September 26th, 2004

classic beard

Moon Shadow

If you've ever needed to explain what goes on during an eclipse, I think this picture of the Moon Shadow as seen from MIR (back in 1999) is one of the most helpful tools you could find... and it's a really cool picture :-)
classic beard

Hydrogen Solar

Ok, now I see a reason that hydrogen-fueled-vehicles might be something other than a new way for the oil companies to stay on top -- the UK firm "Hydrogen Solar" is demoing a high-efficiency solar cracker in Las Vegas soon. They're basically high-efficiency multi-frequency solar cells that use the potential to crack water into hydrogen and oxygen directly - while the article claims they've now reached "8% efficiency" they don't really specify in what units that is. However, they point out a benchmark of 10% efficiency for commercial viability - meaning that a 50m^2 cell generates enough H2 in a year to drive a midsized car for 11,000 miles, which I suppose implies that a suburban house could run one of their cars entirely off of solar energy.

At the other end of the scale: there are roughly half a billion (5e8) cars in the world [source: hypertextbook], 200 million (2e8) in the US alone (yes, that's slightly more than one per driver :-) So, assuming the 50m^2 per car is "enough", 25e9m^2 world (10e9m^2 us) would produce enough hydrogen (ignoring water purity/availability), or 25e3 km^2 (10e3 km^2 us.) So, we could fuel America's vehicles by covering an area roughly half the size of Massachusetts with these panels; we could fuel the world's vehicles by covering all of Maryland.

(Of course, locating these further south works better, so Texas will probably still win out, though Mexico could become useful too.) Sounds like a plan.