Converting sunlight to electricity with solar cells has an efficiency of 15%. It
ID: 1289726 • Letter: C
Question
Converting sunlight to electricity with solar cells has an efficiency of 15%. It's possible to achieve a higher efficiency (though currently at higher cost) by using concentrated sunlight as the hot reservoir of a heat engine. Each dish in (Figure 1) concentrates sunlight on one side of a heat engine, producing a hot-reservoir temperature of 490 degrees C . The cold reservoir, ambient air, is approximately 30 degrees C. The actual working efficiency of this device is 30%.
What is the theoretical maximum efficiency?
Explanation / Answer
To convert from degrees Celsius to Kelvin, add 273.15. (It's just "Kelvin," not "degrees Kelvin.")
The cold temperature:
T_C = 30 degC = 303.15 K
The hot temperature:
T_H = 490 degC = 763.15 K
The Carnot efficiency:
eff = 1 - (T_C / T_H) = 1 - (303.15 K / 763.15 K) = 0.6028
So the theoretical maximum efficiency is 60.28%.