solar power towers on mars - km-high vertical wind tunnel turbo-elec

dicktice · 2004-12-01 21:34:05

Re. Australian power company Enviro Mission Ltd hopes to build a one km tall solar tower, or chimney, in southwest New South Wales state, onlya few hours north of Melbourne. I was struck by the inherent problems, such as height and weight, that such structures impose here on Earth.
While this method of generating turbo-electric power is only about one percent, once built, the solar energy is free for the taking. One of the features of this scheme, involves acres of greenhouse surrounding the base, to heat the air. Wouldn't such a scheme be even more attractive on Mars--casting the lighter-weight towers in place on the floors of the canyon ravines and guy-wiring them to the km-high walls. The solar collectors surrounding the bases would double as plant habitats and, suitably sealed, heat-exchanger habitats for human settlers. The problems of living on Mars, having been discussed here so thoroughly, the incorporation of such a solar power tower in each canyon community would seem to be only a small step further, conceptually if not physically.

GCNRevenger · 2004-12-01 21:47:49

One big problem is the simple lack of solar energy on Mars... it just isn't very strong. You are going to have a hard time insulating the thing overnight too. And you'll have to recycle the shirtsleeve-pressure gasses, which will lower the effective differential probobly and limit the power output. Remember, this thing is operated by the pressure differential of the altitude and temperature, both of which will be limited on the low-gravity Mars and if you have to recycle the warm air.

Shaun Barrett · 2004-12-01 22:24:40

Without wishing to cause any aggravation, GCNR, I confess to having found many of your responses to various suggestions at new Mars more than a little pessimistic, not to say cynical. (Of course, you may defend your positions by saying they're practical and pragmatic, not cynical. And everyone is entitled to his/her opinion.)

However, in this case, I have to say I find your arguments persuasive; I don't think the Enviromission-type solar tower would work well on Mars either.
Your points about the lesser solar energy input on Mars and the difficulties of adapting a device which operates on the free-flow of air are valid objections, in my view. The lesser gravity, producing a lesser vertical pressure gradient in Mars' atmosphere and hence reducing the power and speed of the convection current in the tower, is also a negative factor.
Another point, which we've discussed at length here in the past, is the problem of pouring concrete and getting it to set in martian conditions. No easy task even at or near ground level, never mind hundreds of metres above the ground.

For once, GCNR, I agree with you!

But I suppose I may have overlooked some important details or misunderstood Dicktice's plan, so I'll be interested to see if he comes back with counter-arguments.
I have to admit, I'm a solar tower enthusiast and I'm prepared to be convinced such a thing would work on Mars. But my credulity is stretched somewhat just believing it'll work on Earth!

comstar03 · 2004-12-01 23:33:20

Dicktice,

You are trying to come up with new ways to look at issues, what about wind power and different wind towers instead of solar, because of the atomsphere, distance and as we terra-form the planet it will increase the atomsphere interference with sunlight pentration.

But I do agree that solar power in mars orbit focused and concentrated would provide the power requirements until fusion power has been completed in the development, trial and quality testing phases and enough knowledge has been acquired to scale down the size of the fusion generators.

Keep bring ideas forward, I like your style

GCNRevenger · 2004-12-02 01:04:03

Wind power on Mars? Ummm, the air is over a hundred times thinner, a wind mill isn't going to get you anywhere on Mars.

comstar03 · 2004-12-02 03:00:12

GCNRevenger,

That is an issue also the gravity is less, than earth, yes the air is thinner but the force is still the same, means changes in design and modelling to test wind generation. We can simulate the atomspher density, and velocity of winds over the martian surface the right process could provide the continous energy source required for the outpost.

If you have proof that the idea wouldn't work because of experiments then provide the research documentation, web address or place to get it, because the initial discussions from wind generation companies are promising for creation of alternative energy sources on Mars.

If , you don't have evidence of tested experiments in Martian Wind Gerneration. Then, you don't want to even try a new thought / idea because that would be something you need to use your brain with a postive way for , instead of this cynical remarks.

Austin Stanley · 2004-12-02 05:21:07

Here's the facts that show that wind-power is not practicle on Mars. The http://www-k12.atmos.washington.edu/k12 … tml]Viking Weather Data pretty much tells the whole story. The atmospheric pressure is to low, and the wind speeds are to weak. Mars's atmosphere is 100 times less dense then ours but it's winds speeds are only marginaly greater. The wind is also fairly variable in it's output from one day to the next. All this makes windpower fairly impracticle.

But you still probably don't belive me, so here is some more data for you. Wind power (the amount of energy in the wind) can be calculated by the following equation:

w = 1/2dAV^3
w = wind power (in watts)
d = air density (about .015kg/m^3 for mars)
A = Rotar area (square meters)
V = Wind Velocity (meters per secound)

Now plugging in the best data from the chart (25m/s), we find that even on the windiest day on recoard, the martian wind could only produce about 130 watts per square meter of rotar area. This isn't that great. Terrestrial windmills do about 4 times this amount, and we were using the best data for a whole 2 year period!

You also have to take all alternatives in comparison. While you might be able to build some ultra-giantic/super low-weight windmill on mars and generate some electricity, you have to compare the effort necessary to acomplish that with what would be necessary to build an alternative system. It is not praticle when compared with the alternatives.

For my money the best bet for a home-grown non-nuclear power source on mars is either photo-voltaic or reflectors powering a turbine or stirling engine. Or geo-thermal but I bet finding a good source for it may be tricky.

Palomar · 2004-12-02 07:44:31

Here's the facts that show that wind-power is not practicle on Mars. The http://www-k12.atmos.washington.edu/k12 … tml]Viking Weather Data pretty much tells the whole story. The atmospheric pressure is to low, and the wind speeds are to weak. Mars's atmosphere is 100 times less dense then ours but it's winds speeds are only marginaly greater. The wind is also fairly variable in it's output from one day to the next. All this makes windpower fairly impracticle...
Now plugging in the best data from the chart (25m/s), we find that even on the windiest day on record, the martian wind could only produce about 130 watts per square meter of rotar area. This isn't that great. Terrestrial windmills do about 4 times this amount, and we were using the best data for a whole 2 year period!
You also have to take all alternatives in comparison. While you might be able to build some ultra-giantic/super low-weight windmill on mars and generate some electricity, you have to compare the effort necessary to acomplish that with what would be necessary to build an alternative system. It is not praticle when compared with the alternatives.

*Sorry to know this, although I'm not too surprised. The question of the efficacy of wind-generated power on Mars had come up in my mind again while discussing solar power farms here on Earth, in the Science & Technology folder a few weeks ago.

Was hoping for a bit of good speculation as to how very light-weight windmills might work on Mars. GCNRevenger points out the minimal solar power advantage on Mars, and presumably there are zero fossil fuel resources. A bit depressing overall.

--Cindy

John Creighton · 2004-12-02 08:55:29

I don’t know about a solar power chiminy but I like the idea of a really big power tower (A.K.A Concentrating light with mirrors) The greater the radius of mirrors extending from the tower the hotter the focus point. The higher the tower the greater the distance it is possible to extend the mirrors. The hotter the focus point the greater the efficiency.

GCNRevenger · 2004-12-02 09:21:41

Comstar, I don't think you understand your own business example. That is an absolutely rediculous sum of money to license anything, I think you have made another dumb interpretation to support your crackpot thesis. Your number is too absurd to be believeable. A third of a trillion dollars to license wireless technology? You'll have to do better then that.

"That is an issue also the gravity is less, than earth, yes the air is thinner but the force is still the same... If , you don't have evidence of tested experiments in Martian Wind Gerneration. Then, you don't want to even try a new thought / idea..."

If you are this obcessed with throwing away moutains of money trying to experiment with every idea BEFORE you address the physics of the idea, then you will be the laughing stock of whatever investors' negotiations you might enter into, and will be shooed out of the boardroom like a self-important seventh grader... in which they would be justified.

You must have a physical model without fundimental problem first before building an experiment to prove it. You must do the physics first and then use the experiment to confirm the physics. You don't build an experiment like this just to see what happens, you build it validate and prove that your idea works.

We know alot about the physics of windmills. We know that the air on Mars is much, much thinner then Earth's (over 100 times). If you would bother to consider the principles behind a windmill before trying to invest 7+ digit sums to build one, you would realize what a horrible idea this is. The physics clearly show that the lower the air pressure, the lower the amount of energy you can derive from a windmill. Since the pressure is so much lower on Mars, a windmill will not be efficent enough to be worthwhile as a staple power source.

John Creighton · 2004-12-02 09:37:16

We know alot about the physics of windmills. We know that the air on Mars is much, much thinner then Earth's (over 100 times). If you would bother to consider the principles behind a windmill before trying to invest 7+ digit sums to build one, you would realize what a horrible idea this is. The physics clearly show that the lower the air pressure, the lower the amount of energy you can derive from a windmill. Since the pressure is so much lower on Mars, a windmill will not be efficent enough to be worthwhile as a staple power source.

Well in the case for mars Zubrin said the lower gravity would allow you to build a much bigger windmill to compensate for the lower air pressure. Whether or not he worked out the details I don't know.

GCNRevenger · 2004-12-02 09:55:24

You can build a bigger windmill, but the size required to be worthwhile would be immense, so I don't think its practical for primary power.

As Austin estimates, a Martian windmill would have to be four times bigger then an Earthly one to make the same amount of power, and that is in a Martian "hurricane." Normal wind speeds would probobly require a windmill an order of magnetude bigger to produce comperable power.

comstar03 · 2004-12-02 21:45:21

Forum Administrator, GCNRevenger and other members

Because of your continuing personal insults regarding myself, I have decided to leave this forum. I was here to look over the possible inclusion of the mars society, members and forum participants into our overall strategy to bring like minded individuals into space with us.

I will inform my board that, we will not include any of the people associated with Mars Society and New Mars Forum. As Major Shareholder and CEO of this POCs I will explain my decision and make it know for my reasons within our alliance of POCs that we are creating.

I Hope the next time you consider that the person you insult, and continue to insult may turn out to be the person that could help you or block you. Today, you haven't made anyone that would help you, in your quest for space.

Have a great time being cynical, insulting and nasty to those who are working for the day humanity gets into space, and If my POCs alliance does it, look for another way into space because you won't be with us.

Bye !!!!

GCNRevenger · 2004-12-02 22:02:00

You know what? The more I think about it, the more I wonder if we've been talking to Rick/Eric/ISA... same MO and style, just now carefully avoiding the capslock?

Major Shareholder... I Hope... Martian Wind Gerneration... same big dreams with little explanations while trying to drum up support... supposed cabal/consortium of secret "POC" owners on his "board" that is public but private too... etc. Oh, and more exclamation marks.

GraemeSkinner · 2004-12-02 22:54:26

You can build a bigger windmill, but the size required to be worthwhile would be immense, so I don't think its practical for primary power.
As Austin estimates, a Martian windmill would have to be four times bigger then an Earthly one to make the same amount of power, and that is in a Martian "hurricane." Normal wind speeds would probobly require a windmill an order of magnetude bigger to produce comperable power.

I'm sure the physics of windmills can be plotted as to what effects changing various parameters would have on them. I'll have a look about and try and put something up (anyone who can write Java might prove useful in subjects such as this )

Graeme

Euler · 2004-12-02 23:24:58

Well in the case for mars Zubrin said the lower gravity would allow you to build a much bigger windmill to compensate for the lower air pressure. Whether or not he worked out the details I don't know.

I don't think that the lower gravity would affect the maximum size very much, since gravity is not the most important constraint on terrestrial windmills. The biggest limitation on the size of windmills usually comes from centrifugal effects.

I'm sure the physics of windmills can be plotted as to what effects changing various parameters would have on them. I'll have a look about and try and put something up (anyone who can write Java might prove useful in subjects such as this )

Well, the amount of power available in the wind is 1/2*(wind speed)^3*area swept out by rotor blades*air density. The maximum possible rotor efficiency is 59%, and I think that modern rotors come close to achieving this value.

Austin Stanley · 2004-12-02 23:28:22

Well you've got most of the math there for you. According to the data the Viking probe collected, a windmill would generate ~130W/M^2 of rotar area during the optimal conditions at that location. All you need to do is come up with a model for how much your windmill would mass and cost per unit of rotar area.

I'm not going to say that it would be impossible to build a windmill on Mars, just that other alternatives are more practicle.

GraemeSkinner · 2004-12-02 23:32:58

Well you've got most of the math there for you.

I may have the maths, but not the programming skill, I was thinking of a little Java applet that you could adjust say the blade size and angle and see what the effect would be on power output. As much as I can add java to websites I can't write it

Graeme

SpaceNut · 2004-12-03 10:32:21

Here is some more on what started this thread.

A kilometre-high solar tower, to be built in the Australian outback by EnviroMission Ltd, will become the world's tallest structure when completed in 2006. Designed by Jorg Schlaich of Schlaich Bergermann und Partner, the solar tower (or solar chimney) operates like a hydroelectric power plant, but uses hot air instead of water, and it could provide enough electricity for 200,000 homes. Time calls it one of the best inventions of 2002, and I think it's one of the most ingenious ideas I've ever heard. Another solar chimney project was planned in Rajasthan, India, but I haven't found any information on its current status.

Solar Chimney Power Station - The Future is Near

Palomar · 2004-12-03 11:06:39

the solar tower (or solar chimney) operates like a hydroelectric power plant, http://www.sbp.de/de/html/projects/sola … ex.htm]but uses hot air instead of water

*That's even better.

Interesting stuff. :up: Kilometer high -- wow.

--Cindy

RobS · 2004-12-03 11:43:43

You may want to start by doing some research about wind turbines on the web. The BWC XL-50 Wind Turbine, for example, has a rated power output 50 kw at 24.6 mph windspeed with 46 ft diameter blades. It costs about $90,000 including installation. On Mars it would make perhaps 1 or 2 kw. Presumably once one gets to the point where there is a base on Mars with limited manufacturing capacity, one would only need to import the fancy motor and a few related pieces of machinery; the blades and the tower could be made locally. But if it took half a man-year of Martian labor to produce 1 or 2 kilowatts of power--and not continuously--would it be worth it? Probably not.

There are much larger wind turbines listed on the web. At one point--I think on the General Electric website--I saw information on wind turbines that produced up to 3 or 4 megawatts. They'd produce maybe 50 kilowatts on Mars. If one took the power generator of the BWC XL-50 and mated it to the General Electric blades and towers, one might have a machine able to make 50 kw for a few man-years of work. There might be situations that would be worthwhile. For example, during dust storms wind speeds are up and insolation is down, so wind turbines complement photovoltaics to some extent (they won't when the winds have stopped and the dust hasn't settled out yet, which is a month or two). There might be special places where wind turbines produce more power; the edges of the escarpments of the Mariner Valleys, the edge of the polar caps, and the tops of crater rims.

-- RobS

dicktice · 2004-12-03 22:29:52

I'd like to keep my reply in the "brainstorm" mode, for now. The greater distance from the Sun may be compensated for by the great breadth and depth of the canyons within which the mile-high solar power towers would be erected. The lower gravity may allow light-weight structural design, framed in locally sourced strap-iron, for instance, inside an inflated cover of whatever webbing is in vogue for dome structures. The huge expanse of the high tentlike, open-walled "greenhouse" roofs surrounding the base of each tower, should enable a variety of different domes to inflated underneath--to live in and to grow things--with each pressurized with its own optimum atmospheric gas mixture. The canyon floor Martian air, heated by the wideband solar radiation and trapped as infrared, would warm the habitat domes as it flows past them, with increasing strength towards the circle of turbo-electric generators around the base of each tower. With enough of these in place, might not the vertical air circulation from these "solar convection inhancers" affect the microclimate of the entire system of canyons and ravines? I leave the problems resulting from melting subsurface water-ice beneath the so-called greenhouse roof, to my fellow brainstormers. . . .

MarsDog · 2004-12-03 23:03:05

The problems resulting from subsurface water-ice melting to become briney lakes, I leave to my fellow brainstormers.

Good way to make fresh water. Some of the water vapour could be condensed on the sides of the chimney, and you have a fresh water stream, (hydroelectric power), the start of the Martian Garden of Eden.

Incremental local http://www.sbp.de/de/html/projects/sola … rraforming, including a power plant.
Habitation modules could be conveniently located underneath.

If the colonizers inhabited a crater or valley, the chimney could be made of an inflatible and run up the side, reducing structural strength requirements.

Austin Stanley · 2004-12-04 00:41:03

Well according to the figues you list RobS, the BWC XL-50 is about 37% efficent (not bad). So for the optimal mars condition Viking 1 collected data for the unit would collect about 7kW during optimal conditions, a little better than your estimate, but those are during optimal conditions. Actualy come to think of it, those conditions (25m/s or about 55mi/hr) would probably be sub-optimal in practice. The windmill is not designed to deal with those kinds of windspeeds and so would probably produce alot less energy.

Which brings up my secound point. Windmills are designed to produce energy within an optimal set of wind conditions. Outside of those (either above or below) they lose efficency. Which creates problems when designing a windmill to capture windenergy during a dust-storm. It maybe able to generate alot of energy then, but it will generate little to none the rest of them time. The net effect would be alot less energy produced total. You can see the effect I'm talking about in the http://www.bergey.com/Products/XL.50.Sp … itterature for the unit you are talking about. Notice the curve in the power production graph, above a certian windspeed, power production drops off. This is due to a number of reasons, chief among them is the need to slow the mill to prevent it from damageing itself.

GraemeSkinner · 2004-12-04 02:55:38

Due to the size of windmill that would be required to produce any where near a useable amount of electricity would the size of the props not cause another problem. Say they have to be four times the size of the largest windturbines on Earth, would the thinner air be up to the job on Mars of even getting the turbines moving, or would we have to have a small motor to get them started?

above a certian windspeed, power production drops off.

I know the majority of the ones I've seen are designed to turn out of the wind above a certain windspeed to prevent damage, so in such instances they produce nothing at all.

Perhaps there's a windturbine design that is not suitable for Earth use that will be developed on Mars, once we are there. When you think about it everything we develop (such as windturbines) are designed with Earth in mind, we need to be in the mindset of being on Mars and develop things from scratch that use Mars' particular characteristics from the outset.

Graeme

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#1 2004-12-01 21:34:05

Re: solar power towers on mars - km-high vertical wind tunnel turbo-elec

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Re: solar power towers on mars - km-high vertical wind tunnel turbo-elec

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