"Sustainable Energy - without the hot air" by Professor David MacKay
Comments by Prof Mike Ashby FRS
The industrial world is addictively dependent on energy, most of it
at present generated by burning fossil fuels. With sufficient affordable
energy, its continued growth (meaning its provision of a rising GDP per
capita to an increasing large fraction of the worlds population) can
continue. But it is now clear that this dependence has consequences of
increasingly grave concern. There is the reliance on the uninterrupted
functioning of a free market in oil and gas when the sources from which
they are drawn are localised and vulnerable to cartel action. There is the
effect on climate of the accumulation of atmospheric carbon that is a
consequence of their use. And there is the ultimate, inescapable depletion
and exhaustion of the resource base from which they are drawn.
One answer, frequently offered, is the replacement of fossil fuels by
renewable sources of energy - renewable meaning that they can be drawn upon
without depleting a resource that cannot be replaced. There are,
ultimately, only three sources of renewable energy: the sun, which drives
the winds, wave, hydro, photochemical phenomena; the moon, which drives the
tides; and radioactive decay of unstable elements giving geothermal heat
from the earth's crust or, when concentrated, nuclear power. All three
that offer the possibility of power without atmospheric pollution.
It is accepted that replacing fossil fuel sources with one or a
combination of these would be expensive, but that by-passes a more
fundamental question: is it even possible? If all were exploited in some
balanced combination, would they add up to enough? What would be the
consequences for land usage? What diminishment in other amenities would
the public have to accept? These are questions that politicians, green
campaigners and governments seem to overlook. Failure to answer them
undermines the credibility of any plan that relies on renewable energy as a
solution.
These are the central questions addressed by Professor MacKay in this
illuminating book. It cuts to the heart of the problem, using simple (but
inescapable) facts of physics and chemistry to assess the limits to the
quantities of energy that renewable sources can provide, and the
consequences that tapping them would have. The book is written and
structured in ways that make its arguments particularly accessible. The
reasoning is developed in two parts. The first a readable analysis of the
potential of each renewable source, stacking up their contributions to see
how nearly the total approaches our current energy consumption. The
second develops the physical reasoning in greater depth, explaining where
the numbers in the first part come from.
I will not divulge the conclusions - that would deprive the reader of
the stimulus of the progressive argument that Professor MacKay builds, and
of the fascination in seeing how simple science can be used to explore
issues of global significance. This is an example of order-of-magnitude
physics at its best: physics applied to the clarification of issues of
central economic, social and environmental importance. Fresh air replacing
hot air.
Prof Mike Ashby FRS Engineering Department, Cambridge.
Author of Materials and the environment
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