Whither Carnot Efficiency?

An interesting story about a new method of generating solar power from the inventor of the super-soaker. The article claims efficiencies of 60 % are possible.

As some of the comments point out this idea might not be feasible. The Carnot efficiency of a heat engine is given by:

efficiency = 1-(T COLD/T HOT)

(with absolute temperatures used)

The article suggests temperatures as high as 600 degrees centigrade. So (assuming T COLD is room temperature):

1 - ((273+25)/(600+273)) = 0.66.

Giving a theoretical efficiency of 66%.

Of course it's possible there is some error in my understanding of the article and/or theory.

However the endoreversible process is a slightly more accurate method of measuring the efficiency of a heat engine (at least according to the Wikipedia article), which is given by:

efficiency = 1 - (T COLD/T HOT)^0.5.

So:

efficiency = 1 - ((273+25)/(600+273))^0.5 = 0.41

Giving a theoretical efficiency of 41%, rather less than as advertised.

Science and Technology # 4

There is something amazingly satisfying about this cutting-edge, brass-alloy, white-enameled sextant, made by Cassens and Plath.

Improvements in efficiency in solar panels based on organic solar cells is good news. Keep up the good work, I guess.

In chemical engineering news: some guys at Rutgers have developed a method of spontaneously segregating two sets of mechanically identical sand-grains.

This sort of spontaneous organization is based on electrical charges. Another sort of spontaneous organisation is the Brazil nut effect. This is where, to quote Wikipedia: "the largest particles end up on the surface when a granular material containing a mixture of objects of different sizes is shaken".

It's a weird little corner of physics: it's fairly straightforward-seeming and simply, but gets more complicated the more you consider it.

I indulged in a little Web 2.0 goodness by downloading Last.fm. There are various irritations: like not being able to pause on songs you like, but most of my current irritations are based on ignorance.

It's fun to play but I can already feel myself feeling underwhelmed by the current state of the technology. It's always worth bearing in mind how hard it is to make anything work on a computer.

For me Web 2.o is the gradual removal of the distinction between "my" computer and "my" mobile and the embrace of a mode of existence where you access all your personal data anywhere and in any place.

Ideally, everything should be intuitive and porous: drag and drop, grab and alter etc. I suppose we still have a long way to go until this Platonic ideal is achieved.