United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S7-83-008 Apr. 1983
<&EPA Project Summary
An Assessment of the Effects of
Active Solar Thermal
Technologies on Urban
Emissions
Energy and Environmental Analysis, Inc.
This study analyzes the fuel displace-
ment potential of solar technologies to
determine the benefits of emission
reduction which might result in urban
areas from use of solar energy. Fuel
displacement by solar energy was
found to be greatest in the residential
water-heating and in electric end-uses
in all three cities investigated (Hous-
ton, Chicago, and Philadelphia). Fuel
displacement increased from 1985 to
1995, as solar energy became more
competitive with other fuels. However,
emissions reductions attributable to
the expanding market for solar energy
were relatively small in all three urban
areas, generally less than one percent
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory. Cincinnati. Ohio, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Solar energy systems can have a posi-
tive impact on air quality by displacement
of fossil-fired energy conversion sources.
The objective of this study was to analyze
the fuel displacement potential of solar
systems and to determine the associated
emissions reductions in metropolitan areas.
The study considered emissions reduc-
tions of particulates, sulfur oxides, nitro-
gen oxides, hydrocarbons, and carbon
monoxide resulting from fossil fuel dis-
placemnt by solar energy. Three metro-
politan Air Quality Control Regions (Chicago,
Houston, Philadelphia) were analyzed for
two future points in time: 1985 and
1995. Analysis of solar technologies was
limited to active solar thermal systems
because of their commercial readiness
and their widespread applicability to urban
energy markets.
The study was divided into five sequen-
tial tasks: market definition, technical
assessment of solar systems, economic
analysis, sensitivity tests, and emissions
impacts. Fuel use which could be poten-
tially displaced by solar systems was ident-
ified and disaggregated into market seg-
ments, consisting of a matrix of end-uses
and fuel types (e.g., one market segment
would be gas-fired space heating in single-
family detached residences). These mar-
ket segments reflect both technical factors
(e.g., process temperatures) and economic
factors (e.g., ownership status), which
affect solar competitiveness. The end-
uses considered in the residential,
commercial, and public sectors included
space heating and cooling, and water
heating. These market segments account
fora large portion of energy consumption
in all these sectors. In the industrial
sector, market segments were restricted
to space heating and process heat at less
than 816°C(1500°F).
Atechnical assessment helped to define
viable solar systems for each end-use
market segment and to identify perform-
ance factors affecting end-use solar ener-
gy utilization. For example, collector land
use is expected to limit the size of solar
systems in a number of situations. Tech-
nically viable solar systems were com-
pared with conventional systems on the
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basis of a life-cycle cost analysis. When
the ratio of levelized price of displaced
fossil fuel to annualized solar cost of an
end-use exceeded one, the solar system
was considered competitive in that market
segment. When a solar system was com-
petitive, the entire amount of energy con-
sumed by the particular market segment,
adjusted by a solar load factor, was con-
sidered displaced.
A sensitivity analysis was conducted to
determine how fuel displacement would
be affected by different economic assump-
tions and to establish a fuel displacement
range. Six scenarios were constructed by
pairing three solar cost estimates (low,
medium, and high) with two fuel-price
projections (mid-range and high). Two
scenarios received particularattention: a
"base-case" scenario (medium solar costs
and mid-range fuel price projections) that
was considered the most likely reflection
of future market conditions, and a "best-
case" scenario (low solar costs and high
fuel prices) that was considered most
favorable for solar penetration of the
market place.
Findings
Fuel Displacement
Under the base-case scenario, fuel dis-
placement in the residential, commercial,
and public sectors resulted primarily from
the capture of part of the oil and electric
hot water heating markets in 1985. Dis-
placement increased substantially in 1995
with the capture of certian space-heating
market segments (see Figure 1). More
fuel displacement occurred in the residen-
tial sector than in the commercial and
public sectors, due to the size of the
residential water and space heating mar-
kets and the competitiveness of residential
solar systems. The fraction of total com-
mercial and residential energy consump-
tion displaced in 1 985 was 1.43, 0.70,
and 1.79 percent for Houston, Chicago,
and Philadelphia, respectively. Fuel dis-
placement was less than five percent of
the total consumption for these sectors in
1995, for each AQCR investigated.
Industrial fuel displacement was not
significant in the base-case scenario; in-
dustrial solar systems were not competi-
tive with any fuel type in 1985 and only
marginally attractive in 1 995. The rela-
tively low fuel displacement levels in both
years are attributable to: 1) land restric-
tions which limit solar system size and
output, 2) industrial coal use, 3) low solar
load fractions, and 4) limited low-process-
temperature applications where solar is
competitive.
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1995^
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(6.6)
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(3.8)
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(19.8)
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Electricity Fuel Gas Electricity Fuel Gas Electricity Fuel Gas
oil
Houston
oil
oil
Philadelphia Chicago
Figure 1. Displaced energy in residential, commercial, and public sectors by air quality control
regions — base-case economic and fuel-escalation scenario.
In the sensitivity tests, fuel displace-
ment increased substantially in all three
Air Quality Control Regions (AQCR) under
the more favorable solar scenarios. Gas
displacement in the residential, commer-
cial and public sectors was most noticeable,
because in 1985, under the base-case
scenario, no gas was displaced. The
fraction of total commercial and residential
energy consumption accounted for in the
1985 best-case scenario was 3.2 percent,
5.9 percent, and 6.3 percent for Houston,
Chicago, and Philadelphia, respectively.
Industrial fuel displacement was also
larger under the more favorable solar
scenarios. In these cases, solar became
competitive with gas and oil space heat
systems, process heat, and some steam
applications. However, best-case fuel dis-
placement in the industrial sector in 1985
amounted to less than one percent of the
industrial energy consumption in any of
the AQCR's.
Emissions Reductions
The emissions reductions under the
base-case scenario in 1985 and 1 995 are
identified in Table 1, along with the per-
centage attributed to each fuel type. These
percentages reflect the relative competi-
tiveness of solar systems to different
fuels, as well as the emissions characteris-
tics of the displaced fuel. In most cases,
electricity displacement had the largest
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Table 1. Displaced Emissions, Tonnes/Year (Tons/Year)8
AQCR
Source Category
Houston
Total Tonnes/Year
(Tons/Year)
Percent
Electric0
Gas6
Oifi
Industrial Gas
Industrial Oil
Chicago
Total Tonnes/Year
(Tons/Year)
Percent
Electric
Gas
Oil
Industrial Gas
Industrial Oil
Philadelphia
Total Tonnes/Year
(Tons/Year)
Percent
Electric
Gas
Oil
Industrial Gas
Industrial Oil
Particulates
1985
336.1
(370.6)
99
0
1
0
0
78.7
(86.8)
100
0
0
0
0
200.7
(221.3)
20
0
80
0
0
1995
370.6
(409.6)
76
8
1
0
15
365.7
(403.2)
17
35
48
0
0
346.0
(381.5)
32
29
27
neg
9
Sulfur Oxides
1985
1236.9
(1366.2)
99
0
1
0
0
1495
(1648)
100
0
0
0
0
1140
(1257)
31
0
69
0
0
1995
2555.4
(2821.6)
96
negd
neg
0
4
1700
(1874)
70
neg
30
0
0
2191
(2416)
15
neg
83
neg
2
Carbon Monoxide
1985
44.3
(48.8)
96
0
4
0
0
38.6
(42.6)
100
0
0
0
0
165.2
(182. 1)
16
0
84
0
0
1995
128.7
(141.9)
44
44
2
0
10
373.9
(412.2)
8
68
23
0
0
393.9
(434.3)
6
25
65
2
1
Hydrocarbons
1985
10.2
(1 1-2)
90
0
10
0
0
13.6
(15.0)
100
0
0
0
0
98.2
(108.3)
12
0
88
0
0
1995
51.8
(57.1)
35
44
2
0
19
165.7
(182.7)
7
62
32
0
0
244.7
(249.7)
5
8
85
1
2
Nitrogen Oxides
1985
1135
(1251)
100
0
neg
0
0
287.8
(288.0)
100
0
0
0
0
998.7
(1101)
67
0
33
0
0
1995
1760
(1940)
72
12
neg
0
15
1858
(2049)
37
52
11
0
0
7030
(7751)
9
15
74
1
1
aBase-case scenario.
b Percent of emissions by source category displaced.
cResidential, commercial and public sectors by fuel type.
dNeg = negligible.
impact on emissions because solar was
most competitive with electricity, which
has a higher emissions output than gas or
fuel oil. The increase in emissions from
1985 to 1995, and the shift in source
category shares of emission reductions
reflect solar's greater capture of gas and
oil market segments in 1995.
The range of displaced emissions brack-
eted by the base-case and best-case
scenarios is shown in Table 2. The best-
case scenario increased emissions dis-
placement for a given pollutant and city
from 19 percent to more than 700 per-
cent over the base-case scenario. The
best-case scenario offered the greatest
emissions displacement in the 1995 time-
frame, where space-heating and industrial-
process applications are just marginally
competitive under the base-case scenario.
In the cities investigated, the potential
for reduction of emissions resulting from
solar fuel displacement appears limited.
As shown in Table 3, the overall impact of
Table 2.
Displaced Emissions Range, Tonnes/Yr (Tons/Yr)
Particulates Sulfur Oxides
Carbon Monoxide
Hydrocarbons
Nitrogen Oxides
Base-Case Best-Case Base-Case Best-Case Base-Case Best-Case Base-Case Best-Case Base-Case Best-Case
Houston AQCR
1985
1995
Philadelphia AQCR
1985
1995
Chicago AQCR
1985
1995
NOTE 1 Tonne = 7
336.1
(370.6)
371.5
(409.6)
200.7
(221.3)
346.0
(381.5)
78.7
(86.8)
365.7
(403.2)
metric ton =
441.8
(487.1)
665.4
(733.6)
1 157.6
(1276.3)
1341.2
(1478.7)
693.9
(765.0)
1435.6
(1582.8)
1236.9
(1366.2)
2555.4
(2821.6)
1 140. 1
(1257.0)
2190.9
(2415.6)
1494. 7
(1648.0)
1700.1
(1874.4)
1384.6
(1529. 1)
5008. 1
(5530.8)
2699.6
(2976.4)
2933.8
(3234.6)
2882.2
(3177.7)
3767.5
(4153.8)
44.3
(48.8)
128.7
(141.9)
165.2
(182. 1)
393.9
(434.3)
38.6
(42.6)
373.9
(412.2)
84.6
(93.3)
303.8
(335.0)
561.0
(618.5)
731.0
(806.0)
584.8
(644.8)
1 156.0
(1274.5)
10.2
(1 1.2)
51.8
(57. 1)
98.2
(108.3)
226.6
(249.7)
13.6
(15.0)
165.7
(182.7)
27.5
(30.3)
133.2
(146.9)
310.2
(341.8)
389.3
(429.2)
257.0
(283.3)
537.1
(592.2)
1 134.9
(1251.3)
1 759.3
(1939.7)
998.7
(1101.1)
7030. 1
(7750.9)
261.2
(288.0)
1853.4
(2048.0)
1511.2
(1666.1)
3640.4
(4013.7)
4028. 1
(4441.1)
8955. 1
(9873.3)
4164.9
(4591.9)
7457. 1
(822 1. 7)
1. 102 short tons.
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Table 3. Total Displaced Emissions as Percent ofAQCR Total3
1985 (tonnes/year)
Houston Chicago
Pollutant
Particulates
Sulfur Oxides
Carbon Monoxide
Hydrocarbons
Nitrogen Oxides
Total
Tonnes/year
336.1
1236.9
44.3
10.2
1 134.9
Percent
displaced of
total emissions''
0.2
0.6
<0.1
<0.1
0.3
Total
tonnes/year
78.7
1494. 7
38.6
13.6
261.2
Percent
displaced of
total emissions13
<0.1
0.2
<0.1
<0.1
<0.1
Philadelphia
Total
Tonnes/year
200.7
1 140. 1
165.2
98.2
998.7
Percent
displaced of
total emissions1'
0.1
0.3
<0.1
<0.1
0.3
aBase-case scenario.
bBased on total 1975 emissions data for each AQCR.
active solar thermal technologies on total
AQCR emissions in the base-case in 1985
is less than one percent for each pollutant.
Under the best-case scenario, emission
reductions are never greater than two
percent of total emissions of any pollutant
Emissions reductions as a percentage of
total AQCR emissions are low, mainly
because of the large percentage of emis-
sions from market segments where solar
is not competitive, or from other sources
of emissions, such as road dust
Conclusions
For the metropolitan areas considered
in this study, emissions reductions which
occur throughout the AQCR due to solar
thermal energy development are likely to
be relatively small. The same is expected
to be true for other cities with similar fuel
costs, fuel mixes, insolation and incentives
for solar energy use. However, some other
urban areas of the country have high
insolation, which favors capture of the
energy conversion market by solar sys-
tems. Also, state and local incentives for
solar energy use are stronger in some
regions of the country, increasing the
economic attractiveness of solar systems
and their potential impact on fuel con-
sumption. The resulting emissions reduc-
tions may also be greater, but this will
depend on the fuel prices, space heating
and hot water fuel mix, and industrial mix.
Even in the three AQCR's considered
here, solar energy has the potential to
displace a small amount of fossil fuel in
certain market sectors during the next ten
to fifteen years. Solar energy is most
competitive with water heating and electric
end-uses in the residential, commercial
and public sectors. Area source emissions
reductions (which are typically difficult to
achieve) might ead to significant reduc-
tions in urban background pollutant levels.
This Project Summary was prepared by the staff of Energy and Environmental
Analysis, Inc., Arlington, VA 22209.
Benjamin L. Blaney is the EPA Project Officer (see below).
The complete report, entitled "An Assessment of the Effects of Active Solar
Thermal Technologies on Urban Emissions," (Order No. PB 83-156 927; Cost:
$13.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati. OH 45268
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