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Open cycle gas turbine model and thermal power plant base class (#189)
* Add combustion turbine model * add to hybrid plant * add to utilities * add first test * add new example * add test dicts * address comment * standardize to min_stable_load_fraction * address comment * clean up state_num error checks * clean up step function * add else case * linting * fix long line * fix long line * fix comment * adjust timing * Add tests for Ct * add combustion turbine docs * Add 07 example * remove combustion turbine model * add thermal component base * add tests * update h_dict * linting * add ocgt * route ocgt * rename example * linting * update example 7 * update utilities * bugfix * add shell post-process test * update docs * Add 07 doc * Update hercules/hybrid_plant.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * harmonize comments * clarify comment * Fix comment * add warm start state and hard code start state time definitions * refactor from heat_rate to efficiency * add tests * update test defaults * linting * start shutdown behavior within on state * Fix test * docstring fix * add limit to run up ramp * remove redundant line * Update tests/thermal_component_base_test.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * clearer controller name * Update tests/thermal_component_base_test.py Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Update examples/07_ocgt/hercules_input.yaml Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Refactor states to an enum * Remove .value * Change initial condition behavior * rename fuel values * Refactor to rate * specify effiency in HHV and provide defaults * rename example 7 * linting * remove get initial conditions * add get initial conditions to base class * remove state names property * Make component_name and types to be class attributes * rename calc functions * Update with minor notes on specific turbine * Fix ruff formatting --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Co-authored-by: Genevieve Starke <genevieve.starke@nrel.gov>
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‎docs/_static/thermal_startup_ramp.svg‎

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‎docs/_toc.yml‎

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- file: solar_pv
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- file: open_cycle_gas_turbine
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- caption: Inputs
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- 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)
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## Description
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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.
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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`.
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## Scenario
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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).
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### Timeline
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| Time (min) | Event Type | Setpoint | State | Description |
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|------------|------------|----------|-------|-------------|
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| 0 | Initial | 0 | OFF (0) | Turbine starts off, `time_in_state` begins counting |
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| 40 | Command | → 100 MW | OFF (0) | Setpoint changes to full power, but `min_down_time` (60 min) not yet satisfied—turbine remains off |
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| 60 | State | 100 MW | → HOT STARTING (1) | `min_down_time` satisfied, turbine begins hot starting sequence |
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| ~64 | State | 100 MW | HOT STARTING (1) | `hot_readying_time` (~4.2 min) complete, run-up ramp begins |
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| ~68 | State | 100 MW | → ON (4) | Power reaches P_min (20 MW) after `hot_startup_time` (~8.2 min), turbine now operational |
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| ~76 | Ramp | 100 MW | ON (4) | Power reaches 100 MW (ramped at 10 MW/min from P_min) |
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| 120 | Command | → 50 MW | ON (4) | Setpoint reduced to 50% capacity |
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| ~125 | Ramp | 50 MW | ON (4) | Power reaches 50 MW (ramped down at 10 MW/min) |
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| 180 | Command | → 10 MW | ON (4) | Setpoint reduced to 10% (below P_min), power clamped to P_min |
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| ~183 | Ramp | 10 MW | ON (4) | Power reaches P_min (20 MW), cannot go lower |
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| 210 | Command | → 100 MW | ON (4) | Setpoint increased to full power |
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| ~218 | Ramp | 100 MW | ON (4) | Power reaches 100 MW |
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| 240 | Command + State | → 0 | → STOPPING (5) | Shutdown command; `min_up_time` satisfied (~172 min on), begins stopping sequence |
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| ~250 | State | 0 | → OFF (0) | Power reaches 0 (ramped down at 10 MW/min), turbine off |
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| 360 | End | 0 | OFF (0) | Simulation ends |
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### Key Behaviors Demonstrated
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- **Minimum down time**: The turbine cannot start until `min_down_time` (60 min) is satisfied, even though the command is issued at 40 min
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- **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`
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- **Ramp rate constraints**: All power changes in ON state are limited by `ramp_rate` (10 MW/min)
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- **Minimum stable load**: When commanded to 10 MW (below P_min = 20 MW), power is clamped to P_min
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- **Minimum up time**: Shutdown is allowed immediately at 240 min because `min_up_time` (60 min) was satisfied long ago
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- **Stopping sequence**: The turbine ramps down to zero at `ramp_rate` before transitioning to OFF
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## Setup
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No manual setup is required. The example uses only the OCGT component which requires no external data files.
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## Running
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To run the example, execute the following command in the terminal:
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```bash
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python hercules_runscript.py
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```
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## Outputs
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To plot the outputs, run:
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```bash
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python plot_outputs.py
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```
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The plot shows:
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- Power output over time (demonstrating ramp constraints and minimum stable load)
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- Operating state transitions
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- Fuel consumption tracking
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- Heat rate variation with load

‎docs/open_cycle_gas_turbine.md‎

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# Open Cycle Gas Turbine
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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.
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For details on the state machine, startup/shutdown behavior, and base parameters, see {doc}`thermal_component_base`.
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## OCGT-Specific Parameters
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The OCGT class provides default values for natural gas properties from [6]:
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| Parameter | Units | Default | Description |
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|-----------|-------|---------|-------------|
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| `hhv` | J/m³ | 39050000 | Higher heating value of natural gas (39.05 MJ/m³) [6] |
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| `fuel_density` | kg/m³ | 0.768 | Fuel density for mass calculations [6] |
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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.
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## Default Parameter Values
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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.
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| Parameter | Default Value | Source |
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|-----------|---------------|--------|
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| `min_stable_load_fraction` | 0.40 (40%) | [4] |
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| `ramp_rate_fraction` | 0.10 (10%/min) | [1] |
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| `run_up_rate_fraction` | Same as `ramp_rate_fraction` | — |
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| `hot_startup_time` | 420 s (7 minutes) | [1], [5] |
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| `warm_startup_time` | 480 s (8 minutes) | [1], [5] |
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| `cold_startup_time` | 480 s (8 minutes) | [1], [5] |
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| `min_up_time` | 1800 s (30 minutes) | [4] |
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| `min_down_time` | 3600 s (1 hour) | [4] |
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| `hhv` | 39050000 J/m³ (39.05 MJ/m³) | [6] |
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| `fuel_density` | 0.768 kg/m³ | [6] |
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| `efficiency_table` | SC1A HHV net efficiency (see below) | Exhibit ES-4 of [5] |
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### Default Efficiency Table
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The default HHV net plant efficiency table is based on approximate readings from the SC1A (simple cycle) curve in Exhibit ES-4 of [5]:
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| Power Fraction | HHV Net Efficiency |
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|---------------|-------------------|
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| 1.00 | 0.39 (39%) |
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| 0.75 | 0.37 (37%) |
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| 0.50 | 0.325 (32.5%) |
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| 0.25 | 0.245 (24.5%) |
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## OCGT Outputs
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The OCGT model provides the following outputs (inherited from base class):
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| Output | Units | Description |
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|--------|-------|-------------|
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| `power` | kW | Actual power output |
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| `state` | integer | Operating state number (0-5), corresponding to the `STATES` enum |
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| `efficiency` | fraction (0-1) | Current HHV net plant efficiency |
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| `fuel_volume_rate` | m³/s | Fuel volume flow rate |
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| `fuel_mass_rate` | kg/s | Fuel mass flow rate (computed using `fuel_density` [6]) |
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### Efficiency and Fuel Rate
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HHV net plant efficiency varies with load based on the `efficiency_table`. The fuel volume rate is calculated as:
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$$
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\text{fuel\_volume\_rate} = \frac{\text{power}}{\text{efficiency} \times \text{hhv}}
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$$
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Where:
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- `power` is in W (converted from kW internally)
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- `efficiency` is the HHV net efficiency interpolated from the efficiency table
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- `hhv` is the higher heating value in J/m³ (default 39.05 MJ/m³ for natural gas [6])
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- Result is fuel volume rate in m³/s
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The fuel mass rate is then computed from the volume rate using the fuel density [6]:
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$$
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\text{fuel\_mass\_rate} = \text{fuel\_volume\_rate} \times \text{fuel\_density}
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$$
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Where:
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- `fuel_volume_rate` is in m³/s
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- `fuel_density` is in kg/m³ (default 0.768 kg/m³ for natural gas [6])
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- Result is fuel mass rate in kg/s
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## YAML Configuration
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### Minimal Configuration
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Required parameters only (uses defaults for `hhv`, `efficiency_table`, and other parameters):
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```yaml
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open_cycle_gas_turbine:
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component_type: OpenCycleGasTurbine
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rated_capacity: 100000 # kW (100 MW)
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initial_conditions:
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power: 0 # 0 kW means OFF; power > 0 means ON
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```
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### Full Configuration
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All parameters explicitly specified:
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```yaml
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open_cycle_gas_turbine:
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component_type: OpenCycleGasTurbine
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rated_capacity: 100000 # kW (100 MW)
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min_stable_load_fraction: 0.4 # 40% minimum operating point
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ramp_rate_fraction: 0.1 # 10%/min ramp rate
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run_up_rate_fraction: 0.05 # 5%/min run up rate
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hot_startup_time: 420.0 # 7 minutes
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warm_startup_time: 480.0 # 8 minutes
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cold_startup_time: 480.0 # 8 minutes
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min_up_time: 1800 # 30 minutes
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min_down_time: 3600 # 1 hour
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hhv: 39050000 # J/m³ for natural gas (39.05 MJ/m³) [6]
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fuel_density: 0.768 # kg/m³ for natural gas [6]
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efficiency_table:
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power_fraction:
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- 1.0
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- 0.75
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- 0.50
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- 0.25
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efficiency: # HHV net plant efficiency from SC1A in Exhibit ES-4 of [5]
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- 0.39
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- 0.37
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- 0.325
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- 0.245
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log_channels:
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- power
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- fuel_volume_rate
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- fuel_mass_rate
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- state
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- efficiency
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- power_setpoint
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initial_conditions:
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power: 0 # 0 kW means OFF; power > 0 means ON
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```
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## Logging Configuration
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The `log_channels` parameter controls which outputs are written to the HDF5 output file.
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**Available Channels:**
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- `power`: Actual power output in kW (always logged)
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- `state`: Operating state number (0-5), corresponding to the `STATES` enum
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- `fuel_volume_rate`: Fuel volume flow rate in m³/s
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- `fuel_mass_rate`: Fuel mass flow rate in kg/s (computed using `fuel_density` [6])
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- `efficiency`: Current HHV net plant efficiency (0-1)
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- `power_setpoint`: Requested power setpoint in kW
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## References
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1. Agora Energiewende (2017): "Flexibility in thermal power plants - With a focus on existing coal-fired power plants."
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2. "Impact of Detailed Parameter Modeling of Open-Cycle Gas Turbines on Production Cost Simulation", NREL/CP-6A40-87554, National Renewable Energy Laboratory, 2024.
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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.
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4. IRENA (2019), Innovation landscape brief: Flexibility in conventional power plants, International Renewable Energy Agency, Abu Dhabi.
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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.
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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

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