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MAY 31 2005
UNITED NATIONS COMMISSION ON
SUSTAINABLE DEVELOPMENT
TIDAL ENERGY AND LOW-HEAD
RIVER POWER:
Thomas J. Goreau
Scott Anderson
Alexander Gorlov
Edward Kurth SUMMARY Vast, sustainable energy resources are available in tide and river currents. These resources can now be captured using cutting edge, efficient, Gorlov helical turbines. This non-polluting technology is low-cost, widely applicable, environmentally friendly, simple to implement and operate, and easily scaled from very small isolated rural settings to large power plants on the grid. We call on UNCSD to mandate a strategy to develop and implement this technology to tap these clean energy resources and contribute to sustainable development of island, coastal, and riverine nations. A program to apply this technology wherever it is the most cost-effective energy alternative will immediately contribute to reduce the global warming caused by fossil fuels that is threatening the future of our planet, its citizens, and its ecosystems, and is killing coral reefs worldwide. GLOBAL POTENTIAL OF TIDAL ENERGY AND LOW-HEAD RIVER POWER Tidal energy is distributed widely around the world as is indicated in the map in Figure 1 below. Note the extensive distribution of tidal energy throughout the Indian and Pacific Oceans.
Low-head river power cannot be easily mapped on a world scale because of its local distribution, but in general it is found in wet areas of all continents and islands in the transition zone from highlands to floodplains. Below we discuss the applicability of new, cost-effective, non-polluting technology to convert the energy of tidal and river currents into electrical power, without using dams. This can be used everywhere that water velocity is about one meter per second (two knots) or above, which allows a vast energy source to be obtained where dam power is impossible, including many places currently lacking energy resources. NEW TECHNOLOGY FOR TIDAL ENERGY AND LOW-HEAD RIVER POWER Tidal energy has been almost completely unexploited, despite its vast potential, because until recently there was no way to efficiently tap unconfined currents. Tidal energy could only be captured by building a dam in confined bays with large tides, creating a water level difference ("head") to drive a conventional high-speed turbine. This meant not exploiting the kinetic energy in the tidal flow but exploiting the height difference created by confining the entire flow. Similarly, river water energy could only be affordably tapped at a limited number of sites by damming rivers, instead of capturing the energy in the water flow. High-speed turbines for large-scale, capital-intensive, dammed flow energy production have long been used. For free flow or low head applications there are two options: propeller type or horizontal-axis turbines, which must be rotated in order to face into the flow while current directions change, and vertical-axis turbines, which rotate in the same direction no matter which way the current flows because of the angle of the blade to the rotation axis. Vertical-axis turbines had a troubled history because most designs become unstable at high speed, and had to be shut down to prevent them from vibrating themselves apart just when they should produce the most power. This problem has recently been solved by the Gorlov helical turbine, which is inherently stable at high speeds due to its helical blade design. Stability in high current velocity is crucial above start-up velocity, as power output increases eight times for each doubling of water velocity, allowing Gorlov turbines to tap the most energy-intense conditions. Also the helical turbine has the highest efficiency of conversion of water-flow energy into power of any low-head turbine. A photograph of a small helical turbine is shown in Figure 2 below.
Helical turbines allow unconfined tidal currents, ocean currents, and low-head river flows to be tapped, greatly increasing the locations and flows that can be used to generate electricity, without the negative environmental impacts of dams. Their rotation speed is low enough to pose no danger to fish. In rivers where logs, debris, and rocks may be transported by currents a grate may be needed to protect the turbine from being damaged. Locations with adequate flows for these turbines can be found in many countries. Because different size turbines can be built, and because many small ones can be mounted on the same shaft or separately, strong unconfined tidal flows between rocks and islands and the mainland can be tapped, as can small rivers before they emerge onto flood plains. IMPORTANT APPLICATIONS FOR ISLAND NATIONS OF THE INDIAN AND PACIFIC OCEANS. A particularly important application is in the island nations of the Pacific and Indian Oceans, which often exploit no local energy resources and may use half or more of their foreign exchange to purchase diesel fuel for power plants. This high-cost electricity is usually available only on the capital island, with outer islands using kerosene stoves and lamps. Almost all these islands have one or more passes surrounding reefs through which all tidal flow in the lagoon rushes four times a day. Utilizing these untapped resources could free many island nations from importing fuels for electricity generation, and since the resource is available on virtually all islands, places now lacking electricity could benefit. By using helical turbines, tropical countries can not only produce clean power for direct human use, they can also use tidal currents to restore their devastated coral reefs and fisheries and protect their coastlines from rising sea level. Development of tidal energy resources in the tropics can provide a source of power that can be used to run the Biorock process. This process uses low-power direct current electricity to grow limestone reefs, and greatly increases the growth rate of corals, their ability to survive extreme high temperatures produced by global warming, and their quality as fish and shellfish habitat. These structures create sustainable fisheries and mariculture resources, coral arks to save species from extinction from global warming, and prize-winning eco-tourism resources. They produce hydrogen and construction materials, and grow coral reefs in a few years that act as breakwaters and have turned severely eroding beaches (as in the Maldives) into rapidly growing beaches. PROJECTS CURRENTLY UNDERWAY Two current projects illustrate the range of potential applications: · In Uldolmok Strait, South Korea, between Jindo Island and the mainland, tidal currents reach 13 knots. After an initial, successful test of two helical turbines in 2002, the Korean government has begun a second phase to produce a megawatt of power. If that is successful, thousands of helical turbines could be used to tap the 3,600 megawatts of energy potential in the strait. That is the equivalent of three times the power of the $1.8 billion Merowe Dam that will block the Nile at the 4th cataract or of four nuclear reactors (with no risk of radioactive leaks or bomb production). · On a small scale, a project in a tidal stream near the mouth of the Amazon River in Brazil generates power for a small isolated community. The turbine and power system were built by villagers in local workshops with the only imported item being the turbine blades. The cost of the materials and equipment is considerably less than equivalent photovoltaic panels, and maintenance and operation well below that of diesel generators. These two projects illustrate that clean energy can be produced both a large industrial scale using simple equipment and also be used on a small scale, and replicated in vast numbers of locations adapted to local conditions and energy needs. Large-scale applications of this technology could provide clean low-cost power in many communities that now lack it, improving their quality of life, and allowing sustainable development that is now impossible. Many coastal countries and islands could become energy self sufficient, providing more energy from local resources without importing expensive and polluting fossil fuels. With a hydrogen economy, some island nations that now cannot exploit their energy resources could become energy exporters. Indonesia, which will run out of oil in the near future, has incredible unutilized tidal current resources that will last forever. However extending these pioneering examples to use this technology wherever it is the most cost-effective energy alternative will take policies and funding that do not now exist. It is important for UNCSD to take active steps to allow these energy resources to be utilized as quickly as possible. A DEVELOPMENT STRATEGY Large-scale development of tidal energy and low-head river power will take several steps. At present virtually no funding is available for developing, extending, and applying this technology, despite its proven effectiveness, potentially enormous capacity, and the vast multitude of suitable sites. We call on the United Nations Commission on Sustainable Development to take immediate steps to: 1) Recommend that tidal, ocean current, and low-head river power be explicitly listed as funding priorities for sustainable energy resource development. 2) Call for immediate support to set up demonstration projects and pilot projects so that policy makers and the public can learn of its applications to their own energy needs. 3) Mandate funding for regional centers for training in the technology. 4) Fund studies to identify sites where this technology could be applied and assess their potential magnitude. 5) Implement a crash program to develop and apply this technology wherever it is the most cost-effective alternative on as urgent a time frame as possible, to promote clean energy and sustainable development, reduce the devastating effects of global warming, and repair the damage to coral reefs and fisheries. APPENDIX PowerPoint presentation prepared for the 2005 Mauritius UN Summit of Small Island Developing States REFERENCES J. Davis, 2005, Alexander's wonderful machine, Onearth, Spring 2005, http://www.nrdc.org/onearth/05spr/gorlov1.asp A. M. Gorlov, 2001, Tidal Energy, in Encyclopedia of Science and Technology: 2955-2960 A. M. Gorlov, 2004, Harnessing power from ocean currents and tides, Sea Technology, July 2004: 40-43 For more information on Gorlov turbines please go to: http://www.gcktechnology.com/GCK/ S. Anderson, 2003, The Tide-Energy Project near the Mouth of the Amazon Report to the Ford Foundation T. J. Goreau, 2004, Sustainable Ocean Management for Small Island Developing States: A Vision for the UN SIDS Summit in Mauritius, January 2005, UN Expert Meeting on Ocean Management in Small Island Developing States, Suva, Fiji, |
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