Auction when player has not enough money to buy?
No he is not.

According to the rules (Pdf):


  The player chooses one power plant from the actual market (top row) and then makes a bid to purchase it (the player must bid at least the minimum bid (number of the
  power plant), but may start with a higher bid.


The player starting the auction must start with the opening bid.

If he wins the bid he must pay the bank:


  He pays his highest bid to the bank and takes the power plant.


This implies that one must have enough money for the bid.