Carry coal to Newcastle : This phrase is an interesting idiom. Th meaning is waste your energy in some useless activities. Newcastle is full of coal mines. If you carry coal to such a place you are wasting your efforts by doing so.
Raj has a bizarre habit of reading the same novels repeatedly. It is like carrying coal to New Castle.
Raj has planned to manufacture hand oven carpets in Gujarat and sell them in Kashmir. He is trying to carry coal to Newcastle. His venture is going to be a total flop.