Environmental Conditions

Weather File Selection

The user can select a weather file for use in the prediction by clicking the title of the file. Once the user selects a file, the associated map icon will show where the weather is located, relative to the project location.

Typically, the closer the weather file is to the site location, the more representative the dataset will be to actual site conditions. A summary of each file can also be viewed along with a more detailed comparison of up to six files.

If there are no files present or the desired file is not found, the user can download or import a file by using the Add Additional Weather File feature.

HELP VIDEO Weather Selection

Key Terms

Compare Allows user to compare up to six weather files.

Weather File Upload Guide

The selection of a weather file is one of the first steps in running a prediction. PlantPredict can handle weather files of almost any granularity, from 60 minutes down to single minute granularity. PlantPredict can also handle many different weather file formats:

  • Meteonorm
  • SolarGIS
  • 3Tier/Vaisala
  • AWS
  • Clean Power Research
  • NSRDB
  • Solar Prospector
  • NREL TMY3
  • EPW

In addition to the file formats above, any reasonable excel workbook or CSV file can be uploaded and formatted during the upload process.

 

Step-by-step Process

The user can start uploading their own weather file either from 1) the weather component library, or 2) from within a prediction. In either case, the use will be taken to the following screen:

 

From here, the following steps describe how to upload the desired weather file:

  1. Click on “upload your own weather file” and select the desired file

  2. Define Locality

3. Set Parameters– These values are not required. However, it is highly encouraged to fill in these values for informational purposes

 

4. Format Data – The “meat and potatoes” of the weather file upload. Some items to note:

a) The table on the right shows all the data from the uploaded file. This step aims to trim out unwanted information not needed for the final PlantPredict weather file

b) The section on the left with “Variables” and “Timestamp” tabs contains 1) all potential variables that can be included in a PlantPredict weather file, and 2) inputs required to define the timestamps associated with the data

i) Using the “Variables” tab in the column on the left, the user first selects which variables are to be included in the PlantPredict weather file by using the check boxes. After the checkbox is selected, the user then selects in which column that variable exists in the imported file by using the drop down menu.

ii) “Header Rows to Skip” indicates how many header rows in included in the excel file. These are not to be included in the final PlantPredict weather file and are thus to be skipped

 

iii) Timestamps are not currently able to be read from columns in an imported file. Instead, when defining the parameters on the “Timestamp” tab, the user indicates 1) the Start Date and 2) the Interval Duration. The application then automatically extrapolates the end date of the file. Additionally, the user can toggle on whether to include a leap day(s) in the timestamp definition or not.

c) As a note – the minimum required data series for a PlantPredict weather file is irradience (GHI or POAI) and Temperature.

 5) Quality Check – Here the user can review all the data uploaded before the PlantPredict whether file is created. Users can also visualize how the weather data compares to the clear sky model which is especially useful for detecting timeshifts in the data. A handy data shifting feature is available for cases where a timeshift does exist to avoid having to start the process over.

 

FAQ’s, Tips and Tricks, and Troubleshooting

  • Imported files may contain neither blanks nor NULLS. If the weather file contains blanks or NULLS, fill in “0” for that entry prior to importing (the excel function “=COUNTBLANK()” can be very useful here)
  • It’s extremely easy for measured excel files to unintentionally have duplicate or missing data entries. These situations are especially tricky because an error won’t be thrown upon upload. A good way to identify this problem is to compare the projected End Date in the “Format Data” step of the upload process to the final timestamp in the excel file. If they do not match, that means there are either missing entries or extra entries in the original excel file, and the user should investigate further
  • If variables that affect spectral correction (relative humidity, dewpoint temperature, precipitable water) are not included, then spectral calculations will not be included in  predictions where this weather file is used
  • If the upload is erroring out on the first step, the application is having an issue parsing the file. Check to make sure all headers are correct and contain the correct type of information. Additionally, simplifying the imported file can many times allow for the upload to continue – one easy way of simplifying is to remove all or all-but-one header rows

Monthly Parameters

Clicking the Parameters tab will display a screen depicting monthly albedo & soiling factors, plant design temperature characteristics and horizon scene (if applicable).

All fields are editable to accommodate user defined prediction specifics such as a monthly soiling profile. An annual value is also permissible and can be entered by selecting Annual Override. The spectral profile is an override field; if no spectral input data is included with the weather file or if an alternate spectral profile is desired, the user may override with monthly loss factors.

To override, click the Spectral Override button and enter the desired monthly or annual spectral adjustment(s).

HELP VIDEO Parameters Selection

Key Terms

Spectral If no spectral input data is included with the weather file or if an alternate spectral profile is desired, enter monthly values to be used in the prediction.

Annual Locks monthly inputs and sets all monthly values to the value entered.

Plant Design Temperature

By default, the nearest ASHRAE station is used to provide default design temperatures for the site. The site design temperatures are used to recommend proper series string counts on the DC Field and to size the KVA of the inverter if an elevation and temperature derate profile is applicable.

These temperatures can be overridden to accommodate custom design temperatures.

Key Terms

Override Removes reference to default ASHRAE station temperatures and allows user defined design temperatures.

Horizon Scene

A horizon scene can be added to account for any far shading effects on the system. Clicking the Add (+) button will display an empty field for azimuth and elevation angle of the horizon point.

Repeat this process until the desired number of horizon points are added.

You can also automatically import a Horizon Scene from Meteonorm.  Click the Import Meteonorm Scene button and PlantPredict will use the Latitude and Longitude of your Project to import a Horizon Scene for your prediction.  All 360 degrees of Horizon Scene are available via the Meteonorm API; however, PlantPredict will analyze each point and only import those points where the Elevation Angle changes from the previous point.  This simplifies the scene and reduces the number of points that are required to create your Horizon Scene

Horzon Scene Import