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<< Click to Display Table of Contents >> Conversion protocol |
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(go directly to our Notes on Meteo)
The format file defines all characteristics governing the custom source file reading (Meteo or Measured data files).
The format of the source-file may be very varied; however it has to fulfil the following minimal criteria:
| - | Include the values of one time step (hourly or sub-hourly) per text line. Each line ends with the characters CR,LF, or only LF. Sub-hourly records are gathered in order to give PVsyst hourly internal records. |
| - | Comment lines at the beginning of the file, or of each day or month, can be skipped. |
| - | Data are organized in columns, with a chosen separator (semi-colon, comma, TAB, blank, etc. ) or fixed widths. PVsyst accepts a great variety of date formats, and adjusts the source data physical units. |
| - | The available parameters should include the minimal data which allow the calculation of the horizontal global and the ambient temperature. Since simulation also requires the horizontal diffuse irradiation, this is calculated, for example, horizontal global and beam data. If not available, the diffuse irradiation is reconstituted using the Erbs correlation. |
| - | With measured data, if only the irradiation in the collector plane is available, the program calculates the corresponding horizontal global and diffuse (inverse of the transposition). Nevertheless, due to edge effects, these data will only be valid within the original collector plane. |
| - | Usually the values are consecutive; but if values are missing on the source file (for example night values), the date should be explicitly mentioned on each line of data. Given that the internal file must hold complete days, the data for any missing hour will be completed with zero irradiation values, and with stable temperatures after the last available reading. |
| - | Gaps of more than one day may be acceptable with the option of writing the date for each reading on the internal file. |
| - | It is also possible to automatically chain data monthly or daily files, provided that their name include exploitable identification code (date). |
The standard separator | is the field separator you defined in the general characteristics.
The / character may be one (or several) non-numeric characters.
The values between parenthesis are optional. If months (MM) or year (YY) are not present in the data, put their field number to zero.
The format protocol specifies "sequential dates".
i.e. data are assumed to be contiguous, without any holes.
In this case the program does not read the date on the file, and the beginning date must be supplied by the user.
The internal PVsyst meteo data - in Legal Time - does not take the "Summer Time" hour shift (also called "Daylight Savings Time") into account: the hour is related to the original Time Zone (usually "Winter Time") all over the year.
When importing meteo data, the source data could include such a shift, which has to be corrected.
The shifting dates are never fixed, but obey to rules which may be different in some regions of the world.
PVsyst proposes default settings according to the location of the geographical site :
| - | Europe: the passage to summer time arises on the last Sunday of March, and to Winter time on last Sunday of October at 01:00 in the morning. |
| - | US: the passage to summer time arises on the second Sunday of March, and to Winter time on first Sunday of November at 02:00 in the morning. |
| - | Other: the passage to summer time arises on the first of March, and to Winter time on first of November at 01:00 in the morning. |
The user will be invited to check/correct these dates at each conversion, as they will depend on the year.
NB: Please carefully check the results on daily plots after conversion, i.e. the shift of the hourly data with respect to the Clear Sky model !
Please choose the available variables in the data, and define their field number and multiplicator.
You may also gather several measured data channels in one only PVsyst variable (for example: add several arrays, or calculate energy from available voltage and current). To do this:
-First choose the target PVsyst variable in the list.
-Then choose "Gathering fields" tab, choose this variable and define the number of channels and the operator.
-This will duplicate the corresponding variables in this list, so that you can define a data channel for each one.
When importing a variable, it gives you the choice of the units. Internally, PVsyst will compute the right multiplier to obtain the unit needed for simulation.
If you are recording data with a data-logger, you might want to add a multiplier to your measurements to obtain the right unit (e.g. if you are measuring a reference cell that has a certain tension per irradiance - V / W/m2). This multiplying factor will be applied to your data, in order to obtain values in the units waited by the program.
If your source file is recorded with a time step less than one hour, you have to specify if the data are in Power (ex. [W/m2 ]) or in Energy (ex. [ kJ/m2 ], [Wh/m2]).
With power measurements the interpreter performs an average over the hour.
With energy measurements it will perform a sum.
To gather several variables, you have to :
-Choose the preceding tab "Measured variables", and choose among the available PVsyst variables in the listbox,
-Then come back to this tab, select this variable and define the number of channels and the operator.
-This will duplicate the corresponding variables in this list of the preceding tab, so that you can define a data channel for each one.
As imported data are in daily values, the program has to split them into hourly values. It may do this in two ways:
-By constructing a smooth distribution proportional to the Clear Day model (that is: a clear day with reduced amplitude according to the required daily sum).
-By generating a random distribution according to the Markov matrices, in the same way as when generating synthetic data.
The second method is more realistic, but global simulation results are not very different.
Doubtful data may be eliminated from the simulation / comparison process and accumulations, either in comparison plots, or in the tables.
A Flag code indicates how the elimination was done:
Eliminations in the original measured data table:
0000 0001 : Hourly elimination,
0000 0010 : Daily elimination,
Eliminations in meas-simul. comparison plots:
0000 0100 : Mouse elimination in hourly plot
0000 1000 : Mouse elimination in daily plot
0001 0000 : Limits on measured values
0010 0000 : Limits on simulated values
0100 0000 : Limits on differences meas.-simul. data
1000 0000 : Limits on ratios meas./simul. Data
Yellow lines in tables indicate missing data in the original file.