From Thermodynamics to Economics and Ecology - Thanatia: The Destiny of the Earth's Mineral Resources - page 67

Perhaps surprisingly only 0.023% of the entire solar energy is stored in the form
of biomass. Yet with this tiniest of amounts, the Earth has been able throughout
time to steadily store all the fossil fuels that people have burnt in the last few
generations. This gives thermodynamic hopes to Man's future, since avoiding a
small part of that degradation, i.e. in using technology that could take advantage
of solar energy in all its forms, Man could stop or at least slow down the depletion
of “his” planet.
When one speaks about conserving Nature, it often infers a conservation of
all of the natural energy dissipation processes including rivers full of freshwater
irreversibly mixing with seawater in estuaries, air flows cooling warm areas and
even tectonic activity occurring with some frequency. Maintaining the delicate
equilibrium of life cycles and planet diversity is something rather more subtle than
performing mere entropic balances. However, the Second Law is present in all
natural processes and when analysing why they occur, Second Law-thinking helps.
Ironically, it is life whilst appearing completely anti-entropic, not death, which
dissipates energy. Societies, as living entities, behave similarly. It is important
to clearly understand this phenomenon if humankind as a mere instrument of the
Second Law is ever going to decelerate the passing of time. Only intelligence through
a good housekeeping will prolong life. Equilibrium is death.

3.2.3 Exergy and the Snow White myth

A key contribution of Carnot was to notice that the driving force of thermal engines
was based on temperature differences. This is analogous to the hydraulic turbine
whose ability to produce work is dependent on differences in height. Similarly, in
the case of thermal engines, thermal energy can only be converted into mechanical
work, if a lower ambient temperature than that of the system is available. Where
such a difference exists, heat flows from T to T 0 and thus the work obtained can be
calculated as W = Q(T) Q 0 (T 0 ).
That said, no matter how ideal a thermal engine, it is not possible to convert all
the heating power of a fuel into mechanical work i.e. W 6= Q(T). In the same way
one cannot obtain W = mgZ from the hydraulic turbine but W = mgZ mgZ 0 .
This was an important discovery that changed the course of science forever.
The ratio between what is gained (product) and what is sacrificed (fuel) is
known as e ciency . In the case of the thermal engine this equation becomes
= W=Q = (QQ 0 )=Q. Even in the very best scenario where no frictions or heat
losses occur, this e ciency never equates to a hundred percent. However should
no irreversibilities take place, the entropy generation is zero and Q=T = Q 0 =T 0 , so
that the e ciency becomes:

= W=Q = (QQ 0 )=Q = 1 Q 0 =Q = 1 T 0 =T (3.5)

This expression is also known as the Carnot factor, and represents the maximum
e ciency that can be reached by a heat flux flowing reversibly between two given