EGEE 102
Energy Conservation for Environmental Protection

Entropy and Quality of Energy

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Let’s look at an example of how temperature differences are used to generate power. Power plants convert chemical energy into electrical power. Here is a video overviewing the operation of a geothermal energy system, a classic thermal power generation plant.

Below are two temperature scales. The scale labeled "HOT," shows the range of temperatures for the combustion of gases in a power plant. The scale, "COLD," shows the range of temperatures at which gases are exhausted from the power plant.

Scales showing combustion temperatures ranging from 350 to 1,000 degres C and exhaust gases ranging from 100 to 300 degrees C.
Power Plant Temperatures: red indicates power plant combustion temperatures and blue indicates exhausted gas temperatures.

Instructions: Look carefully at the efficiency numbers in the body of the table. How do the Hot and Cold temperatures' effect on the efficiency.

Power Plant Efficiency
Hot
350°C
Hot
400°C
Hot
500°C
Hot
600°C
Hot
700°C
Hot
800°C
Hot
900°C
Hot
1,000°C
Cold
300°C
8 15 26 34 41 47 51 55
Cold
250°C
16 22 32 40 46 51 55 59
Cold
200°C
24 30 39 46 51 56 60 63
Cold
150°C
32 37 45 52 57 61 64 67
Cold
100°C
40 45 52 57 62 65 68 71

Answer the following questions based on the information in the Power Plant Efficiency table above.