This component reads TMY3 weather data (Wilcox and Marion, 2008) or user specified weather data.
The Modelica built-in variable time determines what row
of the weather file is read.
The value of time is the number of seconds
that have passed since January 1st at midnight (00:00) in the local time zone.
The local time zone value, longitude and latitute are also read from the weather data,
such that the solar position computations are consistent with the weather data.
The weather data format is the Typical Meteorological Year (TMY3) as obtained from the EnergyPlus web site at http://energyplus.net/weather. These data, which are in the EnergyPlus format, need to be converted as described below.
The following variables serve as output and are accessible via weaBus:
| Name | Unit | Description |
|---|---|---|
HDifHor
|
W/m2 | Horizontal diffuse solar radiation. |
HDifNor
|
W/m2 | Direct normal radiation. |
HGloHor
|
W/m2 | Horizontal global radiation. |
HHorIR
|
W/m2 | Horizontal infrared irradiation. |
TBlaSky
|
K | Output temperature. |
TDewPoi
|
K | Dew point temperature. |
TDryBul
|
K | Dry bulb temperature at ground level. |
TWetBul
|
K | Wet bulb temperature. |
celHei
|
m | Ceiling height. |
cloTim
|
s | One-based day number in seconds. |
lat
|
rad | Latitude of the location. |
lon
|
rad | Longitude of the location. |
nOpa
|
1 | Opaque sky cover [0, 1]. |
nTot
|
1 | Total sky Cover [0, 1]. |
pAtm
|
Pa | Atmospheric pressure. |
relHum
|
1 | Relative humidity. |
solAlt
|
rad | Altitude angle. |
solDec
|
rad | Declination angle. |
solHouAng
|
rad | Solar hour angle. |
solTim
|
s | Solar time. |
solZen
|
rad | Zenith angle. |
winDir
|
rad | Wind direction. |
winSpe
|
m/s | Wind speed. |
To add new weather data, proceed as follows:
epw extension from
http://energyplus.net/weather.
Buildings/Resources/weatherdata (or to any directory
for which you have write permission).
cd Buildings/Resources/weatherdata java -jar ../bin/ConvertWeatherData.jar inputFile.epwif inputFile contains space in the name:
java -jar ../bin/ConvertWeatherData.jar "inputFile .epw"This will generate the weather data file
inputFile.mos, which can be read
by the model
Buildings.BoundaryConditions.WeatherData.ReaderTMY3.
The following location data are automatically read from the weather file:
lat,
lon, and
timZone.
By default, the data bus contains the wet bulb temperature.
This introduces a nonlinear equation.
However, we have not observed an increase in computing time because
of this equation.
To disable the computation of the wet bulb temperature, set
computeWetBulbTemperature=false.
This model has the option of using a constant value, using the data from the weather file, or using data from an input connector for the following variables:
By default, all data are obtained from the weather data file,
except for the atmospheric pressure, which is set to the
parameter pAtm=101325 Pascals.
The parameter *Sou configures the source of the data.
For the atmospheric pressure, temperatures, relative humidity, wind speed and wind direction,
the enumeration
Buildings.BoundaryConditions.Types.DataSource
is used as follows:
Parameter *Sou
|
Data used to compute weather data. |
|---|---|
| File | Use data from file. |
| Parameter | Use value specified by the parameter. |
| Input | Use value from the input connector. |
Because global, diffuse and direct radiation are related to each other, the parameter
HSou is treated differently.
It is set to a value of the enumeration
Buildings.BoundaryConditions.Types.RadiationDataSource,
and allows the following configurations:
Parameter HSou
|
Data used to compute weather data. |
|---|---|
| File | Use data from file. |
| Input_HGloHor_HDifHor | Use global horizontal and diffuse horizontal radiation from input connector. |
| Input_HDirNor_HDifHor | Use direct normal and diffuse horizontal radiation from input connector. |
| Input_HDirNor_HGloHor | Use direct normal and global horizontal radiation from input connector. |
If weather data span a year, which is the default for TMY3 data, or multiple years,
then this model can be used for simulations that span multiple years. The simulation
start time needs to be set to the clock time of the respective start time. For example,
to start at January 2 at 10am, set start time to t=(24+10)*3600 seconds.
For this computation, the used date and time (here January 2, 10 am) must be expressed in the same time zone
as the one that is used to define the TMY3 file. This is usually the local (winter) time zone.
The parameter `timZon` represents the TMY3 file time zone, expressed in seconds compared to UTC.
Moreover, weather data need not span a whole year, or it can span across New Year. In this case, the simulation cannot exceed the time of the weather data file. Otherwise, the simulation stops with an error.
As weather data have one entry at the start of the time interval, the end time of the weather data file is computed as the last time entry plus the average time increment of the file. For example, an hourly weather data file has 8760 entries, starting on January 1 at 0:00. The last entry in the file will be for December 31 at 23:00. As the time increment is 1 hour, the model assumes the weather file to end at December 31 at 23:00 plus 1 hour, e.g., at January 1 at 0:00.
In HVAC systems, when the fan is off, changes in atmospheric pressure can cause small air flow rates
in the duct system due to change in pressure and hence in the mass of air that is stored
in air volumes (such as in fluid junctions or in the room model).
This may increase computing time. Therefore, the default value for the atmospheric pressure is set to a constant.
Furthermore, if the initial pressure of air volumes are different
from the atmospheric pressure, then fast pressure transients can happen in the first few seconds of the simulation.
This can cause numerical problems for the solver. To avoid this problem, set the atmospheric pressure to the
same value as the medium default pressure, which is typically set to the parameter Medium.p_default.
For medium models for moist air and dry air, the default is
Medium.p_default=101325 Pascals.
Different units apply depending on whether data are obtained from a file, or from a parameter or an input connector:
USA_IL_Chicago-OHare.Intl.AP.725300_TMY3.mos), the units must be the same as the original TMY3 file used by EnergyPlus (e.g.
USA_IL_Chicago-OHare.Intl.AP.725300_TMY3.epw).
The TMY3 data used by EnergyPlus are in both SI units and non-SI units.
If Resources/bin/ConvertWeatherData.jar is used to convert the .epw file to an .mos file, the units of the TMY3 data are preserved and the file can be directly
used by this data reader.
The data reader will automatically convert units to the SI units used by Modelica.
For example, the dry bulb temperature TDryBul in TMY3 is in degree Celsius.
The data reader will automatically convert the data to Kelvin.
The wind direction winDir in TMY3 is degrees and will be automatically converted to radians.
Pa for pressure,
K for temperature,
W/m2 for solar radiations and
rad for wind direction.
Hourly and subhourly timestamp are handled in a different way in .epw files.
From the EnergyPlus Auxiliary Programs Document (v9.3.0, p. 63):
In hourly data the minute field can be 00 or 60. In this case as mentioned in the previous section, the weather data
is reported at the hourly value and the minute field has to be ignored, writing 1, 60 or 1, 00 is equivalent.
If the minute field is between 00 and 60, the file becomes subhourly, in this case the timestamp corresponds to the
minute field in the considered hour. For example: 1, 30 is equivalent to 00:30 and 3, 45 is equivalent to 02:45.
(Note the offset in the hour digit.)
The TMY3 weather data, as well as the EnergyPlus weather data, start at 1:00 AM
on January 1, and provide hourly data until midnight on December 31.
Thus, the first entry for temperatures, humidity, wind speed etc. are values
at 1:00 AM and not at midnight. Furthermore, the TMY3 weather data files can have
values at midnight of December 31 that may be significantly different from the values
at 1:00 AM on January 1.
Since annual simulations require weather data that start at 0:00 on January 1,
data need to be provided for this hour. Due to the possibly large change in
weatherdata between 1:00 AM on January 1 and midnight at December 31,
the weather data files in the Buildings library do not use the data entry from
midnight at December 31 as the value for t=0. Rather, the
value from 1:00 AM on January 1 is duplicated and used for 0:00 on January 1.
To maintain a data record with 8760 hours, the weather data record from
midnight at December 31 is deleted.
These changes in the weather data file are done in the Java program
Buildings/Resources/bin/ConvertWeatherData.jar that converts
EnergyPlus weather data file to Modelica weather data files, and which is described
above.
The length of the weather data is calculated as the
end time stamp minus start time stamp plus average increment, where the
average increment is equal to the end time stamp minus start time stamp divided
by the number of rows minus 1.
This only works correctly for weather files with equidistant time stamps.
To read weather data from the TMY3 weather data file, there are two data readers in this model. One data reader obtains all data except solar radiation, and the other data reader reads only the solar radiation data, shifted by 30 minutes. The reason for this time shift is as follows: The TMY3 weather data file contains for solar radiation the "...radiation received on a horizontal surface during the 60-minute period ending at the timestamp." Thus, as the figure below shows, a more accurate interpolation is obtained if time is shifted by 30 minutes prior to reading the weather data.
time in the documentation.getAbsolutePath, as this causes in Dymola 2018FD01
the error
"A call of loadResource with a non-literal string remains in the generated code; it will not work for an URI."
when exporting
Buildings.Fluid.FMI.ExportContainers.Examples.FMUs.ThermalZone
as an FMU. Instead, if the weather file is specified as a Modelica, URI, syntax such as
Modelica.Utilities.Files.loadResource("modelica://Buildings/Resources/weatherdata/USA_IL_Chicago-OHare.Intl.AP.725300_TMY3.mos")
should be used.absFilNam to avoid multiple calls to
Buildings.BoundaryConditions.WeatherData.BaseClasses.getAbsolutePath.
This is for
Buildings, #506.
radHorIR to HHorIR.
This is for
#376.
weaBus.
This is for
#376.
cheTemBlaSky. This also allows to graphically
connect the black body sky temperature to the weather bus, which is required
in Dymola 2016 for the variable weaBus.TBlaSky to appear
in the graphical editor.
This is for
#377.
loadSelector
for MSL compliancy as reported by @tbeu at
RWTH-EBC/AixLib#107
connect(TBlaSkyCom.TBlaSky, weaBus.TBlaSky)
statement.
This avoids a warning if
Buildings.BoundaryConditions.SolarIrradiation.BaseClasses.Examples.SkyClearness
is translated in pedantic mode in Dymola 2016.
This is for
#266.
connect(conHorRad.HOut, cheHorRad.HIn);.
Evaluate=true.
HInfHor.
file://, modelica:// and modelica://Buildings
are added in this order to search for the weather file.
This allows using the data reader without having to specify an absolute path,
as long as the Buildings library
is on the MODELICAPATH.
This change was implemented in
Buildings.BoundaryConditions.WeatherData.BaseClasses.getAbsolutePath
and improves this weather data reader.
getAbsolutePath.
computeWetBulbTemperature=false, the computation of the
wet bulb temperature can be removed.
Revised documentation.
radHor to radHorIR and
improved the optional inputs for radiation data.
HGloHor_in in its declaration,
because this gives an overdetermined system if the input connector
is used.
Removed non-required assignments of attribute displayUnit.
pAtm_in_internal and
made propagation of parameter final.