less conventional energy is needed to heat the home. See Figure 5-14. The
energy from the earth reduces heating costs significantly, but the system
has another big advantage over more conventional heating systems. It can
be reversed and used to provide central air conditioning in the warm
summer months.
Geothermal energy and the environment
Geothermal energy plants have raised the ire of a number of environ-
mental groups that regard them as unsightly, smelly, and extremely noisy.
The hydrogen sulfide gases within the steam smell like rotten eggs, and the
minerals commonly found in steam with little moisture have the capability
of poisoning lakes and streams if they become airborne. The moisture from
wet steam plants tends to be heavily laden with salt, which can create main-
tenance problems, due to buildup, and waste disposal problems, once the
steam is brought aboveground. On a positive note, geo thermal plants emit
far less CO2 into the environment than burning fossil fuels, and they make
use of a heat source that is present for the taking.
Wind
For years, people built windmills in places where the wind blew much
of the time. See Figure 5-15. The windmills pump water, grind grain, or
do other useful tasks. Unfortunately, the wind has never been a totally
Hydrogen sulfide
gas: A gas that
smells like rotten
eggs, found within
the steam of geo-
thermal energy
plants.
111
Figure 5-14. A geothermal heat pump has its evaporator coil buried in the
ground. Refrigerant in the evaporator coil picks up heat from the ground (even
in cold weather) and is carried inside, where it passes through a compressor.
In the condenser coil, the heat is given up to the flow of indoor air, warming
the indoor spaces.
Condenser
To rooms
Warm
air
Compressor
110°F
From
rooms
Cold air
65°F
In
Evaporator
Heating cycle
Renewable and Inexhaustible Energy Sources