New study on wind energy

[dpb]

On 7/21/2011 6:32 AM, HeyBub wrote: ...

...

That's what the consortium of the food manufacturers and processors would like you to think; they're spending millions in a campaign to demonize ethanol as the convenient whipping boy to justify higher consumer costs.

From a USDA brief...

...The United States experienced record demand and corn production during 2007/08 that pushed U.S corn exports to 61 million metric tons. However, a slowing world economy and reduced demand for corn are projected to dampen corn exports in the near future. Nonetheless, global population increases and consumer demand for meat products will continue to support expanding feed grain exports in the long term.

World Corn Trade

While the United States dominates world corn trade, exports account for only a relatively small portion of demand for U.S. corn?about 15 percent. ...

From a (somewhat) surprising source; an Indian analysis...

As for the Mexican imports, they've gone up as well, significantly. However, as another noted, all corn for ethanol production is yellow field corn, not white or sweet corn for (direct) human consumption.

It's a complex, global economic system now and the interplay between competing governments various policies are certainly factors but there's far more going on that simply US ethanol. The rise of the EU and their protective and restrictive policies combined w/ the demise of the former Soviet Union has markedly changed the European marketplace. Brazil and Argentina being in the southern hemisphere can play the US weather patterns and target export markets specifically for those years when prices are high owing to poor weather in the US (and, to a far lesser degree, the US can try to anticipate in the other direction).

China has become a wild card; they oscillate between a large importer to a significant exporter depending on current conditions there and the whims of their central government regarding trade and subsidies.

It's all tied together...

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[Home Guy]

Is that your way of saying "yes, a smaller sail would propel a given ship faster than a large sail" ?

If that's not what you're trying to say, then please explain.

[Home Guy]

harry used improper usenet message composition style by full-quoting:

Well shit.

If a conventional airplane wing is a foil, and if a flat plate can be a foil, then f*ck, everything and anything can be a foil according to you. So where does that get us?

No matter which way you cut it, you're still left with capturing a lateral force (ie = wind pressure) and convert it into rotational energy. A flat blade angled at 45 degrees will probably get you the most torque and rotational speed out of a given breeze of air (but it's totally possible that optimal blade angle is a function of RPM), and the more surface area your blade has, the more of that wind energy it can convert into rotational energy.

[Kurt Ullman]

n

You have any data on how the make up of the corn crop has changed? FOr example (and example only as this is n=1 "study", some of the farmers in our area changed from growing sweet corn to yellow field corn precisely because of the extra money they could get.

>

[Home Guy]

harry again used improper usenet message composition style by full-quoting:

The point I was making (which seems to have gone right over your head like a breeze of air) is that the amount of energy you can capture from the wind is proportional to the amount of surface area your "conversion surface" has. Since a wind turbines "conversion surface" must rotate in a stationary location, that surface must be angled with respect to the direction of the wind. But a ship naturally does not want to be stationary and hence it extracts the maximal amount of energy from the wind by having the sails at exactly 90 degrees to wind direction.

I'm surprised I have to explain such a fundamental and elementary concept in such excruciating detail. Are you perhaps female - and hence you have a problem grasping forces and physical principles?

[despen]

>

No I don't.

So?

[Jim Yanik]

[e-mail] wrote in news: [e-mail]:

That video isn't telling you everything. wiping without water means scratches that lower output. It also doesn't remove bird crap or tree sap.

for all those panels? it has to be done more often than every two weeks,too.

what about dust,power surges,electrolytic capacitor dryout,etc? Cap failure is a common occurrence in power systems.

BTW,I note that the system you cited uses TRACKING solar panels,so there's maintenance on the mechanicals that move the panels.Then there's snow/ice removal,seeing as it's up North(N.Jersey?).

Is that peak or average output?

[despen]

Dust lightly with soft towel.

Yes, all those panels. The video said every 2 weeks. How much dirt is in the air where you live? In places with no rain, just dusting will do the job. Downwind of a coal plant, maybe more than every 2 weeks. I still see no evidence that more often than 2 weeks is required.

So I still don't see a lot of water being used.

Yeah, what about them. They're also subject to random meteorite hits. Anything can go wrong. Still the cost of maintenance remains replace every 10 years unless you have some other source to cite.

The system at Bell Labs is not tracking.

They could remove snow if they want, or just wait until it slides off. We get snowfall in Central NJ but it's not going to stick to a slick glass panel for long.

Read the article or do more research.

I don't get it. Are you against power generation or does it just feel good to point out that someone has to push the snow off the panel.

Sure there are problems, I'm well aware of all the issues, I've heard it all before. I still see an open field that wasn't doing anything but growing grass, still growing grass but now also pushing some power into the grid. It's going to take a lot of fancy BS to convince me this is a bad thing.

[chaniarts]

i have 44 panels on my roof. it takes about 2 gallons of water to wash them. no additives to the water, just plain water. at the end, i get dirty water, that goes on a plant.

if you have tree sap on your panels, then you have them installed in the wrong place. there shouldn't be any nearby trees.

simple dusting won't work. the dust gets baked on and sticks.

mine are warranteed for 25 years for failure and will produce 95% of new power ratings.

the converter has a 10 year warrantee. that doesn't mean the need replacement at that time. they could last 25 years or more.

your a/c has a 5 year warrantee. do you replace it every 5 years?

[despen]

No I don't.

Just trying to be generous. The original statement was that inverters required "maintenance". I thought maintenance on a piece of electronics sounded weird so I looked it up. The only thing I could find is someone saying to replace them every 10 years.

If it was my PV array, I'd take that as a cue to have a replacement on hand around year 10 if I really had to keep the array going.

Like you, I wouldn't be surprised at 25 years.

Anyway, all these arguments about the draw backs of PV arrays strike me as weird. As if someone had a belief system that wouldn't survive if they admitted that PV arrays generate power.

[dpb]

...

Nationally, no I don't have any (altho I'm sure it's available in the detailed USDA production statistics data). If I think I'll ask when go into FSA office this afternoon if they have convenient way to get statistics internally that would take me quite some time digging for since don't know where that would be readily accessible (and I don't have high speed connection so random surfing isn't much fun... :( ).

There's never been any sweet/white corn in this area (except for the strip or two planted for own use in regular field that isn't for production anyway) so there's not been any shift here in that direction. We've never irrigated and have only tried dryland corn a few years; it's never been reliable on our ground so we stay w/ milo for the summer grain crop (a shorter corn-like plant w/ a bushing single grain head w/ round orange to red/orange seed; very attractive but much more drought tolerant than even the dryland corn hybrids). Unless this weather breaks very soon, though (and there's no indication that's going to happen), what there is isn't going to make a crop; it's severely stressed already and won't last long w/o some rain...

What there has been in this area this year has been a sizable shift to cotton on dryland and even some irrigated owing to the extended drought and requiring far less water and also more sunflowers; we're marginal bean country and virtually no beans were planted. It's been so hot and dry that many have abandoned irrigated corn or cut back to half or even quarter of circle to try to salvage at least a partial crop letting rest burn up.

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[mkirsch1]

If you look at the old stereotypical "prairie" style windmills, that's how they are. A disk with pie-shaped blades angled at 45 degrees, facing directly into the wind with the help of a fin.

All that surface area catches a lot of wind, but it also creates a lot of aerodynamic drag which makes it require higher wind speeds to turn. The air pushing through the "fan" creates rotational energy, but the air AROUND the fan is creating drag as the tips of the blades contact it.

The reality is that what makes a good propeller or helicopter rotor also makes a good windmill blade. Maximum lift with minimum drag. THAT is why we have thin blades. The cross-section of a modern wind turbine blade is a high lift, low drag airfoil that will catch air and turn the rotor at far lower wind speeds than a solid disk of 45 degree flat plates.

[Malcom "Mal" Reynolds]

Then your understanding is wrong. Once again and slowly: corn used as feedstock for ethanol is corn that was used as animal feed...and is still used as a higher protein feedstock in the form of DDGS.

[Malcom "Mal" Reynolds]

and there would be no land to provide food

[chaniarts]

farmer's switched corn types to feed corn, making both of you right.

[dpb]

On 7/21/2011 8:00 AM, Home Guy wrote: ...

...

The interaction between blades and the competing design factors (weight, strength, speed control, etc., etc., etc., ...)

A ceiling fan is built to keep the occupants of a room comfortable by moving air gently. A primary design consideration is to minimize noise while the fan rotates at low speed and to keep the construction costs, and therefore the purchase price, low. Energy efficiency is not a primary concern, because operation is inexpensive so most ceiling fans incorporate blades that are comparatively inefficient drag devices; rotating the pitched blades pushes air vertically out of the way. Wide, flat blades are inexpensive to build and work well as drag devices. More blades are better, up to a point, and the usual layout of four or five blades is the result of balancing trade-offs between efficiency and expense.

OTOH, a wind turbine must capture the energy in fast-moving air and rotate at relatively high speed. Slow rotation would increase the torque and require heavier and more expensive drivetrain components. For high-efficiency energy conversion lift-type turbine blades, similar to airplane wings, of twisted and tapered airfoil shapes are used. The blade design creates a pressure difference in wind?high pressure on one side and low pressure on the other?that causes the blades to turn.

The reason for taper is the same as that for the shape of airplane wings and/or props--Bernoulli lift/pull. The longer path over a wing surface causes the velocity to rise and that lowers pressure on the upper (behind in the case of the prop/blade) which "pulls" the rotor in that direction for rotation.

A combination of structural and economic considerations drives the use of three slender blades on most wind turbines?using one or two blades means more complex structural dynamics, and more blades means greater expense for the blades and the blade attachments to the turbine.

As noted before (and referenced in the Wikipedia article I bookmarked earlier), the increase in effectiveness of two over only a single blade fan is surprisingly little and the relative gain after that is smaller yet.

Also, again as noted, designs were within 75-80% of the theoretical limit when I last had actual performance data some dozen years or so ago; I'd expect continued refinements have pushed that to the upper value or perhaps even higher for current and next-generation blades (altho that's pretty closely held proprietary data, obviously, and not readily passed out over the 'net). What I'm aware of is what vendor provided to our electric co-op generation unit when evaluating the build/purchase decision to meet the mandated "green" generation reqm'ts coming. In the end, we chose to simply buy what we have to and keep conventional low-cost generation in our pool to minimize our customer costs as much as possible.

Following are some links that may be of interest; they don't delve into the real intricacies of blade design; that's pretty complex but do have some real-world design information and discussion of what actual design efficiencies are, etc., etc., etc, ...

More than the above requires reading far more technical literature than I'm prepared to try to reproduce for usenet; if you're really, really interested, there are engineering texts but you'll need quite a lot of background.

Probably one of if not the standard...

Enjoy... :)

--

[Jim Yanik]

[e-mail] wrote in news: [e-mail]:

"you don't see"; there's the problem.

BTW,how often do you need to wash a car that's left outside? Or just run your windshield wasers? If I leave my car outside for 2 weeks,no rain,it's COVERED in dirt,along with tree sap and bird crap. You can write your name in the dirt,and pranksters often do.

that lowers solar panel output significantly.

read the article again. that is where I got it from.

Denial. besides,the fact that your panels ARE covered by snow means you get ZERO output from them,for some length of time. So,that power has to come from some other,more reliable source.

Likely peak output.

MY point is that it's a "feel good" action,not truly practical. With a lot of money spent,and probably with Federal tax credits,or as the "progressives" call them;"loopholes" to be plugged. And you end up with an intermittent power source,not reliable,won't output it's rated power consistently or at night.And 20 years later,you have to buy all new panels,sooner if there's a hailstorm.

Wait until that grass grows high enough. It appears from the picture included in that article that mowing would be a problem.

[dpb]

On 7/21/2011 2:47 PM, chaniarts wrote: ...

I don't believe that's so in any great acreage amounts (see other response that I don't have actual production numbers in hand but the areas that grow sweet corn aren't the areas that grow the large amounts of field corn). If you have actual production acreage data that shows otherwise, I'd like to see it.

OTOH, there has been some shifting of acres from beans and wheat, but overall not huge amounts; in the few percentage points kinds of numbers, not like in doubling or halving.

Again, individual growers are limited in what their production practices will tolerate; they can't just willy-nilly shift acres for a multitude of reasons including pest control (both plant and insect), ground fertility and crop rotation, inputs availability and field preparation, etc., etc., etc., ...

Despite the Green Acres appearances, farming is _not_ a vocation for the unskilled any longer... :) And, producers aren't going to risk their longer-term viability for one or two crop years; just ain't a'gonna' happen. Many of these folks have been on the same ground for 100 or more years in the family; they have very deep commitments and intentions their heirs are going to be there for another 100 or so.

We're in a relatively recent area in the US; iff'en I can hang on for another 3 years or so we'll be a "century farm", too...there are some around who got started a few years ahead of granddad that have already achieved that distinction. Of course, farther east (and west) they've been there a long time already.

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[HeyBub]

Oh, anything's POSSIBLE.

Just ask the EPA.

[Jim Yanik]

[e-mail] wrote in news: [e-mail]:

"warranteed for 25 years";the company probably will not be in business when you need to replace your failed inverter. B-) If it fails,you are without an inverter until you send yours to the company,have it repaired,and then returned. Or you have to buy TWO,and keep one as backup.

Do you think high power inverters don't produce heat,don't have cooling fans,or don't collect dust?

You need a backup in case of ANY potential failure,that could happen at ANY time. Otherwise,you're "down" until you get yours repaired or replaced. "down" is bad,it means "NO power".

Just because they say "10 years" doesn't mean they all last that long.there's infant failures, and longer term failures.

Oh,I know solar panels generate power,but how much,how reliable,and how cost-effective is the problem.IOW,how PRACTICAL they are. For specialized apps,they're fine.I see them all around Orlando,on poles powering small devices,such as school crossing signs,that are only on a short time.