiency, % Not applicable Not applicable Not applicable
Construction time, months Min.12; Typical 24;
Max.36
Min. 36; Typical 48;
Max.100
Min.12;
Typical24; Max.
36
Technical lifetime, yr 25 80 25
Load (capacity) factor, % 25 22.5–28.5 26
Max. (plant) availability, % 95 98 95
Typical (capacity) size, MW e 200+ 200–8,600 (Severn 20–200+
barrage)
Installed (existing) capacity, GW e Negligible 0.26 Negligible
Average capacity aging
Environmental Impact
CO 2 and other GHG emissions, kg/MWh Negligible Negligible Negligible
SO 2 , g/MWh Negligible Negligible Negligible
Costs (US$ 2008)
Investment cost, including interest during 5,700–7,500 5,000–5,500 5,000–6,500
construction, ($/kW)
O&M cost (fixed and variable), $/kW/a 200 115 150
Fuel cost, $/MWh N/A N/A N/A
Economic lifetime, yr 20 25 20
Interest rate, % 10
Total production cost, $/MWh 335 240 – 265 285
Market share 0.25 Negligible N/A
Data Projections 2010 2020 2030
Technology Wave TB TS Wave TB TS Wave TS
Investment cost, including interest during 6,600 5,300 5,750 4,750 4,200 4,500 3,900 3,900
construction, $/kW (BIN / CHP / HP)
Total production cost, $/MWh 340 255 285 240 200 225 200 200
Market share, % of global electricity
output

© IEA ETSAP - Technology Brief E13 – May 2010 - www.etsap.org
References and Further Information
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6
Please send comments to Paul Lako, Author (lako@ecn.nl), and to
Giorgio.Simbolotti@enea.it and Giancarlo Tosato (gct@etsap.org) (Project Coordinators)