[BLDG-SIM] Weather Normalization Question

[Joe Huang]

The US and Canadian weather services have both gone from manual to automated
observations (ASOS = Automated Surface Observing System or AWOS = Automated
Weather Observing System) starting in 1991, but most since 1997.  At this
point, I believe all stations have switched over to ASOS/AWOS.  The biggest
problem with the ASOS/AWOS data for building simulations is the lack of
observations from which solar irradiance can be estimated. There is reported
cloud cover, but this a laser observation that "sees" clouds only up to
12,000 feet.  Moreover, the correlation of this new data to the previous
manually observed cloud cover data on which almost all solar models have
been based is unknown.  Because of this problem, ASHRAE TC 4.2 (Weather
Information) initiated last year a research project to develop a method or
methods for estimating solar from either ASOS/AWOS data or from other
sources, such as satellite observations.  This project (1226-RP "Integration
of ASOS Weather Data into Building Energy Calculations with Emphasis on
Model-Derived Solar Radiation" )  is expected to be completed early next
year (2004).  Until then, people trying to do calibrated simulations using
actual year weather data will likely encounter a big data hole starting from
1997.

Joe Huang
Vice-chair of ASHRAE TC 4.2


----- Original Message -----
From: "Michael Wilson" <mwilsonbc at yahoo.com>
To: <BLDG-SIM at gard.com>
Sent: Tuesday, March 11, 2003 1:21 PM
Subject: [BLDG-SIM] Weather Normalization Question


> Regarding the first comment from Dave Robison, I've
> received the weather data in WYEC2 format from
> Environment Canada, including solar, wind, etc.
> However, the last time I had to do this was for a 1999
> weather year, and I understand that recent automation
> of the weather stations may make this data harder
> (impossible?) to come by. But without this data, how
> are you making the calibration?
>
> And although I've only calibrated a few of these, not
> hundreds, I'm not sure I'd agree that the model
> doesn't need to be detailed and it's a low cost
> simulation. If you don't put a fair bit of work into
> making sure the simulation of systems is reasonably
> similar to the operation of them, then you're not
> calibrating, you're just matching the bills. And while
> your model might line up nicely with the bills, if
> your end-uses or hourly profiles are off its not going
> to be so useful for running further simulations on.
>
> --- Dave Robison <drobison at teleport.com> wrote:
> > for the most part, I have been lurking on this group
> > because, unlike you
> > designers, our specialty is calibrated models. We've
> > done hundreds of them,
> > and there are very few doing such.
> >
> > >I order up a years worth of weather
> > >data for the most recent year and convert it to
> > Doe2
> > >format.
> >
> > I don't see how one can do that. At best, you can
> > set the actual
> > temperature data into a TMY file. But you still have
> > the old solar,
> > humidity, wind speed etc. Now those data are
> > completely incompatible with
> > the hourly set of temperatures. Or do you have
> > source for those other
> > weather data? I don't believe they are being
> > measured anymore.
> >
> > >To calibrate models to reality, you must also watch
> > out for what's
> > >included in the utility bills.
> >
> > Yes, you have to include things like parking lot
> > lights, if applicable.
> >
> >
> > >And, of course, there's the difference between how
> > equipment is supposed
> > >to operate and how it actually operates
> >
> > As-built and as-operated. That's the whole point of
> > a calibrated model. The
> > process of calibration often reveals operational
> > opportunities for further
> > savings. As such, it is a low-cost commissioning
> > tool.
> >
> > >Calibrating models entails either incredibly
> > detailed investigation of
> > >the actual building,
> >
> > nonsense. If you have only limited reference data
> > (monthly bills), you
> > don't need a detailed hourly model. A monthly
> > simulation works fine and is
> > a whole lot easier.
> >
> > >or else application of the black art of making
> > >informed guesses ("engineering judgment").
> >
> > Any modeling involves informed guesses -- eg) how do
> > you model passive
> > infiltration? At least with the calibrated model,
> > you have a reality check.
> >
> > >  In our experience, there's a
> > >significant portion of models that just won't
> > calibrate, because the
> > >actual energy use is too strange and resources to
> > investigate why are
> > >not infinite.
> >
> > Not so. The monthly bills are a cheap resource and
> > the simulation cost is
> > minimal. The only ones we have had to reject were
> > because the metering was
> > at a different level of aggregation.
> >
> >
> > >The real objective of generating reasonable energy
> > savings estimates,
> > >however, can still be met if the model is overall
> > reasonable.
> >
> > How do you define reasonable? If fact, we have found
> > that using actual
> > weather, rather than TMY, may be necessary to
> > resolve the model sufficiently.
> >
> > >  It's the
> > >delta in energy use attributable to the efficiency
> > measures of interests
> > >that matter, not necessarily tracking down all the
> > unusual quirks of
> > >utility metering and billing systems.
> >
> > Yeah, but if you don't have the building defined,
> > can you be sure of the
> > calculated delta? At least if you start with a
> > calibrated model, then move
> > off it incrementally, you have some confidence that
> > the deltas are reasonable.
> >
> >
> > >Using a whole building simulation can be a big
> > >improvement on that practice.
> >
> > Absolutely
> >
> >
> > ====================
> > David Robison
> > Stellar Processes
> > 1033 SW Yamhill Suite 405
> > Portland, OR 97205
> > (503) 827-8336
> > www.ezsim.com
> >
> >
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>
> =====
> Michael Wilson
> 455 Elphinstone Ave.
> Gibsons, BC, V0N 1V1
> 604-886-9864 phone
> 604-676-2604 fax
>
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