Renewables energy balance - data!!

What should be THE key question and the most commonly known answer in debates about renewables is the payback period for the energy embodied in the power generator.
(ie: Can you use one to make more than another one.)
Sadly it's not, and I've only just found the answer (albeit easily now that I've looked for it).

Here's one site with some good data
http://www.awea.org/faq/bal.html
and another well referenced source
http://www.csudh.edu/oliver/smt310-handouts/solarpan/pvpayback.htm

Short answer:
Solar in the 70's couldn't. Now it can (payback 3~6yrs with a total 15~20yr life)
Wind can easily (2~22 MONTHS)
But coal and nuclear can easily too (0.7 months), I'm guessing the ongoing energy cost is insignficant.


Hrmm, now to look at Ethanol fuels...

invention # ?

Beam balance piggy bank. One side a standard weight hung at the saving goal marker, the other side, coin boxes for each denomination at the right offset for value-vs-weight.
Now to work out how much each denomination weighs.