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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: Sat Mar 12, 2005 9:25 pm
I must say, I like Andy's take on the problem. While I am very doubtful as to the relative benefits of wind-power on mars when compared to other forms, a fan/turbine would help solve the solar/dust problem, as well as could provide a (small) source of energy occasionally at night, when no solar energy may be obtained. The value of the fan would be fairly large, and the modifications to make the fan useful as a turbine would require fairly small increases in mass. The concern then, would be the size and placement of the fan/turbine. As a fan, it would be more useful being close to the solar cells, but as a turbine, it would be more useful up higher, where the wind could provide more energy. To add the capability to move the fanbine up and down, and angling as necessary for blowing dust off the cells, would likely be at a more prohibitive energy and mass cost.

This being said, even in the fan-optimized height, perhaps some energy could be harvested on particularly windy nights that could be used for, say, heating important components.




A question regarding obtaining energy from temperature differential in a stirling engine:

Could water be used as a dual source/sink for this form if energy production? At (the beginning of) night, it would be warmer than the surrounding air, and during sunlight, it would be cooler than the surrounding air. I'm not sure if this would require too much extra bulk to have the system operate both ways, or if the energy obtained by using such a comparatively small source/sink would be negligible enough to make the idea useless.


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Post    Posted on: Sun Mar 13, 2005 10:48 am
Hello, slycker,

optimization and day/night are the right points. The use of the turbine to remove dust from solar cells is too - but wouldn't such turbines consume electricity? If I am right in that then they would be the opposite of the others.

And Thank You Very Much for starting thoughts about making use of differences in temperature.

The topic of night and sunlight has been in my mind regarding the wind turbines as a source of electricity because of spacecowboy's doubts if there will be winds at Mars at all - except dust devils and dust storms. Around the border between day and night there should be differences in temperature between neighboured regions. These differences should cause differences in pressure like here on Earth. So in the evening and in the morning there should be winds in principle. And the dunes on Mars seem to be indicating winds that are not dust devils because these should leave different shapes - but I may be wrong in that.

All this may an argiment for supposing winds in night too.



Peter,

thin air provides less force than thick air. force is required to move a mass and mass is "träge" - the german word "träge" means that something cannot be set to motion without force or energy or impulse or something like that. Is "träge" "dry" in English"? I have to ask for that to be careful because "dry" is translated to "trocken" usually - "trocken" means "not wet". But in this post I will use "dry" for "träge". To resume - force is required to set to motion dry mass. And because thin air doesn't provide as much force as thick air the mass to be set to motion has to be smaller in thin air.

We seem to agree in that now.

The next point is that the currently used GROWIANs in Germany are rotating within a region of atmosphere the thickness don't be varying in - at the upper edge of the GROWIAN the air is as thick as it is at the lower edge. This condition has to be fulfilled at Mars too - at the upper edge of a martian turbine the thickness of the layer of atmosphere has to be nearly the same as at the lower edge of the turbine.

Because of the thinness of the martian atmosphere the layers with nearly no differences between upper and lower edge will be thinner than on Earth I suppose. It should be clarified if that is really the case. If I am right than it means that the turbines must be smaller than on Earth.

And on Earth the atmosphere is thicker at the ground than in altitude - this can be experienced by going or climbing up the mountaines of the Alpes or the Andes. It can be experienced in the Rockies too I suppose but I never have been there. And many of the Himalaya-climbers used oxygene containers.

The example of high-altitude aircrafts can't be used here I suppose - the wings are not used for motion but for keeping the aircraft at desired altitude. The wings are not moved.



Now I have said much concerning wind turbines and winds again - I simply don't have new thoughts about solar cells currently. Has someone else? I would like to see the mix of turbines, solar cells and other sources to be discussed more detailed and the use of temperature differences worked out more detailed...



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Last edited by Ekkehard Augustin on Sun Mar 13, 2005 4:33 pm, edited 1 time in total.



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Post    Posted on: Sun Mar 13, 2005 12:20 pm
If you can achieve this increase in solar panelefficiency with a wind turbine acting as a fan to remove the dust from them then it would be worth consuming the electrical power to turn the fan.

http://space.com/missionlaunches/spirit ... 50312.html

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Post    Posted on: Sun Mar 13, 2005 8:01 pm
Ekkehard Augustin wrote:
The use of the turbine to remove dust from solar cells is too - but wouldn't such turbines consume electricity? If I am right in that then they would be the opposite of the others.)
Electric motors and electric generators are really the same machine. If you apply electricity to the terminals of a motor, the motor turns. If you turn the motor with an outside force, then electricity will be generated. The same turbine can easily be both a fan and wind powered generator.

Ekkehard Augustin wrote:
at the upper edge of the GROWIAN the air is as thick as it is at the lower edge.
I was not speaking about any difference in density with hight. The reason wind is slower near the ground is friction between the moving air and the stationary ground.


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Post    Posted on: Mon Mar 14, 2005 7:53 am
Answer to your second issue: That concerns the location of the turbine only but you have been speaking of the size of the turbine or its wings.

The place of turbines can and should be optimized - they have to be in altitudes where the air isn't too thin and - too - the winds aren't too slow. There are other aspects too that have been considered for optimization of location: in the planes of Mars wind can blow better and easier - but in regions with hills and mountaines there can be nozzle-effects causing the wind to be accelerated. And in the hill-regions there are significant upper restrictions for the altitude.

Near the ground doesn't mean within the first millimeter above the ground - I am speaking of nano-scale turbines currently - the altitude could be ten centimeters or twenty for example. There will be a different optimal location for different size and different kinds of turbines.

This will be valid for solar cells, temperature-difference based technologies etc. too.



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Post    Posted on: Mon Mar 14, 2005 12:58 pm
Hello, Andy Hill,

the article "Spirit Gets A Dust Devil Once-Over" ( http://www.space.com/missionlaunches/sp ... 50312.html ) says that spirit has been cleaned by a dust devil recently.

So this may be indicating that a cleaning trubine would be a good idea - on the other side I suppose a dust devil a much stringer wind than a cleaning turbine could generate. An additional question might be perhaps if such a cleaning turbine might cause dust devils - which could prove to be bad. According to the article the dust devil initially increased the dust at the solar panels which reduced the energy available to Spirit.

The same article says that Opportunity has been cleaned much earlier but it is completely unknown which way it has been cleaned. One possibility is that there was a wind - but then that would have been no dust devil I suppose. The dust devil at Spirit has been observed when it has been born and during action - at Opportunity nothing like this has been seen. So Opportunity might be indicating that there are normal winds at Mars too - these winds may be able to set turbines to rotation that fulfill special conditions: the mass of the turbines together with the friction of the generators they are driving don't require winds of higher force than the wind that cleaned the solar panel of Opportunity. Then it should be sure that the turbines would work.



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Post    Posted on: Mon Mar 14, 2005 7:32 pm
Ekkehard Augustin wrote:
Hello, Andy Hill,

the article "Spirit Gets A Dust Devil Once-Over" ( http://www.space.com/missionlaunches/sp ... 50312.html ) says that spirit has been cleaned by a dust devil recently.


Ekkehard this is the same article I posted in this thread yesterday.

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Post    Posted on: Wed Mar 16, 2005 9:43 am
Sorry - I didn't remark that. It seems the article appeared at the site of space.com after my own (nearly) daily look at their site.

The reason for my post merely were may own thoughts than the article itself - I listed it in the sense of a footmark because of being used to that only.



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Post    Posted on: Fri Apr 01, 2005 1:55 pm
The amount of electricity required at other planets for stations may be reduced by using the upcoming light-diodes. They are predicted to replace the conventional technique in the nearby future.

This and all already discussed here and in some other threads may assist each other in making sure that there will be sufficient electricity at other planets - first moon and next Mars.

Does anyone know if such progress are on the way concerning other electricity consuming equioment too?



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Post    Posted on: Mon Apr 04, 2005 10:23 am
I didn't find the following alternative in any post of this thread: Sunlight simply could be used to heat water. Reflectors and magnifying glasses could direct it into a container that containes water under earthian pressure and conditions. The steam got this way could drive a turbine.

This could be done on Earth too but down here all the equipment is available that is missed at moon and Mars currently. It might be interesting how efficient that would be compared to ISRU-based solar cells that have 1% efficiency.



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Post    Posted on: Wed Apr 06, 2005 11:03 pm
The reason the big turbines do not spin at low speeds is that thrust through a rotor is equal to airspeed cubed. There is pretty much zero energy below 7 mph and it is not worth spinning at that speed.

It is also easier to make a large turbine free wheel than smaller ones because friction does not go up as fast as energy potential in does when you increase size. Most home built wind turbines spin all day, but will not produce power unless the wind gusts to higher than 6 mph so that they can reach their cut in speed.

Also air pressure does not change enough from one meter to the next to where you would have to worry about it in a turbine. You would have to design turbines for their altitude, but not for the change in altitude from the top to the bottom of the rotor.

Anything other than smooth air flowing into a turbine would add lots of stress to the bearings and blades. It would not be easy to design one to handle a disturbed airflow. Any sudden change in wind direction would require a yaw damper.

Erosion would also be a problem. Sand will eat through anything if it is moving fast enough, and the blade tips would be traveling pretty fast.

You would also have to figure out if it could operate with the blade tips below mach speed, faster than mach .9 would destroy the tips and put a lot of stress on the rotor, not to mention kill efficiency by all of the transonic drag it would cause.


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Post    Posted on: Sun Apr 10, 2005 2:56 pm
You mentions erosion by sand and dust - this reminds to the idea of dust turbines. Are these possible? Besides sand turbines working similar to water turbines, steam turbines and wind turbines I could imagine sand turbines at Mars which are driven by sand going up into the air. Each blade could have one non-streamlined side and one streamlined side.

Rising sands would impact the non-streamlined side and thus giving the turbine an impulse and set it to motion whereas the impact on the streamlined side wouldn't provide such a strong impulse.

Is that possible? Could it work?



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Post    Posted on: Tue Jun 28, 2005 11:12 am
An article at www.wissenschaft.de says that swiss scientists have constructed a solar power plant that uses sunlight to vaporize zinc-oxyde which then brakes up into zinc and oxygen. These two elements are stored then and later recombined in batteries to generate electricity. 45 kg of zinc-oxyde per hour can be vaporized.

www.wissenschaft.de refers to www.psi.ch and www.psi.ch/medien/Medienmitteilungen/mm ... gie_e.html .

Is already known if there is zinc-oxyde on Mars? I don't remember to have read something like that. Would that what's known currently include the possibility that it has been formed there? If yes then this could be an additional source of energy there.

What about using zinc-oxygen batteries by rovers?



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Post    Posted on: Tue Jul 12, 2005 6:36 pm
Regarding the use of martian winds for electricity generation I read this evening a very short article saying that the company Matrow developped a wind-based generator which costs a third of solar cells - at euqal efficiency..

That generator delivers electricty regardless of the direction of the wind and at what force of wind - the wings have a special shape to achieve that. It weighs 39 kilograms.

The article says that there is a version generating 3.5 kilowatts or 3000 to 4000 kilowatthours per year - the price is 7000 Euro.

Might a lightweight version of significant less size be working on Mars?

Unfortunately I can't provide the photo of it here. Matrow is a german company in Ladenburg near Mannheim.



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Post    Posted on: Wed Jul 27, 2005 12:08 pm
The article "NASA's Next Mars Probe Takes Aim at Red Planet" ( www.space.com/businesstechnology/050727 ... epare.html )
is reporting that
Quote:
the orbiter’s solar panels span a total of about 20 square meters and carry about 7,000 solar cells. All those cells are need to generate the five kilowatts of power in Earth orbit, though that power output will diminish to about two kilowatts of power at Mars, Calvin said, adding that MRO’s instruments and equipment only requires one kilowatt to function.


As far as I know an average town/city on Earth consumes 1 megawatt at least. So it sounds to me as if a Mars-colony of the size of an average earthian town or city would require 3,500,000 solar cells at least.

Even a permanent Mars station with a crew of less than 20 persons will need very much solar cells but I don't know currently how much - what is the number?

Obviously the efficiency of earthian solar cells is reduced by the factor of 2.5 in the martian orbit.

...



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