Thursday, September 21, 2006

Energy realities

Chris Rhodes has drawn my attention to his blog, linked above.

I would be extremely grateful if other bloggers who cover the question of the realities underlying our future energy supplies would do the same.

If we politicians are going to make sensible decisions, we need to have a grip on the total implications of the energy policies which are being touted around, and not allow ourselves to be seduced by the latest rabbit out of a hat. I find it very difficult to locate information sources which even approximate the truth: so much of industry, and so many pressure groups, seem addicted to lies and distortions.

Claims are made about the energy efficiency of different models of cars, based only on their fuel consumption rather than on their lifetime energy cost. Wind turbines are hymned as the solution to our problems, on the basis of a 15 year payback! Fuel cells (with which I was commercially involved for a while) are promoted as 60% efficient without taking into account the inefficiencies that flow from creating and storing and transporting their fuel.

Chris Rhodes's latest posts address the mathematics of biofuels. Good Stuff.

2 Comments:

Blogger Kirk Sorensen said...

I've enjoyed Dr. Rhodes' blog a great deal--I'm glad that you're enjoying it too. As an engineer, I love to run the numbers!

3:33 am  
Blogger GRLCowan said...

As best I can determine, claims of 60 percent efficiency for fuel cells of the sort being -- I hesitate to say prototyped, because no types will follow, nor were ever meant to -- being put in experimental cars are simply false.

Not, as Lord Lucas says, false when inefficiencies that flow from creating and storing and transporting their fuel are taken into account. No, losses much exceeding the claimed 40 percent occur between the fuel tank and the fuel cell's DC output terminals.

One particular Ballard fuel cell that produces 0.092 kW/kg yields 41 percent of the free energy of its fuel and oxygen as DC electricity. Many more watts per kilogram are needed for a vehicle prime mover, and this implies lower conversion efficiency.

It has been many months since I last looked, but at that time the hydrogen-to-DC efficiencies of air-breathing hydrogen fuel cells in fuel cell vehicles were invariably unpublished.

--- G. R. L. Cowan, former hydrogen fan
Burn boron in pure oxygen for vehicle power

8:09 pm  

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