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Energy generation at the Mars, for the martian rovers etc.

Posted by: Ekkehard Augustin - Fri Feb 25, 2005 2:58 pm
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Energy generation at the Mars, for the martian rovers etc. 
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Post    Posted on: Thu Mar 10, 2005 7:44 am
Big turbines tend to have more mass per wing that small ones and especially nano-scale ones. And more mass requires higher force to move that mass. Earthian winds seem to provide that force or power (what's the right english term here?) required to move the big wings of the big turbines.

I often see the wind parks in the surroundings of Hamburg - and I can feel winds in the area of the wind parks that cannot set the wings of the turbines to motion but they can set to motion the wings of very small turbines like those that are used in agriculture since very long time.

These observations are indicating that smaller turbines or wings are working at winds that are not strong enough to set big turbines to motion.

The force of the winds seems to be of meaning - as far as I know the force (power?) of the winds depends on the speed of the wind as well as on the masses of air per cubemeter moved.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

EDIT: I should add that certainly the force (power) of the earthian winds I can observe working at the wind parks and the agricultural wind turbines seems to depend on the speed mainly because the mass of air per cubemeter moved doesn't very that much.


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Post    Posted on: Thu Mar 10, 2005 2:00 pm
It is not the mass of the blades that makes the turbine hard to turn. It is the load of the generator attached to it. The small pinwheel spins because it does not have to turn a generator. And the more electricity the generator is supplying, the harder it is to turn. Simple conservation of energy.


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Post    Posted on: Thu Mar 10, 2005 2:17 pm
The small turbines used in agriculture in general drive something - different things.

But regardless of what to drive by the turbin - the higher the mass of it the higher the required force to set it to rotation (or the higher the amount of time a constant force has to act on it permanently.)...



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Post    Posted on: Thu Mar 10, 2005 2:56 pm
Here's a rough suimulation of a small earth turbine in the martian atmosphere: a propeller from a 1:72 plastic model kit mounted on a generator. It should see about the same aerodynamic conditions as a 1:1 martian turbine.


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Post    Posted on: Thu Mar 10, 2005 3:34 pm
I am not sure if we are talking about the same thing, properties etc. To set a mass of known size - let's say 1 ton - to rotation by a speed of 100 rotations per minute a special concrete size of force is required. Currently I don't know the connection to aerodynamics.

Even if I add the load of the generator this is true - the force has to be higher yet then.

Regarding wind turbines wind is used to provide that force. Given the masses of air moving by a wind the force seems to be the higher the higher the speed of the wind is. The masses of air moving by a wind will be nearly constant as long as the average thickness of the atmosphere is constant the wind is blowing in. On Mars the masses of air moving are extremely smaller compared to Earth.

I suppose that the wind turbines are not set to motion by the impact of the wind upon the wings directly but by pressure differences between the two sides of the wings. Winds are blowing rom high pressure regions to low pressure regions always - the wings of turbines are shaped so that they change the direction of a wind. This causes a difference of pressure between the both sides of the turbin - the tendency of air to reduce that difference causes the rotation.

If that is correct to a sufficient degree then the average mass of air in an atmosphere should restrict maximum pressure in a high pressure region. And it should restrict the possible differences in pressure between the two sides of the wings of a turbin too. This in turn should restrict the maximum mass of the wing at which the wing would work.

If again that is right then at least the mass of the wing would have to be smaller than on Earth.

But there is an additional environmental difference to be regarded - as far as I know the fact that the martian atmosphere is a hundred times thinner than the earthian one results in large differences of pressure between different altitudes. As far as I know this is valid at meter-scale.

And this would mean then that not only the mass of a wing would have to be smaller - the length etc. of the wing would have to be smaller too.

I didn't go to the details of my knowledge sufficiently because I currently didn't find a good way to say it in English - but the question is: What's wrong in this?



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

PS: The generator won't be the problem - if the turbines are nano-scale the generator will be nano-scale too.


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Post    Posted on: Thu Mar 10, 2005 5:06 pm
The torque required to set a flywheel spinning is (comparitively) as good as zero. The torque required to set a flywheel spinning and keep it spinning, when it is "pushing" against the forces in a generator, are much higher.

Easiest example: go find a battery-powered drill. It's best if the battery is dead, but even if the battery's fully charged, it won't make too much difference. If the drill has an adjustable clutch, set the torque to the highest level. While being very careful not to pull the trigger, rotate the moving part of the drill with your hand. You are manually pushing current through the circuitry of the drill and charging the battery. Now, go find a similarly-shaped object, with roughly the same size and mass as the moving part of that drill. Spin it around its axis. The force required to move the object will be much less than that required to turn the drill.

We don't even care about the mass of the flywheel -- I can make you a windmill that weighs about 20 pounds and is a hundred or more feet across (plastic tubing and sheet cellophane). Making that windmill turn a generator, on the other hand, takes a very large amount of force.

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I might point out here that using wind turbines on Mars is somewhat ridiculous: there's effectively no wind unless you're in the middle of a planetary dust storm, and then the fines will grind practically anything down to a useless hulk in a matter of minutes, much less the rotating hub of a windmill -- moving parts and micrometer-diameter fines suspended in a hundreds-of-miles-per-hour wind do not get along well at all.

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Post    Posted on: Thu Mar 10, 2005 7:14 pm
Mass does not matter, it is friction that matters. A very weak force can set a million ton turbine spinning at the same number of revolutions per minute as a strong force, it just takes hours to get up to speed. But if you add friction, then the weak force may not even be able to move the turbine. The generator acts like friction. And the smaller the turbine the less force the wind exerts on it. The result is small turbines don't work.


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Post    Posted on: Thu Mar 10, 2005 9:48 pm
Add the fact that efficiency of smaller turbines really suck on Mars.


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Post    Posted on: Thu Mar 10, 2005 11:02 pm
The efficiency of turbines sucks on Mars, period.

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Post    Posted on: Fri Mar 11, 2005 11:41 am
Peter,

the friction caused by a generator depends on the generator itself - the generator can be modified to make a small trubine working. The big GROWIANs here in Germany for example have wings that are 10, 15, 20 meters long All these trubines her in Germany together gerate as much electricity as one nuclear reactor.

Long before the GROWIAN have been thought of first there already have been small wind turbines - those used for several different purposes in agriculture. Some of them generated electricity for minor pruposes at the fileds etc. (Other have been used to pump water for example)

These smaller turbines generating energy drove generators much smaller than those driven by the large GROWIANs. These smaller generators caused much less friction.

Scale down the turbines AND the generators AND the amount of electricity generated per generator - AND provide MORE turbines AND MORE generators.

What you said about the question wether mass does matter or does not matter in the end means that mass really DOES matter - because you worked out that given a concrete mass a weak force "just needs hours" to cause the same number of revolutions per minute as a strong force. This "just needs hours" combined with your mentioning of the difference in forces menas by logic that mass DOES matter.

A martian wind will provide or cause a weak force only compared to an earthian wind.

Adjusting the turbines, the generators to each other AND to the martian winds will make smalle trubines and generators work at Mars.

The only question is that one spaccowboy has mentioned - the question if there are really winds at Mars. Something like wind seems really to be there - as the dust devils indicate. Even stroms are there - as the dust stromes observable from Earth indicate. What currently seems to be unknown is if there are normal winds too at Mars. As far as I remember no probe and no rover has been seraching for them or measuring them yet - this should be done. It's very interesting in general.



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

PS: Peter, you and me have been cosidering different forces acting on one given mass here. This can be changed into cosnidering one given force - at Mars - acting at different masses which is what I am thinking about...


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Post    Posted on: Sat Mar 12, 2005 12:05 am
Could this be the first wind powered Mars rover being tested in the antartic. :)

http://www.cmu.edu/cmnews/extra/050309_lorax.html

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Post    Posted on: Sat Mar 12, 2005 10:25 am
Very good article. Thank You Very´Much for that link, Andy Hill.

I think it should be a little bit smaller for Mars and I would prefer significantly smaller and more turbines at significnt less altitude because of the hundred times thinner martian atmosphere - I will look for numbers about the pressure at different altitudes when I find time for it.

But this could be the germ.

And this rover is combining the two sources wind and sunlight.

By the way - the solar panels of vehicles could add to the generation of electricity after such vehicles have landed there until they launch back for Earth.



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Post    Posted on: Sat Mar 12, 2005 10:53 am
I'm not sure whether this is a serious atempt by NASA to develop wind turbines for Mars rovers, it may just be a way of supplimenting the power during testing on Earth. Either way I thought the article was apt given the current thread and at least it shows that NASA is considering different power generation schemes.

My thoughts about the whole concept are that wind turbines are probably able to operate on the Martian surface but how efficient they would be in generating sufficient power to make them worthwhile is debatable. Ultimately they are likely to be heavier than a solar array producing the same amount of power of a similar weight. The best system may be a hybrid that does not rely on any particular power source, for instance a wind turbine could also be used as a fan to blow dust from solar panels (if atmospheric density allows) to stop their degradation.

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Post    Posted on: Sat Mar 12, 2005 12:54 pm
Up to now my point isn't - and never was - the efficiency of wind turbines compared to other sources of electricity. My point currently is only that they can be a siurce in principle but msutn't be of that size and weight they have on Earth - they must be smaller and mor numerous for Mars.

Their efficiency should be analyzed and searched for ways to be improved - which seems to be valid for solar cells too as I calculated in an earlier post in this thread.

What about using the large differences in temperature between the ground and an altitude of two meters above the ground? Which ways could that be used to generate energy? And the movement of the grains of dust?

In principle I am talking about different In Situ Ressources - wind, light, temperature and its relation tlo altitude, dust grains...

So I agree to you in several points - no prblem with your post.



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Post    Posted on: Sat Mar 12, 2005 5:44 pm
Ekkehard Augustin wrote:
they must be smaller and mor numerous for Mars.
Actually they need to be larger and higher and more numerous. Higher because wind speed is lower close to the ground, larger and more numerous due to the thin air for the same reason that ultra high altitude aircraft need really large wings.


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