August 15, 2007 4:00 AM PDT

FAQ: Energy on the high seas

Related Stories

From the Big Bang to big bucks

July 5, 2005

Energy heats up high tech

July 12, 2004

(continued from previous page)

The skate ramp: With the Wave Dragon, wave reflectors more than 100 meters long guide waves up a ramp, where the water dumps into a reservoir. The added pressure forces a turbine at the bottom to turn. The device's developer, a company that is also called Wave Dragon, is building a 7MW prototype off of Wales in 2008 and wants to do a 77MW project in the Celtic Sea by 2010. The Wave Dragon is slack moored, so that it can flow with the power of the ocean. A 20-kilowatt prototype running off Denmark's shore since 2003 has helped iron out the technical kinks, wrote Wave Dragon founder Erik Friis-Madsen in an e-mail. "The device can be up scaled to whatever size is needed, and the efficiency of the device grows in line with the size," he wrote. "The biggest difficulty seems to be to secure the funding for the first years of commercial development."

Tidal power, wave power: What's the difference?
Tidal advocates want to put turbines, similar to wind tunnels, where tides snake in the ocean. The tides would turn a turbine and generate power. Marine Current Turbines has had a prototype for four years in southern England generating 300 kilowatts of power. It will start installing a 1.2MW system off Northern Ireland this fall.

Eling Tide Mill in England is more than 900 years old.

Why are none of these past the prototype stage?
Cost and unknowns. The 1.2MW system from Marine Current, for instance, will run 7.5 million pounds, or nearly $15 million. It has been delayed several times because of corporate management changes, a lack of funds, and other projects getting priority on construction equipment. "It is like wind was in 1980," said Marine Current Turbines' Fraenkel. At the moment, investors aren't gushing. Few venture capital firms have paid much attention to sea power. In April, Ocean Power Technologies, which makes a buoy system, held a U.S. initial public offering, selling its shares for $20. At the end of trading on Tuesday, it was down to $12.39.

What are some of the environmental risks?
Animals, plants and birds are the main concerns. Ocean-power advocates, however, point to the relatively minimal impact wind turbines have had on birds over the past 20 years. Other dangers include debris and escaping oils, but these can be minimized.

Overbuilding, conceivably, could also present problems by attenuating the force of tides or waves. A large, dense wave facility could reduce wave power by 10 percent to 15 percent in its vicinity, NREL projected, although the impact will be minimal a few kilometers away. The impact on the biological community is unknown. Fraenkel argues that high capital costs will help minimize that problem.

Can you leverage the sea in other ways?
European utilities have already erected offshore wind farms in the United Kingdom and Denmark. These farms--which sport turbines with blades that can measure more than 100 meters long--sit in about 30 meters of water. Offshore winds can be steadier, thus generating more power. Putting the turbines offshore also eliminates some of the "not in my backyard" problems.

RePower Systems of Germany has created a 5MW offshore turbine. Right now, it is creating a 300MW field in water 82 feet deep and 18 miles off the coast of Belgium. Combined, the six turbines in Belgium will be only 54 megawatts smaller than the largest solar thermal plant in the world, located in California.

A significant portion of the U.S. offshore wind potential is located in deep-water areas, but that would require building more robust turbines that can withstand harsher winds, waves and tides. Instead of being anchored directly into bedrock, deep-water turbines might have to be anchored to floating platforms, which in turn are anchored into earth. Corrosion and maintenance are issues, as are environmental concerns. The turbines also need to be connected to the grid via electrical transmission cables. Luckily, a large portion of the U.S. population lives near the sea. The same would go for solar power farms at sea, which could convert sunlight or heat into electricity. (Such facilities do not exist, however.)

Hydrogen on the high seas?
Put this in the "Great idea, but I might be on Social Security then" category. Under this scenario, offshore platforms would harvest power from deep-sea waves and then exploit that power to split water molecules into hydrogen and oxygen. The hydrogen could then be pumped into a carrier and then shipped to shore. (Transporting hydrogen through pipelines or liquefying it presents whopping technical and economic problems).

But right now, demand for hydrogen is low and converting wave power to hydrogen and then to electricity is not cost-effective. Some have proposed delivering power generated at something like the deep sea platform described above over a submarine cable. This would eliminate the conversion inefficiencies, but then there's the question of how far offshore you can go.

What is ocean thermal technology?
Another far-off experimental technology. Electricity can be generated from differentials in temperature. Some companies are already trying to employ temperature differentials to power small sensors. Because the surface of the ocean is warmer than water deeper down, it could be possible to harvest the difference for electricity, but the colder water would have to be made to come in contact with the warmer water.

 

Correction: This article incorrectly stated how much power the average home uses. It is 3 kilowatts.

Previous page
Page 1 | 2

See more CNET content tagged:
sea, turbine, ocean, energy, wave

7 comments

Join the conversation!
Add your comment
We can improve the efficiency of a Solar panel solution by 300%
The answer for our energy needs is right above us. Conservation should always come first but then look to the sun which delivers enough energy in 1 day to power all of the worlds energy requirements for an entire year. This does not mean we suggest everyone put a solar panel on his or her roof. We actually think no one connected to the power grid should install a solar panel on his or her rooftop. Do away with the million solar roofs program. It is shinning a bad light on solar. Our Solar Transfer solution will be released shortly but in the meantime run the numbers yourself and say no to rooftop installation of solar panels. The precious material and panels should be placed in the center of a parabolic dish where the sun shines brighter and longer every day. The answer may be to look toward the Ocean but not in the way described in this article. If you have already installed Photovoltaic Solar Panels look into a Solar Transplant to improve your power gain and help the environment 3 times as much!
Posted by Manhattan2 (329 comments )
Reply Link Flag
Interesting proposition....
It's clear that you are no fan of what CitizenRE is trying to do to
make PV solar panels on a large portion of the population more
comon place. I'm not sure why you think that anyone 'on the
grid' would cause more problems then they are trying to
remedy???

But perhaps you can expand on your ideas about a parabolic
dish to harness the power of the sun so that we have a better
idea about what you are talking about rather then just teasing us
'future tech.' Perhaps you can supply the curious masses with a
link or two about what you are talking about.

You've tickled my curiosity, but I don't like to be tased without
some additonal information to substantiate a claim.

More info please!
Posted by Jim_Mattos (69 comments )
Link Flag
Solar Transfer - The Explanation
IT'S ********. Manhattan2 always hog the comment section to BS about this terms so you'll google it and go to their website for who know what reason.
Posted by jsmith2007.lol (8 comments )
Link Flag
Say no to Centralization
Saying no to individual roof top installations is not the answer. There is no shortage of silicon on this planet. Centralized power production is not the most efficient because look at all the infrastructure required (power grid, maintenance of power lines, etc.) When you install your own power production you are no longer controlled by big energy, and you actually recover your cost. Big energy will gladly produce loads of power for as cheap as they can, then charge you up the wazu for it. Then look at things like storms and outages, not an issue if you produce your own power. Support Free, individual-distributed energy production, not centralized control.
Posted by chash360 (394 comments )
Reply Link Flag
Not enough energy can be captured on a roof
The fixed angles of rooftops in Northern states are no place for photoviltaic panels. You cannot capture enough power for a low enough cost and you will always need the grid. Fix the grid! Power needs to be produced for the lowest cost with the highest gain and lowest CO2 emissions if we will ever have a true option for the future. Our solution does just that. Federal power generation with individual tax-free panel or mirror ownership. We don't really care how it gets done. We just know we have the final solution! You will always get twice the power capture in Arizona or Nevada than in Maine or Michigan. That doesn?t mean the Maine resident can?t go Solar. That resident simply goes solar at a co-located "United Solar Array". Remember the power does not get pushed across the country only the higher profits for the green investor. The power gets used by someone within 300 miles of the collectors or farther once the grid gets fixed. Economies of scale. Location, Location, Location, plus American ingenuity. Yes, we also feel, Google, Wal-Mart and others that have done rooftop installations have made a bad choice. They may be in the Al Gore reasoning mode of Public Relations importance over science and math!
Posted by Manhattan2 (329 comments )
Link Flag
 

Join the conversation

Add your comment

The posting of advertisements, profanity, or personal attacks is prohibited. Click here to review our Terms of Use.

What's Hot

Discussions

Shared

RSS Feeds

Add headlines from CNET News to your homepage or feedreader.