How Energy Plus Calculates Carbon
You can give the program emission factors which are calculated based on the SITE energy, and include
within them the site to source conversion factor. Below are the emission factors that I am currently
using:
CHICAGO ELECTRICTITY
kg,
!- Units of Measure
3.546,
!- Source Energy Factor {J/J}
341.7,
!- CO2 Emission Factor {g/MJ}
0.1186,
!- CO Emission Factor {g/MJ}
0.7472,
!- CH4 Emission Factor {g/MJ}
0.6222,
!- NOx Emission Factor {g/MJ}
0.008028,
1.872,
0,
0.01739,
!- N2O Emission Factor {g/MJ}
!- SO2 Emission Factor {g/MJ}
!- PM Emission Factor {g/MJ}
!- PM10 Emission Factor {g/MJ}
0,
!- PM2.5 Emission Factor {g/MJ}
0,
!- NH3 Emission Factor {g/MJ}
0.01019,
!- NMVOC Emission Factor {g/MJ}
0.000005639,
!- Hg Emission Factor {g/MJ}
0.00002778,
!- Pb Emission Factor {g/MJ}
0.4309556,
!- Water Emission Factor {L/MJ}
0,
!- Nuclear High Level Emission Factor {g/MJ}
0;
!- Nuclear Low Level Emission Factor {m3/MJ}
PHOENIX ELECTRICTITY
kg,
!- Units of Measure
3.163,
!- Source Energy Factor {J/J}
197.2,
!- CO2 Emission Factor {g/MJ}
0.0775,
!- CO Emission Factor {g/MJ}
0.5056,
!- CH4 Emission Factor {g/MJ}
0.3333,
!- NOx Emission Factor {g/MJ}
0.004667,
1.117,
0,
0.01053,
!- N2O Emission Factor {g/MJ}
!- SO2 Emission Factor {g/MJ}
!- PM Emission Factor {g/MJ}
!- PM10 Emission Factor {g/MJ}
0,
!- PM2.5 Emission Factor {g/MJ}
0,
!- NH3 Emission Factor {g/MJ}
0.006722,
!- NMVOC Emission Factor {g/MJ}
0.000003028,
!- Hg Emission Factor {g/MJ}
0.00001494,
!- Pb Emission Factor {g/MJ}
8.251222,
!- Water Emission Factor {L/MJ}
0,
!- Nuclear High Level Emission Factor {g/MJ}
0;
!- Nuclear Low Level Emission Factor {m3/MJ}
NATURAL GAS
m3,
37631000,
!- Units of Measure
!- Energy per Unit Factor
1.092,
!- Source Energy Factor {J/J}
52.1,
!- CO2 Emission Factor {g/MJ}
0.0399,
!- CO Emission Factor {g/MJ}
0.00106,
!- CH4 Emission Factor {g/MJ}
0.0473,
!- NOx Emission Factor {g/MJ}
0.00106,
!- N2O Emission Factor {g/MJ}
0.000268,
!- SO2 Emission Factor {g/MJ}
0,
0.00359,
!- PM Emission Factor {g/MJ}
!- PM10 Emission Factor {g/MJ}
0,
!- PM2.5 Emission Factor {g/MJ}
0,
!- NH3 Emission Factor {g/MJ}
0.00261,
!- NMVOC Emission Factor {g/MJ}
0.000000111,
!- Hg Emission Factor {g/MJ}
0.000000213,
!- Pb Emission Factor {g/MJ}
0,
!- Water Emission Factor {L/MJ}
0,
!- Nuclear High Level Emission Factor {g/MJ}
0;
!- Nuclear Low Level Emission Factor {m3/MJ}
EnergyPlus gives monthly and annual emission results for CO2, NOx, SO2, PM, HG, Water, and Carbon
equivalents. This is from the EnergyPlus Engineering Reference on how Carbon equivalents are
calculated:
The Intergovernmental Panel on Climate Change has studied the effects on the relative radiative forcing
effects of various greenhouse gases. This effect, called Global Warming Potential (GWP), is described in
terms of the Carbon Equivalent of a particular greenhouse gas. This equivalent is based on a factor of 1.0
for carbon. This group of gases includes carbon dioxide (CO2), carbon monoxide, nitrous oxide, methane,
halocarbon emission, hydrofluorocarbons (HFC), perfluorocarbons (PFC), and chlorofluorocarbons
(CFC). For building energy use, the main gases of concern are carbon dioxide, carbon monoxide,
methane, and nitrous oxide. Although carbon monoxide has a relatively short life, CO emissions into the
atmosphere may have a significant impact on climate forcing due to chemical impact on CH4 lifetime, and
tropospheric O3 and CO2 photochemical production normally reacts to produce carbon dioxide, but it can’t
be ignored since it is produced in incomplete combustion and the carbon remains to interact as CO 2. Yet
there is no agreement on its carbon equivalent (IPCC 2001). The carbon equivalent of carbon dioxide,
methane, and nitrous oxide are calculated and then multiplied by their GWP on a 100 year time frame.
The Carbon Equivalents of the following gases have been determined and used in the program are
shown in the following table.
Table 65. Carbon Equivalents (IPCC 2001)
Gas
NOx
CH4
CO2
Carbon Equivalent
80.7272
6.2727
0.2727
The resulting carbon equivalents by fuel type are shown in the output of the program along
with the individual gas pollutants.
Based on the calculations used for EnergyPlus, the Carbon equivalent emissions factor in Chicago is
148.1 kg/GJ of energy and 83.9 kg/GJ in Phoenix. Natural gas is 18.0 kg/GJ of energy. So although
there is only a slightly higher fuel usage in Chicago than Phoenix, there is a significantly higher
emissions rate. Below are my results from EnergyPlus:
Site Energy
Annual CO2
Annual Carbon
Equivalents
kWh/m2
kBtu/sf
kg
lbs
kg
lbs
CHI, Conc.
111.84
35.43
5,253,310
11,581,566
2,251,995
4,964,799
CHI, Stl.
117.34
37.17
5,382,225
11,865,775
2,304,610
5,080,795
PHX, Conc.
98.51
31.20
3,332,475
7,346,850
1,413,010
3,115,010
PHX, Stl.
101.67
32.20
3,398,490
7,492,388
1,439,790
3,174,194