June 05, 2004

Energy Scaling: Separating Wheat from Chaff

Poor SDB. Apparently every time the USS Clueless enters the wild and wooly waters of alternative energy, he gets inundated with ideas that simply won't scale and won't work. For the most part, he's holding up admirably well but I have my usual nits to pick.

One of the biggest is that just because there are people who provide ideas that simply do not fly, it does not follow that there aren't serious, reasonable methods of going forward with a solution. Mea culpa, I googled up a link that solved the problem of high efficiency electricity to microwave conversion and missed that this particular approach was unlikely to scale (at least according to Steven Den Beste's dismissal). Upon further research, the papers at JUSPS provides several papers examining the specific problem of space to earth power transmission and seems to be an awful lot more optimistic even though they're also realistic enough to know that this is not going to happen tomorrow.

One paper I found particularly interesting was this one from the University of Michigan (PDF) which contrasted the vacuum tube approach that SDB characterized this way:

This is one of the few remaining applications where semiconductors have not yet displaced vacuum tubes. In a modern TV transmitter rated for 500 KW or 1 MW, everything is transistorized right up to the very last amplification stage, which uses vacuum tubes the size of garbage cans.

The satellite downlink will have to generate and transmit as much RF as a thousand such TV stations. Doing that is difficult. Doing that with 90% efficiency is "nontrivial".

The recommendation of the paper is to use semiconductor components in a decentralized fashion. Apparently the current state of the art for doing the space power to ground is currently 60% efficiency. Losing 40% of your power getting it to ground is no walk in the park but considering that you're gaining over 5x the energy by going above the atmosphere, this is an acceptable loss since your net gain is thus a bit over 3x terrestrial solar energy potential. Distributed conversion also creates larger surface areas for heat dissipation, a real problem for space applications.

Whether the original link that provides a 90% solution can be combined with the decentralized, distributed approach currently rated at 60% is not something that I'm really qualified to judge. I do suspect that the answer to such challenges is much more likely to be in the engineering realm of "tough and challenging" rather than "nontrivial". With cheap enough lift costs 60% efficiency might be feasible today. We don't have enough numbers in our debate to be sure yet where the tipover points are.

I've gotten burned myself on things I thought would "never" happen, or not in my lifetime. In 1978, environmental airheads were touting synfuels as a panacea and I, in my youth, sneered at the idea that I'd ever see anything practical come out of such pie in the sky research. They were extracting tar sand oil for about $40/barrel in 1979. In today's money (2003) that's somewhat north of $101 a barrel. The current extraction cost is $12 a barrel which puts Canada's Albertan oil sands right around Russia's Siberian extraction costs.

The skeptics were right that it was far too little and too late to fix an oil shock that died away in the next few years but the optimists were right to pursue the technology. A few hundred thousand barrels out of Canada (limited only by water availability), and who knows how many other hundreds of thousands of barrels available in nontraditional oil areas (Brazil for example) and you have a significant addition to world supply that isn't going to run out anytime soon.

So one problem is not one of technological difficulty but of time. I think that it will take decades, not centuries to solve the problems because serious scientists are putting out papers showing progress that's going along at a fair clip and they seem to have at least conceptually solved an awful lot of the problems already.

Another time component is that we're talking about a crisis that isn't going to go away after a few years like the 1979 oil shock did. We're talking about a multi-decade effort that is going to roll up the Gap and pull the third world into intimate contact with the first, creating a place where everybody has a stake in the system and there is no place where you can go off and plot for many years to create WMD in some sort of safe haven where the locals are with you.

So if you combine the shortening of time from thousands of years to tens of years on the solution side and the lengthening of the crisis time from the few years that some people (not necessarily SDB) think that this GWOT is going to last to the decades I believe will be the minimum time it's going to take to really solve the problem and you have an inescapable conclusion. Hunting after new energy sources including unconventional sources is an important component to winning the war.

Posted by TMLutas at June 5, 2004 12:58 PM