What is Windmill: Definition and 40 Discussions

A windmill is a structure that converts wind power into rotational energy by means of vanes called sails or blades,
specifically to mill grain (gristmills), but the term is also extended to windpumps, wind turbines and other applications. The term wind engine is sometimes used to describe such devices.Windmills were used throughout the high medieval and early modern periods; the horizontal or panemone windmill first appeared in Greater Iran during the 9th century, the vertical windmill in northwestern Europe in the 12th century. Regarded as an icon of Dutch culture, there are approximately 1,000 windmills in the Netherlands today.

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  1. K

    Raising a farm windmill tower

    I have a retirement project in restoring an old farm windmill and am close to being ready for the install. I want to pick the 35' tower and mill head together in one operation using a crane. My last statics class was 45 years ago so I'm a little rusty. I know the mill weight of 250 lbs will add...
  2. hugo_faurand

    Looking for advice on motors for a small windmill (for kids)

    Hello everyone ! I speak about energy to a fifth grade class. I want to build small windmills made of paper cup for the blades. The goal is to light a LED when the windmill is running. I was looking for a small motor to do the alternator. I found this one and I wanted to know if it could fit...
  3. T

    Venturi effect or Coanda effect or a combination of both in this windmill?

    I have recently find this video and just curious about the working principle behind this concentrated windmill. Apparently it seems that the basic principle is Venturi effect but the shape of the entry point is more suitable for Coanda effect with its curved surface at the entry. And it's also...
  4. K

    Question about a Windmill / Turbine

    Homework Statement Consider a turbine which actuates the windmills by blowing air into it. (If we use beat steady windmills (which is called reverse windmills) instead of movable windmills, deliberate the following conditions by parametric view. (Ignore the friction power (force)) A. Compare...
  5. Andres Padilla

    FBD of an aerogenerator (Windmill)

    Homework Statement Good afternoon, I hope someone could help me with this problem, it is killing my head. I have an aerogenerator, I already find the torque excerted by the air (75.8N) and the force transmitted by the gear (1010.6N). The problem comes when I try to draw the free body diagram to...
  6. JTC

    Windmills and Power Generation

    I tried yesterday with the gyro and did not make myself clear. So let me try with a windmill, please. I look at a windmill and I see the blades are spinning. Thus, the shaft axis has an angular velocity. I can ballpark and check the angular velocity with my eyes. I want a ballpark...
  7. Steven Robinson

    How to calculate max current potential in a windmill generator....

    Hi, new member with a question that I might be asking wrong. A week ago I read an article or something on building a windmill generator, which I come back to every few years. So, this week, I was reading about how to calculate the voltage based on loops, turns, Teslas, area, RPMs and such, and I...
  8. Alettix

    Pointmass colliding with windmill

    Homework Statement A toy windmill consists of four thin uniform rods of mass m and length l arranged at rigth angles, in a vertical plane, around a thin fixed horizontal axel about which they can turn freely. The moment of intertia about the axel is ##I = \frac{4ml^2}{3}##. Initially the...
  9. I

    Finding the best height for windmill towers

    To approximate windspeeds we normally use the natural logarithm relation: u_air = V ln [ (z-d) / z_0 ]Where: V - Characteristic speed, constant z - height from the ground z_0 - roughness length, constant d - zero plane displacement, constant The Betz limit tells us that in theory that the max...
  10. B

    Looking to build a backyard windmill

    Hey all. I'd like to build a small windmill in my backyard. Small is I'm going to guess maybe 5 foot blades or so. I do CAD work so I can design most of the parts I need EXCEPT the blades. I have no idea where to start. I understand the basic shape, but I'm unclear where to start to get one...
  11. T

    Optimization of windmill power with use of gears

    < Mentor Note -- thread moved to HH from the technical Engineering forums, so no HH Template is shown > Okay so I'm a freshman BE student and one of our first projects is designing a windmill that can produce a voltage of 5 for 2 seconds or longer. We are having trouble find the optimal gear...
  12. G

    Where in the world can i purchase a A ram air turbine Rat_

    where in the world can i purchase a A ram air turbine Rat.._ i want to mount it on the roof of my rv trailer build. and use it as a wind turbine generator as i drive down the road, to recharge my batteries.. i heard you really can't use a regular wind turbine or can you..?? or will it just...
  13. W

    Someone know a bit about Generators? (windmill project)

    Hi just started working on a hobby project with making a wind mill. I got to the part were i have made the blades and the casing, for the wind mill. I was wondering what type of generator should i use for a 1,5m diameter blade. I really don't have anything special that i want the power to go to...
  14. M

    What Is the Optimal Size for a Windmill Given Constant Wind Speed?

    Hello folks, I tried googling this but found surprisingly little on it. Here is the problem: Assume that you have some constant wind speed. I want to run a windmill but I need to decide how big a windmill I want. The size is characterized by the length of the blades, r. There are no...
  15. S

    Model windmill, exhibition stand -

    Hello everyone :) I have a problem which I would love help with, very briefly I am having a model windmill built as an exhibition stand. As it's height is just over 3 metres I am being asked some pretty tough questions by the health and safety team at the show. Specifically "what weight...
  16. L

    Is It Possible to Charge an iPod Using a Windmill on a Car?

    I'm a high school physics student, so keep my limited knowledge in mind. Basically the other day I had the idea to create a charger for my iPod that's powered by a windmill, which I could attach to the outside of my car. I've never actually built a windmill before, but I'm pretty confident I...
  17. pmd28

    Mini Golf Windmill: Find Minimum Linear Speed of Ball

    Homework Statement A golf ball passing through a windmill at a miniature golf course. The windmill has 6 blades and rotates at an angular speed of 1.65 rad/s. The opening between successive blades is equal to the width of a blade. A golf ball (diameter 4.50x10-2 m) has just reached the edge...
  18. pmd28

    Mini-Golf Windmill: Find Minimum Linear Speed

    Homework Statement A golf ball passing through a windmill at a miniature golf course. The windmill has 6 blades and rotates at an angular speed of 1.65 rad/s. The opening between successive blades is equal to the width of a blade. A golf ball (diameter 4.50x10-2 m) has just reached the edge of...
  19. M

    Windmill direction based on illustration.

    How can you tell which way a windmill will blow based upon an illustration of it's blades? I've done some research and can't understand it! The wind is blowing directly at it. There are different shapes of the blades but I haven't been able to determine how that shape determines direction. The...
  20. B

    Can a funnel or cone shape increase the power output of a windmill?

    [I have been searching for an answer to this puzzling question for the past two hours. (To no avail.) A few search results lead me hear, but nobody had raised the question that is in my mind] Would building a funnel/cone improve the power output of a given windmill? Let us say, for...
  21. U

    Power of a Fan and WindMill using Energy vs dynamic method)

    Homework Statement Determine the power of a windmill using constants where appropriate.Homework Equations P = Fv K = (1/2)mv2The Attempt at a Solution Dynamics Method P = Fv In time Δt, Δm amount of wind passes through the windmill, at speed of v. Δp = vΔm = v(AρΔx) Dividing both sides...
  22. E

    Force needed to turn a windmill generator

    Many sites describe their windmills in terms of wind speed, minimum or max etc. Can anyone share with me how much force in terms of how much torque or kg force is needed to get it rotating? Is there any conversion formula to it? I'm sure different size of generator would require different force...
  23. I

    Windmill rotates with constant ang. accel. What time does Tangetial = Centripetal

    Homework Statement A windmill starts from rest and rotates with a constant angular acceleration of 0.25 rad/s2. How many seconds after starting will the magnitude of the tangential acceleration of the tip of a blade equal the magnitude of the centripetal acceleration at the same point...
  24. S

    Why Can't a Windmill Be Powered by Magnets?

    I know it can't work but can someone explain why? The U thingys are the magnet. So the magnet attracts the fan and it keep moving.
  25. S

    Designing a Windmill for Maximum Power

    Homework Statement I need to design a windmill in a competition that can produce the maximum power given every participant has the same gears and dynamo. so basically we have to concentrate on the blade's design. What is the best design and its orientation on the rotor. Also what type of...
  26. U

    Windmill power generation problem

    Homework Statement A windmill is designed to operate at 20 rpm in a 15 mph wind and produce 300 kW of power. The blades are 1.75 ft in diameter. A model 1.75 ft in diameter is to be tested at 90 mph wind velocity. What rotor speed should be used, and what power should be expected...
  27. C

    Windmill Generators: Debunking the Noise Myth

    The first big myth about windmills and wind turbines is that they are very noisy. http://windpowerspecialist.com/articles_3.html
  28. S

    Moment of Inertia of a windmill or fan

    My lab partners and I did an experiment for my general physics class in which we constructed a windmill with wooden dowels. We added clay to the ends to set the concentration of mass about the ends. The distance (radius) of the clay balls from the center of the fixed axis is our control...
  29. H

    Harry Wertmuller's Doubt on Windmill Energy Proportionality

    Reading about renewable energy on the Internet a short time ago, I came across the statement that "energy is proportional to the cube of the velocity". Huh? I thought energy was proportional to the _square_ of the velocity. After all, we're not talking relativity here. -Harry Wertmuller
  30. T

    Windmill Blade Design: Learn Science & Math Behind Design for Tech Competition

    I've searched the net and this site, and although I've found several sites and posts related to the idea of wind turbine / windmill design, I have yet to find anything explaining the science and math behind windmill blade design. I've entered into a technology competition which involves...
  31. J

    Alternative Energy Windmill Ideas

    Here's the problem... I am to build a simple windmill (small scale) to lift an x amount of weight twelve inches above the base plane. The required amount is to lift 200 grams, 12 inches in 2 minutes or less. The materials are to be mostly recycled; however, I am alotted $15 to buy any new...
  32. A

    Laddermill- novel windmill design

    what do you all think of this idea? It's being developed by people at TU DELFT in holland... http://www.lr.tudelft.nl/live/pagina.jsp?id=8d16d19a-e942-45aa-9b52-48deb9312e92&lang=en promising?
  33. J

    Efficient Water Pumping with Wind: Calculating Rate in Liters per Minute

    Air moving at 14.5 m/s in a steady wind encounters a windmill of diameter 2.30 m and having an efficiency of 28.0%. The energy generated by the windmill is used to pump water from a well 36.5 m deep into a tank 2.30 m above the ground. At what rate in liters per minute can water be pumped into...
  34. P

    Windmill boat on river, no wind

    A boat with a windmill rotating a water propeller can sail directly upwind. It has been done many times, so take that as a given. (The maximum speed so far is about 0.5 times the speed of the wind. For a land yacht, the maximum speed so far is about 1.0 times the speed of the wind.) My...
  35. P

    Windmill boat on river, no wind

    Assume a windmill boat is drifting down a fast flowing river during windless conditions. It uses its relative wind to outrun the speed of the river. What is the correct way to describe this situation in terms of energy and power? Can we say that its energy is derived from the river but its power...
  36. M

    Discover the Science Behind a Photon Powered Windmill | Explained by Experts

    Okay, I got one for you all. Years ago, in school, I saw a propellor shaped thing, mirror side up, black side down. It was resting on a pin in, what I assume was, a vacuumed bell jar. It spins in sunlight as per what you'd expect... But what is the physics behind this? As light never...
  37. B

    Physics of Windmills - Get Info & References

    hi every physics guy :smile: i have a project about windmill and i would like to get a lot of information about that. Can anyone give me some reference. Thankyou :!)
  38. M

    Windmill in Space: Solar Wind Power Output Analysis

    How fast could a space based windmill turn when driven by the solar wind? Would such a device produce more or less energy than a solar panel of the same cost?
  39. tandoorichicken

    How Does Windmill Power Depend on Blade Diameter and Wind Speed?

    I had trouble with this, probably because there are no numbers in it: "The power P delivered by a windmill whose blades sweep in a circle of diameter D by a wind speed v is proportional to the square of the diameter and the cube of the wind speed. Show that this dependence on diameter and...