ME-346 Thermodynamics II

ME-346 Thermodynamics II
Project: Solar Power
Note: The input provided below is intentionally incomplete (just like in real life assignments). Missing information
can be either assumed, or (better) varied in a parametric study in EES. Clearly state any assumptions you make.
Strive to make your assumptions realistic.
Photovoltaic cell system is not the only way to convert solar energy into electricity. A competing method
is to use solar radiation to heat up a heat transfer fluid and use the hot fluid as a heat source for a Rankine
cycle heat engine to generate electricity. The objective of this project is to investigate this approach and to
maximize the thermal efficiency of the heat engine.
The assumed inputs are:
1. The goal is to generate 1 MW of electricity. Assume 95% generator efficiency. Neglect the pump
power consumption.
2. The available solar collectors can deliver the heat transfer fluid at 250 ?C (see schematic). This hot
fluid can then be used in one or more heat exchangers to provide the input heat for the heat engine.
3. The available heat sink is either the ambient air or water in a
lake, both assumed to be at 25 ?C.
4. All heat exchangers in the system are of counter-flow type (as
shown in the schematic) have negligible pressure losses, and the
approach temperature difference (at the hot end) of zero for
ideal cycle and 10 ?C for all real cycles.
5. The moisture content in the turbine cannot exceed 5%.
Your job is to investigate various heat engines based on the Rankine
cycle and to maximize the thermal efficiency. It is also desired to have
low mass flow rate through the condenser.
Part 1 – 40 points: Start with the ideal Rankine cycle with water. Try
a range of boiler pressures and calculate the thermal efficiency, mass
flow rate, quality at turbine exit and second law efficiency of the heat engine. Graph results.
Part 2 – 30 points: Repeat the analysis of Part 1, but now with more realistic assumptions of the approach
temperature differences and the isentropic efficiency of 85% for the turbine and the pump.
Part 3 – 30 points + 10 e.c. for the design with the highest efficiency: Improve the thermal efficiency of
the system in Part 2 by modifying the hardware (e.g., adding reheat, regeneration, etc.). Study textbook
examples for ideas, especially Section 8.2.3. For full credit, you need to improve the thermal efficiency
using only one of the methods. (If your team has 3 members, you must investigate two methods.) The team
with the highest thermal efficiency will receive 10 additional points of extra credit (assuming the
calculations are correct).
Part 4 (Optional: up to 20 points e.c.) – Investigate the same problem using toluene as the working fluid
(see page 397). Compare with the results for water.
Most relevant textbook material: Section 8.2.3.
General Instructions
Submit one report per team. Neat handwritten work is acceptable. Unless your hand is steady, use a ruler.
All computer files (Word, Excel, EES) should be printed out and also submitted electronically to Canvas.
The project reports should be formal, and the submission should include:
1. Project description, including hardware schematics and T-s diagrams
2. Setup for EES, including (a) assumptions made; (b) energy balances, with all systems defined
3. EES solutions and parametric studies
4. Presentation of most significant results in graphic and/or tabular form
5. Discussion of the results
6. Conclusions and recommendations
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