# Harvesting the sun's energy

1. Dec 24, 2013

### jaydnul

So I was thinking about something today. Tell me if it's possible. I don't care if its plausible, just physically possible.

Somehow, we design a huge solar panel that is extremely resistant to heat. We send it out on a trajectory towards the sun, coming very close before being pulled into an orbit around it. Now its orbit would be perpendicular to the plane of earth's orbit. In order for there to be a continuous line of site between this solar panel and the earth, we would have the solar panel's orbit precess in exactly the right amount to compliment earth's orbital speed, therefore maintaining consistent line of sight. Is that at all possible or am I just spouting nonsense?

Now how would we transmit the power to earth? I was wondering if there was such a thing as power transmission by laser. A continuous, and very energetic laser beam would be directed towards some sort of receptors at earth. That would be more ideal than a wire, because you can't really damage a laser beam with flying space debris. Is this possible? I mean the laser wouldn't lose any energy, right? It would just take about 15 minutes to initially arrive at earth.

2. Dec 24, 2013

### SteamKing

Staff Emeritus
What's the purpose of sending this solar panel into a funky orbit about the sun? The sun's rays already can reach the earth without bouncing off anything, in orbit or otherwise.

3. Dec 24, 2013

### davenn

there's no need to put it anywhere other than in earth orbit, its still going to gather the same amount of light from the sun

Dave

4. Dec 24, 2013

### Staff: Mentor

The OP is right that if located closer to the sun it will gather more light.

The downsides? Cost. Cost. Cost. And how to beam the energy back.

5. Dec 24, 2013

### Bandersnatch

Wouldn't this require application of thrust in the orbit-normal/antinormal direction every time the panel passes the polar regions of the Sun?

6. Dec 24, 2013

### sophiecentaur

But there really is no shortage of that right down on the Earth's surface. As they say - cut to the middleman.

7. Dec 24, 2013

What is important here is how to transmit the energy to Earth.

8. Dec 24, 2013

### tfr000

The major problem with beaming any significant power from somewhere out in space to Earth's surface is that if, for any reason, you miss the receiver you are now vaporizing targets with your beam weapon.

9. Dec 24, 2013

Staff Emeritus
That's just silly. If all you care about is "possible" and not "plausible", why stop at the sun? Why not Rigel? Much more energy there.

10. Dec 24, 2013

### phinds

Actually, what they say is "cut OUT the middleman"

11. Dec 24, 2013

### sophiecentaur

Danged predictive text / auto spell check. I usually read first what I post.

12. Dec 24, 2013

Make the laser computerized VERY precisely,taking in account of orbit,speed,gravity,Whatever.Then you won't miss it.
The problem is actually it is very expensive to do this.(Or is it possible at all?)

13. Dec 24, 2013

### jaydnul

Ya i agree. I should have said plausible in the future (near future?).

Sounds like this will be way too expensive. I am curious however, is there an application of the power transmitted by laser being used today? Google was very informative. The further away, the harder it would be to transmit accurately, but I mean the Hubble can already do this. Can't it focus on a point something like no larger than a grain of sand held out at arms length?

14. Dec 24, 2013

### Staff: Mentor

Yes, but the focal length of the HST is only a couple of meters. Double the focal length and the spot is twice the size it was. So increasing the focal length to hundreds of kilometers or more results in a vastly increased spot size.

15. Dec 24, 2013

### andrewbbrown

What about a giant magnifying glass 1000 feet in the air?

16. Dec 24, 2013

### Staff: Mentor

I don't quite see how this relates to the thread topic.

17. Dec 25, 2013

### phinds

I've always said you have no sense of humor

18. Dec 25, 2013

### sophiecentaur

Is there Any shortage of energy arriving at the surface to the Earth?

19. Dec 25, 2013

### OmCheeto

Yes. We might wipe out Disneyworld.

hmmm....

143,000,000,000,000,000 watt hours annually consumed by our planet
24 hours per day
365.2422 days per year
16,313,375,982,658 watts continuous
16 blocks per mile (that's how big they are in my neighborhood)
1.6 km / mile
0.1 km diameter
1000 m/km
100 meters apparent diameter of the Xindi beam
3.1416 pi
7854 m2 area
2,077,078,684 watts/m2

Does anyone know of a material which could harness 2 billion watts of power per square meter without vaporizing?

I do believe that this method of power generation is going to take some serious engineering skills.

I think I'll stick with conventional solar panels, as I'm not that bright. Actually, I could probably figure it out, but it's Christmas day, and I've been invited to a cruise on the river, so I don't have time today.

Wait! I just found out that the biggest nuke plants generate a bit more than a billion watts, and cost about 14 billion dollars each.

1,358,000,000 watts from a big nuke plant
14,000,000,000 $cost each 12,013 equivalent plants$168,179,133,841,840 $total cost There you go: 168 trillion dollars. Ballpark of course. And that's just for the Earth base collector. And imagine the power lines required to transmit that energy all over the world. Pfft! We can't even fund the infrastructure to keep wind farms from dumping excess energy. ref 98,000 mWh = 98,000,000 kWh 98,000,000 kWh *$0.10/kwh ≈ \$10,000,000

hmmm....

I'd say that if we, as a species, are willing to throw away perfectly good energy/money like that, then we're not ready to build a Xindi type solar collector system.

20. Dec 25, 2013

### Staff: Mentor

I find a great many things quite humorous. Such as Om's post above.

21. Dec 25, 2013

### OmCheeto

I love you Drak......

----------------------------
Yes, I'm drunk. And I'm sure it's 4am somewhere.
ps. My friends have summoned me to the river. Ciao, and then Chow, for now, and then.
Stay safe and warm everyone. BBABLTATISSFP.

22. Dec 26, 2013

### Malverin

There are some similar thoughts

http://en.wikipedia.org/wiki/Dyson_sphere

23. Dec 26, 2013

### Crazymechanic

the idea itself may be good , yet I doubt we will ever have a physical material capable of being so large , hold it's own weight etc.
Honestly a net power producing fusion reactor or a flying saucer is as easy as ABC compared to these ideas.

24. Dec 26, 2013

### sophiecentaur

But what is the point of collecting energy in such an inconvenient place as out there in space? Is there any shortage of solar energy reaching Earth? Every square metre receives up to 1kW in direct sunlight. A square metre of receiver out there, at a similar solar distance, will receive much the same (a bit more, in fact). a space born system would cost many times as much as an Earth sited system and the overall efficiency of getting this energy down to Earth could not be high. Furthermore, you would still need a massive, expensive, receiving site for this energy. So why bother? Just because it 'could' be done? It sounds to me like a total waste of time and a very bad engineering proposition (shocking value for the money).

25. Dec 28, 2013

### klimatos

Not really. An average of some 1,366 joules per square meter per second arrive at the outside of the Earth's atmosphere (the Solar Constant). The atmosphere scatters 23% of this energy back into space and the surface reflects another 9%. The rest supports us and all other life on Earth.

As to the OP query, I seem to recall all of mankind's energy production is equivalent to ten minutes of sunshine. Why bother with expensive and laborious transmission devices when we get more than we can use for free?

Kiehl, J. T. and Trenberth, K. E., 1997: “Earth’s Annual Global Mean Energy Budget”, Bulletin of the American Meteorology Society, Vol. 78, No. 2, February 1997.