Pelamis Offshore Wave Energy Project

A Portuguese energy company called Enersis is funding a commercial wave energy project in Northern Portugal. Construction of Pelamis Offshore Wave Energy Project will begin at the end of October 2006. The project will use Pelamis wave generator technology (manufactured by Ocean Power Delivery) to harness energy from the ocean. After two decades of research and testing at the Lisbon Technical Institute, the first stage of this ocean energy project is intended to produce 2.25 megawatts and power homes through the nation’s state-run electrical grid system. Ocean Power Delivery is considered to be the world’s leading ocean energy company.

“This project, begun in 2003, is now in the world vanguard,” said Rui Barros, Enersis director of new projects. “Of all the varieties of renewable energy, perhaps harnessing the waves is the only one where Portugal might have a real future,” he said. With its geographical position and extensive coastline giving access to the larger and more powerful Atlantic waves, official estimates from Portugal’s State Secretariat for Industry and Innovation have predicted wave power could account for up to 30 percent of the country’s gross domestic product by 2050. Renewable energy experts have determined wave farms in Portugal could yield as much as three times as much energy as that produced by a wind turbine park for the same investment cost.

A report published by the Portuguese Wave Energy Center has confirmed the long-term economic benefits of wave energy for the country and calls on the government to put in place a strategy to attract foreign investment into Portuguese wave power ventures. “The utilization of wave energy may have a significant socio-economic impact on Portugal, namely regarding renewables, creation of job opportunities, opportunity of exportation of equipment and services, innovation and development of technology, as well as companies dedicated to the exploitation of other oceanic resources,” the report says.

Relatively new in development, modern research into wave power had its beginnings in response to the 1973 oil crisis. Professor Stephen Salter of the University of Edinburgh pioneered research into wave energy with his prototype machine “Salter’s Duck.” Though the duck remains a laboratory prototype, the machine remains the standard for wave energy. The experimental device converted around 90 percent of the wave power by bobbing up and down on the surface of the water – like a duck. Despite its early promise though, setbacks and a general lack of government support saw the project shelved.

However, with the Portuguese system set to be the world’s first commercial wave energy venture, the exploitation of wave power has found itself back on the renewable energy agenda.

Following the Enersis announcement, other countries naturally suited to the development of wave power have expressed their interest in introducing the technology. Following his recent visit to Aguadoura, Scottish Executive Enterprise Minister Nicol Stephen announced that a portion of the 8 million pounds already set aside for renewable marine energy in Scotland would now be directed towards installing the Pelamis wave devices at the European Marine Energy Center in Orkney.

“I am committed to supporting Scotland’s huge wave and tidal energy resource. Scotland has a real opportunity to be a world leader in this field,” said the minister shortly after his visit to view the wave energy project in northern Portugal. “The opportunity now exists to create a multi-million pound industry based in Scotland, employing thousands of highly skilled people,” he said.

However, environmental group Friends of the Earth, while supporting the minister’s announcement, sounded a warning that any delays in introducing the wave power technology could lead to an exodus of Scottish expertise.

“Wave and tidal power could supply a fifth of U.K. energy needs and Scotland is ideally placed to generate significant amounts of this pollution-free energy,” said Friends of the Earth chief executive Duncan McLaren. “However, there is a danger that unless we see full-scale devices in our waters soon that the world-leading expertise Scotland has built up will rapidly depart these shores,” he said.

As part of the government supported alternative energy plan, another 28 wave power devices will be installed in Portugal within a year, reaching a target of 22.5 megawatts of electricity produced using wave energy. The project is supported by state run power company Energias de Portugal.

PG&E’s 5MW Wave Energy Project

A project that could’ve helped to advance wave energy development is no more. At least for now. The Pacific Gas and Electric Co. has suspended a 5-megawatt project off Northern California coast primarily because it’d cost too much.

The pilot project would’ve provided a valuable opportunity to test promising technologies to convert the wave’s motion into electricity about three miles off the coast of Humboldt County. PG&E began investigating the feasibility of the project back in 2007 and had filed an application with the Federal Energy Regulatory Commission for a 5-year license earlier this year.

The utility had planned to select three or four developers of wave energy converter equipment by the end of this year and secure the federal permit by June 2011 (here is a list of wave energy technologies that PG&E considered). The company quietly announced the suspension of the project last Friday by issuing a press release only to Humboldt-area media.

Though promising, wave energy development is still in the early stages. FERC has only issued one license to build and operate a wave project, according to its website. The license holder, Finavera Renewables, surrendered that license last year, citing difficulties in raising enough money to do the 1-megawatt project off the coast of Washington state. FERC has issued 11 permits for studying the feasibility of building wave power farms in the country, all of them located in the Pacific Ocean.

At the end, though, PG&E opted to discontinue with the project because of the costs of financing a project that would’ve involved unproven technologies and been limited in its ability to expand, said company spokesman Brian Swanson. In PG&E’s permit application, it had estimated that the project would require $50 million just to cover the expenses of installing the infrastructure for the power transmission, monitoring and other equipment. The figure didn’t include the cost of the wave energy converters. The utility also pegged the operating and maintenance costs at about $5 million annually, though the number didn’t include any environmental protection measures.

PG&E could have been a pioneering wave energy developer if it had continued and completed the project. But blazing the trail would’ve required some extra costs that the private, investor-owned utility wasn’t willing to take on.

“There is no precedent and no other project to compare to, and there is a need for monitoring and adoptive management plans to evaluate and respond to the potential environmental impact. That management plan had a high cost associated with,” Swanson said.

Plus, Swanson said the Humboldt project was set for a location that wouldn’t have allowed it to expand its generation capacity, something that could’ve made the operating of the project cheaper in the long run.

Although PG&E ditched the Humboldt project, it isn’t ready to give up wave energy yet. The company is continuing with its proposed plan to do a pilot project off the coast of Santa Barbara County in central California. The company is still studying the feasibility of building a 10-megawatt project, which would float in an area that is large enough to accommodate a 100-megawatt farm, Swanson said. The Humboldt region remains a potential site for future projects, he said.

The utility hasn’t only been interested in building its own wave energy projects. It once proposed to buy electricity from what could have been the country’s first wave energy power plant. Finavera was set to develop the 2-megawatt project off Northern California coast. But the California Public Utilities said no to the power purchase agreement in 2008 because the technology was unproven and costly.

PG&E also abandoned a plan to build another pilot project off the cost of Mendocino County in Northern California in 2009.

Ocean Thermal Energy Conversion

Ocean thermal energy conversion (OTEC or OTE) uses the temperature difference that exists between deep and shallow waters to run a heat engine. As with any heat engine, the greatest efficiency and power is produced with the largest temperature difference. This temperature difference generally increases with decreasing latitude, i.e. near the equator, in the tropics. Historically, the main technical challenge of OTEC was to generate significant amounts of power efficiently from this very small temperature ratio. Changes in efficiency of heat exchange in modern designs allow performance approaching the theoretical maximum efficiency.

The Earth's oceans are continually heated by the sun and cover over 70% of the Earth's surface; this temperature difference contains a vast amount of solar energy, which can potentially be harnessed for human use. If this extraction could be made cost effective on a large scale, it could provide a source of renewable energy needed to deal with energy shortages and other energy problems. The total energy available is one or two orders of magnitude higher than other ocean energy options such as wave power; but the small magnitude of the temperature difference makes energy extraction comparatively difficult and expensive, due to low thermal efficiency. Earlier OTEC systems had an overall efficiency of only 1 to 3% (the theoretical maximum efficiency lies between 6 and 7%). Current designs under review will operate closer to the theoretical maximum efficiency. The energy carrier, seawater, is free, though it has an access cost associated with the pumping materials and pump energy costs. Although an OTEC plant operates at a low overall efficiency, it can be configured to operate continuously as a Base load power generation system. Any thorough cost-benefit analysis should include these factors to provide an accurate assessment of performance, efficiency, operational, construction costs, and returns on investment.

The concept of a heat engine is very common in thermodynamics engineering, and much of the energy used by humans passes through a heat engine. A heat engine is a thermodynamic device placed between a high temperature reservoir and a low temperature reservoir. As heat flows from one to the other, the engine converts some of the heat energy to work energy. This principle is used in steam turbines and internal combustion engines, while refrigerators reverse the direction of flow of both the heat and work energy. Rather than using heat energy from the burning of fuel, OTEC power draws on temperature differences caused by the sun's warming of the ocean surface.

The only heat cycle suitable for OTEC is the Rankine cycle using a low-pressure turbine. Systems may be either closed-cycle or open-cycle. Closed-cycle engines use working fluids that are typically thought of as refrigerants such as ammonia or R-134a. Open-cycle engines use the water heat source as the working fluid.

CETO Wave Power

CETO is a wave energy technology that harnesses the power of the ocean waves to generate electricity or produce desalinated water. CETO is owned and operated by Carnegie Wave Energy Limited (ASX: CWE), the Australian ASX-listed clean tech developer. Carnegie will own and operate all commercial CETO wave farms in the Southern Hemisphere. In the Northern Hemisphere CETO wave farms will be joint ventures with CETO technology licensee, EDF Energies Nouvelles SA (EDF EN), the renewable subsidiary of French energy giant Électricité de France (EDF). The technology development is being demonstrated at commercial scale in 2010 off Garden Island in Western Australia, home of Australia's largest naval base HMAS Stirling. Subsequent projects may happen at La Reunion Island and off British Columbia where Government grants have been awarded.

Named after a Greek ocean goddess, the CETO system distinguishes itself from other traditional wave energy devices by being a fully submerged, pumping technology with the power generated onshore by a standard hydro-electric turbine system.

Submerged buoys are moved up and down by the ocean swell, driving pumps which pressurize seawater that is delivered ashore by a pipeline. Once onshore, the high-pressure seawater is used to drive hydro turbines, generating zero-emission electricity. Traditionally, wave technologies are characterized as offshore, floating power stations.

The high-pressure seawater is also used to supply a reverse osmosis desalination plant, creating zero-emission freshwater. Currently, seawater desalination plants are large emitters of greenhouse gases due to the amount of energy required to drive grid-connected pumps that deliver the high pressure seawater to reverse osmosis membranes which remove the salt from the seawater.

Other wave energy & CETO characteristics
  • Wave energy is a renewable, zero emission source of power.
  • 60% of the world lives within 60 kilometers of a coast, minimising transmission issues.
  • Since water is about 800 times denser than air, the energy density of waves exceeds wind many times over, dramatically increasing the amount of energy available for harvesting.
  • Waves are predictable in advance, making it easy to match supply and demand.
  • CETO sits underwater, moored to the sea floor, meaning there is no visual impact.
  • CETO units operate in deep water, away from breaking waves. The waves regenerate once they pass the CETO units, meaning there is no impact on popular surfing sites.
  • CETO units are designed to operate in harmony with the waves, rather than attempting to resist them. This means there is no need for massive steel and concrete structures to be built.
  • CETO is the only wave energy technology that produces fresh water directly from seawater by magnifying the pressure variations in ocean waves.
  • Any combination of power and water can be achieved from 100% power to 100% water.
  • CETO contains no oils, lubricants or offshore electrical components. It is built from components with a known sub-sea life of over 30 years.
  • CETO units act like artificial reefs, because of the way they attract marine life.

Modern Technology of Wave Energy

Wave power devices are generally categorized by the method used to capture the energy of the waves. They can also be categorized by location and power take-off system. Method types are point absorber or buoy; surfacing following or attenuator oriented parallel to the direction of wave propagation; terminator, oriented perpendicular to the direction of wave propagation; oscillating water column; and overtopping. Locations are shoreline, nearshore and offshore. Types of power take-off include: hydraulic ram, elastomeric hose pump, pump-to-shore, hydroelectric turbine, air turbine, and linear electrical generator. Some of these designs incorporate parabolic reflectors as a means of increasing the wave energy at the point of capture. These capture systems use the rise and fall motion of waves to capture energy. Once the wave energy is captured at a wave source, power must be carried to the point of use or to a connection to the electrical grid by transmission power cables.

These are descriptions of some wave power systems:

  • In the United States, the Pacific Northwest Generating Cooperative is funding the building of a commercial wave-power park at Reedsport, Oregon. The project will utilize the PowerBuoy technology Ocean Power Technologies which consists of modular, ocean-going buoys. The rising and falling of the waves moves hydraulic fluid with the buoy; this motion is used to spin a generator, and the electricity is transmitted to shore over a submerged transmission line. A 150 kW buoy has a diameter of 36 feet (11 m) and is 145 feet (44 m) tall, with approximately 30 feet of the unit rising above the ocean surface. Using a three-point mooring system, they are designed to be installed one to five miles (8 km) offshore in water 100 to 200 feet (60 m) deep.
  • An example of a surface following device is the Pelamis Wave Energy Converter. The sections of the device articulate with the movement of the waves, each resisting motion between it and the next section, creating pressurized oil to drive a hydraulic ram which drives a hydraulic motor. The machine is long and narrow (snake-like) and points into the waves; it attenuates the waves, gathering more energy than its narrow profile suggests. Its articulating sections drive internal hydraulic generators (through the use of pumps and accumulators).
  • With the Wave Dragon wave energy converter large "arms" focus waves up a ramp into an offshore reservoir. The water returns to the ocean by the force of gravity via hydroelectric generators.
  • The Anaconda Wave Energy Converter is in the early stages of development by UK company Checkmate SeaEnergy. The concept is a 200 metre long rubber tube which is tethered underwater. Passing waves will instigate a wave inside the tube, which will then propagates down its walls, driving a turbine at the far end.
  • The AquaBuOY is made by Finavera Renewables Inc. 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 commercial wave power production facility utilizing the AquaBuOY technology is beginning initial construction in Portugal. The company has 250 MW of projects planned or under development on the west coast of North America. This technology seems to be on-hold as of February 2009. Finavera Renewables surrendered wave energy permits from FERC.
  • The SeaRaser, built by Alvin Smith, uses an entirely new technique (pumping) for gathering the wave energy.
  • A device called CETO, currently being tested off Fremantle, Western Australia, consists of a single piston pump attached to the sea floor, with a float tethered to the piston. Waves cause the float to rise and fall, generating pressurized water, which is piped to an onshore facility to drive hydraulic generators or run reverse osmosis water desalination.
  • Another type of wave buoys, using special polymeres, is being developed by SRI
  • Wavebob is an Irish Company who have conducted some ocean trials.
  • The Oyster wave energy converter is a hydro-electric wave energy device currently being developed by Aquamarine Power. The wave energy device captures the energy found in nearshore waves and converts it into clean usable electricity. The systems consists of a hinged mechanical flap connected to the seabed at around 10m depth. Each passing wave moves the flap which drives hydraulic pistons to deliver high pressure water via a pipeline to an onshore turbine which generates electricity. In November 2009, the first full-scale demonstrator Oyster began producing power when it was launched at the European Marine Energy Centre (EMEC) on Orkney.
  • Ocean Energy have developed the OE buoy which has completed (September 2009) a 2-year sea trial in one quarter scale form. The OE buoy has only one moving part.
  • The Lysekil Project is based on a concept with a direct driven linear generator placed on the seabed. The generator is connected to a buoy at the surface via a line. The movements of the buoy will drive the translator in the generator. The advantage of this setup is a less complex mechanical system with potentially a smaller need for maintenance. One drawback is a more complicated electrical system.
  • An Australian firm, Oceanlinx, is developing a deep-water technology to generate electricity from, ostensibly, easy-to-predict long-wavelength ocean swell oscillations. Oceanlinx recently began installation of a third and final demonstration-scale, grid-connected unit near Port Kembla, near Sydney, Australia, a 2.5 MWe system that is expected to go online in early 2010, when its power will be connected to the Australian grid. The companies much smaller first-generation prototype unit, in operation since 2006, is now being disassembled.
  • An Israeli firm, SDE ENERGY LTD., has developed a breakwater-based wave energy converter. This device is close to the shore and utilizes the vertical motion of buoys for creating an hydraulic pressure, which in turn operates the system's generators. S.D.E. is currently building a new 250 kWh model in the port of Jaffa, Tel Aviv and preparing to construct it's standing orders for a 100mWh power plants in the islands of Zanzibar and Kosrae, Micronesia.
  • Another Australian company BioPower Systems uses the biomimicry of the floats of swaying sea plants in the presence of ocean waves in its BioWave system.
  • A Portuguese company, Martifer, is developing an attenuator and offshore device, FLOW.

Challenges to Deploying Wave Power devices

These are some of the challenges to deploying wave power devices:

  • The device needs to capture a reasonable fraction of the wave energy in irregular waves, in a wide range of sea states.
  • There is an extremely large fluctuation of power in the waves. The peak absorption capacity needs to be much (more than 10 times) larger than the mean power. For wave power plant the ratio is typically 4.
  • The device has to efficiently convert wave motion into electricity. Generally speaking, wave power is available at low speed and high force, and the motion of forces is not in a single direction. Most readily-available electric generators operate at higher speeds, and most readily-available turbines require a constant, steady flow.
  • The device has to be able to survive storm damage and saltwater corrosion. Likely sources of failure include seized bearings, broken welds, and snapped mooring lines. Hence, designers may create prototypes that are so overbuilt that materials costs prohibit affordable production.
  • The total cost of electricity is high. Wave power will be competitive only when the total cost of generation is reduced (or the total cost of power generated from other sources increases). The total cost includes the primary converter, the power take-off system, the mooring system, installation & maintenance cost, and electricity delivery costs.
  • There is a potential impact on the marine environment. Noise pollution, for example, could have negative impact if not monitored, although the noise and visible impact of each design varies greatly.
  • In terms of socio-economic challenges, wave farms can result in the displacement of commercial and recreational fishermen from productive fishing grounds, can change the pattern of beach sand nourishment, and may represent hazards to safe navigation.
  • In the US, development of wave farms is currently hindered by a maze of state and federal regulatory hurdles and limited R&D funding.
  • Wave power plant generate about 2,700 gigawatts of power. Of those 2,700 gigawatts, only about 500 gigawatts can be captured with the current technology.

Agucadoura Wave Farm

The Aguçadoura Wave Power Plant is the world's first commercial wave farm. It is located 5 km (3 mi) offshore near Póvoa de Varzim north of Oporto in Portugal. The farm uses three Pelamis wave energy converters to convert the motion of the ocean surface waves into electricity, totalling to 2.25MW in total installed capacity. The farm was officially opened on the 23rd of September 2008, by the Portuguese Minister of Economy.

Developed by the Scottish company Pelamis Wave Power, the Pelamis machine is made up of connected sections which flex and bend relative to one another as waves run along the structure. This motion is resisted by hydraulic rams which pump high pressure oil through hydraulic motors which in turn drive electrical generators. The three machines which make up the Aguçadoura Wave Park are each rated at 750KW, giving an installed capacity of 2.25MW, enough to meet the average electricity demand of more than 1,500 Portuguese homes.

The project was originally conceived by the Portuguese renewable energy company Enersis, which developed and financed the project and which was subsequently bought by the Australian infrastructure company Babcock & Brown in December 2005. In the last quarter of 2008 Babcock & Brown had its shares suspended and has been in a managed process of selling its assets, including the Agucadoura project. In March 2009 Babcock & Brown went into voluntary administration.

In November 2008 the Pelamis machines were brought back to harbor at Leixões due to a technical problem with some of the bearings for which a solution has been found. However the machines are likely to remain offline until a new partner is found to take over Babcock & Brown’s 77% share in the project.

Wave farms

The world's first commercial wave farm opened in 2008 at the Aguçadora Wave Park near Póvoa de Varzim in Portugal. It uses three Pelamis P-750 machines with a total installed capacity of 2.25MW. However, in November the units were removed from the water, and in March 2009 the project was suspended indefinitely. A second phase of the project planned to increase the installed capacity to 21MW using a further 25 Pelamis machines is in doubt following Babcock's withdrawal from the project.

Funding for a 3MW wave farm in Scotland was announced on 20 February 2007 by the Scottish Executive, at a cost of over 4 million pounds, as part of a £13 million funding package for marine power in Scotland. The farm will be the world's largest, with a capacity of 3MW generated by four Pelamis machines.

Funding has also been announced for the development of a Wave hub off the north coast of Cornwall, England. The Wave hub will act as giant extension cable, allowing arrays of wave energy generating devices to be connected to the electricity grid. The Wave hub will initially allow 20MW of capacity to be connected, with potential expansion to 40MW. Four device manufacturers have so far expressed interest in connecting to the Wave hub.

The scientists have calculated that wave energy gathered at Wave Hub will be enough to power up to 7,500 households. Savings that the Cornwall wave power generator will bring are significant: about 300,000 tons of carbon dioxide in the next 25 years.

A CETO wave farm off the coast of Western Australia has been operating to prove commercial viability and, after preliminary environmental approval, is poised for further development.

Wave Energy, Wave Power

Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example for electricity generation, water desalination, or the pumping of water (into reservoirs).

Wave power plant is distinct from the diurnal flux of tidal power and the steady gyre of ocean currents. Wave power generation is not currently a widely employed commercial technology although there have been attempts at using it since at least 1890. The world's first commercial wave farm is based in Portugal, at the Aguçadoura Wave Park, which consists of three 750 kilowatt Pelamis devices.

The first known patent to utilise energy from ocean waves dates back to 1799 and was filed in Paris by Girard and his son. An early application of wave power plant was a device constructed around 1910 by Bochaux-Praceique to light and power his house at Royan, near Bordeaux in France. It appears that this was the first Oscillating Water Column type of wave energy device. From 1855 to 1973 there were already 340 patents filed in the UK alone.

Modern scientific pursuit of wave energy was however pioneered by Yoshio Masuda's experiments in the 1940s. He has tested various concepts of wave energy devices at sea, with several hundred units used to power navigation lights. Among these was the concept of extracting power from the angular motion at the joints of an articulated raft, which was proposed in the 1950s by Masuda.

A renewed interest in wave energy was motivated by the oil crisis in 1973. A number of university researchers reexamined the potential of generating energy from ocean waves, among whom notably were Stephen Salter from the University of Edinburgh, Kjell Budal and Johannes Falnes from Norwegian Institute of Technology (now merged into Norwegian University of Science and Technology), Michael E. McCormick from U. S. Naval Academy, David Evans from Bristol University, Michael French from University of Lancaster, John Newman and Chiang C. Mei from MIT.

In the 1980s, as the oil price went down, wave-energy funding was drastically reduced. Nevertheless, a few first-generation prototypes were tested at sea. More recently, following the issue of climate change, there is again a growing interest worldwide for renewable energy, including wave energy power plant.