Solar wind electricity generation

[tathagata]

hi friends,
i came across this piece of news...

"Until 2010, no solar sails had been successfully used in space as primary propulsion systems. On 21 May 2010, the Japan Aerospace Exploration Agency (JAXA) launched the “IKAROS” (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) spacecraft deployed the sail.
"
they were using solar sails!
tapping solar wind energy for acceleration..
so

for the past 2 months i am wondering if we can tap energy from solar wind.i thought high velocity charged particles zooming around the Earth can be made to run turbines..but the impulse was too low to run a turbine...for the turbine to rotate heavier particles were required...then i thought about thermocouples. the solar particles have high energy, may be thermocouple's connected together in series can generate enough voltage and supplement the traditional solar energy. but the problem is how to get it to the earth?
can anybody suggest more ideas ?
or is it a waste of time??

 

[zhermes]

IKAROS is a pretty exciting accomplishment!

I really like your thinking, but it is definitely a 'waste of time,' in that it won't be a good way to get power; its definitely not a waste of time (no matter what people with thousands of posts on physicsforums might tell you) in that its still an interesting and cool idea.

You could radiate the power collected back to Earth with microwaves or something; I think the big issue is harvesting energy effectively.
Whenever thinking about a big issue like this, consider the large-scale (order of magnitude) simple ideas first. How much energy in solar-wind passes across an area the size of the earth, at a distance of about an AU per day, or per year? How does that compare to the light?

 

[tathagata]

thank you for your reply..
considering your view..
i came up with this..
The density of the solar wind is 10 protons/cc on average, and the average solar wind speed is 425 km/s. The mass of the Earth is 5.98 x 10²⁴*kg, and its radius is 6.37 x 10⁶*meters.
So, the cross-section of the Earth is pi * R²*= 1.27 x 10¹⁴*m².
The number of solar wind protons that hit this cross-section in 1 second is the number of density times the length of the column of particles that cross the surface in 1 second. Converting the number density to p/meters-3*gives 10 * 10^6** 4.5 x 10⁵= 4.5 x 10¹²*protons/sec. Their individual mass is 1.67 x 10^-27*kg, and their speed is 4.5 x 10⁵*m/s, so the momentum of this many particles is 3.4 x 10^-9*kg-m/s.
that means around 65 joules of energy per day..
A much better alternative is provided by the Sun's light, which delivers about 1400 W/m2, i.e. a 4,000,000 times higher power density. The total solar power intercepted by the Earth is more than 10,000 times as much as we currently consume. With solar cells that have an efficiency of 10%, just covering less than 1% of the Earth's surface with solar cells would be sufficient to produce the power needed, even considering day and night and occasional cloud cover. ...
however we could still consider setting up this solar wind harnessing setup nearer to the sun.. this would increase the density and as you suggested we could bring energy back to the Earth by using microwaves...

 

[zhermes]

Awesome analysis, I'm surprised the wind energy is that small!

 

[sophiecentaur]

however we could still consider setting up this solar wind harnessing setup nearer to the sun.. this would increase the density and as you suggested we could bring energy back to the Earth by using microwaves...

But we get 1kW /square metre of solar radiation right here. Isn't that enough, when integrated over a few thousand hectares (or as many as you like) of collectors on the Earth's surface? And it would already be down here for us to use. No microwave links with associated conversion efficiency, pointing and beam spreading errors etc. etc.