5.) One renewable energy scheme involves using the temperature between ocean sur
ID: 2002027 • Letter: 5
Question
5.) One renewable energy scheme involves using the temperature between ocean surface temperature and subsurface (roughly 1000 feet deep) temperature to power a heat engine for electrical generation.
a) If the surface ocean temperature is 18oC and the temperature 1000 feet below the surface is 5 oC, calculate the ideal (Carnot) efficiency of a heat engine using this temperature difference.
b) Will the actual efficiency of such a system be greater or less than the efficiency you calculated in part a? Why?
Explanation / Answer
(a) Tc = 5oC = 278 K
Th = 18oC = 291 K
Carnot efficiency = 1 - (Tc / Th )
= 1 - (278 / 291)
= 0.0447
= 4.47 %
(b) There is LOTS of sea water! The temperature gradient in the ocean provides an abundant source of energy although the small temperature gradient means the efficiency is very low.