MEMORANDUM

To:	Margaret Sheppard , U.S. EPA 

From:	Emily Herzog, Veronica Kennedy, Marian Van Pelt, and Mark Wagner,
ICF International 

Date:	September 13, 2010

Re:	Summary of Updates to the Vintaging Model that Impacted HFO-1234yf
Emissions Estimates (Deliverable under EPA Contract Number EP-W-06-008
Task Order 038, Task 01)



This memorandum summarizes the updates made to the Vintaging Model (VM)
that impacted the HFO-1234yf emissions estimates used in the August 2009
[EPA-HQ-OAR-2008-0664-0037] and May 2010 versions of the revised
Assessment of the Potential Impacts of HFO-1234yf and the Associated
Production of TFA on Aquatic Communities and Local Air Quality (referred
to below as the ”TFA Assessment”).  The emissions estimates used in
the revised versions of the TFA Assessment varied slightly, as
summarized in   REF _Ref270679435 \h  \* MERGEFORMAT  Table 1  below.

Table   SEQ Table \* ARABIC  1 : HFO-1234yf Emissions Estimates from the
2009 and 2010 TFA Assessments (Metric Tons)

Scenarios	2020	2030	2040	2050

Scenario 1- MVAC  (2009)a	6,244	28,327	33,196	36,478

Scenario 1- MVAC (2010)b	6,244	28,327	33,093	35,851

% change	0.0%	0.0%	-0.3%	-1.7%



Refrigeration (2009)a	3,484	12,261	18,216	23,379

Refrigeration (2010)b	3,636	12,748	18,046	20,318

% change	4.4%	4.0%	-0.9%	-13.1%



Stationary AC (2009)a	617	2,212	3,936	4,467

Stationary AC (2010)b	620	2,221	3,931	4,447

% change	0.6%	0.4%	-0.1%	-0.4%



Scenario 2 – Sum of All Ref/AC (2009)a	10,345	42,800	55,349	64,324

Scenario 2 - Sum of All Ref/AC (2010)b	10,501	43,296	55,070	60,616

% change	1.5%	1.2%	-0.5%	-5.8%

a ICF projected emissions of HFO-1234yf using special scenarios designed
specifically for the August 4, 2009 analysis and run on the U.S. EPA
Vintaging Model, Version VM IO File v4.1 5-19-09.   

b ICF projected emissions of HFO-1234yf using special scenarios designed
specifically for the May 25, 2010 analysis and run on the U.S. EPA
Vintaging Model, Version VM IO File v4.4_12-16-09.   

The scenarios described in Table 1 are in reference to the scenarios
identified in both the August 2009 and May 2010 versions of the TFA
Assessment.  Scenario 1 and scenario 2 are defined as follows:

Scenario 1: HFO-1234yf is used in the United States as a new car
refrigerant in the MVAC sector.  HFO-1234yf begins penetrating the
market in 2016 reaching 100 percent market penetration by 2020. 

Scenario 2: HFO-1234yf is used in the United States as a new car
refrigerant in MVAC systems, refrigeration, and stationary AC systems.
Similar to scenario 1, by 2020, HFO-1234yf is used in all new MVAC
systems. For refrigeration and stationary AC systems, HFO-1234yf enters
the market in 2010, reaches 30 percent penetration of the market in
2015, and 100 percent by 2020. 

Refrigeration systems include equipment used in all refrigeration end
uses, such as household refrigerators and freezers, retail food
refrigeration, cold storage warehouses, and vending machines. 
Stationary AC systems include equipment used in all air conditioning end
uses for stationary equipment, such as chillers, residential air
conditioning and heat pumps, and dehumidifiers.  

Factors that Contributed to a Change in Emissions Estimates

Overall, changes from the 2009 estimates to the 2010 estimates were
relatively small, equaling less than 6% for all Ref/AC end-uses combined
for all projected years. The change is driven primarily by changes in
the growth rate assumed for the refrigeration end-uses. Specifically,
the updates that were made to the Vintaging Model that contributed to
this change were as follows:

For all Ref/AC end-use sectors, the annual growth estimates from
2031-2050 were updated to assume a blanket growth rate of 0.8% based on
population projection growth from the Census Bureau.  Previously, the
post-2030 growth rates were projected from the growth rates from
2010-2030.  This change had the most significant impact on the
refrigeration end-use sector due to the previously assumed average
growth rate of roughly 2.4% for all end-uses within the sector.

In addition to the VM updates, for the refrigeration and stationary AC
end-uses, the market penetration assumptions were modeled differed
slightly:  

In the 2009 version of the TFA Assessment, HFO-1234yf penetrates 30% of
the market from 2010 to 2015 in a linear transition.  

In contrast, in the 2010 version of the TFA Assessment, the transition
takes two steps.  First HFO-1234yf penetrates 6% of the market
instantaneously in 2010.  Then, another 24% transitions linearly from
2011-2015, totaling 30% market penetration by 2015.  

While the text in the 2009 version of the report indicates that the same
assumptions were used in both versions of the report, a closer look at
the model run uncovered this minor discrepancy.  As a result, the
emission estimates for years prior to 2035 for the refrigeration and
stationary AC end-use sectors are slightly higher (<5%) in the 2010
version of the TFA Assessment.  This minor difference had no impact on
emissions estimates post-2040 and therefore had no significant impact on
the outcome of the analysis.

Generally, the Vintaging Model is routinely updated to modify any of the
100+ end-uses as new data are available or new research is conducted
into end-uses.  Modeled parameters that could change for a given end-use
include growth rates, leak, service, and disposal rates, substitution
patterns, charge sizes, lifetime, and market size.  To perform off-line
analyses such as the TFA assessment, ICF builds from the version of the
Vintaging Model that was used for the most recent US Greenhouse Gas
Emission Inventory.  This Inventory version of the model is updated
annually and takes into account the years’ worth of model
improvements.

Please contact Mark Wagner at 202-862-1155 with any questions or
comments.	

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