POSTED: 7 DECEMBER 2005 - 8:30pm HST

This is a serious alternative with local significance

Energy from Pelamis: a hinged semi-submerged floating cylinders. Careful charting will be in order.

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

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