Ecology And Environment

How the oceans can supply alternative energy sources



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Rising energy costs, rumors of depleting fossil fuels, global warming, environmental toxins; it sounds like the Christmas wish list of Dr. Seuss' the Grinch. In an article in the Wall Street Journal (WSJ), entitled Electric Industry Grds for Delays In Coal, Gas Flows, it is discussed how in New England, the grid operator expects another moderate increase in winter-electricity demand. It warned that the region relies on two major interstate pipelines for natural gas from the Gulf Coast, and if production problems limit supplies "most of the region's gas-fired power plants could be adversely affected."

Another WSJ article, Big Oil Firms Join Hunt for Natural Gas in U.S. Independent Producers Pave Way for New Kind of Field tells how unlocking fuel from RockBig Oil's new interest highlights significant changes in the U.S. onshore energy industry. It tells how gone are the days when companies looked for big reservoirs of oil trapped underground in places like the Texas Permian Basin. It would appear that the oil giants largely lost interest in the United States when these deposits began to be sucked dry. They are no longer looking for oil because they think any untapped pools would be too small to be worthwhile.

Still another recent article in the WSJ, Some States Take On Greenhouse Gases, discusses how plans to regulate carbon dioxide emissions is sparking feuds, mainly around the northeast and west coast. Electricity producers, oil refiners and producers, and land fills and cement production, all emit substantial amounts of greenhouse gases. States such as California are proposing that a power plant selling into the state's market must have no more emissions than a modern power plant fired by natural gas. The feuds are political and financial as at least 20 coal-fired power plants are being built in surrounding regions that could serve California's electricity needs, but under the new standards would make them obsolete.

As has been discussed for over 40 years, prudence would suggest we look into other innovations for supplying our energy and electricity needs. We do not have to look far, after all, Earth is known as the blue planet, or the big blue marble, and for good reason. The global ocean is certainly the most prominent feature of the planet, blanketing nearly 71 percent of Earth's surface. It has average depth of about 3800 meters (12,500 feet), accounts for about 97 percent of Earth's water, and contains a vast reserve of resources of which we are only beginning to tap to their full potential. The oceans can provide a wide variety of foods, minerals, electricity, desalinated water, transportation, and recreation for the people of our world. The many possibilities of the usage of our seas are limited only by our imagination. For that reason, this discussion will be limited to sources of electrical energy that can be harnessed from the seas.

The sea has long been seen as a source of energy. In the Middle Ages (1200-1500 AD) farmers trapped sea water in mill ponds and used it to power water mills as the tide dropped. The first modern device for generating electricity from wave power was patented by two French scientists in 1799. In the United States, more than 150 patents for wave power machines have been granted.

According to The International Energy Outlook 2005, the world's energy consumption is expected to rise 63.8 percent between 2002 and 2025. Total world consumption of marketed energy is expected to expand from 412 quadrillion British thermal units (Btu) in 2002 to 553 quadrillion Btu in 2015 and then to 645 quadrillion Btu in 2025, or a 57percent increase over the 2002 to 2025 time period. The report projects increased consumption of primary energy from all sources over the next two decades; however oil is expected to remain the dominant energy source over the projection period, with its share of total world energy consumption declining only slightly, from 39 percent in 2002 to 38 percent in 2025.

Our heavy dependence on fossil fuels is becoming increasingly apparent and numerous studies suggest that present reserves of oil and natural gas may be consumed within a few decades and coal within a few centuries. Political instability in the Middle East has also been a strong factor in the economic consequences of oil dependency. Environmental and political concerns are just two reasons why alternative energy sources, such as ocean energy conversion, need to be considered.

Over the last fifty years, engineers have begun to look at tidal and wave power on a larger, industrial scale. Though viable alternatives, it has often been seen as uneconomical. Although some pilot projects, many of which were in Europe, showed that energy could be generated, they also showed that, even if cost of the energy generated was not considered, there was a real problem making equipment, which could withstand the extremely harsh marine environment. In the late 1990s, it finally became clear that technology has advanced to the point where reliable and cheap electricity from the oceans is becoming a real possibility.

Forms of alternative power generation

Thermal Energy
The oceans are the world's largest solar collectors and one theory for obtaining electricity is based on the temperature differences between surface water, which is heated by the sun, and deep water, which stays very cold. According to The Solar Energy Research Institute, on an average day, 60 million square kilometers (23 million square miles) of tropical seas absorb an amount of solar radiation equal in heat content to about 250 billion barrels of oil. If less than one-tenth of one percent of this stored solar energy could be converted into electric power, it would supply more than 20 times the total amount of electricity consumed in the United States on any given day. This solar energy can be converted to electricity by a process known as Ocean Thermal Energy Conversion or OTEC. These systems use the fact that the ocean's layers of water have different temperatures to drive a power-producing cycle. As long as the temperature between the warm surface water and the cold deep water differs by about 20C (36F), an OTEC system can produce a significant amount of power. The cold, deep seawater used in the OTEC process is also rich in nutrients, and it can be used to culture both marine organisms and plant life near the shore or on land.

The benefits of an OTEC plant can be measured in value as both economic and non-economic. First and foremost is that it has significant potential to provide clean, cost-effective electricity for the future. It also helps produce fuels such as hydrogen, ammonia, and methanol. It produces desalinated water for industrial, agricultural, and residential uses. Furthermore, it is a resource for on-shore and near-shore marine culture operations. Non-economical benefits, which help us achieve global environmental goals, include promoting competitiveness and international trade, enhancing energy independence and energy security, and has potential to mitigate greenhouse gas emissions resulting from burning fossil fuels. For small island nations, the benefits of OTEC include self-sufficiency, minimal environmental impacts, and improved sanitation and nutrition, which result from the greater availability of desalinated water and marine culture products.

The primary drawback of the project is the limited area that OTEC can be utilized. Due to the required temperature variations, it is not a viable solution for northern tier nations.

Wave Power
Ocean waves are a tertiary form of solar energy, in that unequal heating of the Earth's surface generates wind, and wind blowing over water generates waves. The reality is that the power is there, the challenge is to harness it. Just as electrical power is not stored in transmission lines, but flows from the generator to the user, so wave energy is not static, but flows in the direction of wave propagation. If the energy flowing past a particular point in the ocean or arriving at a shoreline is not captured there then it is lost. Because the energy is flowing, we can consider the amount of power in kW contained in each linear meter of wave front. Wave energy is the most predictable and dependable form of renewable energy. Good wave power sites are available around the world, especially close to population centers. Generating energy from wave power is possible across the globe.

The values are the average power flux in kW/m at different points across the globe. The quoted values are for deep water sites; however, a single point value of annual wave power hides the wide variation between the differing powers available in different seasons of the year.

Wave energy has two components, potential energy and kinetic energy, both of which can be harnessed by changing it into another form, such as mechanical motion or fluid pressure. Various varieties of wave energy conversion devices currently exist, including oscillating water columns, surge devices, heaving floats, pitching devices, heaving and pitching floats, and heave and surge devices. These devices may be designed to float on the surface or be moored to the ocean floor and can be located in either shallow or deep water.

Perhaps the most common device in use for harnessing the wave's power is the oscillating water column (OWC). The OWC is connected to a buoy and as the buoy heaves up and down in the waves, the OWC in the centre pipe of the buoy's hull acts like a piston, alternately pushing air out the top of the pipe and drawing it in. This pneumatic power can be converted directly to sound through a foghorn, or indirectly to light by spinning a turbine-generator, which charges an electrical storage battery.

Energy is stored in the waves until they reach the shallows and beaches, sometimes with destructive force. If only two trillion watts of electricity could be harvested from the sea, it would be the equivalent of twice the world's energy produced from nuclear, oil, gas, and coal-fuelled power stations (oceanpowertechnologies.com). As a general rule, coastlines with an ocean frontage greater than 250 miles are suitable for development.

Of course, as with the Ocean Thermal Energy Conversion system, the wave harnessing has significant potential to provide clean, cost-effective electricity for the future. It is highly modular and, therefore, less costly to implement and easier to scale as needs change. As an example, conventional power stations must be built on a large scale to be economical, making them difficult to maintain, and vulnerable to failure and acts of terrorism. The footprint of a 100MW conventional power plant superstructure, including surrounding grounds, fuel unloading areas, waste settling ponds, and additional facilities can require up to 2 square miles of valuable real estate. A comparable wave power plant, as suggested by Ocean Power Technologies, would occupy less than one square mile of unused ocean surface out of sight from the shore.

A wave energy system offers many advantages over wind and solar power stations; it is placed between 0.5 and 5 miles offshore, meaning energy can be generated without sacrificing land or creating an eyesore and large wind farms require hundreds of acres of valuable open land or ocean space, create noise pollution, and become the dominant visual element of the landscape or seascape. Solar farms also require considerable open space for installation and, more important is their dependence on consistent sunny weather, making them a viable alternative in a relatively small portion of the world
Wave energy provides power without creating waste. It does not threaten marine life or the environment with spillage, CO2 emissions, or pollution from radiation and particle matter.

Though the idea of harnessing the awesome power of our most abundant resource has been in existence for ages, many research and development goals remain to be accomplished if these types of ocean energy sources are to be feasible. Initial investment cost reductions are imperative to make renewable energy an attractive alternative to fossil-based fuels. The reliability and efficiency of the associated technologies, though greatly improving over the last few years, must continue to build and set higher standards. Suitable sites need to be identified while taking into consideration navigational hazards created by offshore devices, fishing industries, ecological impacts, as well as the aesthetics like scenic views from the shorelines.

Public awareness and education concerning the benefits of renewable energy sources need to be increased. Perhaps most importantly, the global political climate must also change, with greater emphasis being placed on long-term benefits and costs rather than focusing on the short-term. Challenge the fossil-fuel industry; make them see how their product must eventually dwindle to nothing and to see themselves as a dying breed. We must also gain a much better understanding of the impacts of these technologies on marine life and on our shorelines. We must go forward bearing in mind a lesson many in the traditional fuel systems have forgotten; the oceans can continue to be a valuable resource for our planet, but only if we take steps to preserve this natural wonder and use it responsibly.

References and additional sources:

Bregman, R.; Knapp, R.; and Takahashi, P. (1996). Ocean Energy Resource Systems. Sea Technology, 37, 16-25.

Currie, R., Elrick, B., Ioannidi, M., Nicolson, C., Renewables in Scotland. University of Strathclyde,

Glasgow, Scotland, May 2002, http://www.esru.strath.ac.uk/EandE/Web_sites/0102/RE_info/Tidal%20Power.htm

Flalka, John J. "Some States Take On Greenhouse Gases." Wall Street Journal 13 December 2005, Natl. ed.: A4

Gold, Russell. "Big Oil Firms Join Hunt for Natural Gas in U.S. Independent Producers Pave Way for New Kind of Field." Wall Street Journal, 29 November 2005, Retrieved from http://online.wsj.com/public/us

International Energy Outlook 2005, Report #:DOE/EIA-0484(2005) Released Date: July 2005, http://www.eia.doe.gov/oiaf/ieo/world.html

Ocean Thermal Energy Conversion: An Overview. SERI/SP-220-3024. Golden, CO: Solar Energy Research Institute; 36 pp., Solar Energy Research Institute. (November 1989)., http://www.nrel.gov/otec/

Smith, Rebecca. "Electric Industry Girds for Delays In Coal, Gas Flows." Wall Street Journal, 25 November 2005, Retrieved from http://online.wsj.com/public/us

Wave Energy vs. Conventional Energy, Ocean Power Technologies, Pennington, New Jersey, http://www.oceanpowertechnologies.com/news/

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