Problem
Evaluate four performance improvement pathways for a Chevron combined cycle cogeneration facility and quantify the energy output, efficiency, and cost impact of each upgrade scenario. The goal was to identify which modifications offered the best return relative to capital and operational tradeoffs.
Approach
Full thermodynamic modeling of the Brayton cycle combined cycle cogeneration facility using EES (Engineering Equation Solver) across four upgrade cases. Each case modified a single facility parameter and held all other conditions equal for direct comparison.
- Baseline: Brayton gas turbine driving a steam Rankine bottoming cycle with cogeneration extraction. Reference state for all comparisons.
- Case 1 (Evaporative cooler): Inlet air cooling sized for Golden, CO October conditions at 85% effectiveness. Lowers compressor inlet temperature to increase mass flow and power output.
- Case 2 (OEM turbine upgrade, T7 = 2,100 degrees Fahrenheit): Raises turbine inlet temperature to increase power output. NOx emissions concern noted at elevated temperature.
- Case 3 (Finer inlet filter, 2 psi pressure drop): Traces the compressor isentropic efficiency increase required to offset the additional pressure drop with no net power penalty.
- Case 4 (Steam reheat): Addition of a reheat stage to the steam bottoming cycle. Increases cycle thermal efficiency and reduces duct burner natural gas demand.
Results
| Case | Net Power | Thermal Efficiency | Delta vs. Baseline |
|---|---|---|---|
| Baseline | 42.78 MW | 32.72% | reference |
| Case 1 (Evap cooler) | 45.12 MW | 33.05% | +2.35 MW |
| Case 2 (OEM upgrade) | 44.45 MW | 32.96% | +1.67 MW |
| Case 3 (Finer filter) | 42.78 MW | 32.72% | 0 net |
| Case 4 (Steam reheat) | 42.78 MW | ~37.74% | efficiency gain |
Case 1 payback: approximately 75 days continuous on $1,000,000 capital. Case 3 requires compressor efficiency to increase from 84.02% to approximately 92.25% (a 4.3% gain) to offset the filter pressure drop with no power penalty. Case 4 reduces duct burner demand by 70%, generating approximately $2.08M per year in natural gas savings and approximately 30,000 tonnes CO2 per year reduction.
My Role
Partner project with Noah Whitaker. I contributed EES code development for the four cases, thermodynamic cycle validation, and the executive summary report.