The electrical (power) and CHP efficiencies feature opposite trends
with increasing the steam generation pressure. These are plotted in
Fig. 13. It can be seen that, by increasing the steam generation
pressure, the electrical efficiency increases and the CHP efficiency
decreases simultaneously. This can be easily explained using
thermodynamic reasoning. At fixed steam exhaust pressure, by
increasing the inlet one, the driving force for energy conversion—
the pressure differential between the steam turbine interfaces,
grows. It is clear that the larger this driving force is, the
larger is the potential to generate power and at the same time the
energy dissipation (losses) also increases due to the increasing
‘‘irreversibility’’ of the process.