Deck 2: Past, Present, and Future World Energy Use

Question 1

Assume that the historical growth rate of the human population was constant
at 1.6% per year. For a population of 7 billion in 2012, determine the time in the past when
the human population was 2.

Answer 1

As the annual percentage growth rate is small then we can use the approximation
of equation (2.4) to get the doubling time from R so

Question 2

the example of energy use on page 31, leading to equation (2.1), consider
a family (two people) who use gasoline at the rate indicated but who heat their home
electrically in accordance with the efficiencies given in the text above equation (2.1). How
would this affect the per person power consumption?

Answer 2

Assuming an efficiency of 40% for electricity generation the primary energy use
for two people will be

Question 3

A person in the United States consumes 2000 Calories of food per day.
What fraction of the average per capita energy use, as indicated in Table 2.1, does this
represent?

Answer 3

From the Table the per capita power consumption is 11,730 W. This represents

Question 4

If a quantity has a doubling time of 30 days and its value is 1000 units at
noontime today, what will be its value at noontime tomorrow?

Question 5

Assume that the combustion of coal is approximated by the burning of
carbon. If a coal-fired generating station operates at 40% efficiency, calculate the amount
of CO2 emitted per MWh of electricity produced.

Question 6

Repeat problem 2.15 for the combustion of natural gas (methane). How
does the use of the HHV affect your answer?

Question 7

For an annual growth rate of 1.6%, use the data in Table 2.3 to estimate the
year in which the human population will reach 200 per km2 of land area.

Question 8

The population of a state is 25,600 in the year 1800 and 218,900 in the year
1900. Calculate the expected population in the year 2000 if (a) the growth is linear and (b)
the growth is exponential.

Question 9

Consider a solar photovoltaic system with a total rated output of 10 MWe and
a capacity factor of 29%. If the total installation cost is $35,000,000, calculate the decrease
in the cost of electricity per kilowatt-hour if the payback period is 25 years instead of 15
years. Assume a constant interest rate of 5.8%.

Question 10

The population of a country as a function of time is shown in the following
table. Is the growth exponential?

Question 11

What is the current average human population density (i.e., people per square
kilometer) on earth?

Question 12

The total world population in 2012 was about 7 billion, and Figure 2.11
shows that at that time the actual world population growth rate was about 1% per year. The
figure also shows an anticipated roughly linear decrease in growth rate that extrapolates to
zero growth in about the year 2080. Assuming an average growth rate of 0.5% between
2012 and 2080, what would the world population be in 2080? How does this compare with
estimates discussed in the text for limits to human population?

Question 13

(a) If the total amount of a resource available is calculate its

Question 14

Consider an island with a current population density of 50 people/km2 (about
equal to the present world average). If the annual growth rate is 2%, determine the year in
which the population density be equal to 20,000 people/km2 (approximately the population
density of Macau, the world's most densely populated nation).

Question 15

If world energy use increases linearly, use Figure 2.13 to estimate the
annual percentage increase for OECD and non-OECD countries from 1990 to 2035 relative
to the use in 1990.

Question 16

A quantity has a doubling time of 110 years. Estimate the annual percent
increase in the quantity.

Question 17

(a) Assume that human population growth is described as exponential
growth and the current population is 7.5 billion. If the current daily increase in population
is 250,000, calculate the doubling time.
(b) For the conditions in part (a), what is the current annual growth rate?

Question 18

If a facility has a capital recovery factor of 0.12 and the annual interest rate
is 5%, what is the payback period?

Question 19

The population of a particular country has a doubling time of 45 years. When
will the population be three times its present value?

Question 20

From the data in Table 2.1 and Figure 2.3, estimate the total energy
production per year from hydroelectricity in the United States.