than one means there is an overall energy loss. Table20.2shows several energy sources
commonly used for heating our homes and schools. It shows their net energy ratios. Higher
ratios mean that the source provides more useable energy than those with lower ratios.
Table 20.2:Energy Source Net Energy Ratio
Solar Energy 5.8
Natural Gas 4.9
Petroleum 4.5
Coal-fired Electricity 0.4Notice from the table that renewable solar energy gives you much more net energy than
other sources and that coal-fired electricity actually consumes more energy than it produces.
Why do you think this is so? Burning coal for electricity requires a large input of energy
to get energy. We have to find the coal, mine the coal, transport the coal, and build power
plants to burn the coal (Figure20.9). All of these take energy and reduce the net energy
available for us to use. Solar energy, however, requires very little energy to get in the first
place. We don’t have to mine it or transport it in trucks. Sunshine is abundant globally and
can be used in the same place where it is collected.
Figure 20.9: Transporting coal requires a large input of energy. It takes energy to run the
train that transports the coal. ( 4 )