# Gasturbine energy balance

I have a question regarding gasturbine energy balance,

the total energy that flows into the gasturbine is given 12 MW and the power needed for the compressor is 4.4 MW and the turbine power is 9.3 MW. So the net output is 9.3-4.4 = 4.9 MW which is around 40% efficiency.

But what happened to the 12-9.3 = 2.7 MW, where it is lost ?

It also says, 60% losses but actually 4.4 MW of the turbine power is needed to run the Compressor which I dont think is a loss, how would you explain this ?

At last, how do I create a Sankey Diagram of this energy flow ?

• Are these numbers are of ideal gas turbine? I calculated efficiency based on your numbers, turns out it's efficiency is 64.47% (not included any frictional or combustion losses). – SRD Apr 12 '19 at 23:07

energy flow rate towards turbine after compression and combustion is 12MW (chemical energy of fuel + compression energy of compressor). Energy extracted by turbine is 9.3MW. Efficiency of turbine 9.3(output) / 12(input) * 100 = 77.5%

rest of the energy flow 12MW - 9.3MW = 2.7 MW is in outgoing hot gases / rejected heat to environment.

The energy to drive the compressor is Work ie not useful output. Remember Q - W is change in internal energy.

Any engine « burning » or combusting fuel is not 100% efficient - internal combustion engines are between 20 and 40% efficient.

So, other losses such as friction, unburnt fuel, losses due to clearances etc The first and second laws of thermodynamics always apply: you can change energy from one form to another, but you never get all of it...

Now have a look at the following pic. you should get a fair understanding of your question: 