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An Ocean of Energy
There for the Taking
Tundi Agardy, Ph.D.
Introduction
Some look to the ocean and take in seascapes that calm the mind and soothe the senses, while others see a bounty of living resources and biodiversity. The oceans have supported great societies and civilizations, and have been the setting for innumerable historical events. But more and more, people are looking to the sea for something the land is increasingly unable to provide at the levels we demand: energy. Oceans offer a vast array of energy options, whether conventional sources of oil and gas, renewable energy such as wind, wave and tidal, or radical new forms of energy such as algal-based biofuels. As our energy demands continue to grow and our conventional sources dwindle or become inaccessible, the oceans will be looked to more and more to meet our energy needs.
The oceans span nearly three quarters of the earth’s surface, and directly support 70% of the planet’s photosynthesis. There is thus a huge resource base and vast amounts of space in which to derive and exploit energy. Solar, mechanical (wave and tidal), thermal, and wind energy can all be generated at sea, to supplement conventional sources of non-renewables such as oil and gas. And the oceans can support biofuel production as well.
It is true that whether we are at or near peak oil is a matter of great controversy. What is indisputable is that new supplies and even new forms of energy are needed to meet ever-growing demands, reduce the risks of continuing to emit high levels of greenhouse gases, and allow countries to develop energy-independence. The ocean of energy is there for the taking, and if we use it wisely and carefully, ocean energy may well be central to supporting human life on the planet for many centuries to come.
Non-Renewables: Offshore Oil & Gas
That the oceans harbor oil and natural gas reserves has long been recognized, but finding and extracting those resources have proved challenging in the marine environment. The first offshore oil well was drilled off the coast of California in 1897 and rapid expansion of the industry occurred thereafter, however early drilling was limited to depths of only about 100 meters. Modern technology today allows recovery from water over three kilometers deep.
The United States and the countries of Northern Europe have a strong dependence on oceanic fossil fuels. In recent years, offshore (or OCS, standing for Outer Continental Shelf) oil and gas accounted for about a quarter of U.S. domestic supply; it is estimated that 30% of undiscovered oil and gas reserves in the U.S. exist as offshore fields. Some areas, like the Gulf of Mexico and the North Sea, are dotted with fixed oil rigs able to pump massive amounts of oil and gas to shore-based processing facilities. Floating rigs are also used in offshore areas.
 Offshore platform located in the Gulf of Mexico Photo credit: Chad Teer, Wikipedia Commons
Naturally seeping oil can similarly be recovered. When oil escapes from deep sea fields, it rises to the surface, sometimes in significant quantities. In the Santa Barbara Channel off California (USA), for instance, 150 barrels of oil seep out per day. In addition, millions of cubic meters of gas seep out and escape into the atmosphere. In 1982, oil and gas companies built two huge steel pyramids to place over the seeps in California and recover otherwise wasted energy resources. Such seep recovery efforts have subsequently sprung up in many other parts of the globe.
Many countries have recognized the potential of offshore reserves but have curbed oil exploration and extraction activities in sensitive coastal areas. A moratorium has been in place in the Canadian eastern seaboard for decades, and in 1990, President George H. Bush established an OCS moratorium in parts of Aleutian Islands, Pacific Coast, Eastern Gulf of Mexico, and the North Atlantic within U.S. jurisdictions. The latter restriction was renewed by President Clinton and remained in effect until this year [2007]. Increasingly, local jurisdictions have tried to limit offshore oil and gas activity. In the U.S., coastal states have exerted their jurisdictional authority, hoping to reduce risks of environmental catastrophe and reduce environmental effects within state waters (from 0-3 miles offshore).
Recent research has highlighted the potential for seabed-based methane hydrates to meet some energy demands. Methane hydrates are ice-like deposits found in the top few hundred meters of sediment in certain deep ocean areas of the continental margins. The methane gas is actually trapped in ice cages, and can be easily extracted from it, but removing the hydrates from the seabed has proved problematic. Russian energy experts have tried using antifreeze to remove the methane from hydrates, and recent research has focused on trying to pipe warm surface water down to melt the hydrates and then piping the gas to the surface using a parallel set of pipes. However, melting the hydrates to release methane may cause the seafloor to become unstable, and could have untold ecological impacts as well. In addition, if methane is lost to the atmosphere during the process, it could add to the global warming phenomenon, since methane is a potent greenhouse gas.
Nevertheless, methane hydrates have caused excitement in the energy field. Some researchers also believe that there is free-flowing methane gas beneath the several hundred meters deep hydrate layers1. The National Energy Education Project (US) suggests that methane hydrates may contain over 30 times the existing natural gas resources and reserves worldwide2.
 Burning Hydrate - Photo credit: USGS, Wikipedia Commons
Ocean-Based Renewable Energy
Fossil fuels like petroleum or other hydrocarbon resources are considered nonrenewable, since it takes millions of years to convert organic matter into these energy resources. As oil and gas becomes increasingly difficult to recover, as geopolitics complicate the access to both the resources and the markets for such energy products, and as existing supplies diminish and the world approaches peak oil production, interest in renewables has increased. Additionally, recent attention on carbon emissions from hydrocarbon use and their role in global warming and other climate changes means that renewable energy resources are fast becoming a preferred alternative. However, renewable energy resources are still at this point in time generally more expensive than conventional non-renewables, and production tends to be small scale.
There are four major classes of renewable energy available at sea: 1) kinetic energy unique to the ocean, such as energy provided by surface waves and tides, 2) renewable energy not unique to the ocean, such as wind and solar energy, 3) thermal energy, such as that produced by the temperature differential of surface and deep ocean waters, and 4) marine biofuels, such as those derived from algae.
Kinetic
Attempts have been made to harness the enormous energy potential of moving ocean water for decades. As far back as the middle of the 11th century, people were making the logical extension from exploiting energy in running rivers, streams, and canals (an ancient technology that probably predates even waterwheels for grinding flour) to trying to harness that same mechanical energy contained in waves and tides. The first commercial scale wave energy plant was commissioned for the Isle of Islay (Scotland) in 2000; at about the same time, the Japan Marine Science and Technology Center created a large scale experimental wave energy platform.
Early attempts to harness the kinetic energy contained in moving seawater were focused on estuaries, where both river hydrology and tides influence the movement of seawater or brackish water. But wave energy can be harnessed, in theory, anywhere where there are predictable waves, including in offshore areas. The first commercial scale wave power station was established in Scotland at the beginning of the century.
 Tidal Turbine Farm, Photo credit: www.windenergy.co.uk
Oceanlinx, a company formerly known as Energetech, has developed wave energy projects in three areas of Australia (New South Wales, Victoria, and Tasmania), in two sites in the U.S. (Rhode Island and Hawaii), in South Africa, in Mexico, and in the United Kingdom. The wave energy devices follow the simple principle of the model below:
 http://www.energyquest.ca.gov/story/chapter14.html
Water inside a chamber which is open on the bottom rises and falls as waves pass through, compressing and displacing the air inside which then drives a turbine. Wave energy is converted to mechanical energy that drives an electric generator. In some units, the turbine is driven on both the upward and the downward movement of water in the chamber. This is the case with the Oceanlinx turbine, which has variable pitch blades that produce maximum energy efficiency – each unit can produce enough energy to power 1,500 homes and can save thousands of tonnes of CO2 and SO 2 annually3. Other units rely on what is known as heaving buoy technology, which captures the kinetic energy in the orbital motion of surface waves. And tapering channels funnel waves into natural or artificial channels, filling an elevated reservoir which then allows water to flow back to the sea past turbines that capture and convert the energy.
 Tidal Turbine Farm, Photo credit: www.windenergy.co.uk
Tidal energy also has great potential as a renewable energy source, and has the advantage over waves of high predictability. Tides are caused by the gravitational pull of the moon and sun and their effects on the rotating Earth. In near shore areas, the differential between low and high tide (both of which occur twice a day) can approach 15 meters. However, there are a limited number of areas around the world where tidal range is high and topographic conditions would allow the utilization of tidal energy. According to the U.S. Department of Energy, only about 20 locations have good inlets and a large enough tidal range - (at least 3 meters) - to produce energy economically4.
Most tidal energy plants use a dam, known as a barrage, which spans a narrow bay or inlet. Sluice gates on the barrage allow the tidal basin to fill on the incoming high tide and empty through the turbine system on the outgoing, or ebb tide. As in wave energy systems, there are units that generate electricity on both the incoming and outgoing tides5. The La Rance Station in France began making electricity by harnessing kinetic energy of tides in 1966 and now produces enough energy to power 240,000 homes (240MW/year – or about 1/5 the power generated by a nuclear power plant). According to an article in the Financial Times, total wave and tidal power could eventually exceed 2TWh/year (2 trillion watts) of electrical energy generation.
Open ocean currents also contain potential power for energy generation. The government of Taiwan is looking into harnessing the strong Kuroshio Current to generate an expected 1.68TWh per year6.
Wind and Solar
Wind and solar energy generation are of course not unique to oceans. Yet oceans provide not only vast amounts of space and sufficient sunlight and wind – but also provide these as a commons property that can in theory be more easily accessed than private property to meet the public good.
Offshore windfarms are common in some parts of the world, such as Northern Europe. Oceanic wind is a preferred alternative to other forms of energy generation in areas where land is in short supply, and where coastal winds are sustained and strong. Denmark has led the effort in harnessing sea wind, and constructed the first offshore wind farm in 1991 off the Port of Vineby. According to the Financial Times, wind farms are expected to supply 8% of Denmark’s electricity by 20087. The UK opened its first offshore wind farm in 2000 in Northumberland, and is following Denmark’s lead with expanded wind farms and feasibility studies for siting in new areas.
 World's largest wind turbine Photo credit: www.reuk.co.uk
The oceans are also the world’s largest solar collector: one square mile contains more energy potential than 7,000 barrels of oil8. Solar arrays with unfettered access to sunlight can be installed in virtually any coastal area sheltered from excessive wind or waves. Currently most offshore solar plants are used to power oil platforms and in situ research equipment.
 Windfarm off the coast of Denmark Photo credit: www.sandia.gov
Thermal
The oceans can also be harnessed for energy by using the temperature differential of surface and deep waters to drive energy generation The differential exists because the sun warms the surface layers of the ocean, especially in the tropics, while deep waters stay cool. In order for the technology to be able to capture the thermal energy, this temperature differential must be more than 25 degrees Celsius.
Using the temperature of water to make energy actually dates back to 1881, when a French Engineer by the name of Jacques D'Arsonval first thought of using ocean thermal energy gradients. His student, Georges Claude, built the first OTEC plant in Cuba in 1930, producing 22 kilowatts of electricity with a low-pressure turbine. OTEC (Ocean Thermal Energy Conversion) is shorthand for all such thermal energy technologies, but it also refers specifically to the best known and largest scale pilot effort to harness ocean thermal energy, initiated in Hawaii in 1974.
 OTEC in Hawaii Photo credit: Wikipedia commons
Three types of systems are used to convert ocean thermal energy to electrical energy. Closed cycle systems use the warm surface water to vaporize a low-boiling point fluid such as ammonia. As the vapor boils and expands, it drives a turbine, which then activates a generator to produce electricity. Open cycle systems operate at low pressure and actually boil the seawater, which produces steam to drive the turbine/generator. Hybrid systems use elements of each, in an attempt to improve conversion efficiencies.
Although the temperature differential between surface waters and the deep ocean is significant in almost all parts of the globe, there are constraints to being able to harness this potential energy. Main among them is having deep cold water in close proximity to warm surface waters. Tropical island nations in the Pacific Ocean that have narrow continental shelves are particularly suited. According to NASA, some 98 tropical countries could benefit from the technology9.
OTEC also has spin-off benefits, including air conditioning, chilled-soil agriculture, aquaculture, and desalination10. And OTEC also may one day provide a means to mine ocean water for 57 trace elements, many of which are very valuable.
 Ocean Thermal Energy Conversion Photo credit: www.seao2.com
Thermal energy conversion has great potential, but enormous challenges remain. The technology is still very inefficient and piping large volumes across great depths of ocean (a kilometer or more) is a major engineering feat. Yet some energy experts believe OTEC could produce billions of watts of electrical power if it could be made cost-competitive with conventional power technologies.
Marine biofuels
At the moment there is a flurry of interest in alternative fuels, especially biofuels. Biofuels can be derived from agricultural and forestry residues, energy crops, landfill gas, and the biodegradable components of municipal and industrial wastes. Such fuels can be used for transportation fuel, to provide heat, or to generate electricity. Biomass residues have been burned to create power since at least the middle of the 19th Century, but inefficiencies tended to be extremely high until R&D became focused on making biofuels economically viable.
 Growing Algae for Biodiesel Photo credit: www.greentechnolog.com
Corn and switchgrass have received most of the attention as biofuel sources, but there is no reason why marine plants cannot provide the same cellulose for fuel conversion. This emerging technology is being tested in various venues.
 Photo credit: Tundi Agardi
Potential Downsides of Ocean Energy
According to a 2001 article in the Financial Times, ocean energy systems are becoming both more efficient and more economically viable. But these energy systems are not without cost.
First, there are the prospective ecological impacts. Constructing and operating facilities will undoubtedly have environmental costs, as will diverting, moving, or variously treating large volumes of seawater. Facilities will be generating their own pollution and wastes, including light pollution. Wind turbines and underwater turbines generate noise, which is a newfound concern of marine conservationists (see Exporting Pollution in the June isse of the World Ocean Observer). And removal of nonrenewable resources such as methane hydrates and renewable ones like algae may alter both the geology or oceanography and the ecology of some marine areas.
Underlying all of these ecological unknowns is the primary, unassailable fact that surveillance, monitoring, and protection of offshore facilities are infinitely more difficult than on land. This also means that security is more challenging, and energy plants may be more vulnerable to sabotage.
Converting the energy the oceans harbor is a technological puzzle that has been largely solved by enterprising engineers and scientists equipped with ever more sophisticated tools. But supplying that energy to users remains a daunting challenge. Energy is lost as it is brought from offshore onshore, and most large scale facilities are put as far offshore as possible to minimize conflicts with other ocean users.
Entrepreneurs face huge hurdles as well, which has resulted in constrained ocean energy development. In most developed countries the regulatory burden is immense, and the complexity of jurisdictions is reflected in a corollary complexity in obtaining the necessary permits for even demonstration projects. Recognizing these disincentives, the U.S. Federal Energy Regulatory Commission (FERC) announced a proposal to shorten the permitting process for pilot ocean energy projects to as little as six months11.
Finally, an inadequately informed public has sometimes resisted (and in some cases even blocked) the development of new sustainable energy technologies at sea, despite the fact that the alternative -- i.e. continued reliance on conventional energy sources -- is likely to have far greater impacts on the environment of the oceans12.
Conclusions
Our collective reliance on energy to support our lives and our industries has driven an unending search for new, lost-cost and accessible sources of energy across the entire planet. The vast oceans of the world hold great potential to meet our energy needs, especially as land-based fossil fuels become harder to find and exploit, and as concern for global warming begins to drive more forceful movement toward renewable energy use.
There are three factors that currently constrain us from using ocean energy to meet our needs. First is the lack of investment in researching new energy sources and technologies. Costs of developing and then utilizing these new technologies are prohibitive; investors cannot be assured of returns on investment for small scale experimental projects, but larger scale economically viable projects cannot be developed without the small scale prototypes. Few governments are progressive enough to sufficiently subsidize R&D in ocean energy technologies. And the few stalwart private sector companies who have embarked on the exploratory trail are understandably not willing to share their trade secrets with other companies or with government energy agencies. The solution thus lies in strong public private partnerships.
The second obstacle is insufficient education of the public at large. For too long the people of the developed world have taken energy for granted; it is only in times of high energy costs (particularly rising costs at the fuel pump or on home heating bills) that the public is even conscious of the fact that supplying energy is a costly, and sometimes unpredictable, endeavor. The sudden surge of interest in the effects of global warming, and increasing geopolitical tensions between oil supplying and oil consuming countries has opened many people’s minds to considerations of new sources of energy, as well as to issues of energy conservation. But even those open minds have had difficulty accessing good information about the costs and benefits of ocean energy. Public education and outreach which is based on the best available science, and uninfluenced by vested economic interests or political ones, is a top priority.
The last constraint is related to the first two. The public sector must find ways to increase incentives for the private sector to research and develop cost-effective and environmentally sensitive ocean energy ventures. And in order for that to happen, there needs to be political will – political will built on the realization of ocean energy potential, and political will driven by the demands of an increasingly educated and informed public. Such political will cannot blossom if politicians continue to yield to the enormous political pressure being brought down upon them by the lobbyists and spokespeople of conventional energy corporations, so developing this political will requires courage. Under the direction of good political leadership, we may soon realize the enormous potential that the oceans hold in meeting our energy needs.
Endnotes
1. http://www.eia.doe.gov
2. National Energy Education Project 2007. Ocean Energy. US Department of Energy, Washington DC
3. http://www.oceanlinx.com
4. http://www.eia.doe.gov/kids/energyfacts/sources/renewable/ocean.html
5. Charlier, R.H. 2003. Sustainable co-generation from the tides: bibliography Renewable and Sustainable Energy Reviews 7:215-247
6. http://www.renewableenergyaccess.com/rea/tech/oceanenergy
7. A.T. Jones, 2001. Renewable ocean energy systems becoming more viable. Available at http://www.waveberg.com/pdfs/financial_times.pdf
8. DiChristina, M. Sea Power.accessed 8/1/2007 at http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/ps_power.html
9. DiChristina, M. Sea Power.accessed 8/1/2007 at http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/ps_power.html
10. According to the U.S. Department of Energy, an OTEC plant that generates 2-MW of net electricity could produce about 4,300 cubic meters (14,118.3 cubic feet) of desalinated water each day (http://www.eere.energy.gov/consumer/renewable_energy/ocean)
11. http://www.renewableenergyaccess.com/rea/tech/oceanenergy
12. According to http://www.iea-oceans.org/index1.htm:
“There is a growing awareness of economic, energy security and environmental values of renewables and of its critical role to sustainable development. This is leading to political initiatives to promote their development, such as the EU Directive that establishes the target of increasing the 1997 6% share of renewables to 12% in 2010, and the recently approval of ratification of the Kyoto Protocol. Renewables are also high on the agenda of developing countries, and expanded renewable energy deployment is one of the key goals of the World Bank.” The U.S., Canada, Mexico, the U.K., Ireland, Sweden, Norway, Denmark, Belgium, France, Australia, New Zealand, Japan, China and India are all invested in ocean energy development. “The Implementing Agreement on Ocean Energy Systems commenced in October 2001. The Agreement's mission is to enhance international collaboration to make ocean energy technologies a significant energy option in the mid-term future.”
For more information, http://www.mtpc.org/cleanenergy/wavetidal/overview.htm provides many links to ocean energy sites
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