06-10-2016, 11:40 AM
1457982540-5.EnergyEfficiency.ppt (Size: 781.5 KB / Downloads: 15)
Efficiency of Energy Conversion
If we are more efficient with the energy we already have there will be less pollution, less reliance on foreign oil and increased domestic security.
Heat Engine
A heat engine is any device which converts heat energy into mechanical energy.
Accounts for 50% of our energy conversion devices
Illustration
For a coal-fired utility boiler, The temperature of high pressure steam would be about 540°C and T cold, the cooling tower water temperature would be about 20°C.
Calculate the Carnot efficiency of the power plant
Inference
A maximum of 64% of the fuel energy can go to generation. To make the Carnot efficiency as high as possible, either T hot should be increased or T cold should be decreased.
Consequences
For every watt of power used to drive this ideal heat pump, 13.3 W is delivered from the interior of the house and 12.3 from the outside.
Theoretical maximum is never achieved in practice This example is not realistic. In practice, a C.O.P in the range of 2 - 6 is typical