Thanks bobjengr (although I think you meant me, not Elizabeth). I was also glad to see such a thorough, well-designed study done by a reputable institution. I hope that the results are actually used, instead of ignored.
There's always potential for other unintended consequences. Let mechanical vibrations transmitted into the sea-bed pilings affect marine life in some catastrophic way (think whales, or dolphins beaching) and you'll find yourself scrambling to save a billion dollar investment. Maybe an occasional electrical fault that causes all marine life within a click to do that upside-down belly float thing...
Great Post Elizabeth. For me, the most striking take-away is that institutions are looking. Looking at alternate energy sources that just might aid existing energy production and lessen our dependence on fossil fuels. I suspect we will never completely eliminate our need for existing sources of energy. It would be nice to extend their availability and mollify to some degree the expense of finding additional areas to "mine". We all know economics represents a huge factor in the success or failure of alternate sources. Also, the special interest groups factor into most political desicions greatly. I believe a program such as this would have a better chance if we could eliminate politics from the equation. For this reason, I think the study is valuable.
It usually costs a lot more to send humans to the top of wind towers, or out in space, or almost anywhere, than it costs to send robots there. Some of the cost is in wages, but there's also safety systems and insurance to protect the humans. In any case, it's usually cheaper to send a machine. The robots described in the story at the link I gave http://www.designnews.com/author.asp?section_id=1386&doc_id=247655 are equipped with test equipment and real-time wireless communication systems, plus vision, so they don't need to be smart. They just need to be a lot like a Mars rover, or a rescue robot, plus climb a tall tower.
Designing a system to be serviceable by robots is not a trivial thing, since they are not nearly as smart as the avaerage human service person. So a system designed to be serviced by robots would cost more because of that. In addition, robots that can climb a tower and service the equipment at the top are not cheap. So from those points it makes more sense to put the minimum of hardware atop the tower.
I read an article about some very high altitude robot wind turbine systems that would be flown up using the generators as motors, until they reached the altitiude where the wind was located. Then they would serve as power generation systems. The problem that they had with these systems is that it is a challenge to deliver multi-megawatts down a cable of reasonable weight. There was quite a description of how to insulate the two or three conductors bringing power down. My suggestion is to separate the conductors, moving them to opposite corners of the airborn structure, since space is a good insulator, and adds very little weight. Such a generation platform could be flown back down to ground level for service, which would remove the expense of climing completely.
UNfortunately it does not appear that this approach has gained favor yet.
One main reason for using wind turbines at higher altitudes was discussed in our article on the Altaeros airborne wind turbine, which is aimed at altitudes of 1,000 feet and up:
Winds at those heights, anyway, are 5x stronger so more energy gets harvested; at least that's the theory.
One question is why is it so obvious to me, an electrical engineer, that most of the mechanicals should be at ground level, when the others all want the generators high up in the air? It is fairly simple to go through the numbers and see that high altitiude service calls will cost lots more than those at ground level. Is it really that hard to figure out? I suggested using compressed air because it can be stored until needed, and because an air leak would not cause much pollution. Hydraulics can easily be more efficient, that is true. But hydraulic pressure is harder to store.
William, your idea of moving the turbine to ground level and powering, not with compressed air (as you suggested) but with fluid power - hydraulics has been pushed by Eaton Corporation recently.
I like the fact that everyone is finally realizing that economic efficiency drives implementation, not electromechanical efficiency. Wind and sunlight are free. The expense comes in installation, space, maintenance and permits. Like biodiesel, bio ethanol, and other alternative energy, the raw economics are generally unfavorable for the process owner until the government subsidies are distributed. The owners of the incumbent technology can be profitable over a much broader selling price than alternative energy sources as long as utilization is reasonably high. Notice that only the coal mining companies are screaming now? The owners of coal fired plants are happily making cash with the low priced coal.
SO in one sentence, the "risk" is thought to be that excessive Wind Turbines would absorb too much natural wind, and our climate would be left without natural air-flow. Well, If that's the scientific "down-side" then bring on the windmills, because that's not going to happen!
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