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 Author Topic: Hydroelectric station  (Read 10411 times) 0 Members and 1 Guest are viewing this topic. Click to toggle author information(expand message area).
GwenArBreizhou
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 « Embed this message on: April 08, 2009, 04:02:08 am »

Hello,
I'm looking for an animation which shows an hydroelectric station like
http://perso.id-net.fr/~brolis/softs/domodidac/hydro.html
where I could change the height of the hole where water flows and see how it changes the rotation speed of the turbine and the amount of electric energy transformed.

Is it possible for you to do it ?

best regards,
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Fu-Kwun Hwang
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 « Embed this message Reply #1 on: April 08, 2009, 07:59:59 am » posted from:Taipei,T'ai-pei,Taiwan

To simulate an event, a physics model need to be created.
If it is an ideal case, assume No energy loss and all the potential energy convert to rotational energy of the turbine.
mgh=(1/2) I w2.
where m is the mass of the water flow into turbine, I is the Moment of inertia of the turbine, w is the angular velocity.
Since the water flow into the turbine is increasing all the time, then the angular velocity will keep increasing.
d/dt(mgh)=I w dw/dt  i.e. dw/dt=(dm/dt)gh / (I w)
where dm/dt is the water flow into the turbine per unit time.
It means that the angular velocity of the turbine will keep increase if there is no energy loss.

However, in real turbine, there are internal impedance.
And for a turbine to generate electric power, we would like it to rotate at a constant angular velocity ( f=60Hz per seconds-- w=2*π*f).
The impedance of the turbine should produce an angular acceleration = -(dm/dt)gh / (I w) ,
so that the turbine can be rotated at a constant angular velocity at a fixed (dm/dt) and h.
The system should keep dm/dt at the same rate.

For different height of the hole , different turbine machine should be designed so that the angular velocity will be the same, but the output electric power will be different.
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GwenArBreizhou
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 « Embed this message Reply #2 on: April 08, 2009, 06:17:09 pm »

So leave the hydroelectric station and just think about something like

They sell it with what they call "Level gauge of power "

which is constituted of series of LED. The larger the number of lighted LED is, more important is the power provided by the turbine.

Is it possible to simulate it ?

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Fu-Kwun Hwang
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 « Embed this message Reply #3 on: April 08, 2009, 11:37:35 pm » posted from:Taipei,T\'ai-pei,Taiwan

I should be able to create a simulatin for you as long as you give me the physics model.
You can create any differnt kind of simulation. Even simulation violate physics laws.
But I do not want to do something like that unless there is a good reason.

There are too many unknown/parameters you did not provide.

I can make more lighted LED when there is more power provided by the turbine.
But what is the relation between number of lighted LED and the power of the turbine.
Normally, it is the other way around.
If there are more LED in parallel, more power will be need if the brightness of the LED is the same.
If there are fixed number of LED in series, when more electric power is generated , the LED will get brighter.

What is the purpose for the simulation? Let me knwo what is the physics concept you want to be simulated.
It is not good if we provide a non-physical simulation.
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GwenArBreizhou
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 « Embed this message Reply #4 on: April 09, 2009, 05:59:52 am »

As I said in a previous post (about magnet and steel marple), my students are newbies in physics and all I want to show them is that there is a "position energy" (potential in fact but I don't have to use this word because they are too young ;o)).
If the water fall one meter high, I got less energy than if it falls two meters. And that's all ...

So I think you can make a non realistic simulation with a very poor model because we don't need here to have the true angular velocity and the good number of lightning LED ;o))

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Fu-Kwun Hwang
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 « Embed this message Reply #5 on: April 09, 2009, 09:09:02 am » posted from:Taipei,T\'ai-pei,Taiwan

May be we should work out some other solution.
Because the output power should not be proportion to number of lighted LED.
For electric power generation:
All the power generated will be gone if there is no load conntected to the output of power generator.
The power generator try to output a constant voltage (with the same AC frequence).
It is the current flow through LED which will determine the brightness of the LED.

I am agree that, we can connect more LEDs with the same brightness if there is more power generated.
But the studnets will not know so much.

I am afraid this might introduce another mis-concept to students.
And they might remember if more power generated, more LEDs will be light up -- which is not true.
I do not think this is good.

If it is about "position energy" only  (unless you also want to make connection to electric power generator?)
When a ball is moving higher and let go. It will gain more energy when it moving down.
Or may be you some other better ideas?

As you can see from another simulation (Re: Magness and steel marble) I created for you:
I can use picture as background image in the simulation if you can provide me some picture (which is better for young students).
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GwenArBreizhou
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 « Embed this message Reply #6 on: April 09, 2009, 07:58:45 pm »

The connection to electric power generator is not necessary. So we can just imagine water falling on turbine, a red spot on turbine to see how fast it turns. And the rotation speed will be bigger if water falls from highest position.

Regards,
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Fu-Kwun Hwang
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 « Embed this message Reply #7 on: April 09, 2009, 10:08:42 pm » posted from:Taipei,T\'ai-pei,Taiwan

I hope the following simplified version is what you need.
It might liik nicer if you/someone can provide me some nice picture to used as background image.
You can drag the slider or drag the water level (move mouse near center of water level) and drag it up/down.

Embed a running copy of this simulation

Embed a running copy link(show simulation in a popuped window)
Full screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
• Please feel free to post your ideas about how to use the simulation for better teaching and learning.
• Post questions to be asked to help students to think, to explore.
• Upload worksheets as attached files to share with more users.
Let's work together. We can help more users understand physics conceptually and enjoy the fun of learning physics!
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GwenArBreizhou
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 « Embed this message Reply #8 on: April 09, 2009, 11:59:55 pm »

All right. Thanks. It'll be enough for what I want to show.

I tried on Google images to find something nice for the background but in vain ...

Regards,
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