Okay, here is a werid question...

[Javaman]

suppose you had a giant windmill and mounted solar panels to the blades.

Could it be possible to draw power from both sources?

[BoneDaddy]

1. interesting question

I guess ya could.

[Canuckistanian]

2. Why not?

The only problem would be if the wind were NOT coming from the direction the sun is shining.

Which would probably be most of the time.

And besides, the added weight would make the turbine blades harder to start in mild winds.

[Javaman]

11. I thought about the weight, but why not make it part of the design?

rather than adding them to the blades, make them the blades.

[MindPilot]

14. I think you'd run into some structural problems

The material that makes the best solar collectors is simply not strong enough to be a turbine blade, and then the shape that would maximize the blade's aerodynamic efficiency is in all probability not the same shape to maximize solar collection efficiency.

Plus there would be significant electrical losses conducting the power from the solar panels through the rotating hub of the turbine. The friction of that conducting mechanism (probably a slip ring design) would also reduce the efficiency of the turbine.

[izzie]

3. Why not? But sound like a harder job for both to do what is needed.

Now I must tell you I hated science as a subject.

[Drifter]

4. No ...

Simply because the wind would have to be blowing the same (or different) direction as the sun is shining.

Typically a windmill is designed to swivel such that the wind has the greatest impact on the blades. The same is true of solar panels. They would be designed to move with the sun to maximize sun exposure.

I also suspect that moving the solar panels like a blade would create a whole new set of problems.

Seems like a good idea, but it is in no way practical.

Cheers
Drifter

[Javaman]

10. Well, since windmills pivot to get the most out of the wind, why

don't they just pivot them on none windy days to get the most out of the sun?

[Drifter]

16. Because ....

Most of the time you would not be getting the maximum potential from at least one part of the system. You are talking about building something that is twice as complex, and will most likely be half as efficient.

Building separate dedicated systems will be far less expensive, and far more efficient.

This is kind of like the Car/Boat hybrid car. While it seems like a good idea, what was created was a vehicle that could act as both a car and a boat, and it sucked at both of them.

Cheers
Drifter

[Whoa_Nelly]

5. Would think that only when the blades were stationary

would the solar panels be able to absorb the rays...

However, there are windmills that have solar generators.
This one is just a toy:
http://store.sundancesolar.com/solpowexwin.html

[MindPilot]

8. you'd have to have turbines so efficient that they could spin at

close to the speed of light for that to be a problem. Assuming of course that the wind and sun are always coming from the same direction.

[MindPilot]

6. I suppose it would be possible, but...

I'm going to guess that the engineering requirement to make them work together, aerodynamic efficiency, weight, conducting the power through the rotating hub, etc, would result in a net reduction of efficiency.

[not_a_robot]

7. The answer is yes.

with a windmill the blades would require flexible panels and the windmill would have to be a fairly unique situation of facing the sun at all times. The alternative being a vertical axis wind turbine designed with large blade surfaces and a well designed backdraw circut for the panels as they will alternate between sun exposure and shade.

[Dead_Parrot]

9. I don't see why not...

although as Drifter points out, they wouldn't be pointed in the optimal direction. You'd get something, though. If you could attach them to the horizontal arm of a vertical axis turbine you might do a bit better.

Next question - why would you want to? :D It's not a lot of area for the effort involved. Stick 'em next to it...

[Javaman]

12. Just an idea. I'm thinking that in a future were we need to optimize

all power sources, it would be an idea to have something like this do double duty.

Figuring, that most windmills are located in large open areas, it would also be ideal for solar.

I also thought about having a duel wind solar farm. With the solar panels located between the rows of windmills.

[Dead_Parrot]

13. Using the same land for both seems sane...

But I would be surprised if we got so short of space we had to use the blades...

Putting solar on the ground would also allow you to use solar thermal / conc. PV, which would be more effective anyway...

Nice bit of thinking, though. :D

[not_a_robot]

15. In most states

windmills require clearance, sometimes up to 150 feet from other structures (including antanae, solar panels, well heads, greenhouse, etc.) So putting panels next to the windmill is often not an option. Current panels are 11-14% efficient, so a 12 foot tall vertical axis turbine using large blades could do nearly 1kw, enough power to run a very efficient home (an average consumerism obsessed home is 3-5kw depending on the occupants). I failed to mention in my other post too, in some areas stalling is a common occurance, so there needs to be a motorized system for positioning the blades in such a situation.

[NNadir]

17. It depends on the bandwidth of your solar cells.

There is a doppler shift of about 1.6 parts per 100,000 if your tip blades are moving with respect to the light source are moving at 50 m/s.

OK, that's a joke and not a very good one.

Two practical problems I see is that ultimately the solar cells would be scratched by small particles moving in the wind, reducing the efficiency with which the light is transmitted. One might also have to worry about the mass of the cell flowing under the forces involved in windmills with very large vanes. I don't know all that much about the technical details of solar cells, but it would seem that thickness of materials is a factor in their performance. Soft metals and glasses would tend to flow over time when subjected to the forces involved in very large vanes moving at a fair angular clip. In addition, one would have brushes or other transmission devices that would suffer wear in transmitting the current from the moving blade. The blades have a relatively small surface area, and depending on the angle of the sun, the upper part of the blade would shade the lower part of the blade.

It would seem to me, given that the world production capacity of solar cells is far smaller by vast order of magnitudes relative to the amount of attention paid to to the subject of solar energy by the general public. Once all of the world's roofs have been filled with solar cells - as will surely happen in California in the next few weeks now that Governor Hydrogen Hummer has been returned to office - we can start worrying about where else to put them. In fact though, the world's production capacity is insufficient to fill even a tiny fraction of the world's energy demand, and thus a tiny fraction of the world's roofs. In fact the solar industry is not likely to be challenged by running out of space. It cannot fill the space already available to it. Typically the solar cell manufacturing industry can produce, in a given year, a few thousand megawatts of "peak" power on the entire planet. It will be a long time therefore before we have to start worrying about the space in which to put these cells.

Let us assume that the world's solar power production is 10,000 MWe (peak) per year. It isn't, but let's pretend it is. If we say that the world's PV cells have 30% efficiency overall and that the solar flux is 1300 MW/m² we see that the total area that could be covered in a single year is a square about 5 km on a side each year. We still have plenty of room to fill before we need the space on the blades of windmills.

[Nihil]

18. A much better investment (of time & money) would be ...

... to use solar cells to clad the structure of the windmill tower.

That way, you would get the benefit of solar power when (as usual) it is on
the opposite side to the driving wind.

On the occasions where the wind is coincidental, the windward side cells
would assist the wind generation whilst, for the rest of the time, the
leeward cells would provide the boost.

This keeps the two options sufficiently separate as to not complicate the
generation mechanism (i.e., no complex commutator mechanisms but simply
sum as for any two power sources).

[XemaSab]

19. I'd worry that they'd blow off in high winds

It seems a lot easier to just incorporate rooftop PV and solar thermal plants. :shrug: