Chapter 24 Energy Conservation
399
the necessary cooling of these areas. One
idea is to increase the albedo (refl ective
ability) of the surfaces so they do not absorb
as much sunlight. Increasing the albedo
means a possible reduction in the peak elec-
trical demand of the surrounding area and in
cooling costs. One way to raise the albedo is
by changing the roof to lighter-colored and
more refl ective materials.
Changing the material of parking lots
could help cool the parking lot surfaces. One
material with this potential is called porous
concrete, Figure 24-9. Normal concrete
and blacktop surfaces force rainwater away
from the area they cover rather than into the
ground. Porous concrete provides a higher
void content and allows water to seep into
the ground. The water can help keep the area
cool. This material is designed for low-traffi c
areas, such as driveways and parking lots,
Figure 24-10. Porous concrete is also lighter-
colored than blacktop, which increases the
albedo and reduces the heat buildup.
Electricity and Vehicles
Many companies have experimented
with electricity-powered transportation.
Some cities have made all of their public bus
transportation electrical. Other cities have
converted their buses to run on natural gas.
Both of these plans help reduce air pollution
in the city.
The most common type of automobile
that is powered, at least partially, by elec-
tricity is the hybrid automobile, Figure 24-11.
A hybrid vehicle still has a gas engine, but it
also has a large capacity battery (over 200 V)
that can run the vehicle. The gasoline engine,
regenerative braking, and a very large gener-
ator are used to keep the battery charged.
All-electric vehicles are still very
uncommon for the road; although, they are
very common on golf courses, as golf carts
are electric. The battery of an electric vehicle
needs to be charged. The time for charging
can be inconvenient for commuters, but it is
Figure 24-9. The holes in porous concrete allow
water to run down into the ground underneath
the concrete.
Figure 24-10. A porous concrete driveway in
Atlanta, Georgia.
Figure 24-11. Hybrid vehicles help conserve
gasoline.