#Google Sheets, 76 bytes

 =ArrayFormula(Join(,Text(Code(Mid(A1,Row(Indirect("1:"&Len(A1))),1))-96,"00"

Sheets will automatically add three closing parentheses when you exit the cell. 
Input is in cell `A1`


`Indirect("1:"&Len(A1))` returns a range as tall as the input is long. 
`Row(Indirect(~))` returns the row numbers, so it's a list of numbers from 1 to the input length. 
`Mid(A1,Row(~),1)` returns each character from the input, one at a time. 
`Code(Mid(~))-96` returns the ASCII code for each character, down-shifted so `a` = `1`. 
`Text(Code(~),"00")` pads the result above to two digits. 
`Join(,Text(~))` joins all those padded results without a delimiter. 
`ArrayFormula(Join(~))` makes all the stuff above operate on arrays. Without, the result would just be the first padded alphabet code: `helloworld` would return `08`.

[![Example][1]][1]


 [1]: https://i.sstatic.net/V9Rgz.png