### Problem 4.4 - Solar Pond Hybrid
Steam Power Plant

We wish to evaluate the proposed **Solar-Pond
Steam Power Plant** shown in the following
diagram. A **solar
pond** is a large body of water having a
varying salinity gradient (halocline) which traps the sun's energy
such that the storage layer at the bottom of the pond can reach
temperatures of greater than 100°C. The diagram following shows the
initial design of a low pressure solar-pond steam power plant, using
the storage layer as the boiler heat source, and the upper layer as
the heat sink. Notice the wood-fired superheater in which the steam
at the outlet of the boiler is heated from 100°C to 250°C.

1) Neatly sketch the
complete cycle on the pressure-enthalpy *P-h*
diagram below, indicating clearly all 5 stations on the diagram.

2) Using steam
tables, and assuming that the turbine is adiabatic, determine the
power output of the turbine [976kW].

3) Assuming that the
feedwater pump is adiabatic, and that the compressed liquid
experiences no change in temperature while passing through the pump,
determine the power required to drive the pump [0.23kW].

4) Using steam
tables, determine the heat transferred to the boiler [6210kW]
as well as the heat transferred to the superheater [747kW].

5) Determine the
overall thermal efficiency η_{th}
of this power plant [14%].
(Thermal efficiency is defined as the net work done by the system
(turbine and feedwater pump) divided by the total heat supplied
externally).

6) Discuss the proposed system with respect to
its environmental impact and feasibility. Is this a well designed
system? What do you consider to be the major advantages and
disadvantages of this system? Your discussion should include a
comparison of the external fuel used and the turbine power, as well
as the practical aspects of maintaining a system with a low pressure
of 10kPa.

*Justify* all values used
and *derive* all
equations used starting from the basic energy equation for a flow
system.

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Engineering Thermodynamics by Israel
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