
66 Principles of Sustainable Energy Systems
© 2008 Taylor & Francis Group, LLC
while wind turbines directly generate mechanical energy and then electricity. In principle,
some of the heat-producing technologies can also make hydrogen by thermolysis of water,
that is, heating of water to a sufciently high temperature (greater than 3000 K) to break
it into hydrogen and oxygen. However, practical engineering obstacles such as the cost
and manufacture of materials to withstand these ultrahigh temperatures make this route
impractical.
In Figure 1.29, the dashed box isolates that portion of the pathway in which electric-
ity is used to produce hydrogen ...