I am reposting a recent reply I made on the eQuest_Users bulletin board
explaining the status of California Energy Commission's new weather
files for Title-24 compliance, because I thought it might be of interest
to other modelers who might be doing work in California.
Joe Huang
Michael,
Your first statement is not quite correct. The California Energy
Commission had commissioned in 2009 the creation of a new set of
standard weather files to replace the pre-existing 16 CZXXRV2 weather
files, for which I was the contractor. This work, which was finished in
December 2011, resulted in a set of 86 CZ2010 weather files and are
available for public download on my company Web site at
http://weather.whiteboxtechnologies.com, click on CZ2010 (all files
contain the same weather file in three formats - archival *.TM2,
*.EPW, and *.BINM).
The California Energy Commission has yet to decide whether to allow the
use of all 86 weather files in Title-24 calculations, or to limit it to
a subset of 16, i.e., one standard file per Climate Zone as before.
From a technical point of view, I strongly support the former position,
although there are administrative issues that need to be addressed to
avoid creating confusion or "gaming the system" that I hope the
Commission will address in the coming year.
As an interim place-holder, I worked with the Commission staff and
consultants in late 2011 to assign representative locations out of the
86 for each of the 16 Title-24 Climate Zones. This list was shown at a
Nov. 2011 workshop in Sacramento (see attached, full PPT available on
the Commission Web site - search for "Huang Weather Data Presentation")
and is probably the basis for what you've heard about the CZ08 file
changing from El Toro to Fullerton.
Although I am not violently opposed to such an interpretation, I do wish
to mention the following caveats:
1) the pre-existing CZXXRV2 weather files were adjusted in the early
1990's (that's the reason for the RV2 designation) to be more
representative of the climates within each Climate Zone; therefore, it's
incorrect to refer to any of them as being from a specific location,
i.e., CZ08RV2 != El Toro.
2) the new CZ2010 weather files have not undergone any such adjustment
process (nor would I recommend so doing), and should be regarded as
"representative" rather than "average" weather files for each Climate
Zone, selected based primarily on population and only secondarily on
climate considerations.
The last point I want to make is that the CZ2010 files are different
from the TMY3 weather files for the same stations in many ways:
1) uniform period of record (1996-2009)
2) uniform typical months for all 86 stations
3) solar radiation from remotely-sensed data, i.e., satellite-derived
4) different software used to fill missing data
So, to make a long story short, if you're concerned about the
Commission's change in standard weather data, please download the new
CZ2010 weather files at http://weather.whiteboxtechnologies.com/CZ2010
Joe Huang
