Wave
Energy Potential Warrants Further Research
published
3 February 2005 by EPRI
A new report from the Electric Power Research Institute (EPRI) suggests
that generation of electricity from wave energy may be economically
feasible in the near future. The study was carried out by EPRI in
collaboration with the DOE's National Renewable Energy Laboratory
(NREL) and energy agencies and utilities from six states.
[to see the
EPRI report on sites in Hawaii click here
for a 90 page PDF file. The punch-line is Nawiliwili Harbor is identified
on Kauai as a reasonable site]
Conceptual designs for 300,000 megawatt-hour (MWh) plants (nominally
120 MW plants operating at 40% capacity factor) were performed for
five sites: Waimanalo Beach, Oahu, Hawaii; Old Orchard Beach, Cumberland
County, Maine; WellFleet, Cape Cod, Massachusetts; Gardiner, Douglas
County, Oregon; and Ocean Beach, San Francisco County, California.
The study determined that wave energy conversion may be economically
feasible within the territorial waters of the United States as soon
as investments are made to enable wave technology to reach a cumulative
production volume of 10,000 - 20,000 MW. (Land-based wind turbines,
in comparison, generate 40,000 MW.)
"Wave energy is an emerging energy source that may add a viable
generation option to the strategic portfolio," said Hank Courtright,
EPRI's vice president, Generation and Distributed Resources. "The
bedrock of a robust electricity system is a diversity of energy
sources, and wave energy could provide an energy source that is
consistent with our national needs and goals."
According to the study, wave energy will first become commercially
competitive with land-based wind technology at a cumulative production
volume of 10,000 or fewer MW in Hawaii and northern California,
about 20,000 MW in Oregon and about 40, 000 MW in Massachusetts.
Maine is the only state in the five site study whose wave climate
is such that wave energy may never be able to economically compete
with a good wind energy site. This forecast was based on the output
of a 90 MW Pelamis wave energy conversion plant design and application
of technology learning curves that will enable cost savings.
The forecast results have convinced the project team of the rationale
for investment in wave energy technology research and development,
including demonstration projects to prove the feasibility of wave
energy conversion technology in actual sea-state environments.
There are several compelling arguments for investing in offshore
wave energy technology. First, with proper siting, conversion of
ocean wave energy to electricity is believed to be one of the most
environmentally benign ways to generate electricity. Second, offshore
wave energy offers a way to minimize the 'Not in my backyard' (NIMBY)
issues that plague many energy infrastructure projects. Wave energy
conversion devices have a very low profile and are located far enough
away from the shore that they are generally not visible. Third,
wave energy is more predictable than solar and wind energy, offering
a better possibility of being dispatchable by an electrical grid
systems operator and possibly earning a capacity payment.
A characteristic of wave energy that suggests that it may be one
of the lowest cost renewable energy sources is its high power density.
Processes in the ocean concentrate solar and wind energy into ocean
waves, making it easier and cheaper to harvest. Solar and wind energy
sources are much more diffuse, by comparison.
Wave power was delivered to the electrical grid for first time in
August 2004. The electricity was generated by a full-scale preproduction
Pelamis prototype in Orkney, Scotland by Ocean Power Delivery Corporation.
The offshore wave energy reports are currently available.
EPRI, with major locations in Palo Alto, Calif., and Charlotte,
NC, was established in 1973 as an independent, non-profit center
for public interest energy and environmental research. EPRI's collaborative
science and technology development program now spans nearly every
area of power generation, delivery and use. EPRI's members represent
over 90% of the electricity generated in the United States. International
participation represents over 10% of EPRI's total R&D program,
with 62 members and more than 130 funders.
The
Pelamis Wave Energy Converter
by Ocean Power Delivery www.oceanpd.com
The Pelamis 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 oil 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 sea bed. Several devices can be connected together
and linked to shore through a single seabed cable.
A novel joint configuration is used to induce a tuneable, cross-coupled
resonant response, which greatly increases power capture in small
seas. Control of the restraint applied to the joints allows this
resonant response to be 'turned-up' in small seas where capture
efficiency must be maximised or 'turned-down' to limit loads and
motions in survival conditions. The machine is held in position
by a mooring system, for which a patent has been applied for, comprising
of a combination of floats and weights which prevent the mooring
cables becoming taut. It maintains enough restraint to keep the
Pelamis positioned but allows the machine to swing head on to oncoming
waves. Reference is achieved by spanning successive wave crests.
The 750kw full-scale prototype is 120m long and 3.5 m in diameter
and will contain three Power Conversion Module, each rated at 250kW.
Each module contains a complete electro-hydraulic power generation
system.
Ideally the
Pelamis would be moored in waters approximately 50-60m in depth
(often 5-10km from the shore). This would allow access to the great
potential of the larger swell waves but it would avoid the costs
involved in a longer submarine cable; if the machine was located
further out to sea.
Throughout the construction of the full-scale Pelamis, OPD has been
working closely with WS Atkins who have independently verified the
prototype design according to (DNV) offshore codes and standards.
OPD Ltd is an Edinburgh based company set up in
January 1998 to develop the Pelamis WEC concept.
In March 2002, OPD Ltd. secured £6m (EUR 9.8m) funding from
an international consortium of venture capital companies led by
Norsk Hydro Technology Ventures, the venture capital arm of Norway's
largest industrial company and including 3i, Europe's leading venture
capital company and Zurich-based Sustainable Asset Management (SAM).
Each organisation provided an equal level of funding to produce
the largest investment of its kind in a wave power company.
In June 2004, OPD Ltd. completed the first round of investment of
over £7.5m, including £1.5m new investment from the
Carbon Trust, which co-invested alongside OPD's existing venture
capital investors.
W.S.Atkins, a premier offshore consultant, has been advising OPD
over the past two years. With their enormous experience in design
and construction of offshore structures, they bring invaluable expertise
to the development, demonstration and future production of the Pelamis.
The first full-scale pre-production protoype is now undergoing a
staged testing programme at the European Marine Energy Centre in
Orkney.Contact Details
OPD Ltd Offices
104 Commercial St, Edinburgh EH6 6NF, Scotland, UK.
Telephone: +44 (0) 131 554 8444 Fax: +44 (0) 131 554 8544
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