Energy savingsin industry 285Technologies for reducing carbon dioxide emissions
from motor cars^20
An important recent development is that of the hybrid electric motor car
that combines an internal combustion engine with an electric drive train
and battery. The gains in efficiency and therefore fuel economy achieved
by hybrid vehicles are typically around fifty per cent. They mainly arise
from: (1) use of regenerative braking (with the motor used as a generator
and captured electricity stored in the battery), (2) running on the bat-
tery and electric traction only when in slow moving or congested traffic,
(3) avoiding low efficiency modes of theinternal combustion engine and
(4) downsizing the internal combustion engine through the use of the
motor/battery as a power booster. Both Toyota and Honda have intro-
duced commercially available hybrid models and other manufacturers
are not far behind.
Other significant efficiency improvements have come from the use
of lower weight structural materials, improvements in low-air-resistance
design and theavailability of direct injectiondiesel engines, long used
in heavy trucks, for automobiles and light trucks.
Biofuels generated from crops can be employed to fuel motor ve-
hicles thereby avoiding fossil fuel use. For instance, ethanol has been
extensively produced from sugarcane in Brazil and from maize in the
USA.Biodiesel is also becoming morewidely available. However, such
fuels can as yet only compete with fossil fuels if they are strongly sub-
sidised.
During the next few years we will begin to see the introduction of
vehicles driven by fuel cells (see Figure 11.15) based on hydrogen fuel
that can potentially be produced from renewable sources (see page 310).
This new technology has the potential to have a large influence on the
transport sector.potential forenergy reduction at a substantial net saving in cost. The
co-generation of heat and power, which already enables electricity gen-
erators to make better use of heat which would otherwise be wasted, is
particularly applicable to some industrial plants where large amounts
of both heat and power can be required. To take an example: British
Sugar in 1992 with an annual turnover of £700 million spent £21 million
p.a. on energy. Through low-grade heat recovery, co-generation schemes
and better control of heating and lighting, in 1992 the spend on energy
per tonne of sugar had been reduced by forty-one per cent from that in
1980.^21 Other potential decreases in carbon dioxide emissions can occur
through the recycling of materials, the use of waste as an energy source