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# Help with calculating efficiencies? Watch

1. The question I understand, it's the diagram that has me confused? The question is as follows, A thermal power station involves transfers from chemical energy to thermal energy, thermal energy to mechanical energy and then mechanical energy to electrical energy. Work out the overall efficiencies using the values given in the diagram overleaf.

I have tried doing each process so for example chemical to energy the way I see it is it is 95% efficient with 5% wasted. But I don't understand what the extra values are for like electrical to thermal because it doesn't state anything about it in the question. Help!!!
2. I think you're supposed to say

chem -> thermal 95%
thermal -> mech 40%
mech -> electric 95%

which tbh should come out somewhere in the right area for the efficiency of a real world coal burner (i.e. between 30-40%)

but it's a confusing diagram, (sankey diagrams are preferable)... I think it's trying to show that all energy inputs to the station ends up as waste heat eventually - and I'm not sure what the 7% thermal to electrical is from either.

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Updated: June 29, 2016
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