Wind Power Thread
How Wind Power Works
http://www.howstuffworks.com/wind-power.htm Quote:
Parts of a Wind Turbine The simplest possible wind-energy turbine consists of three crucial parts:
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Modern Wind-power Technology
When you talk about modern wind turbines, you're looking at two primary designs: horizontal-axis and vertical-axis. Vertical-axis wind turbines (VAWTs) are pretty rare. The only one currently in commercial production is the Darrieus turbine, which looks kind of like an egg beater. Vertical-axis wind turbines (VAWTs) http://static.howstuffworks.com/gif/wind-power-2.jpg http://static.howstuffworks.com/gif/...r-vertical.gif In a VAWT, the shaft is mounted on a vertical axis, perpendicular to the ground. VAWTs are always aligned with the wind, unlike their horizontal-axis counterparts, so there's no adjustment necessary when the wind direction changes; but a VAWT can't start moving all by itself -- it needs a boost from its electrical system to get started. Instead of a tower, it typically uses guy wires for support, so the rotor elevation is lower. Lower elevation means slower wind due to ground interference, so VAWTs are generally less efficient than HAWTs. On the upside, all equipment is at ground level for easy installation and servicing; but that means a larger footprint for the turbine, which is a big negative in farming areas. Horizontal-axis wind turbines (HAWTs) http://static.howstuffworks.com/gif/...horizontal.gif As implied by the name, the HAWT shaft is mounted horizontally, parallel to the ground. HAWTs need to constantly align themselves with the wind using a yaw-adjustment mechanism. The yaw system typically consists of electric motors and gearboxes that move the entire rotor left or right in small increments. The turbine's electronic controller reads the position of a wind vane device (either mechanical or electronic) and adjusts the position of the rotor to capture the most wind energy available. HAWTs use a tower to lift the turbine components to an optimum elevation for wind speed (and so the blades can clear the ground) and take up very little ground space since almost all of the components are up to 260 feet (80 meters) in the air. Large HAWT components: * Rotor blades - capture wind's energy and convert it to rotational energy of shaft * Shaft- transfers rotational energy into generator * Nacelle - casing that holds: o gearbox - increases speed of shaft between rotor hub and generator o generator - uses rotational energy of shaft to generate electricity using electromagnetism o electronic control unit (not shown) - monitors system, shuts down turbine in case of malfunction and controls yaw mechanism o yaw controller (not shown) - moves rotor to align with direction of wind o brakes - stop rotation of shaft in case of power overload or system failure * Tower - supports rotor and nacelle and lifts entire setup to higher elevation where blades can safely clear the ground * Electrical equipment - carries electricity from generator down through tower and controls many safety elements of turbine |
Turbine Aerodynamics
Unlike the old-fashioned Dutch windmill design, which relied mostly on the wind's force to push the blades into motion, modern turbines use more sophisticated aerodynamic principles to capture the wind's energy most effectively. The two primary aerodynamic forces at work in wind-turbine rotors are lift, which acts perpendicular to the direction of wind flow; and drag, which acts parallel to the direction of wind flow. http://static.howstuffworks.com/gif/...-wind-flow.gif Turbine blades are shaped a lot like airplane wings -- they use an airfoil design. In an airfoil, one surface of the blade is somewhat rounded, while the other is relatively flat. Lift is a pretty complex phenomenon and may in fact require a Ph.D. in math or physics to fully grasp. But in one simplified explanation of lift, when wind travels over the rounded, downwind face of the blade, it has to move faster to reach the end of the blade in time to meet the wind travelling over the flat, upwind face of the blade (facing the direction from which the wind is blowing). Since faster moving air tends to rise in the atmosphere, the downwind, curved surface ends up with a low-pressure pocket just above it. The low-pressure area sucks the blade in the downwind direction, an effect known as "lift." On the upwind side of the blade, the wind is moving slower and creating an area of higher pressure that pushes on the blade, trying to slow it down. Like in the design of an airplane wing, a high lift-to-drag ratio is essential in designing an efficient turbine blade. Turbine blades are twisted so they can always present an angle that takes advantage of the ideal lift-to-drag force ratio. See How Airplanes Work to learn more about lift, drag and the aerodynamics of an airfoil. Aerodynamics is not the only design consideration at play in creating an effective wind turbine. Size matters -- the longer the turbine blades (and therefore the greater the diameter of the rotor), the more energy a turbine can capture from the wind and the greater the electricity-generating capacity. Generally speaking, doubling the rotor diameter produces a four-fold increase in energy output. In some cases, however, in a lower-wind-speed area, a smaller-diameter rotor can end up producing more energy than a larger rotor because with a smaller setup, it takes less wind power to spin the smaller generator, so the turbine can be running at full capacity almost all the time. Tower height is a major factor in production capacity, as well. The higher the turbine, the more energy it can capture because wind speeds increase with elevation increase -- ground friction and ground-level objects interrupt the flow of the wind. Scientists estimate a 12 percent increase in wind speed with each doubling of elevation. |
Calculating Power
To calculate the amount of power a turbine can actually generate from the wind, you need to know the wind speed at the turbine site and the turbine power rating. Most large turbines produce their maximum power at wind speeds around 15 meters per second (33 mph). Considering steady wind speeds, it's the diameter of the rotor that determines how much energy a turbine can generate. Keep in mind that as a rotor diameter increases, the height of the tower increases as well, which means more access to faster winds. At 33 mph, most large turbines generate their rated power capacity, and at 45 mph (20 meters per second), most large turbines shut down. There are a number of safety systems that can turn off a turbine if wind speeds threaten the structure, including a remarkably simple vibration sensor used in some turbines that basically consists of a metal ball attached to a chain, poised on a tiny pedestal. If the turbine starts vibrating above a certain threshold, the ball falls off the pedestal, pulling on the chain and triggering a shut down. Probably the most commonly activated safety system in a turbine is the "braking" system, which is triggered by above-threshold wind speeds. These setups use a power-control system that essentially hits the brakes when wind speeds get too high and then "release the brakes" when the wind is back below 45 mph. Modern large-turbine designs use several different types of braking systems:
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You should do a post about the claimed negative health affects caused by wind turbines in close proximity to homes.
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:previous:
Regulars can post and post threads, you post that! |
Well you just seem so much more eager to post things here, I thought it would look better if you did it. I mean, you do format those posts ever so well.
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:previous:
I whipped out google sketchup real fast and made this. I basically took the same design and added lights. Wouldn't these make good streetlights? http://i486.photobucket.com/albums/r...greenlight.png http://i486.photobucket.com/albums/r...reenlight2.png Pictures courtesy of ME! |
I think the moving shadows would drive people insane, and I am willing to bet that so little energy would be produced (small turbine and low wind speeds) that it wouldn't be of much benefit to society. That's not even considering the cost of such a thing. In many places, regular street lights with solar panels on top (but still connected to the grid just in case) are probably sufficient, especially suburban areas where the street lights don't have to be so bright.
Try designing something that could be put onto a person's home though. I'd like to see things like that and solar panels become standard in single-family housing in the future. |
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I guess the light could be directed so as not to make people go crazy like you said. No light has to actually illuminate the blades and the blindspot underneath could be illuminated by a small set of LED's wrapped around the pole. Plus it would be hooked into the grid so its extra power could be harvested and just in case it can't generate enough on a stagnant day. Plus it's not like we can't add solar panels on top of it all. Actually, it wouldn't even need to be street lighting. I was thinking something more on the scale of athletic field lighting. We also have huge highway lights here in Vegas. |
You still have to consider how a strobe effect would affect drivers and athletes in those situations. You might not be able to avoid the flicker, especially with highway lights since those point pretty much straight down.
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every residential and office building should have one of those on top of it. We need more independence from power companies.
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The problem with wind power is that is that large turbines are usually isolated and far from areas of demand. And the electricity generated fluctuates because of fluctuations in wind speed. So for both of these reasons, a lot of extra transmission capacity is needed to deal with the higher volumes of electricity. Plus, electricity is wasted during transmission, so longer distances just means more wasted electricity.
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But that isn't as much of a problem when it is small scale, home use wind turbines, or if they're in a parking lot or something.
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Yeah, since they can be located right where the demand is, then they would be even more efficient than conventional power.
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What kind of wind projects have been constructed near everyone? About 30 min north of my hometown in Wisconsin almost 300 MW of Wind Turbines have been constructed.
Here's a turbine being assembled in Wisconsin: http://jcwinnie.biz/wordpress/imageS...dconnect_2.jpg jcwinnie.biz |
Windbelts: wind power without the turbine
http://www.terrapass.com/blog/posts/windbelt http://www.terrapass.com/images/blogposts/windbelt.jpg We’ve covered micro-wind a number of times here, but I think this may be the coolest innovation I’ve seen in a while: inventor Shawn Frayne has come up with a device that harnesses the power of wind without any rotating parts. Instead, his company’s Windbelts capture energy using fluttering fabric. You can best understand the process by watching this short video, but basically as moving air passes over a taut membrane, it induces a vibration, somewhat akin to a violin bow. Magnets mounted on the membrane bounce back and forth between metal coils, inducing an electric current. Like solar cells, the technology is modular and can scale up or down to fit numerous applications. At the micro end of the scale, a palm-sized version of the device can act as the equivalent of dozens of AA batteries. Such tiny generators can be used to power remote sensors or other distributed infrastructure that would otherwise require costly wires or regular battery changes. Scaling up, Frayne’s company has arranged Windbelts into modular arrays that can be deployed like fencing. The technology could find use in urban environments, to capture the energy from air moving past buildings or bridges. Or the systems can be deployed in the developing world, to provide electricity in places that the grid doesn’t yet reach. Because the materials involved aren’t exotic — the belts themselves are made of mylar-coated taffeta, which is basically kite fabric — the systems can be easily serviced in the field. Best of all, they’re cheap. At a cost of about $1 per watt of capacity, Windbelts are many times cheaper than today’s solar panels. MORE ON WINDBELT TECHNOLOGY |
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