Energy Solutions to Air Pollution and Global Warming - Air Pollution and Global Warming: History, Science, and Solutions - page 336

Table 13.8. Mean (and range) of environmental externality costs of electricity generation in the United States
in 2007 (U.S. cents/kWh)

2005 2030

Air pollution Climate Total Air pollution Climate Total

Coal 3.2 3.0 6.2 (1.2-22) 1.7 4.8 6.5 (3.3-18)

Natural gas (NG) 0.16 1.5 1.7 (0.5-8.6) 0.13 2.4 2.5 (0.9-8.9)

Coal/NG mix 2.4 2.6 5.0 (1.0-18) 1.3 4.2 5.5 (2.7-15)

∼ ∼ ∼ ∼ ∼ ∼

Wind, water, sunlight 0 0 0 0 0 0

The coal/NG mix is 73 percent/27 percent in 2005 and 75 percent/25 percent in 2030.
Source: Delucchi and Jacobson (2011).

generation costs of energy from old coal plants can be 2
to 3 U.S. cents/kWh. However, the externality costs of
such plants are much greater than those in Table 13.7.
The future costs of onshore wind, geothermal, and
hydroelectric power are expected to remain low. Costs
of other WWS technologies are expected to decline.
If WWS technologies are compared on the basis of
direct plus externality costs, WWS options, including
solar PVs, should cost less than new conventional fuel
generation by 2020 (Table 13.7).
Table 13.7 includes the cost of electricity transmis-
sion in a conventionally configured system over dis-
tances common today. However, many future wind
and solar farms may be far from population cen-
ters, requiring extra long-distance transmission. Fur-
thermore, there is an efficiency advantage to increasing
interconnection among geographically dispersed wind
and solar farms (Section 13.8.1). Namely, the more that
dispersed wind and solar generating sites are intercon-
nected, the less the output of the whole interconnected
system varies.
Asystem of interconnected transmission lines among
widely dispersed generators and load centers is referred
to as a supergrid .The configuration and length of trans-
mission lines in a supergrid depends on the balance
between the cost of adding more transmission lines
and the benefit of reducing system output variability
as a result of connecting more dispersed generation
sites. A supergrid has been proposed to link Europe
and North Africa (e.g., Czisch, 2006). Supergrids are
also needed within Australia/Tasmania, North Amer-
ica, South America, Africa, Russia, China, eastern and
Southeast Asia, and the Middle East.
Forlong-distance transmission, high-voltage direct
current (HVDC) lines are generally used instead of
alternating current (AC) lines because of the lower

transmission losses per unit distance with HVDC lines
overalong distance. The cost of HVDC transmission
is a function of the cost of the towers and lines; the
distance of transmission; the cost of equipment such as
converters, transformers, filters, and switchgear; elec-
tricity losses in lines and equipment; the life of the
transmission line; maintenance costs; the discount rate;
and the efficiency of power generated for the line.
The most important and uncertain cost components are
the costs of lines and towers. The cost of extra long-
distance HVDC transmission on land ranges from 0.3
to 3 U.S. cents/kWh, with a best estimate of about 1
U.S. cent/kWh (Delucchi and Jacobson, 2011). A sys-
tem with up to 25 percent undersea transmission, which
is relatively expensive, would increase the best estimate
of the additional long-distance transmission cost by less
than 20 percent.

13.10. Policy Mechanisms
Current energy markets, institutions, and policies have
been developed to support the production and use of fos-
sil fuels and biofuels. New policies are needed to ensure
that clean energy systems develop quickly and broadly
and that dirtier energy systems are not promoted. Sev-
eral economic and noneconomic policies have either
been implemented or considered to accomplish these
goals.
Renewable portfolio standards (also called renew-
able electricity standards) are policy mechanisms
whereby a certain fraction of electric power genera-
tion must come from specified clean energy sources by
a certain date (Section 12.6.3).
Feed-in tariffs (FITs) are subsidies to cover the
difference between generation cost (ideally including
grid connection costs) and wholesale electricity prices.