The relative impacts of distributed and centralized generation of electricity
on local air quality in the South Coast Air Basin of California
, Akula Venkatram
Department of Mechanical Engineering, University of California, A343 Bourns Hall, 900 University Ave., Riverside, CA 92521, USA
Received 2 November 2010
Accepted 19 May 2011
Available online 2 July 2011
Local air quality impact
This paper examines the air quality impact of using distributed generation (DG) to satisfy future growth
in power demand in the South Coast Air Basin of Los Angeles, relative to the impact when the demand is
met by expanding current central generation (CG) capacity. The impact of decreasing boiler emissions
by capturing the waste heat from DGs is not examined. The air quality impacts of these two alternate
scenarios are quantiﬁed in terms of hourly maximum ground-level and annually averaged primary NO
concentrations, which are estimated using AERMOD. This study focuses on the impact of primary
emissions at source–receptor distances of tens of kilometers. We ﬁnd that the shift to DGs has the
potential for decreasing maximum hourly impacts of power generation in the vicinity of the DGs.
The maximum hourly concentration is reduced from 25 to 6 ppb if DGs rather than CGs are used to
generate power. However, the annually averaged concentrations are likely to be higher than for the
scenario in which existing CGs are used to satisfy power demand growth. Future DG penetration will
add an annual average of 0.1 ppb to the current basin average, 20 ppb, while expanding existing CGs
will add 0.05 ppb.
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Several studies have examined the impact of distributed
generation (DG) on air quality at urban and regional scales.
Allison and Lents (2002) examined the tradeoff between the
increase in emissions associated with urban DG emissions and
the decrease in emissions by replacing heating plants with waste
heat generated from DG plants. They found that realistic DG
scenarios were likely to lead to net increases in emissions in
urban areas. Their relatively simple analysis focused on aggre-
gated emissions and did not relate these emission changes to air
Heath et al. (2006) and Heath and Nazaroff (2007) have
examined the air quality impact of DGs relative to central
generating stations. They found that the air quality impact of
DGs, quantiﬁed in terms of intake factors, could be several times
that of central generating (CG) stations because (a) the ground-
level concentrations normalized by emissions from the high stack
of a CG plant are much smaller than the corresponding concen-
trations associated with the near ground emissions from DGs,
such as microturbines, and (b) CG plants are likely to be located
far from populated urban centers, while DGs are located in urban
areas close to energy consumers. These conclusions are based on a
simple Gaussian model that assumes an effective emission height
of 5 m for DGs. As we will see later, this assumption might
exaggerate the relative impact of DGs relative to central generat-
ing stations with large effective stack heights. Furthermore, the
intake fraction used to estimate the relative impacts of the DG
and CG stations normalizes the concentrations by the emission
rates, which means that comparison of the relative impacts is
effectively a comparison of the dispersive abilities of tall CG
stacks with much shorter DG stacks. A more realistic comparison
has to account for the fact that CG stations have much higher
emission rates than DG stations. Thus, the results from Heath
et al. (2003) do not directly address the impact of DG emissions
relative to emissions from CG stations.
The region considered in this paper is the South Coast Air
Basin (SoCAB) in southern California, covering Ventura, Orange,
Los Angeles, San Bernardino, and Riverside counties. The geogra-
phy, meteorology, and the population of the SoCAB have com-
bined together to give rise to poor air quality, which is among the
worst in the country, even though automobile emission controls
have led to major improvements in air quality over the last thirty
emissions from power plants required to accommo-
date future growth in electricity demand are of concern in view of
the recently promulgated one hour federal standard for NO
100 ppb (USEPA, 2010). This is the level that cannot be exceeded
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Corresponding author. Tel.: þ1 951 827 2195; fax: þ1 951 827 2899.
E-mail addresses: firstname.lastname@example.org (Q. Jing),
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Energy Policy 39 (2011) 4999–5007