EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Project Summary
Feasibility Study of Energy Extraction from Deep Ocean Waves
Anthony Mack, Principal Investigator
This project aims to study the feasibility of cost-effectively extracting energy from waves
in the deep ocean, tapping an energy source estimated to be considerably larger than
4,000 TWh/year, and producing environmentally friendly, renewable energy with no
carbon emissions.
Wave energy converters currently being tested and designed all operate near the shore.
Such a model suffers from several problems, including (a) the waves near the shore are
smaller than those on the open ocean, (b) the devices themselves are usually considered
eyesores, and (c) the available real estate for placing the devices is limited. The design
being proposed in this project works on the larger, more abundant waves in the deep
ocean. Because the amount of energy in an ocean wave is proportional to the sqare of the
height of the wave (so that waves three times as high have nine times as much energy),
larger waves offer themselves as obvious targets for energy extraction.
The innovation being presented in this project is two-fold. First, a new method of energy
extraction is offered that defines a new class of wave energy converters: distributed
volume absorption. The idea is that a set of flexible bladders, held below the wave crests
but allowed to sway horizontally, expel air as the waves pass over. The expelled air turns
a turbine and generates electricity which is used to make hydrogen.
The second aspect of the innovation is that the array of bladders is supported by a new
type of stable, low-cost, floating platform. The platform sits on submerged, variabledensity tanks positioned deep beneath the waves. Minimal structure pierces the water at
the surface, allowing the apparatus to operate unaffected by large, rogue waves. Energy
not captured and converted is allowed to pass harmlessly through the structure. In
addition, the lack of attachment to the shore and the placement in international waters
allows the structure to be easily moved to locations of higher energy density when
required.
The grant being proposed here will fund research on the feasibility of the design to
produce energy at a rate at or below that of other renewable sources. The proposed
funding will cover wave tank experiments to characterize and optimize bladder
performance over different configurations using different materials. Additionally,
research on the scalability of the design will be conducted. Team members will design
and construct a wave tank, conduct and analyze experiments, and research cost and
efficiency of using the design to transport energy with hydrogen. Partners at the Scripps
Institute of Oceanography will research bladder-ocean interaction, and partners at TM
Engineers will conduct analysis and produce platform design drawings.
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Statement of Work
Feasibility Study of Energy Extraction From Deep Ocean Waves
Anthony Mack, Deep Wave Energy, Inc., Principal Investigator
Project Goal: The goal of this project is to determine the feasibility of economically
extracting energy from deep ocean waves using gas-filled, flexible bladders supported by
a stable, floating platform, and transporting the energy using hydrogen.
Project Tasks
Performance/Cost Objectives
1) Construct a wave tank and research
bladder shapes, bladder materials,
head designs, and bladder layouts.
Deep Wave Energy
1) Demonstrate the following results:
a) The maximum bladder diameter is
most efficient at ½ the mean wave
height.
b) A hexagonal pattern, 20 bladders
deep, can convert at least 50% of
the wave energy.
2) Determine optimal shape for head.
3) Determine best-performing material for
bladders.
2) Identify problems using software
simulation, model calculation and
experimental data analysis.
Identify load stresses arising from wavebladder interactions. Characterize bladder
behavior in ocean environment.
Scripps
3) Finalize deep-sea bladder design.
Produce preliminary plans for a Module,
including bladder dimensions, head design,
Deep Wave Energy and Scripps
hold-down system, valve design, and flex
hose design.
4) Research deep-sea platform design
Produce preliminary plans for a Section.
Marine Engineer
5) Research the transportation of energy
using hydrogen.
Deep Wave Energy
Demonstrate that no more than 50% of the
energy will be lost during generation,
transportation and conversion.
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Project Narrative
Feasibility Study of Energy Extraction from Deep Ocean Waves
Anthony Mack, Principal Investigator
Project Goal
The goal of this project is to determine the feasibility of extracting energy from deep
ocean waves using an array of compressible bladders which expand and contract with the
vertical motion of the waves and force air through a turbine. The research will cover (a)
the interaction between the waves and the bladders, (b) the feasibility of using hydrogen
to transport the energy, and (c) the engineering feasibility of the stable ocean platform
design.
State of the Art
Currently, wave energy converters (WECs) are broadly divided into five main categories:
 Overtopping devices
These are devices that direct waves into a raised tank, and use the potential energy
of the raised water to generate electricity.
 Oscillating water column devices
These devices consist of a column passing through the ocean surface and open to
the sea at the bottom. Air is trapped in the column above the water, and as the
waves move up and down, the water acts like a piston, forcing the air through a
turbine.
 Point absorbers
These are floating devices that move at or near the surface and absorb energy
from waves in all directions using components that move relative to one another.
 Terminators
These are devices that float and extend in a direction perpendicular to the motion
of the waves. Energy is absorbed in one direction only.
 Attenuators
These are long floating structures oriented parallel to the direction of wave travel.
Power is generated from the relative motion of two or more floating components.
One of the most successful wave engergy converters to date is the Pelamis system from
Scotland’s Pelamis Wave Power, Ltd. The Pelamis device is an articulated structure and
floats on the surface, parallel to the direction of wave travel. It has a number of
cylindrical sections, connected by hinged joints. The wave action causes the joints to
rotate, forcing hydraulic fluid through a motor which turns an electric generator. Pelamis
has several working installations in Scotland, and has recently completed another funding
round of £5 million [1]. The first wave farm went live on September 24, 2008. According
to Yale Environment 360, “Assuming the devices continue to perform well, Portugeuse
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
utility Energis expects to soon purchase another 28 more of the generators.” This would
add approximately 21 megawatts to the Portuguese power grid [2].
A successful example of the overtopping style of WEC is the Wave Dragon, built by
Wave Dragon, ApS (Ltd.). of Denmark. In 2003, they deployed a 1:4.5 scale prototype,
which was the world’s first off-shore, grid-connected wave energy converter. According
to Wave Dragon’s website, they are “ready to construct and deploy a full-scale
commercial demonstration unit in Pembrokeshire, with a capacity of 7 megawatts.” [3]
Notable in the point absorber category is Finavera Renewables’ AquaBuOY. With farms
at Makah Bay, Washington (5 MW planned) and Ucluelet, BC, Canada (5 MW planned),
Humboldt County, California (2 – 100 MW planned) and South Africa (20 MW planned),
Finavera is planning on spinning off the wave energy technology projects into a separate
entity.
Also notable in the point absorber category is the PowerBuoy by Ocean Power
Technologies. PowerBuoys have been deployed in Honolulu, Hawaii (up to 1 MW),
Atlantic City, New Jersey (40 KW installed), and Santoña, Spain (1.39 MW planned).
The successful demonstration of a variety of wave energy conversion technologies has
proven the overall technical feasibility of extracting energy from ocean waves. The
research proposed in this application will extend this technology by addressing the three
key challenges in extant designs, namely limited energy density, intermittency of waves,
and high cost. (See the Technical Feasibility Issues section below for more information.)
Energy Problem Targeted
The proposed research specifically targets the PIER problem area of renewable energy
generation. The large-scale problem being addressed is that of cost-effectively generating
energy from a clean, renewable source. WECs in general offer an approach to this
problem, and the current proposal aims to research a WEC that makes use of a highenergy wave environment.
Primary Project Tasks
Wave Tank Research
We at Deep Wave Energy will construct a wave tank of dimensions ½  1.8  7 meters.
The tank will have a wave driver at one end capable of producing both regular and
irregular waves at different periods and amplitudes. The opposite end will have a wave
absorber. The tank will be fitted with hold-downs to support up to 20 bladders, up to 40
cm wide. It will also have windows to allow the videotaping of calibration marks on the
bags and far wall for analysis purposes.
Experiments with the wave tank will include analysis of variations in
 Bladder material
 Head design
 Bladder shapes, configuration and hold-downs
Tests for bladder-to-bladder interactions, reverse pendulum sway, bladder inflation and
deflation timing, and low- and high-pressure hose behavior will be conducted.
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
(See appendix B for illustrations.)
Problem Identification
Dr. Richard Seymour, head of the Ocean Engineering Research Group at the Scripps
Institution of Oceanography, will conduct research on problem identification. Included
will be calculations on wave loading, floating object and inverse pendulum behavior,
ocean state predictability and wave energy density. This research will lead to the
identification of problems to drive the design of the bladder assemblies and modules.
Bladder Design
Using the problems identified by Scripps and the results of the wave tank experiments, a
bladder and head design will be finalized. This will proceed in an interative fashion, with
a cycle of experiment, analysis, and design repeating. The goal will be to move the design
parameters towards a point that produces an optimal energy capture profile.
The result will be a set of design drawings of the bladder assemblies (flexible hoses,
heads, bladders, bag bar, and hold-downs). See Appendix B for explanatory illustrations.
Deep Sea Platform Design
A marine engineer will conduct research on loads and structure. Given the structural
design, data on the forces applied to the floating structure by the ocean, ocean state
information, and expected winds, the marine engineer will produce calculations and
designs as follows:
Wind Loads
The amount of force that will be applied to the structure by
wind, in the case of extreme conditions, to determine structural
and tie-down strength.
Deck Strength
An approximate calculation of the strength of the deck and the
needed support beams, including the main spars that run the
length of the structure.
Support Leg Strength
The required strength of the support legs, which are thin, strong
cylinders or box girders that support the deck.
Float Size and Strength
The required size and strength of the main floats which contain
water and air and support the structure through the support
legs.
Lower Grid Strength
The required size and strength of the steel I-beam grid used
deep underwater to hold down the bladders.
Keel Weight
The required weight and depth of the keel. The keel is situated
deep underwater to place the center of gravity of the entire
structure beneath the main floats.
The objective of this research will be to produce the specified calculations and design
drawings.
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Hydrogen Generation and Transportation
We at Deep Wave Energy will research the current state of hydrogen generation and
transportation. This will involve
Hydrogen generation
Research manufacturers for information on efficiency, pricing,
scalability and maintenance of hydrogen generators.
Hydrogen pump
Research pumps capable of reaching 3000 psi, with emphasis
on efficiency, pricing, scalability and maintenance.
Tanks
Research tanks for hydrogen storage, with emphasis on the
price of 3000-psi hydrogen tanks that can be used as floats.
Station-to-ship Transfer Research possible methods of loading pressurized hydrogen
onto a transfer ship
Fuel cells
Research modern fuel cell manufacturers, with emphasis on
efficiency, pricing, scalability and maintenance.
The objective of this research is to produce a report on the results of the work with a
recommendation for each area listed.
Technical Feasibility Issues
This project faces three main technical obstacles. These are addressed as follows:
Energy Density
All current designs are based near the shore. While this placement offers convenience of
energy delivery by cable, it suffers from the limitation that waves are smaller on the
Continental Shelf, and contain much less energy than deep ocean waves. The following
diagram shows yearly mean significant wave heights from 1971 – 2000 (the significant
wave height is the mean of the top third of waves).
Figure 1 Worldwide significant wave heights
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Source: European Center for Medium Range Weather Forcasts (ECMWF)
As can be seen in the picture, the Northern Pacific and Northern Atlantic Oceans have
large areas with mean significant wave heights of over 3 meters. Although the initial
placement will be on the Continental Shelf for operational assessment, the proposed
design is based in the deep sea, with ultimate placement far beyond the “far offshore”
designation, and off the Continental Shelf (the location in the Northern Pacific Ocean is
being used as an assumption for design purposes), affording access to a much higherenergy environment. Placement in the Antarctic Ocean will also be researched.
The energy density issue is addressed by the proposed design in another way: having a
large array of closely-packed absorbers without resonance (the bladders) allows the
energy available in smaller waves and waves from all directions to be extracted; such
energy will be missed in many designs.
Intermittency
There is great variability in ocean wave height and period, for both deep-sea and
Continental Shelf waves. However, deep-sea waves are larger on average, and
KNMI/ERA-40 data shows that the number of days of small waves is significantly less in
the deep sea than near the shore. The following diagram shows this difference:
Figure 2 Worldwide large wave frequency
Source: European Center for Medium Range Weather Forecasts (ECMWF)
The diagram shows that the target area for the proposed design has more than 180 days
per year with 5-meter waves. This significantly lessens the impact of wave intermittency.
In addition, this project intends to demonstrate that the proposed design is able to extract
energy over a broader range of ocean states than extant designs, because (a) there is no
inherent resonant frequency in the proposed design and (b) the large array of closelySolicitation 08-03
EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
packed absorbers combined with the large physical extent of the structure allows the
high-energy, long-period waves to be exploited.
Cost of Construction and Operation
The cost of constructing and maintaining large structures in the open ocean can be
prohibitive. The proposed design addresses the cost issue in several ways:
 Simple construction. The bladders are the most common item in the design, and
each bladder assembly contains very few parts and can be produced
automatically. The structure itself is made from I-beams, steel cylinders, and steel
cables—all mass-produced, low-cost items.
 Modern materials. The bladders, heads, air ducts, and other non-load-bearing
members will be made from modern, low-cost materials (such as polyurethane
compounds and PVC) with modern production techniques (such as injection
molding and overmolding).
 Large scale. The proposed design results in a large amount of collected energy,
which reduces the per-watt construction cost by distributing fixed overhead costs
over a large project.
 Modularity. The proposed design is extremely modular. Sets of 25 bladder
assemblies constitute a Module, and Modules fit together very simply, with no
needed adjustments to the rest of the structure. This enables the generated energy
to grow consistently over the lifetime of
the structure. Replacement and
maintenance of modules is kept simple
and cost-efficient, and does not cause the
station to shut down. The simplicity of
connecting and disconnecting modules
allows maintenance to be conducted offsite, onshore in California. This
increases the reliability of the whole
station dramatically.
 Reliability. The proposed design uses
materials that are known to last more
than 10 years in an ocean environment
without maintenance. In addition, the
modules automatically shut down in the
case of a breech in a bladder, flexible
hose, or manifold; this is done by
monitoring the humidity in the air in the
closed system—a rise in humidity
indicates a fault. All off-the-shelf
components are duplicated, so that faultFigure 3 Bladder assembly
tolerance is achieved. All main plenums
are connected together, so that if one section loses function, the whole station is
able to continue generating power, usually at the same rate.
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Proposed Innovations
The innovations proposed in this grant application are threefold:
Bladder Assembly
The bladder assembly consists of a flexible bladder that inflates and deflates with the
rising and falling of the waves, a head to connect the bladder to flexible hoses, and the
hoses themselves, which feed air to and from a high-pressure and low-pressure plenum.
During bladder inflation, air is pumped from the low-pressure plenum into the bladder.
This happens as the wave falls. As the wave rises, the bladder deflates, and the highpressure air flows from the bladder into the high-pressure plenum and is forced to turn a
turbine, which generates electricity. The bladder assembly is shown in Figure 3.
The operation of the bladder proceeds in four phases:
1. Low Hold. For any given wave cycle, the bladder reaches maximum inflation at
the bottom of the wave trough. As the wave rises, the intake valve closes. The
pressure in the bladder rises until the differential is high. This happens when the
surface of the water is approximately one meter above the pinch point. During this
period, the pinch point is stable at the lower position (shown in the diagram).
2. Deflation. As soon as the pressure in the bag reaches that in the high-pressure
plenum, the output valve opens, and the bladder begins to deflate. This continues
as the wave rises. The largest waves will completely deflate the bladder. This is
the “key” phase in which energy is transitioned to the output plenum.
3. High Hold. As the wave begins to drop, the high-pressure valve closes. As the
wave continues to drop, the pressure in the bladder decreases. During this phase,
the pinch point on the bag stays at the current level.
4. Inflation. Eventually, the wave drops low enough that the pressure in the bladder
equals that in the low-pressure plenum, and the low-pressure valve opens. At that
point, the bladder begins to inflate as the wave continues to drop. At the lowest
point in the trough of the wave, and the cycle repeats.
The following diagram shows the phases described.
Figure 4 Phases of bladder operation
A fundamental feature of the proposed design is that the bladders are free to move back
and forth with the wave motion. This is important because no energy is wasted fighting
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
that component of the wave motion. Laterally fixed designs not only turn that component
into heat, but have to be built strong enough to endure the force. This feature allows the
proposed design to handle and exploit larger waves, since the amount of the vertical
component that is captured is controllable, and the lateral component is allowed to flow
through without placing a large horizontal load on the structure. Fixed offshore platforms
have to be built extremely strongly to handle that same load.
The altitude of the bladder heads and the pressures of the low- and high-pressure plenums
can be varied dynamically during operation, allowing for adjustability in the amount of
energy extracted from different sizes of waves.
In normal wave mechanics, the horizontal component of the kinetic energy of water
molecules in the wave trough is converted into potential energy of neighboring
molecules, thus raising the height of the wave in the downstream direction. [5] In the
proposed design, that energy is converted into air pressure. Rather than “bumping up”
neighboring molecules, the fast-moving trough molecules spend their energy squeezing
the bladders. This means that waves emerging from the apparatus are significantly lower
(in the final version of the device this number will be one half for waves in the useful
range) than the incoming waves.
Module
In the proposed design, multiple bladders (the proposed design assumes 25, but this
number will be studied for an optimum) are connected together to form a module. This
connection consists of an intake and an output manifold made of PVC supported by a
light-weight truss. The bladder assemblies hang from the manifolds and are held in place
by tie-downs to a bar beneath the water (labeled “bag bar” in the diagram). Modules are
easy to construct, connect, and disconnect, and are made of low-cost components.
Platform
A platform as proposed in this project consists of a number (on the order of 150) modules
connected together. The precise details of the engineering required for platform
construction are beyond the scope of this initial study, but overall design and expected
loads will be calculated as part of the feasibility research carried out here by the marine
engineer. The proposed design uses a pier-like backbone made of two strong I-beams
supporting a deck from below and the modules from above. Between the I-beams are the
main air plenums. The I-beams themselves are supported by vertical legs, running down
to a large, deep-underwater float. The legs are designed to interact with the water surface
region as little as possible. The float is constructed like a ballast tank, being open to the
sea at the bottom and having a reservoir for air at the top. In order to keep the center of
gravity of the whole structure below the support point, a heavy keel is used; this keel is
situated far below the float, and is supported using steel cables. See Appendix B for
explanatory illustrations.
The overall design is intended to keep the bladders interacting with the top portion of the
waves, independent of the waves’ size. This is accomplished by using the air reservoir in
the float combined with the buoyancy of the bladders to raise and lower the structure.
Refer to the marine engineer’s statement of work for more details (Appendix C).
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Impacts on Energy Problems
The potential impact of the ultimate design on a number of problems facing Californians
in the modern energy environment is extremely large. If the results of the feasibility study
proposed in this application and future feasibility studies show that the proposed ultimate
design is both technically and economically sound, then an enormous energy source with
an environmentally clean extraction procedure will be made available for exploitation.
The proposed design has several beneficial impacts on California rate payers, including
 The reduction of CO2 emissions and other pollutants. Currently, each kilowatthour of energy generated and delivered to the grid produces approximately 2
kilograms of CO2. The proposed design delivers power with precisely zero CO2
emissions.
 Significant reduction of California’s dependence on oil purchased from foreign
sources.
 Because the proposed design delivers energy to the grid through a fuel cell, subsecond response times in service of energy demands can be maintained.
“Micropeaks” in energy demand can thus be mitigated.
 The proposed design does not impinge on the aesthetic environment of California
rate payers, and avoids the “Not In My Back Yard” problem.
Other renewable energy sources, including near-shore wave energy converters, solar, and
wind, address only some of the above issues.
Market Connection
The proposed design stores generated energy in the form of hydrogen gas. That gas can
be directly sold to hydrogen consumers such as
 Refueling stations for hydrogen-powered cars
 Agricultural producers (vegetable oil hydrogenation)
 Power consumers far from the grid, needing on-premises generation using fuel
cells
 Petrochemical plants, with uses in desulphurization, hydrochloric acid production,
etc.
 Fossil fuel electricity plants. These plants can mix hydrogen with the existing
fuels and significantly reduce CO2 emissions, helping them comply with
mandated decreases.
In addition, the hydrogen generated by the proposed design can be used in fuel cells
connected to the grid.
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Appendix A: Existing Technologies and Comparison
Finavera’s AquaBuOY
Finavera’s offshore power plants
consist of patented wave energy
converters that are based on proven,
survivable buoy technology. Clusters of
these small, modular devices called
AquaBuOYs are moored several
kilometers offshore where the wave
resource is the greatest. The power
plants are scalable from hundreds of
kilowatts to hundreds of megawatts.
Finavera power plants are designed to
provide clean, renewable energy for
large population centers. The offshore
plants are suitable as distributed
generation and load balancing at coastal
transmission points.
Energy transfer takes place by
converting the vertical component of
wave kinetic energy into pressurized
seawater by means of two-stroke hose
pumps. Pressurized seawater is directed
into a conversion system consisting of a
turbine driving an electrical generator.
The power is transmitted to shore by
means of a secure, undersea
transmission line.
A cluster of AquaBuOYs would have a
low silhouette in the water. Located
several miles offshore, the power plant
arrays would be visible to allow for
safe navigation and no more noticeable
than a small fleet of fishing boats.
Source:
http://www.finavera.com/en/wavetech
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
The Pelamis Wave Energy Converter
The Pelamis Wave Energy Converter is a
semi-submerged, articulated structure
composed of cylindrical sections linked by
hinged joints. The wave-induced motion of
these joints is resisted by hydraulic rams,
which pump high-pressure fluid through
hydraulic motors via smoothing accumulators.
The hydraulic motors drive electrical
generators to produce electricity. Power from
all the joints is fed down a single umbilical
cable to a junction on the seabed. Several
devices can be connected together and linked
to shore through a single seabed cable.
Current production machines are 140m long
and 3.5m in diameter with 3 power conversion
modules per machine. Each machine is rated
at 750kW. The energy produced by Pelamis is
dependent upon the conditions of the
installation site. Depending on the wave
resource, machines will on average produce 25
– 40% of the full rated output over the course
of a year. Each machine can provide
sufficient power to meet the annual electricity
demand of approximately 500 homes.
Source: http://www.pelamiswave.com
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Wave Dragon
Wave Dragon
Wave Dragon is a floating, slackmoored energy converter of the
overtopping type that can be deployed in
a single unit or in arrays of Wave
Dragon units in groups resulting in a
power plant with a capacity comparable
to traditional fossil based power plants.
The first prototype connected to the grid
is currently deployed in Nissum
Bredning, Denmark. Long term testing
is carried out to determine system
performance; i.e., availability and power
production in different sea states. The
energy absorption performance stated at
this website has now been
independently verified and focus will
now be on power production
optimization.
These tests will lead to a multi-MW
deployment in 2009.
Due to its size, service, maintenance and
even major repair works can be carried
out at sea leading to low O&M cost
relatively to other concepts
Source: http://www.wavedragon.net
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Wavegen OWC
Source:
http://www.wavegen.co.uk
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Require a marine power line
Minimum wave height (m)
Maximum wave height (m)
Tide independent
Accidental detachment liability
Able to store energy
Resonant – best at 1 wave length
Direction – best at 1 direction
Destructive to beach
Comparison Table
AquaBuOY
Yes
0.5
3.5
Yes
Yes
No
Yes
No
No
Pelamis
Yes
.75
5.0
Yes
Yes
No
No
Yes
No
Wave Dragon
Yes
1.5
4.0
Yes
Yes
No
No
Yes
No
Wavegen
Yes
1.5
4.0
No
No
No
Yes
Yes
Yes
DeepWave (proposed design)
No
1.5
24.0
Yes
No
Yes
No
No
No
Comparison Comments:
 All WECs other than the proposed design must be located near the coast, where
the wave energy density is low and intermittent.
 Along the continental US coast, Washington and Oregon have the highest waves,
but cheap hydroelectric power is already available there.
 All WECs other than the proposed design produce power for the grid at the wrong
time. The grid needs power on hot summer days when many air conditioners are
running and the waves are small.
 All WECs other than the proposed design and Wavegen have a liability problem
if a large wave should detach a buoy and it drifts into something.
 When one buoy in a farm needs maintenance, a boat must tow it out and tow a
replacement in. Navigation around the other buoys can be difficult even on a calm
day.
 All WECs other than the proposed design and Wavegen are navigational hazards
for small boats, which travel near the shore. The lower they sit in the water, the
less of an eyesore they are, but the more of a navigational hazard they are.
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Appendix B: Proposed Design
Bladder Phases
Inflation: Wave Trough
Bladder is filled with low-pressure air.
Lower Hold: Wave Rising
As wave raises, pressure builds.
Deflation: Wave Crest
Water pressure forces air out of the bladder.
Upper Hold: Wave Falling
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Bladder does not re-inflates while underwater.
EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
This X-ray view of a head shows how injection molding can be used to attach and seal to
the flexible hoses and bladder using modern PVC overmolding techniques.
Module – A massed produced part that contains 25 bladder assemblies, two manifolds, a
support truss and bag bar. Maintenance is done by replacing entire modules.
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EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Looking down from above with the flex hoses removed, the wave crest bushes up between
the bladders. The modules are placed close together and staggered to reach a density of
70%. The bladders sway with the water like seaweed.
The bladders are suspended from a light-weight section with contains the a deck, cabin,
plenums, tanks and support legs.
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Support legs sit on the float, far beneath the waves.
The lower grip holds the bladders down.
Sections can be connected
together.
The cabin contains all the equipment.
EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Solicitation 08-03
EISG Grant Application: Feasibility Study of Energy Extraction from Deep Ocean Waves
Appendix C: References
[1] http://www.pelamiswave.com/news.php?id=29&categoryId=3
[2] http://www.e360.yale.edu/content/feature.msp?id=2093
[3] http://www.wavedragon.net/index.php?option=com_content&task=
view&id=42&Itemid=67
[4] http://www.energyandcapital.com/articles/marine-energy-investing/665
[5] Sorensen, Robert M., Basic Wave Mechanics for Coastal and Ocean Engineers,
Wiley-Interscience, 1993, pp. 20 – 25.
Solicitation 08-03