I 64% n.th + COP4 = more heat out of fuel than its calorific value?

  • Thread starter Thread starter cmb
  • Start date Start date
  • Tags Tags
    Fuel Heat Value
Click For Summary
A CCGT generating power at 64% efficiency combined with a COP4 heat pump suggests a theoretical output of 256% thermal energy from the fuel's calorific value, raising questions about the source of the extra heat. The discussion highlights that while this seems counterintuitive, it is explained by the heat pump's ability to transfer environmental heat, not create energy. The concept of Coefficient of Performance (COP) is clarified as a measure of efficiency that can exceed 100%, which does not violate thermodynamic laws. The conversation also explores the potential for directly harnessing combustion temperatures to capture additional heat without electrical generation. Overall, the principles of energy transfer and thermodynamics are central to understanding these efficiencies.
cmb
Messages
1,128
Reaction score
128
TL;DR
If a CCGT generates electrical power at 64% efficiency, and a heat pump generates 4 times the thermal power to electrical power, is that more heat energy out than the fuel has?
Something that has been on my mind a while.

If a CCGT generates electrical power at 64% efficiency, and a COP4 heat pump, powered by that generator, generates 4 times the thermal power to electrical power, wouldn't that mean we can get 256% heat out of the fuel's calorific value?

Maybe that is OK, but seems non-intuitive.

Where does the extra heat come from, or what am I not understanding?

I presume the answer is that because we're going from 'very hot' heat to colder heat, we can suck up some of the environmental heat? If so, is there not a more direct way to use the combustion temperature from a burning fuel to directly suck in extra heat from the environment, missing out the electrical generation bit?
 
Physics news on Phys.org
Short summary of @Llewelyn 's point: COP is like efficiency, but it is not efficiency. It is always way over 100%. That's not a violation of the laws of thermo. The energy isn't being created, just moved, and there are hard restrictions on the available temperature deltas.
 
Thread 'Why higher speeds need more power if backward force is the same?'

Thread 'Why higher speeds need more power if backward force is the same?'

Power = Force v Speed Power of my horse = 104kgx9.81m/s^2 x 0.732m/s = 1HP =746W Force/tension in rope stay the same if horse run at 0.73m/s or at 15m/s, so why then horse need to be more powerfull to pull at higher speed even if backward force at him(rope tension) stay the same? I understand that if I increase weight, it is hrader for horse to pull at higher speed because now is backward force increased, but don't understand why is harder to pull at higher speed if weight(backward force)...
View full post »

Similar threads

I Can Self-Running Heat Pumps Revolutionize Home Efficiency?
  • · Replies 7 ·
Replies
7
Views
3K
B Can a Heat Pump and Stirling Engine Create a Perpetual Energy Cycle?
  • · Replies 6 ·
Replies
6
Views
3K
Synhelion -- Using solar heliostat farms to create liquid fuels from Water Vapor and CO2
  • · Replies 7 ·
Replies
7
Views
2K
A practical way to vaporize fuel for high MPG?
  • · Replies 35 ·
2
Replies
35
Views
2K
How can energy lost due to expansion be minimized in heat engines and ships?
  • · Replies 2 ·
Replies
2
Views
2K
Modeling a kongming lantern (sky lantern)
  • · Replies 6 ·
Replies
6
Views
2K
How Does Fuel Composition Affect Combustion Efficiency and Steam Generation?
  • · Replies 9 ·
Replies
9
Views
8K
Heating efficiency of a Heat Pump and a Space Heater
  • · Replies 1 ·
Replies
1
Views
2K
Heating a Cabaret during the winter
  • · Replies 4 ·
Replies
4
Views
1K
Possible webpage title: How Does Condensing Water Improve Furnace Efficiency?
  • · Replies 1 ·
Replies
1
Views
1K