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Unformatted text preview: where wind-driven waves reach the shore after accumulating energy over long distances. For cur- rent designs of wave generators the economically exploitable resource is likely to be from 140 to 750 TWh per year. 92 The only operating commercial system has been the 2.25 MW Agucadora Wave Park off the coast of Portugal. (However, this was recently pulled ashore, and it is not clear when it will be redeployed). Research into wave energy has been funded by both governments and small engineering companies, and there are many prototype designs. Once the development stage is over and the price and siting problems of wave energy systems are better under- stood, there may be more investment in them. In order for costs to decrease, problems of corrosion and storm damage must be solved. PLUS: Once installed, wave energy devices emit negligible greenhouse gases and should be cheap to run. Since the majority of the world’s population lives near coastlines, wave energy is convenient for providing electricity to many. It may also turn out to provide an expensive but sustain- able way to desalinate water. MINUS: In addition to high construction costs, there are concerns about the environmental impact of some designs, as they may interfere with fishing grounds. Interference with navigation and coastal erosion are also potential problems. Wave energy fluctuates seasonally as well as daily, since winds are stronger in the winter, making this a somewhat intermittent energy source. EROEI: The net energy of wave energy devices has not been thoroughly analyzed. One rough esti- mate of EROEI for the Portuguese Pelamis device is 15:1. 93 PROSPECTS: Wave power generation will need more research,development,and infrastructure build-out before it can be fairly assessed. More needs to be understood about the environmental impacts of wave energy “farms” (collections of many wave energy machines) so that destructive siting can be avoided.The best devices will need to be identified and improved, and production of wave devices will need to become much cheaper. OTHER SOURCES In addition to the eighteen energy sources dis- cussed above,there are some other potential sources that have been discussed in the energy literature, but which have not reached the stage of applica- tion. These include: ocean thermal (which would produce energy from the temperature differential between surface and deep ocean water), “zero- point” and other “free energy” sources (which are asserted to harvest energy from the vacuum of space, but which have never been shown to work as claimed), Earth-orbiting solar collectors (which would beam electrical energy back to the planet in the form of microwave energy), Helium 3 from the Moon (Helium 3 does not exist in harvestable quantities on Earth, but if it could be mined on the Moon and brought back by shuttle, it could power nuclear reactors more safely than uranium does), and methane hydrates (methane frozen in an ice lattice—a material that exists in large quantities in...
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This note was uploaded on 09/04/2011 for the course CHEM 1B taught by Professor Fossum during the Spring '10 term at Laney College.
- Spring '10