physics calculation mega watt to joules?

Question

An electric power plant that would make use of the temperature gradient in the ocean has been proposed. The system is to operate between 5.00°C (water temperature at a depth of about 1 km) and 20.0°C (surface water temperature).

(b) If the useful power output of the plant is 80.0 MW, how much energy is taken in from the warm reservior per hour?
answer is wanted in TJ/h

so 80MW at a 5.2% efficiency is 1538MW so i figured i joule per watt so 10^6 times 1538 = 1538000000 in TJ/h i dont know if i calculated that right or if its wrong because if its seconds and not hours but it says im off by orders of magnitude

Answer 1

You are assuming ideal Carnot efficiency (which won't be quite accurate, but it's an assumption to give you a lower bound at least on the energy taken).

A megawatt is one million joules per second. A terrawatt is a trillion (million million).

So multiply MJ/s by 3600 seconds per hour and by 1 T / 1 million M. It looks like you forgot to convert the seconds to hours.

Answer 2

I Watt is one Joule per second.
You seem to have forgotten to multiply by 3600 seconds in an hour.

Doug