yeah, I've heard that thing about "the earth receives more energy from the sun in one day than the whole world uses in a year."  What are the assumptions behind that?  I am pretty sure that one assumption is:  the EARTH receives the solar input, and what it's compared to is the amount of energy that HUMANS use.  As in, if humans expand their niche to take more solar income, there will be less solar income for the rest of nature to use.  If we use wind power, I can imagine that we would't be stealing solar energy from other life forms.  But if we cut down forests in order to plant things (plants, solar photovoltaics) that bring solar power into our economy, we're not decreasing our ecological footprint by going solar.

Biologists say that humans are currently using 40% of the Net Primary Productivity of the planet.  That ratio  is not sustainable, and has to be--will be--reduced in the future.

I'll check out that link.

Industrial society is not sustainable. Unsustainable systems change--or disappear.