Energy From Water Wave
There is some fascinating research going on off the shore of Oregon on gathering energy from waves. The approach that appeals to us the most is the use of small floating generators that ride the ocean swells up and down and convert that motion into usable Electricity. However the technique that is gathering the greatest attention so far is tidal energy.
One reason that there is a great deal of interest is that because water is so much more dense than air, the amount of extractable energy in a given volume of water is about 800 times greater than from the same volume of air. And of course ocean waves and tides are constantly available.
Tidal energy refers to tapping the power of the motion of tides, primarily at the ocean or river-mouth floor. However, there are technologies for capturing vertical flows as well as horizontal. There are already 11 tidal energy projects under way in New York, Florida, California and Washington, and there are another 11 applications in with the Federal Energy Regulatory Commission for projects in Alaska, the Pacific Northwest and the Northeast.
The approach is similar to capturing power from the winds. Windmill-like tidal turbines are placed at the bottom of a river or ocean.
Wave energy captures energy from the rise and fall of ocean waves. Oregon is particularly well suited to wave energy because the Pacific swells off the coast range from five feet or more in the summer to 11 1/2 feet in the winter. Over the length of the coastline, this could, in principal, provide 13,800 megawatts each year to a state that uses 5000 to 6000 megawatts annually.
Concerns include those of the fishing industry and those for marine life. If these can be satisfactorily addressed however, buoys could be slowly deployed over the next five years and then go to a full array in the country’s first commercial ocean wave park off Gardiner Oregon.
Lava sometimes is seen at the earth’s surface. But most magma, as lava is known when still underground, stays well beneath the surface. There it heats nearby rock and water. The water comes from rainwater that has seeped deep into the earth. This water can be heated as high as 700 degrees F. Some of it reaches the surface as hot springs or geysers, but most stays trapped far underground in geothermal reservoirs.
Currently geothermal power plants can find enough heat, water and permeable rocks at three miles beneath the surface to generate affordable electricity. The potential for geothermal is vast, although at present it is the source of less than 1% of US electricity. There are now more than 60 geothermal plants with the capacity of about three big coal-fired power plants. Additional research should permit the use of places under the earth that currently have good heat but not enough water and other places lower in the earth with lower temperatures.
Newer approaches require boring down into solid rock from one to six miles. Power plants would inject water down one well, passing it through crevices in the hot rock, and then extract it as steam through another well.
Geothermal plants can be run clean. They don’t need to burn fossil fuels to generate the steam they run on, so very little carbon emission results.
The Department of Energy says that geothermal energy has already become a standard source of energy. Although there are large areas of the US suitable for geothermal, the budget for R&D is being reduced due to budgetary pressures. Already last for funding among renewable sources, in 2007 geothermal funding was eliminated at the Department, but Congress voted to restore $5 Million to keep the program alive. It was funded at $24M in 2006.
MIT produced an interdisciplinary study finding that geothermal could produce 10% of the nation’s electricity by 2050 at prices competitive with fossil fuel. One reason it is valuable is that it can be used to generate electricity around the clock, unlike solar or wind power. Geothermal plants have a small footprint, too.
Iceland has an extraordinary amount of geothermal power available. And there are more direct uses. 9 out of 10 Icelanders rely on the 10 degree F. water coming out of the earth for their heating and hot-water needs. Geothermal power is so cheap to produce in Iceland that Keykjavik has some heated sidewalks in winter.
There are over 5,400 known potential sites in the US for ‘small hydro’ power projects that could produce about 20,000 megawatts of power, according to a DOE study. (As comparison, remember that Oregon uses 5000 to 6000 annually.) Most of them could require no new dams. Rather, a portion of a small river flow could be shunted to one side to make electricity.
Water wheels are what we picture capturing energy for mills in the old days. Water turbines added a swirl component of the water, which passes energy to a spinning rotor. This additional component of motion allowed the turbine to be smaller than a water wheel of the same power. They could process more water by spinning faster and could harness more power. Later, impulse turbines were developed which didn’t use swirl. Variations on these technologies are actively being developed. We saw one recently that looks very promising. It captures energy effectively, but permits the free flow of fish through it.
Iceland is fortunate in this category too. With its mountains and glaciers, Iceland has strong water flows from the mountains to the oceans, with many natural and man-made waterfalls along the way. With exceptionally cheap power constantly generated in Iceland, we’d have to believe that many energy-intensive industries will be moving there as energy alternatives continue to escalate.
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