Converting sunlight to electricity with solar cells has an efficiency of 15%. It
ID: 1532965 • Letter: C
Question
Converting sunlight to electricity with solar cells has an efficiency of 15%. It's possible to sunlight as the hot reservoir of a heat engine. Each dish in concentrates sunlight on one a hot-reservoir temperature of 470 degree C. The cold reservoir, ambient air, is approximately efficiency of this device is 30%. achieve a higher efficiency (though currently at higher cost) by using concentrated side of a heat engine, producing 26 degree C. The actual working efficiency of this device is 30% What is the theoretical maximum efficiency? Express your answer using two significant figures. Air conditioners are rated by their coefficient of performance at 64 degree F inside temperature and 96 degree F outside temperature. An efficient but realistic air conditioner has a coefficient of performance of 3.2. What is the maximum possible coefficient of performance? Express your answer using two significant figures.Explanation / Answer
1) emax = 1-(Tc / T) = 1-(299/743) = 1-0.4024 = 0.59
2) COPmax = Tc / (Th - Tc) , Tc= (64-32)*5/9+273= 290.77 , Th= (96-32)*5/9 + 273= 308.55
COPmax = 290.77/(308.55-290.77) = 290.77/17.78 = 16.35