Energy - Environmental Science - page 309

diesel fuel, or natural gas and uses a small battery
(recharged by the internal combustion engine) to pro-
vide the energy needed for acceleration and hill climb-
ing (Figure 13-24).
Toyota introduced its first hybrid vehicle in 1997.
Carmakers plan to introduce as many as 20 hybrid
models, including cars, trucks, SUVs, and vans, in the
next 4-5 years. Sales of hybrid motor vehicles are pro-
jected to grow rapidly and will probably dominate
motor vehicle sales between 2010 and 2030.
Another type of efficient car uses a fuel cell —a de-
vice that combines hydrogen gas (H 2 ) and oxygen gas
(O 2 ) in the air to produce electrical energy to power the
car and water vapor (H 2 O), which is emitted into the
atmosphere (Figure 13-25, p. 310).
Fuel cells are at least twice as efficient as internal
combustion engines, have no moving parts, require
little maintenance, and produce little or no pollution,

depending on how their hydrogen fuel is produced.
Most major automobile companies have developed
prototype fuel-cell cars and plan to market a variety
of such vehicles by 2020 (with a few models avail-
able by 2010) and greatly increase their use by 2050.
Until then, hybrids will probably retain an advantage
because they are available now and get their fuel
from gasoline filling stations instead of having to de-
pend on building a new network of hydrogen filling
stations.

Science: Designing Buildings
to Save Energy
We can save energy in buildings by getting heat from
the sun, superinsulating them, and using plant-
covered eco-roofs.
Atlanta's 13-story Georgia Power Company building
uses 60% less energy than conventional office buildings
of the same size. The largest surface of the building
faces south to capture solar energy. Each floor extends
out over the one below it. This blocks out the higher
summer sun to reduce air conditioning costs but allows
warming by the lower winter sun. Energy-efficient
lights focus on desks rather than illuminating entire
rooms. In contrast, the conventional Sears Tower build-
ing in Chicago consumes more energy in a day than
does a city of 150,000 people.
Another energy-efficient design is a superinsulated
house (Figure 13-26, p. 310). Such houses typically cost
5% more to build than conventional houses of the
same size. The extra cost is paid back by energy sav-
ings within about 5 years and can save a homeowner
$50,000-100,000 over a 40-year period. Superinsulated
houses in Sweden use 90% less energy for heating and
cooling than the typical American home.
Since the mid-1980s, interest has been growing in
strawbale houses (Figure 13-27, p. 311). The walls of
these superinsulated houses are made by stacking
compacted bales of low-cost straw and then covering
the bales on the outside and inside with plaster or
adobe. The main problem is getting banks and other
moneylenders to recognize the potential of this and
other unconventional types of housing and to provide
homeowners with construction loans. See the Guest
Essay about strawbale and solar energy houses by
Nancy Wicks on the website for this chapter.
Eco-roofs or green roofs covered with plants have
been used in Germany, in other parts of Europe, and in
Iceland for decades. With proper design, these plant-
covered roof gardens provide good insulation, absorb
storm water and release it slowly, outlast conventional
roofs, and make a building or home more energy effi-
cient. Designing and installing such systems could be
an interesting career.

Regulator:
Controls flow of
power between electric
motor and battery bank.

Fuel tank:
Liquid fuel such as gasoline,
diesel, or ethanol runs small
combustion engine.

Transmission:
Efficient 5-speed
automatic
transmission.

Battery bank:
High-density batteries
power electric motor
for increased power.

Combustion engine:
Small, efficient internal
combustion engine
powers vehicle with
low emissions.

Electric motor:
Traction drive provides
additional power,
recovers braking energy
to recharge battery.

Fuel
Electricity

Figure 13-24 Solutions: general features of a car powered by
a hybrid gas - electric engine. The bodies of future models will
probably be made of lightweight composite plastics that offer
more protection in crashes, do not need to be painted, do not
rust, can be recycled, and have fewer parts than conventional
car bodies. (Concept information from DaimlerChrysler, Ford,
Honda, and Toyota)