Energy and Human Ambitions on a Finite Planet, 2021a

C Selected Answers 389
Chapter 13
1. How big are the packages?
2. Something times 10 21
3. Roughly 10 16
4. About 1,000
5. About 4,000 times
6. Use Eq. 13.3 to guide your reasoning
7. Should match Figure 13.1
8. One micron for each finger?
9. Think about spill-over into UV <strong>and</strong>/or IR
10. Peak around 2.5 × 10 8 , about 1 μm wide;
matches up well
11. Think energetics <strong>and</strong> depth
12. Is the answer transparent?
13. Just comparing two energies
14. Several hundred km/s
15. Condense the saga to that of a winner
16. Answer might involve physics, biology,
rooftops
17. Inversely: larger in one means smaller in
the other
18. Already extremely similar
19. Think of current as a rate of electron flow
in the circuit
20. Get very close to 1,360 W/m 2
21. Sweltering is not preferred
22. Between 5–6 kWh/m 2 /day; between 200–
250 W/m 2
23. Involves interpreting kWh/m 2 /day as fullsun-hours
24. Not far from 200 W/m 2
25. Range straddles 200 W/m 2 , varying about
10%
26. Best at latitude; almost 15% better than
flat
27. Approaches 6 kWh/m 2 /day
28. Large house (<strong>and</strong> just the PV for one person)
29. Square is about as wide as Arizona or
California east-to-west
30. Cost, surely—but other challenges <strong>and</strong>
mismatches as well
31. A little over 200 W
32. Roughly the size of a bedroom
33. Will spend a little over $4,000
34. A little over a decade
35. Even lower than ∼20% from insolation vs.
overhead
36. About $2-worth of sun
37. Hint: study Figures 13.23 <strong>and</strong> 13.24
38. In absolute terms. . .
Chapter 14
1. About a dozen tons of CO 2
2. Between 0.1–0.5%
3. Almost 100 logs per person per year
4. In the neighborhood of half-dozen logs per
day
5. Won’t be exactly 15 years, but close
6. Almost 1.5 L of ethanol
7. Roughly consistent with Table 14.1 for coal
8. Net is one-third production
9. Extra l<strong>and</strong> is twice the yield-l<strong>and</strong>
10. A bit longer than a U.S. Presidential term
11. Nothing to spare
12. Corn now approximately 15% as much as
this; still more than total arable l<strong>and</strong>
© 2021 T. W. Murphy, Jr.; Creative Commons Attribution-NonCommercial 4.0 International Lic.; Freely available at:
https://escholarship.org/uc/energy_ambitions.