Quantifying the Air Pollution Exposure Consequences of - Houston ...

There are many potential benefits of the use of DG to society. These include
reduced grid congestion; increased overall efficiency of providing electrical and thermal
energy through maximal use of waste heat in combined heat and power (CHP)
applications; reduced losses from long-distance transmission of electricity (line losses);
and deferred siting and construction of new central station plants. Focusing on these
benefits, the US Department of Energy (DOE) has established a goal that “[by] 2010 …
distributed energy resources [will] achieve 20% of all new electric capacity additions in
the US” (DOE, 2000). 2 At the time of adopting this recommendation, DOE translated 20
percent of new capacity additions to 26.5 gigawatts (GW) and the agency has initiated
programs to meet that goal. The California Energy Commission, after deciding that more
analysis was prudent before setting a numerical goal, has published a strategy that calls
for promotion of DG technologies within the state (CEC, 2002c).
Already, the DOE estimates that more than 53 GW of distributed energy
resources are installed in the US (DOE, 2000). 3 The CEC estimates that greater than 2.0
GW of DG is installed in California with another 3.0 GW of emergency back-up
generation (often undifferentiated in definitions of DG even though back-up power is not
considered DG by most authorities). From January 2001 through May 2002, 400 MW of
new capacity were proposed in California (CEC, 2002c). By far, the majority of these
installations are household-sized, renewable energy units; however, as with central
stations, most of the capacity is in the larger units of up to 50 MW (DOE, 2000 and CEC,
2002c).
In addition to overall societal benefits, there are many commercial benefits of DG
driving its adoption. During the California energy crisis of 2000-2001 and before, the
cost of self-generation was substantially lower than the retail cost of electricity, mainly
due to the low cost of natural gas. Today, the most economical configuration is to
identify nearby heat loads that can take advantage of the waste heat of electricity
generation in combined heat and power operations (formerly known as co-generation).
However, “premium power”— i.e., supplying very reliable, high quality power to highvalue
activities such as the operation of critical electronic equipment — is emerging as a
primary market niche for DG applications (CEC, 2002c).
Ironically, one attribute that makes DG innovative and appealing to many parties
— that the generation units are sized appropriately to the local demand — causes concern
to many regulators. Their small size places most DG units outside of most existing
regulatory structures, which have focused on large, central station sources. For criteria
pollutants, the US Environmental Protection Agency (EPA) sets standards for ambient
concentrations to be protective of public health, including susceptible subpopulations. To
ensure that these standards are not exceeded, the states determine the maximum amount
of certain primary pollutants that can be emitted by various source classes, as well as
2 The US Department of Energy defines “distributed energy resources” (DER) to mean supply- and
demand-side resources. However, by referring to DER as supplying “20 percent of new electric capacity”
(emphasis added) it would seem that they use this term synonymously with the definition of DG as a
supply-side resource, as used in this report (DOE, 2000).
3 This estimate includes units used solely for back-up, peaking, or baseload power and may include an
estimate of demand-side resources.
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