1) Obtain local solar data:
- Find the GPS coordinates of your birthplace or some other unique location using Google Earth, Yahoo Maps, or any other similar software.
Download solar radiation data:
Go to the following websites and download the hourly Direct Normal Radiation data for the cell nearest your birthplace. Enter “5” for the time zone. The data should download as a .csv file. Data: http://rredc.nrel.gov/solar/new_data/India/nearestcell.cgi
If your GPS coordinates are not in the right format, go to a website such as the one below to convert it to the correct format. www.csgnetwork.com/gpscoordconv.html
After downloading the correct data, the data file will open using WinRAR. Documentation for how to interpret the data is at: http://rredc.nrel.gov/solar/new_data/India/about.html
It's worthwhile to download and read the "Users Manual for TMY3 Data Sets" on the above page.
"Field Number" is the same as the "Column" in Excel. For example, Field Number 1 is Column A in Excel, or the Date. Field Number 5 is Column E in Excel, or the Global Horizontal Irradiation, Field Number 8 is Column H in Excel, or the Direct Normal Irradiation, and Field Number 11 is the Diffuse Horizontal Irradiation.
Each year of data is in a separate data file. Column A will display properly by making the column wider. You only need to use columns A, B, E, H, and K. The rest of the data you can hide or delete.
- Import the data into spreadsheet and data analysis software, such as Microsoft Excel / LibreOffice / OpenSpreadsheet or a similar program. If the data does not open automatically, you may have to “Import” the data as a “comma separated values (csv)” file. Check your software options or read on the internet how to do this. Once the data is imported, take the headers from the documentation page above and paste them into the spreadsheet above the data. You may have to insert a line above the data to make room for these values. If the date is Column 1, then the DNI data that you want is in Column H.
- Save your spreadsheet. Open a new worksheet. For each year of the data, copy and paste the data for your birthdate into the new worksheet. Make sure the header values are copied. Delete or hide the unnecessary data so that you are able to easily look at just the Direct Normal Irradiance Data.
2) Determine the following values:
- Average hourly Direct Normal Irradiation (DNI) - you should get one data value for each hour of the day. Average over all years of data to get the most accurate results.
- Average daily DNI
3) Plot the hourly Direct Normal Irradiation (DNI) using the Graph functions. (Time of day should be your x-axis, Irradiance should be your y-axis).
Caution: In some software packages, you may have to use the “Average” function to omit hidden data from your calculations.