Energy and Human Ambitions on a Finite Planet, 2021a

2 Economic Growth Limits 29
7. Come up with some of your own examples (at least three; not
listed in the text) of economic activities 29 that have little resource
footprint <strong>and</strong> are therefore fairly decoupled. These are transactions
for which the intensity (energy or resource expenditure) is very
low compared to the dollar amount.
8. If a c<strong>and</strong>le has a luminous efficacy of 0.3 lm/W <strong>and</strong> a modern LED
light bulb achieves 100 lm/W, by what factor 30 have we improved
lighting efficiency? If the theoretical limit is around 300 lm/W,
what factor do we still have to go?
9. In going from 0.3 lm/W c<strong>and</strong>le technology to the theoretical
maximum luminous efficacy, we see a factor of 1,000 increase.
Taking about 300 years to do this, we might recognize that we are
following along our familiar factor-of-ten each century trajectory.
Approximately how long 31 might we expect it to take to achieve
the final factor of three to go from our current technology to the
theoretical limit, at this same rate? Is it within your lifetime that
we hit the limit?
10. Provide your own example of a sequence of substitutions comprised
of at least two qualitatively superior 32 substitutions over
time (thus three steps: original, first replacement, second replacement).
29: ...things that cost money
30: A factor is just a multiplicative scale:
e.g., 24 is a factor of 6 larger than 4.
31: You can just estimate, use appropriate
math, or refer to the guiding line in Figure
2.3 to arrive at a rough number.
32: . . . perhaps defined by widespread or
universal adoption or replacement.
11. List three substances or critical concepts we rely on that have no
superior substitutes in the universe.
12. Based on your present state of knowledge, detail what you think
an optimist might say about the superiority of post-fossil energy
substitutes?
You might pick any subset of solar, wind,
hydroelectric, geothermal, nuclear, etc. to
guide your thinking.
13. Based on your present state of knowledge, detail what you think
a pessimist might say about the lack of superiority of post-fossil
energy substitutes?
14. Justify what, In your mind, is a reasonable lower limit to the
percentage of the economy that could be based on decoupled (not
energy or resource heavy) activities? Make an argument for what
leads you to this “floor.”
15. One form of decoupled activity that some will bring up is virtual
reality: you can travel the world (or solar system?) without resourcehogging
transportation <strong>and</strong> other material costs. Do you see this
as a viable alternative that is likely to largely supplant physical
travel? Why or why not?
16. Are you sold on the argument that the physics-imposed limit
to resource/energy growth dem<strong>and</strong>s an ultimate cessation of
economic growth as well? If so, highlight the persuasive elements.
If not, why not?
© 2021 T. W. Murphy, Jr.; Creative Commons Attribution-NonCommercial 4.0 International Lic.;
Freely available at: https://escholarship.org/uc/energy_ambitions.