Open cycle gas turbine model and thermal power plant base class

docs/_toc.yml

@@ -26,6 +26,8 @@ parts:
     - file: solar_pv
     - file: battery
     - file: electrolyzer
+    - file: thermal_component_base
+    - file: open_cycle_gas_turbine
   - caption: Inputs
     chapters:
     - file: hercules_input
@@ -43,3 +45,4 @@ parts:
     - file: examples/04_wind_and_storage
     - file: examples/05_wind_and_storage_with_lmp
     - file: examples/06_wind_and_hydrogen
+    - file: examples/07_open_cycle_gas_turbine

docs/examples/07_open_cycle_gas_turbine.md

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+# Example 07: Open Cycle Gas Turbine (OCGT)
+
+## Description
+
+This example demonstrates a standalone open-cycle gas turbine (OCGT) simulation. The example showcases the turbine's state machine behavior including startup sequences, power ramping, minimum stable load constraints, and shutdown sequences.
+
+For details on OCGT parameters and configuration, see {doc}`../open_cycle_gas_turbine`. For details on the underlying state machine and ramp behavior, see {doc}`../thermal_component_base`.
+
+## Scenario
+
+The simulation runs for 6 hours with 1-minute time steps. A controller commands the turbine through several operating phases. The table below shows both **control commands** (setpoint changes) and **state transitions** (responses to commands based on constraints).
+
+### Timeline
+
+| Time (min) | Event Type | Setpoint | State | Description |
+|------------|------------|----------|-------|-------------|
+| 0 | Initial | 0 | OFF (0) | Turbine starts off, `time_in_state` begins counting |
+| 40 | Command | → 100 MW | OFF (0) | Setpoint changes to full power, but `min_down_time` (60 min) not yet satisfied—turbine remains off |
+| 60 | State | 100 MW | → HOT STARTING (1) | `min_down_time` satisfied, turbine begins hot starting sequence |
+| ~64 | State | 100 MW | HOT STARTING (1) | `hot_readying_time` (~4.2 min) complete, run-up ramp begins |
+| ~68 | State | 100 MW | → ON (4) | Power reaches P_min (20 MW) after `hot_startup_time` (~8.2 min), turbine now operational |
+| ~76 | Ramp | 100 MW | ON (4) | Power reaches 100 MW (ramped at 10 MW/min from P_min) |
+| 120 | Command | → 50 MW | ON (4) | Setpoint reduced to 50% capacity |
+| ~125 | Ramp | 50 MW | ON (4) | Power reaches 50 MW (ramped down at 10 MW/min) |
+| 180 | Command | → 10 MW | ON (4) | Setpoint reduced to 10% (below P_min), power clamped to P_min |
+| ~183 | Ramp | 10 MW | ON (4) | Power reaches P_min (20 MW), cannot go lower |
+| 210 | Command | → 100 MW | ON (4) | Setpoint increased to full power |
+| ~218 | Ramp | 100 MW | ON (4) | Power reaches 100 MW |
+| 240 | Command + State | → 0 | → STOPPING (5) | Shutdown command; `min_up_time` satisfied (~172 min on), begins stopping sequence |
+| ~250 | State | 0 | → OFF (0) | Power reaches 0 (ramped down at 10 MW/min), turbine off |
+| 360 | End | 0 | OFF (0) | Simulation ends |
+
+### Key Behaviors Demonstrated
+
+- **Minimum down time**: The turbine cannot start until `min_down_time` (60 min) is satisfied, even though the command is issued at 40 min
+- **Hot startup sequence**: After `min_down_time`, the turbine enters HOT STARTING, waits through `hot_readying_time`, then ramps to P_min using `run_up_rate`
+- **Ramp rate constraints**: All power changes in ON state are limited by `ramp_rate` (10 MW/min)
+- **Minimum stable load**: When commanded to 10 MW (below P_min = 20 MW), power is clamped to P_min
+- **Minimum up time**: Shutdown is allowed immediately at 240 min because `min_up_time` (60 min) was satisfied long ago
+- **Stopping sequence**: The turbine ramps down to zero at `ramp_rate` before transitioning to OFF
+
+## Setup
+
+No manual setup is required. The example uses only the OCGT component which requires no external data files.
+
+## Running
+
+To run the example, execute the following command in the terminal:
+
+```bash
+python hercules_runscript.py
+```
+
+## Outputs
+
+To plot the outputs, run:
+
+```bash
+python plot_outputs.py
+```
+
+The plot shows:
+- Power output over time (demonstrating ramp constraints and minimum stable load)
+- Operating state transitions
+- Fuel consumption tracking
+- Heat rate variation with load

docs/open_cycle_gas_turbine.md

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+# Open Cycle Gas Turbine
+
+The `OpenCycleGasTurbine` class models an open-cycle gas turbine (OCGT), also known as a peaker plant or simple-cycle gas turbine. Since this class is focused on peaker plant behavior, this class was developed based on aeroderivative engines. It is a subclass of {doc}`ThermalComponentBase <thermal_component_base>` and inherits all state machine behavior, ramp constraints, and operational logic from the base class.
+
+For details on the state machine, startup/shutdown behavior, and base parameters, see {doc}`thermal_component_base`.
+
+## OCGT-Specific Parameters
+
+The OCGT class provides default values for natural gas properties from [6]:
+
+| Parameter | Units | Default | Description |
+|-----------|-------|---------|-------------|
+| `hhv` | J/m³ | 39050000 | Higher heating value of natural gas (39.05 MJ/m³) [6] |
+| `fuel_density` | kg/m³ | 0.768 | Fuel density for mass calculations [6] |
+
+The `efficiency_table` parameter is **optional**. If not provided, default values based on approximate readings from the SC1A curve in Exhibit ES-4 of [5] are used. All efficiency values are **HHV (Higher Heating Value) net plant efficiencies**. See {doc}`thermal_component_base` for details on the efficiency table format.
+
+## Default Parameter Values
+
+The `OpenCycleGasTurbine` class provides default values for base class parameters based on References [1-5]. Only `rated_capacity` and `initial_conditions` are required in the YAML configuration.
+
+| Parameter | Default Value | Source |
+|-----------|---------------|--------|
+| `min_stable_load_fraction` | 0.40 (40%) | [4] |
+| `ramp_rate_fraction` | 0.10 (10%/min) | [1] |
+| `run_up_rate_fraction` | Same as `ramp_rate_fraction` | — |
+| `hot_startup_time` | 420 s (7 minutes) | [1], [5] |
+| `warm_startup_time` | 480 s (8 minutes) | [1], [5] |
+| `cold_startup_time` | 480 s (8 minutes) | [1], [5] |
+| `min_up_time` | 1800 s (30 minutes) | [4] |
+| `min_down_time` | 3600 s (1 hour) | [4] |
+| `hhv` | 39050000 J/m³ (39.05 MJ/m³) | [6] |
+| `fuel_density` | 0.768 kg/m³ | [6] |
+| `efficiency_table` | SC1A HHV net efficiency (see below) | Exhibit ES-4 of [5] |
+
+### Default Efficiency Table
+
+The default HHV net plant efficiency table is based on approximate readings from the SC1A (simple cycle) curve in Exhibit ES-4 of [5]:
+
+| Power Fraction | HHV Net Efficiency |
+|---------------|-------------------|
+| 1.00 | 0.39 (39%) |
+| 0.75 | 0.37 (37%) |
+| 0.50 | 0.325 (32.5%) |
+| 0.25 | 0.245 (24.5%) |
+
+## OCGT Outputs
+
+The OCGT model provides the following outputs (inherited from base class):
+
+| Output | Units | Description |
+|--------|-------|-------------|
+| `power` | kW | Actual power output |
+| `state` | integer | Operating state number (0-5), corresponding to the `STATES` enum |
+| `efficiency` | fraction (0-1) | Current HHV net plant efficiency |
+| `fuel_volume_rate` | m³/s | Fuel volume flow rate |
+| `fuel_mass_rate` | kg/s | Fuel mass flow rate (computed using `fuel_density` [6]) |
+
+### Efficiency and Fuel Rate
+
+HHV net plant efficiency varies with load based on the `efficiency_table`. The fuel volume rate is calculated as:
+
+$$
+\text{fuel\_volume\_rate} = \frac{\text{power}}{\text{efficiency} \times \text{hhv}}
+$$
+
+Where:
+- `power` is in W (converted from kW internally)
+- `efficiency` is the HHV net efficiency interpolated from the efficiency table
+- `hhv` is the higher heating value in J/m³ (default 39.05 MJ/m³ for natural gas [6])
+- Result is fuel volume rate in m³/s
+
+The fuel mass rate is then computed from the volume rate using the fuel density [6]:
+
+$$
+\text{fuel\_mass\_rate} = \text{fuel\_volume\_rate} \times \text{fuel\_density}
+$$
+
+Where:
+- `fuel_volume_rate` is in m³/s
+- `fuel_density` is in kg/m³ (default 0.768 kg/m³ for natural gas [6])
+- Result is fuel mass rate in kg/s
+
+## YAML Configuration
+
+### Minimal Configuration
+
+Required parameters only (uses defaults for `hhv`, `efficiency_table`, and other parameters):
+
+```yaml
+open_cycle_gas_turbine:
+  component_type: OpenCycleGasTurbine
+  rated_capacity: 100000  # kW (100 MW)
+  initial_conditions:
+    power: 0  # 0 kW means OFF; power > 0 means ON
+```
+
+### Full Configuration
+
+All parameters explicitly specified:
+
+```yaml
+open_cycle_gas_turbine:
+  component_type: OpenCycleGasTurbine
+  rated_capacity: 100000  # kW (100 MW)
+  min_stable_load_fraction: 0.4  # 40% minimum operating point
+  ramp_rate_fraction: 0.1  # 10%/min ramp rate
+  run_up_rate_fraction: 0.05  # 5%/min run up rate
+  hot_startup_time: 420.0  # 7 minutes
+  warm_startup_time: 480.0  # 8 minutes
+  cold_startup_time: 480.0  # 8 minutes
+  min_up_time: 1800  # 30 minutes
+  min_down_time: 3600  # 1 hour
+  hhv: 39050000  # J/m³ for natural gas (39.05 MJ/m³) [6]
+  fuel_density: 0.768  # kg/m³ for natural gas [6]
+  efficiency_table:
+    power_fraction:
+      - 1.0
+      - 0.75
+      - 0.50
+      - 0.25
+    efficiency:  # HHV net plant efficiency from SC1A in Exhibit ES-4 of [5]
+      - 0.39
+      - 0.37
+      - 0.325
+      - 0.245
+  log_channels:
+    - power
+    - fuel_volume_rate
+    - fuel_mass_rate
+    - state
+    - efficiency
+    - power_setpoint
+  initial_conditions:
+    power: 0  # 0 kW means OFF; power > 0 means ON
+```
+
+## Logging Configuration
+
+The `log_channels` parameter controls which outputs are written to the HDF5 output file.
+
+**Available Channels:**
+- `power`: Actual power output in kW (always logged)
+- `state`: Operating state number (0-5), corresponding to the `STATES` enum
+- `fuel_volume_rate`: Fuel volume flow rate in m³/s
+- `fuel_mass_rate`: Fuel mass flow rate in kg/s (computed using `fuel_density` [6])
+- `efficiency`: Current HHV net plant efficiency (0-1)
+- `power_setpoint`: Requested power setpoint in kW
+
+## References
+
+1. Agora Energiewende (2017): "Flexibility in thermal power plants - With a focus on existing coal-fired power plants."
+
+2. "Impact of Detailed Parameter Modeling of Open-Cycle Gas Turbines on Production Cost Simulation", NREL/CP-6A40-87554, National Renewable Energy Laboratory, 2024.
+
+3. Deane, J.P., G. Drayton, and B.P. Ó Gallachóir. "The Impact of Sub-Hourly Modelling in Power Systems with Significant Levels of Renewable Generation." Applied Energy 113 (January 2014): 152–58. https://doi.org/10.1016/j.apenergy.2013.07.027.
+
+4. IRENA (2019), Innovation landscape brief: Flexibility in conventional power plants, International Renewable Energy Agency, Abu Dhabi.
+
+5. M. Oakes, M. Turner, "Cost and Performance Baseline for Fossil Energy Plants, Volume 5: Natural Gas Electricity Generating Units for Flexible Operation," National Energy Technology Laboratory, Pittsburgh, May 5, 2023.
+
+6. I. Staffell, "The Energy and Fuel Data Sheet," University of Birmingham, March 2011. https://claverton-energy.com/cms4/wp-content/uploads/2012/08/the_energy_and_fuel_data_sheet.pdf