Michael Deru ASHRAE Albuquerque, NM June 30, 2010 Better Green House Gas Calculations for Buildings NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
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Michael Deru ASHRAE Albuquerque, NM June 30, 2010 Better Green House Gas Calculations for Buildings NREL is a national laboratory of the U.S. Department.
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Michael Deru
ASHRAE
Albuquerque, NM
June 30, 2010
Better Green House Gas Calculations for Buildings
NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.
Why?
Source: Energy Information Administration, Emissions of Greenhouse Gases in the United States 2008
17.6%
19.2%
35.6%
27.6%
36.8%
Equals emissions from India
Calculating GHGs is Easy, right?
Step 1: Find a GHG calculator
Step 2: Plug in your energy use
Step 3: Done, next project
But,
Which GHG calculator should I use?
Where do the numbers come from and what do they mean?
A survey by Texas A&M found 48 GHG calculators and large differences between them
0
1,000
2,000
3,000
4,000
5,000
6,000
1
Emis
sion
s (m
etri
c to
nne)
1 State CO2e (+ precombustion)
2 State CO2
3 NERC Subregion CO2
4 State CO2e
4 State CO2e (elec. only)
5 National CO2 (elec. only)
GHG Calculator Comparisons
Credit: Michael Deru, NREL
Potential Issues in Building GHG Calculations
• Finding and interpreting emission factors• Regional variations in electric grid• Transmission and distribution losses• Time of day variations• Life-cycle emissions• On-site fuel combustion• On-site renewable energy• Accounting for electricity exports• Accounting for energy and CO2 offsets
Where do GHG Emissions Come From?
Combustion
CO2, CH4, N20Leakage
CFC, HFC, SF6
Scope-1 Emissions
Combustion
CO2, CH4, N2O
Precombustion
CH4, CO2, N2O
Scope-2 Emissions
Leakage
SF6
Scope-3 Emissions Typically only combustion emissions are
accounted for
Credit: Michael Deru, NREL
Global Warming Potential
• GWP compares the ability to trap radiant energy in the atmosphere relative to CO2 over a defined period.
100-year
CO2 1CH4 25N2O 298SF6 22,800
R11 4,750
R12 10,900
R22 1,810
404A 3,922
407A 2,107
410A 2,088
Sources: IPCC 2007 and ASHRAE 2006 Handbook
Global Warming Potential
• GWP compares the ability to trap radiant energy in the atmosphere relative to CO2 over a defined period.
Total Average of CAISOTotal Min of CAISOTotal Max of CAISO2
Recommendations
• Clearly define the project scope• Use eGRID subregion or larger region data • Include T&D losses• Include precombustion emissions• Don’t forget on-site combustion and refrigerant
leakage (if applicable)• Use time-of-day factors to evaluate load
shifting and renewable energy
Conclusions
• Can’t get exact GHG emissions• Hopefully, we can get close and understand
whether they are going up or down• Nation wide hourly and time of use emissions