Let the Sunshine In: A Solar Power Blog

January 11, 2010

Space Is the Place, Part I

In my youth, practically everything having to do with outer space conveyed a glamour that nothing else quite matched. Astronauts were to me near-mythic beings, more heroic than soldiers or cowboys. (John Wayne, after all, never had to cope with zero gravity.) Outer space was the place — more than any foreign country or remote area on earth — where nearly any possibility could be imagined. On TV and video, I devoured just about everything that had to do with space, from epic visions like 2001: A Space Odyssey to fables such as ET: The Extra-Terrestrial to the sleaziest sci-fi dreck… much as wholesome meals and sugary junk tasted much the same to my hungry and undiscriminating palate.

So there is a sense of satisfaction for me, after absorbing so much fantasy, in the idea that one of the greatest real-life wonders of space is its potential to help save humanity from our energy emergency through space-based solar power (SBSP). Something like the concept of SBSP has existed, at least in fiction, since 1941, when Isaac Asimov published the short story Reason, which is set on a spaceship from which energy is beamed by sentient (and highly temperamental) robots to distant planets. In 1968, the notion was promoted from science fiction speculation to science theory by Peter Glaser. Many people, including the Department of Defense, have recently been taking SBSP very seriously indeed. Everybody’s talking solar… but why is it so important?

SBSP, if and when it is successfully implemented, might well solve many of humanity’s energy problems. The sun is the most constant and dependable source of energy on earth. In what appears to be the “darkness” of space, there is, in fact, no night: solar panels could receive sunlight 24 hours a day, with no interference from the atmosphere nor any obstruction through bad weather. All this, of course, does not mean that space solar power will or should replace terrestrial solar power. But if and when it becomes viable, it might well become the main energy source for many on this planet.

Three basic elements are necessary for a viable SBSP system:

1. a way to transform, in space, the energy from the sun into electrical energy and collect that energy;

2. a way to transmit this collected energy from space to earth;

3. a way to receive on the earth’s surface the energy from space and distribute it to users.

The good news is that much of the technology necessary for making SBSP a reality not only exists, but is actually quite commonplace. Commercial space satellites — the machines necessary to carry out the first element above — have been in existence since Telstar, launched way back in 1962. Photovoltaic (PV) cells for harnessing solar energy are of course in increasingly common use. (Even the International Space Station employs solar arrays, though strictly for its own use.) As for the second element, both microwaves and lasers have been proposed as the means to convey solar energy from space to earth; both these technologies are well advanced. For the third element above, rectangular antennas (called “rectennas“) are the most commonly proposed method of catching the energy from space on earth.

So what’s holding us back?

The most significant problem seems to be one of scale… and here is revealed the “profitability paradox” at the heart of the SBSP project. Simply put, to produce the sheer quantity of electrical power necessary to make the program affordable would seem to require devices of colossal size and complexity, both in space and on the ground. But the fact that the devices need to be so large and complex makes creating and assembling them deeply problematical… and potentially unprofitable.

It has been estimated that an adequate receiving antenna in space (which would, of course, be only one part of the entire satellite) would need to be a kilometer (over six-tenths of a mile, or about 11 football fields long) in diameter — which is almost two miles in circumference and over three-tenths of a square mile in area. How to get such a Godzilla of a device into orbit — and keep it functioning once it’s there — may be the biggest single challenge of SBSP technology. And then there’s the rectenna, an enormous structure in its own right, estimated at perhaps 10 kilometers (6.2 miles) wide and 14 kilometers (8.7 miles) long… though at least no one has to lug the damn thing into space. (Note: the dimensions above represent one theoretical estimate; Solaren, the California-based corporation, envisions a satellite array several miles across, while the Japanese space agency, JAXA, proposes a receiving station on earth that would “only” be 1.8 miles wide.)

[Continued in Part II]

2 Comments »

  1. When I was young I also dreamt about space. What do you think about plasma energy which a Russian scientist discovered not so long ago? He wants to use it in rocket engines.

    Comment by James — February 2, 2010 @ 9:35 am | Reply

  2. […] for this campaign, including perhaps in an area (which I have previously discussed in an early post in this very blog) whose ultimate possibilities are as yet unknown: space-based solar […]

    Pingback by The Case for a Solar Race | Let the Sunshine In: A Solar Power Blog — September 13, 2013 @ 8:09 am | Reply


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