[Equest-users] PHOTOCELL-CTRL Idea/Suggestion

Pasha Korber-Gonzalez pasha.pkconsulting at gmail.com
Wed Jan 25 08:43:59 PST 2012


Hi Nick,

Interesting findings on your part.  I can offer some info regarding the
integrity of the weather files that might be useful for understanding.

My experience shows that the majority of the weather files that are still
being referenced by default in eQuest are typically a TMY file ( for the
North American locations).  TMY files were the fist set of bin files
available for use with DOE-2.  The data sets in these files include weather
data collected from 1952-1975.   Which makes the weather info in the pretty
old by comparason to the weather phenomena that we have experienced in the
present (..at least going back to the mid 1990s.)

The next version (or updated weather data sets) are referred to as TMY2
files, and this data was collected from 1961-1990.  The latest version of
data sets is referrenced as TMY3 files which was collected from 1991-2005
(note***  a consideralbly short set of data complied into bins for us  --14
years compared to 29 years for TMY2 and 23 years for TMY.)

Also, when the TMY3 versions became available they were available for
hundreds more cities in North America than before.   For example, the small
town that I live in (population less than 10,000) actually has a TMY3 data
set available because we have an airport here with collectable weather
data.   Without the TMY3 file being available if I were to simulate the
energy usage on my house or business building I would have to reference a
TMY file for either Omaha or Denver, but either of these weather choices is
not even close to being like the weather micro-climate characteristics that
we have in our rural area.  The TMY2 version of data does bring another
option for a city about 60-90 miles away from my town.   This is doable,
but with the new technology and the amount of data that is available via
internet resources and a multitude of weather stations, I was delighted to
see that a TMY3 existed for such a small place 'in the middle of nowhere'
which is how we are considered by so many people/visitors to our town.

The statement to take away from this knowledge is two-fold:  a)   the
majority of weather files still being referrenced by default in eQuest is
mostly TMY and/or TMY2 files;  and b)  the older sets of weather data were
more limited on the type of climate data that was collected during the
specific time periods noted.   THEREFORE;   in some cases you might be
experiencing a weather file/data set that is absent of the clear-ness
factors that you might be looking for & trying to reference in your
model(s).   It is also known that some weather files completely lack any
solar-type data, ground water temp data, daylighting variable factors and
such, simply due to the fact that it wasn't available in the area that
weather info was being collected for some cities.

Now recognizing that TMY-type files are only for North American locations
and more specifically USA locations, there are other types of weather files
available for other Non-USA locations.   For example; the CWEC type files
are noting Canadian locations; WYEC files which is an acronym for "weather
year for energy calculations" are representative of many other
international locations, but are typically based on the collection years
anywhere between the TMY and TMY2 eras.

Once energy-plus came about in its development it was also a new
opportunity in time to reference more updated weather files especially
since we (the world) started experienencing more significant weather
phenomena in the past 20 years.  The EPW weather files are data sets
collected more recently (I can't verify the time period from the DOE
website though), and this is what was stated about these sets of weather
data:


Weather data for more than 2100 locations are now available in EnergyPlus
weather format — 1042 locations in the USA, 71 locations in Canada, and
more than 1000 locations in 100 other countries throughout the world. The
weather data are arranged by World Meteorological Organization region and
Country.

   - Africa<http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data2.cfm/region=1_africa_wmo_region_1>(WMO
Region 1)
   - Asia<http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data2.cfm/region=2_asia_wmo_region_2>(WMO
Region 2)
   - South America<http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data2.cfm/region=3_south_america_wmo_region_3>(WMO
Region 3)
   - North and Central
America<http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data2.cfm/region=4_north_and_central_america_wmo_region_4>(WMO
Region 4)
   - Southwest Pacific<http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data2.cfm/region=5_southwest_pacific_wmo_region_5>(WMO
Region 5)
   - Europe<http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data2.cfm/region=6_europe_wmo_region_6>(WMO
Region 6)
   - Antarctica<http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data2.cfm/region=7_antarctica_wmo_region_7>(WMO
Region 7)

This is probably WAY more information than you hoped to consider, but it is
imperative to be aware of the integrity of your weather data in your
models, because sometimes we can observe interesting anomolies in our
energy models due to the lack of incorrect or missing weather information
from which we base our energy calculations on.

ALSO--on a side note, other energy modelers might be thinking----" that
doesn't seem right, when I select my location in eQuest wizard I can select
my specific city in the Wizard screens."    Yes, you can select your
specific city/town in the wizard screens of eQuest, but it may actually be
referrencing a more 'regional' weather file for the largest city/airport
location near your actual project site.   Don't be fooled by what you see
in the user interface, you will have to dig into files deeper to
specifically confirm the default weather file that is being used in your
models.  You can do this by going into DDedit mode and clicking on your
Project Name at the top of the navigation tree and then referencing the
actual .bin file name that is being used in your energy calculations.

Don't believe everything you see in your user interfaces---always go into
DOE-2 itself to confirm what is actually being used.   An additional
example of this would be using TRACE700 for Underfloor air system
simulations---I actually had a Mech Designer tell me, "TRACE can simulated
UFA systems!  I can choose the system type in the program."    I told them
no it can't specifically model these systems, they are applying
work-arounds and modified algorithms to "Represent" the sytem operation,
but TRACE700 and other sim programs including eQuest/DOE-2 do not
specifically stratify loads in the conditioned spaces to actually represent
these types of systems.   I believe that EnergyPlus is the closest
simulation software that can most accurately represent UFA & TDV systems,
and all others are fooling us by using work-a-round strategies.

Cheers,
Pasha

On Tue, Jan 24, 2012 at 11:24 AM, Nick Caton <ncaton at smithboucher.com>wrote:

> Hey all!****
>
> ** **
>
> Something new occurred to me recently triggered by a photocell scheduling
> question. ****
>
> ** **
>
> To ground and set up this idea – first check out this interesting online
> visual explaining how annual day/night hours vary based on latitude… play
> around a bit with the bars to see how daylight hours vary based on latitude
> and time of year:
> http://astro.unl.edu/classaction/animations/coordsmotion/daylighthoursexplorer.html
> ****
>
> Note that regardless of location, the yearly average on a daily basis
> always works out to 12 hours.****
>
> ** **
>
> Now take the typical case of a simple ON/OFF photocell control for
> exterior lighting.  From an exterior lighting control standpoint, the model
> linked above is simplified from reality in that the effects of cloud
> cover/weather are not accounted for.   While the sun on a given day may
> officially set at 6PM, for example, overcast cloud cover, rain, smog, fog
> and similar conditions may cause a photocell to turn on the exterior lights
> hours earlier, by reducing the daylight illumination reaching the
> photocell/ground. ****
>
> ** **
>
> Based on some explorations – the current PHOTOCELL-CTRL schedule appears
> to demonstrate something like a  “simplified” model per the above link,
> assuming clear skies.  I’m observing approximately 12 hrs of photocell
> operation per day averaged over the year for different locations’ TMY
> weather files (slightly less, actually… ~11.95).  I would assume by
> extension it’s using a function based on the location’s latitude or perhaps
> referencing something like the “sun up flag” in the weather files.  Does
> this jive with what anyone knows to be going on under the hood?****
>
> ** **
>
> If my understanding is correct, I would like to suggest a few improvements
> for present discussion and future development:****
>
> **1)      **First I think it’s worthwhile to retain the “clear sky”
> PHOTOCELL-CTRL function as it currently exists – I can conceive
> applications where a simplified “on when the sun sets” model could be both
> desirable & useful, such as in comparing output with simple daylight
> simulation models.  It could also perhaps be more specifically named
> “ASTRONOMICAL-CTRL” in reference to mechanical/digital astronomical
> timeclocks which calculate daily on/off times very much like the animated
> model linked above.****
>
> **2)      **An improved PHOTOCELL-CTRL scheduling function could be
> defined working around the following:****
>
> **a.       **It’s my understanding that weather files may contain hourly
> measured illuminance readings that inherently account for cloud cover and
> other weather conditions.  ****
>
> **b.      **Actual photocell systems will turn on and off at prescribed,
> sometimes different levels.  For example, here’s a link to a product which
> turns fixtures on at 3fc and off at 8fc, with a nominal delay to minimize
> nuisance cycling:  LINK<http://www.cooperindustries.com/content/dam/public/crousehinds/Industrial%20EX%20Products/Catalog%20PDFs/Lighting/Photocells%20for%20Champ%20HID%20Luminaires.pdf>.
> The equipment literature I’ve checked cite values from 1fc to 10fc.  ****
>
> **c.       **Per the above, an improved PHOTOCELL-CTRL scheduling option
> could accept inputs for one (possibly two) exterior footcandle levels to
> define on/off behavior.  Hourly ON/OFF behavior could then be determined
> directly referencing the exterior hourly horizontal ground illuminance
> measurement from the weather file used, switching lights when the
> appropriate threshold is crossed.****
>
> **d.      **Such a scheduling option could more accurately  gauge the
> full impact of exterior lighting retrofit and controls upgrades.  This is
> often relatively low-hanging fruit, in my experience.****
>
> ** **
>
> A related query for the weather gurus:  I’m uncertain whether TMY weather
> files, representing averaged data over many years, would be particularly
> constructive or not for representing the effects of cloud cover and so
> forth… Growing up in FL, I recall a definite “rain-season” mid-summer which
> I expect would be captured in the daylight measurements of any FL weather
> station… but where weather/cloud cover is much less regular (such as here
> in KS), perhaps the effects would be lost in averaging?****
>
> ** **
>
> Thoughts?****
>
> ** **
>
> ~Nick****
>
> ** **
>
> [image: cid:489575314 at 22072009-0ABB]**
>
> * *
>
> *NICK CATON, P.E.***
>
> SENIOR ENGINEER****
>
> ** **
>
> Smith & Boucher Engineers****
>
> 25501 west valley parkway, suite 200****
>
> olathe, ks 66061****
>
> direct 913.344.0036****
>
> fax 913.345.0617****
>
> www.smithboucher.com* *****
>
> ** **
>
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