# Solar Windmill

## Main Question or Discussion Point

How fast could a space based windmill turn when driven by the solar wind?

Would such a device produce more or less energy than a solar panel of the same cost?

## Answers and Replies

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enigma
Staff Emeritus
Gold Member
Less. You'd need to use fuel to keep it stationary.

turin
Homework Helper
Originally posted by enigma
You'd need to use fuel to keep it stationary.
Why would you need to keep it stationary?

drag
Greetings !
Originally posted by turin
Why would you need to keep it stationary?
A normal windmill is turned by an air stream but it
is also pushed by the airstream. If you want to do the
same in space (very ineffective in most cases, btw)
then there'll be nothing to keep this "sunmill" in place.

Live long and prosper.

turin
Homework Helper
Originally posted by drag
Greetings !

A normal windmill is turned by an air stream but it
is also pushed by the airstream. If you want to do the
same in space (very ineffective in most cases, btw)
then there'll be nothing to keep this "sunmill" in place.
That still doesn't answer my question.

enigma
Staff Emeritus
Gold Member
If you don't keep it at a stationary distance from the sun (sorry... probably should have quantified that), it will just soar out of the solar system and you will need to build another one.

turin
Homework Helper
Couldn't you just put it in orbit and let gravity take care of that little problem?

enigma
Staff Emeritus
Gold Member
Not if the sun is pushing it away.

Gravity will keep an object in a set orbit. If you could possibly gather enough energy from the solar wind to be competitive with photoarrays, the wind would be providing a very large force pushing the "windmill" away. Gravity gets weaker the further out you go, so unless you actively push yourself back, you'll get pushed all the way out after a while.

turin
Homework Helper
Originally posted by enigma
... to be competitive with photoarrays, ...
Good point; I lost track of the original question.

Originally posted by enigma
Less. You'd need to use fuel to keep it stationary.
Lets nail it to the moon.

drag
Greetings !
Originally posted by turin
Couldn't you just put it in orbit and let gravity take care of that little problem?
Actually that would work. If you put it in an
orbit with a slower than required orbital velocity,
around the sun, then the force acting to push
it away will be balanced by gravity. Of course,
you'll either have to put it very close to the
sun or have a poor power generation capability
(which is probably gon'na be the case anyway).

It could, perhaps, be possible to build some kind
of a solar-wind-mill using magneticly trapped huge
clouds of gas which will capture solar-wing particles
(like the M2P2 propulsion technology principle).
But then, containing the gas may be a problem,
yet it should still be more efficient than just
a normal sunlight-mill.

Live long and prosper.