Environmental Engineering Reference
In-Depth Information
In energy terms, these investments translate to as much
as 20 PJ of embodied energy for the entire system.
About 110 MW of electricity are needed for compression
and 60 MW for cooling, adding up to annual consump-
tion of about 5 PJ of electricity, or nearly 15 PJ of pri-
mary fuel. Even so, given the very high energy density
of the shipped product (25 GJ/m
3
vs. @36 MJ/m
3
for
gaseous CH
4
), the lifetime cost of roughly 320 PJ over
20 years is less than 6% of the cumulative throughput of
5.5 EJ.
Published values of EROI for electricity generation
range over 2 OM (fig. 10.2). Calculations of EROI for
thermal generation include three major components: in-
vestment in the plant and high-voltage transmission lines,
usually an equivalent of less than 5% of the plant's gener-
ation when prorated over at least 30 years of its lifespan;
the plant's internal electricity use, as low as 2%, as high as
8%, with efficient fly-ash removal and flue gas desulfuriza-
tion (FGD) facilities; and losses during long-distance
transmission, typically 7%-9% of the generated electricity.
These energy costs add up to 10%-20% of the plant's
generation, resulting in EROI of 5-8 for mine mouth
coal-fired stations, and 7-9 for natural gas-fired stations
located near a hydrocarbon field. Long-distance gas
transportation, often in excess of 1000 km, can halve
EROI even where the gas is used in a combined cycle.
However, Penner, Kurish, and Hannon (1980) put
EROI of U.S. coal-fired generation using surface mined
coal and no FGD as high as 43 for Eastern coal and 24
for Western fuel.
Alternatively, EROI of thermal electricity generation
will always be considerably less than 1 if its calculation
also includes all fuel inputs during a station's lifetime.
This is an inevitable consequence of inherently limited
10.2 EROI for major categories of electricity generation.
Based on Gagnon, B´langer, and Uchiyama (2002).
efficiencies of thermal electricity generation. In modern
stations they range mostly between 35% and 42%, can
be as low as 25% for some old plants, and surpass 50%
only in the best combined-cycle natural gas plants. In
the last case, EROI (quotient of electricity output and
all direct and indirect energy inputs) may be as high as
0.43 (Meier 2002); for most modern coal-fired stations,
it will be 0.30-0.35, and for the least efficient plants as
low as 0.20. But these EROIs should not be compared
to the net energies of primary fuel extractions. We are
