Thursday, 25 February 2010

Solar power and space elevators

A space elevator is basically a satellite with a string attaching it to the Earth. Centrifugal force from the Earth's rotation makes what ever is on the end of the string want to move away from the Earth, but the line tethers it. You can then attach a climbing machine to the line and have it go up and down to the satellite. It's a well established idea in theory, but we're waiting for materials technology to provide something that is both strong enough and light enough to serve as a line.

But such a line need not only be a rope. It could also be a power cable. I reckon we could put some great big solar panels up in orbit, and send the power down the line. Put it far enough away from the planet, and the amount of sunlight reaching the surface of the world would not really be affected.

Just a thought. I doubt if I'm the only one to have thought it.


Jim Bliss said...

You're certainly not the only one to have thought of that idea. Though engineers would point out that a far more practical way of doing it would be to beam the captured solar energy down to a receiving station as microwave radiation. This would overcome several problems with your scheme... firstly, the inconvenient problem of inventing a conductive material strong and light enough to carry the power (most research into the area of superstrong and light materials is focussing on carbon fibres which aren't great conductors). Secondly the problem of electrical resistance would mean that you'd lose a vast amount of the energy captured as it came down the cable. You'd basically need a superstrong, superlight and superconducting cable. Not saying such a thing is theoretically impossible, but it's unlikely to show up in our lifetimes and certainly not in time to affect our immediate energy crisis.

However, while the "energy beam" solution is more practical, it's far from being practical. Certainly it doesn't require any new technology, and could be done right now if it were a good idea.

But it's not, I'm afraid.

I recommend Robert Zubrin's wonderful book, "Entering Space: Creating a Spacefaring Civilization" for information on why it's not. Zubrin's book is wonderfully accessible considering it's written by one of the most brilliant aerospace engineers on the planet (ex-Chief Engineer at Lockheed Martin, he now runs Pioneer Astronautics and NASA tend to consult him whenever they discuss the idea of sending humans beyond orbit).

In Chapter 4 of the book (Doing Business in Orbit) he pretty much destroys the idea of orbital power collection by pointing out that the cost of lifting the required material into orbit, as well as maintaining and servicing the panels, would run to about $1 trillion per year to power a city the size of Denver, Colorado (he calculates $3.3 trillion for launch costs alone).

Put that in perspective... if the USA were to spend $3.3 trillion on ground-based windfarms and solar panels they'd probably make a significant dent in their entire national energy needs, rather than just that of one mid-sized city.

See, the point is that we currently have all the technology we need to power our society; we just don't have the political will to divert so much resources into sustainability.

As someone who was raised on science fiction, I'm sorry to say that massively expensive orbital solar collectors are a red-herring.

Paul said...

The energy beam idea has been around for a while too. Isaac Azimov put his positronic robots on board a space station that was beaming energy down to Earth back in the 1950's. Since the robots in question had religious mania, their human handlers were convinced the beam would go out of focus and turn thousands of square miles of land into incandescent slag.

There are other advantages of course, to a way of climbing thousands of miles without having to use thousands of gallons of liquefied hydrogen peroxide. I just ordered the Zubrin book from Amazon. I look forward to reading it :)

I first heard of Space Elevators through Iain M Banks' book, Feersum endjinn. It's a concept that interests me hugely, although you wouldn't catch me going up in one of those things. The more firma, the less terra, and all that.

Banks points out that space is where the energy is. Solar at least is sustainable, even if putting the systems in place to harness is anything but easy.

I've heard people seriously suggesting that we mine other bodies for hydrocarbons. If digging millions of tons of oil and coal from our own planet's crust is buggering things up, importing the things from the moons of Jupiter could only make things far worse I reckon.

Jim Bliss said...

In "Entering Space" Zubrin paints a pretty optimistic picture of humanity's future in the solar system and beyond. However (and it's a pretty damn big "however") his entire thesis is predicated upon the development of a new energy source.

He seems to put a lot of faith in a breakthrough in fusion research. It's definitely an area we should be putting more resources into (along with every other clean, renewable energy solution), but I'm sadly not as hopeful as Zubrin.

All the same, once that "minor" detail is dealt with, the book is a fascinating examination of what is possible from the point of view of a serious scientist and engineer rather than a science-fiction writer.

I suspect you'll enjoy it.