20 January 2011

Rant no. 2 of 3: the Challenge Answer

From my long rant in three parts a few weeks ago, which were some of my most productive and creative several days ever by the way, part 2 issued a challenge based on a science- and president-bashing Slate journalist's apparent misinterpretation of President Obama's recent appearance on the Discovery Channel series MythBusters:
"Obama tasks the Mythbusters to take a stab, their second, at reconstructing Archimedes' heat ray, supposedly an array of bronze shields or perhaps mirrors that, reflecting and concentrating sunlight, incinerated approaching ships during the Siege of Syracuse.  Why did the White House and Discovery pick this myth to re-bust?  Is there a metaphor about national security in there?  A parable of collectivism?  Is this the light of the unum out of the pluribus?  Does the Pentagon think this technology might have practical applications?  Such questions do not trouble the lively minds of our likable hosts..."
Conceptual diagram of
Archimedes' Heat Ray configuration,
from Wikimedia Commons.
I issued a challenge to the journalist, as well as my readers, to identify the practical significance of such a technology as Archimedes' Heat Ray, something big enough for the President to ask to see it again.  I gave three clues, for good measure:
  1. It's not a parable, or the one that arises from our many, or any other sort of metaphor;
  2. It does have national security implications, if only by collective association with other such technologies;
  3. It does have practical applications--the technology is, in fact, already in use--but not yet (overtly) for the Department of Defense
I even offered a prize for the first correct answer, from anyone who chose to write in a comment on this blog post.  Alas, no comments or answers from readers, so the prize will wait.  Just so that you know, there is a prize...appropriately enough, it's water.  Bottled water, from Mexico.  It just struck me as very curious and ironic when it was given to me at a meeting, my first visit south of the border in Nogales while I was working at the University of Arizona.  I guess you could say it has its own little story, and so it's something I've kept around, but that story is for a time when I pass it on to someone else.  It just struck me as odd that Mexico gets beat on so mercilessly for the quality of its drinking water, and here they have bottled it for consumption at a time when studies in the U.S. have shown that bottled water is little different in quality from tap water, in fact is tap water in some cases...

So, I say that the Slate story was an "apparent" misinterpretation because the story of President Obama's planned appearance on the show was also picked up by the New York Times, albeit in their "Caucus" blog on politics and government, where it was not necessarily dismissed so impetuously except by nearly 30 commenters on that story, none of whom took the opportunity to ask or answer "Why?"  When a story in a political blog from one of the most well-read news outlets in the world gets so (relatively) little response to something so potentially meaningful, I'm not surprised my challenge here went unanswered.  I would be surprised if the White House, the President's Science Adviser, and the President's Office of Science Technology Policy (OSTP) all did not know how useful this suggestion for MythBusters really was, so the question then comes to "Who suggested this to the President, and why?"  Actually, I wrote to the OSTP to ask that very question right after I posted my rant, but have not received any response.  It's too bad, because all I wanted to do was confirm that someone in that office had the same reason for the demonstration that I present here...

Journalists and commenters have also brought up that Mythbusters declared the "myth" of Archimedes heat ray "busted" in 2006 because it took simply too long for the concentrated sunlight to set a wooden target afire; if it doesn't work very quickly today, with our modern know-how, how could it possibly have worked more than 2300 years ago to save Syracuse from a naval siege?  The thing is, though the actual use of the method by Archimedes in Syracuse may remain in some doubt for lack of surviving historical accounts, the efficacy of the method has been proven more than once and in most cases long before the MythBusters ever heard of it.

So, in context, there were even more clues than the three that I provided explicitly.  From my own story, first, I write a water-oriented blog, so the solution must have something to do with that.  Second, I explicitly mentioned in the third clue that the technology was not necessarily of use to the Department of Defense, as suggested by the journalist, but that it was indeed already in use elsewhere.  Perhaps there is another U.S. cabinet-level Department of Something that recognizes the utility of this technology?  Archimedes' Heat Ray was an energy-based technology, albeit with a distinctly military application at the time.  Perhaps the Department of Energy thinks some combination of the persistent supply of solar energy striking the Earth, along with the water and other elements we have lying around here on Earth, could result in something useful...

Solar power is mostly clean, mostly renewable, and comes in a couple of flavors.  Photovoltaic (PV) cells convert solar energy to electricity through the photovoltaic effect on specially-designed electronic chips exposed to sunlight.  It takes quite a bit of water to make those chips, sure, but the installed solar panels require no more water than in the cleaning solution that is used to wash the protective windows covering the chips.  PV is a pure solar-electric power source.

The Planta Solar 10 power plant in Spain, from Wikimedia
Commons.  Light rays converging on the tower are visible
because of atmospheric dust; the obscured side of the
tower receives the brightness of hundreds of Suns.
Concentrated solar power (CSP) is, instead, a solar-thermal power source and has several forms, but the structural configuration is based on the same principle of Archimedes' "heat ray."  In fact, the Wikipedia entry on CSP calls out this connection explicitly:
"A legend has it that Archimedes used a 'burning glass' to concentrate sunlight on the invading Roman fleet and repel them from Syracuse. In 1973 a Greek scientist, Dr. Ioannis Sakkas, curious about whether Archimedes could really have destroyed the Roman fleet in 212 BC lined up nearly 60 Greek sailors, each holding an oblong mirror tipped to catch the Sun's rays and direct them at a tar-covered plywood silhouette 160 feet away. The ship caught fire after a few minutes; however, historians continue to doubt the Archimedes story."
There are several methods for energy generation and cooling in CSP: steam recirculation, molten salt recirculation, Stirling engine, and hybrids including CPV (concentrated photovoltaic).  Some CSP plants also use natural gas to drive their turbines when electricity demand remains high at night and there's no solar power in the system, though advances in battery technology will probably change that soon.

The Planta Solar 10 (left) and Solar 20 (right) power plants
in Spain, from Wikimedia Commons.
Of the more picturesque and established CSP plants, the Planta Solar 10 (PS10) and its neighbor PS20 in southern Spain, with 11MW and 20MW capacities respectively, accumulate heat as steam in pressurized tanks for recycling through a turbine system.  Here lies the key when determining whether solar power generation really does draw on water resources: if the cooling cycle is an open system, which really only applies to water-based systems (since an open vat of molten salt is not likely very safe), then the steam that drives the turbines that generate the electricity subsequently escapes into the atmosphere.  This is the same kind of cooling system that we see at many nuclear power plants: the white steam escaping from a nuclear cooling tower is the exhaust of an open cooling system, and consumes a huge quantity of water.  For several reasons, including their water footprint, many nuclear plants are switching to closed-cycle cooling just like those recirculation systems available for CSP mentioned above.  Even if the closed system is water-based, it still uses only a fraction of the water consumed and "lost" by an open system for a comparable power plant.  According to a report published in the Fall 2007 issue of Southwest Hydrology on the water costs for various traditional and alternative power generation methods now in use in California (pdf), CSP ranks among the lightest on water use.

It's certainly possible that the President and the OSTP had no reason at all to ask for this "myth" to be busted again, Slate's commentary notwithstanding.  Nevertheless, Archimedes' Heat Ray remains an accurate and useful (and fun) demonstration of the origin of a water-light alternative energy technology in use today...

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