## Solved Problem 7.1 - Exergy Analysis of a
Geothermal Power Plant

Assume that a village has discovered an underground
geothermal well containing water at 95°C, 100m below the surface.
They are evaluating the option using the water from this well to
provide power to the village. Determine the maximum available work
[kJ/kg] that could be obtained from a power plant that will pump
water from the well, extract energy from the water and discharge the
water to a lake at the surrounding temperature T0 = 25°C. Assume
that the water temperature can be reduced to 35°C at the outlet of
the power plant.

We now do an Exergy Analysis to determine the maximum
available (reversible) work by eliminating q from the above Energy
and Entropy equations:

This equation could have been derived directly from
the definition of exergy:

Finally, we obtain our numerical answer by
considering the question "**What**" above, in
which we substitute the enthalpy (h) and entropy (s) values for
liquid water, an incompressible liquid:

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