CHP Independent Thermal

[Bill-Becker]

This pull request introduces support for Combined Heat and Power (CHP) systems that can produce thermal energy independently of electric production, enabling modeling of technologies such as nuclear or geothermal plants. It adds new constraints, variables, results reporting, and tests for this "independent thermal" operating mode, while maintaining backward compatibility for traditional CHP. The update also includes comprehensive tests and scenario files for validation.

Independent Thermal CHP Mode Support

• Adds a new boolean field can_produce_thermal_independently and associated min/max thermal capacity fields to the CHP struct, allowing the model to distinguish between traditional and independent thermal CHP technologies. [1] [2]
• Introduces new constraints and variables in chp_constraints.jl for independent thermal operation:
  • Adds a decision variable dvThermalSize for thermal source sizing when in independent mode.
  • Implements constraints for thermal utilization, capacity bounds, and fuel burn that reflect the decoupled nature of thermal and electric production in these systems. [1] [2] [3]

Results and Reporting Enhancements

• Updates results reporting to include new keys:
  • size_thermal_kw for thermal capacity.
  • annual_thermal_production_from_source_mmbtu for total thermal output (including that used for electric generation), both only when independent thermal mode is active. [1] [2] [3]

Testing and Validation

• Adds a new scenario file (chp_independent_thermal.json) and a comprehensive test script (test_chp_independent_thermal.jl) that verifies the physics, constraints, and results for independent thermal CHP, including detailed checks on energy balances and efficiency calculations. [1] [2]
• Adds a comparison scenario and test for boiler plus steam turbine versus CHP, ensuring consistency and correctness in the new modeling approach. [1] [2]

These changes significantly extend the flexibility and accuracy of the CHP modeling framework, enabling robust analysis of advanced thermal generation technologies.