310 Energy andtransport for thefuture
be safely disposed of, that the distribution of dangerous nuclear material
can be effectively controlled and that it can be prevented from getting
into the wrong hands.
A further nuclear energy source with great potential depends on
fusion rather than fission (see box below in next section, page 312, ‘Power
from Nuclear Fusion’).Technology for the longer term
This chapterhas concentrated mostly on what can be achieved with
available and proven technology during the next few decades. It is also
interesting to speculate about the more distant future and what relatively
new technologies may become dominant during the twenty-first cen-
tury. In doing so, of course, we are almost certainly going to paint a
more conservative picture than will actually occur. Imagine how well
we would have done if asked in 1900 to speculate about technology
change by 2000! Technology will certainly surprise us with possibilities
not thought of at the moment. But that need not deter us from being
speculative!
There is general agreement that a central component of a sustainable
energy future is the fuel cell that with high efficiency converts hydrogen
and oxygen directly into electricity (see box below). In the fuel cell the
electrolytic process of generating hydrogen and oxygen from water is
reversed – the energy released by recombination of the hydrogen and
oxygen is turned back into electrical energy. Fuel cells can have high
efficiency of fifty to eighty per cent and they are pollution free; their
only output other than electricity is water. They offer the prospect of
high efficiency, small-scale power generation. They can be made in a
large range of sizes suitable for use in transport vehicles or to act as
local sources of electrical power for homes, for commercial premises or
for many applications in industry. Much research and development has
been put into fuel cells in recent years that has confirmed their potential
as an important future technology. There seems little doubt that they will
come into widespread use within the next decade.
Hydrogen for fuel cells can be generated from a wide variety of
renewable sources (see box above). Of these,from many points of
view, the one that is most attractive is through the hydrolysis of water
using electricity from photovoltaic (PV) cells exposed to sunlight
(Figure 11.16) – a very efficient process; over ninety per cent of the
electrical energy can be stored in the hydrogen. There are many regions
of the world where sunshine is plentiful and where suitable land not
useful for other purposes would be readily available. It is a very clean,
non-polluting technology, easily adaptable to mass production. The cost