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Google Makani – Wind Energy Kites

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Re: Google Makani – Wind Energy Kites

#101

Post by maxerickson »

lotsofmangos wrote: post #90
maxerickson wrote: post #89

Earlier quoted context omitted.

Sure, that's why I said Those estimates are probably going to be reasonable , because I don't think it is a problem that they are estimates. But it is sometimes nice to peer through the wikipedia and see what lies beneath.

Your point seemed to be that the first of the studies you picked was based on estimates for things like total lifetime and decommissioning. But the fact that the first thing you picked relied on estimates for those things tells us nothing at all about the quality of the data, just that estimates were used for something where estimates are always used.

I suppose my point was that it is unfortunate that so much context is lost by the time a chart ends up in Wikipedia. At a minimum, they should probably get rid of some of the decimal places in their table.

I was not trying to paint it as likely that the other studies would be similar to the one I looked at (I see why my phrasing doesn't necessarily communicate that, but I was simply trying to say that I hadn't done more than look at the 1 study).

Re: Google Makani – Wind Energy Kites

#102

Post by igonvalue »

> The energy kite simulates the tip of a wind turbine blade, which is the part of a turbine that makes most of the energy. The kite is launched from the ground station by the rotors, which act like propellers on a helicopter. Once in the air, the kite generates power by flying in large circles where the wind is strong and consistent. Air moving across rotors mounted on the kite forces them to rotate, driving a generator to produce electricity, which travels down the tether to the grid.

Are the rotors that launch the kite the same as the ones that generate the electricity?

Re: Google Makani – Wind Energy Kites

#103

Post by madeofpalk »

anigbrowl wrote: post #96
austenallred wrote: post #51

Earlier quoted context omitted.

I'm probably a "power user" as well, but I literally cannot navigate the site. It's like 1/3 of my scrolls don't even register. This isn't "design for the masses," it's just plain broken. Edit: I don't know why I'm being downvoted, it must be working for some people. Here is a video of me trying to scroll (in Chrome) https://www.youtube.com/watch?v=ulAw0P2geRE

Have you tried pressing those buttons in the lower right hand corner of the keyboard?

No, I have not and I won't.

Re: Google Makani – Wind Energy Kites

#106

Post by imaginenore »

clebio wrote: post #62
spot wrote: post #24

Earlier quoted context omitted.

presumably it would go into helicopter mode and return to base.

There's also autorotation, which means you need very little power for a controlled descent (still need some power to steer). http://en.wikipedia.org/wiki/Autorotation

Autorotation only really works for large heavy propellers, like the ones on helicopters.

Re: Google Makani – Wind Energy Kites

#107

Post by mikeyouse »

elihu wrote: post #98
ryen wrote: post #78

Earlier quoted context omitted.

The majority of noise you hear from a small prop plane flying above is from the engine. Also, the advanced height they're trying to achieve limits the amount of noise relative to what you would hear from a small drone overhead.

I'm sceptical that that's true. We can put mufflers on gas engines to make them quieter. The prop, though, is moving a lot of air, and there's no way to get around that and have it still work.

I found an old JPL document detailing "Aerodynamic Noise from Rotors, Propellers, and Lift Fans" (http://cafefoundation.org/v2/pdf_tech/Noise.Technologies/NAS...) which has some interesting details.

A 300hp hub, spinning a 9ft diameter propeller at 1584 RPM should be roughly 72dB as measured from 1,000 feet. From a mile away, it will be more like 57dB or about TV volume from 6 feet away. -- Then again, these are spinning far faster than you'd expect from a wind turbine.

Re: Google Makani – Wind Energy Kites

#108

Post by teddyknox »

tarequeh wrote: post #55

For a second a tried to imagine a satellite view of the earth with many of these flying. It'd look mesmerizing. I really applaud Google for funding research on affordable renewable energy. It's unfortunate that the scrolling doesn't work, but hey the prototype does!

You mean an airplane view? From the top down I imagine they wouldn't look very interesting.

Re: Google Makani – Wind Energy Kites

#110

Post by dredmorbius »

tjradcliffe wrote: post #52
dredmorbius wrote: post #41

Earlier quoted context omitted.

EROEI of wind turbines is about 20:1. That is, you recover 20x the energy that goes into constructing and maintaining the turbines over their lifespan. The argument that some of the materials used in turbine manufacture presently rely on fossil fuels (e.g., coal used for coking steel) doesn't mean that other options for such processes aren't possible. Though shortages of fuelwood were among the key reasons for switch…

Metallurgical coal is going to be the very hardest thing to get away from. Improvements in the coking process (carbon capture) are plausible, but the chemistry basically demands burning a butt-load of carbon. Thermal coal is replaceable by conservation, nuclear power, and to some extent wind/solar plus storage, and if I were in charge I'd be pushing to ban new thermal coal development. But metallurgical coal is going…

It's a a big use, 14% of global coal use from memory based on a recent query.

BP's annual energy review 2014 gives total global coal use as 3,881.4 Mtoe (million tons of oil equivalent), which works out to 5.54 billion tonnes of coal. 14% of that is still a large number, 776 million tons.

I happened to look up total forestry production in the US recently, let's see if I can't find that ....

Here: https://plus.google.com/104092656004159577193/posts/NVg1UQ5W...

Total US lumber production is equivalent to 928 Mboe. So, yeah, applying 84% of US timber production to coking activities would supply the world with steel.

(Sources: http://www.loggers.com/timber_facts.htm http://www.fpl.fs.fed.us/documnts/fplrp/fplrp615/fplrp615.pd... http://generatorjoe.net/html/energy.asp )

US steel production is just under 100 megatonnes (2007). Global production is 1,600 megatonnes. So US production is 6.25% of global. The US could provide for its own steel manufacture somewhat more feasibly.

http://www.worldsteel.org/media-centre/press-releases/2014/W... http://www.indexmundi.com/minerals/?country=us&product=raw-s...

Incidentally, energy use in producing construction materials is among the reasons I see a possible future not for biofuels but for biomaterials -- utilizing plants or organic processes to directly provide structural materials (or replacements for them) that we use.

Carbon separation from seawater seems another possible approach, though I haven't specced out that for coking purposes:

https://www.reddit.com/r/dredmorbius/comments/22k71x/us_navy...

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