### 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 ηth 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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