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Add initial coal plant model (#226)
* Add initial coal plant model * Update docs and example * Add tests * Update controller to scale with total simulation time * Update hercules runscript doc strings * Example number update * Update documentation
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‎docs/hard_coal_steam_turbine.md‎

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# Hard Coal Steam Turbine
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The `HardCoalSteamTurbine` (HCST) class models a hard coal power production plant using steam turbines. This class 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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Set `component_type: HardCoalSteamTurbine` in the component's YAML section. The section key is a user-chosen `component_name` (e.g. `hard_coal_steam_turbine`); see [Component Names, Types, and Categories](component_types.md) for details.
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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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## HCST-Specific Parameters
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The HCST class provides default values for bituminous coal properties from [4]:
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| Parameter | Units | Default | Description |
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|-----------|-------|---------|-------------|
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| `hhv` | J/m³ | 29310000000 | Higher heating value of bituminous coal (29.31 MJ/kg) [4] |
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| `fuel_density` | kg/m³ | 1000 | Fuel density for mass calculations |
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The `efficiency_table` parameter is **optional**. If not provided, default values based on approximate readings from the [2] 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 `HardCoalSteamTurbine` class provides default values for base class parameters based on References [1-4]. 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` | 0.30 (30%) | [2] |
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| `ramp_rate_fraction` | 0.03 (3%/min) | [1] |
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| `run_up_rate_fraction` | Same as `ramp_rate_fraction` | — |
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| `hot_startup_time` | 7.5 hours | [1] |
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| `warm_startup_time` | 7.5 hours | [1] |
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| `cold_startup_time` | 7.5 hours | [1] |
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| `min_up_time` | 48 hours | [2] |
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| `min_down_time` | 48 hours | [2] |
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| `efficiency_table` | Average plant efficiency | [2,3] |
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### Default Efficiency Table
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The default HHV net plant efficiency table is based on [2,3]:
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| Power Fraction | HHV Net Efficiency |
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|---------------|-------------------|
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| 1.00 | 0.35 (35%) |
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| 0.5o | 0.32 (32%) |
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| 0.30 | 0.30 (30%) |
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## HCST Outputs
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The HCST 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` |
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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
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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:
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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
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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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hard_coal_steam_turbine:
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component_type: HardCoalSteamTurbine
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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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hard_coal_steam_turbine:
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component_type: HardCoalSteamTurbine
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rated_capacity: 500000 # kW (500 MW)
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min_stable_load_fraction: 0.3 # 30% minimum operating point
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ramp_rate_fraction: 0.03 # 3%/min ramp rate
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run_up_rate_fraction: 0.02 # 2%/min run up rate
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hot_startup_time: 27000.0 # 7.5 hours
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warm_startup_time: 27000.0 # 7.5 hours
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cold_startup_time: 27000.0 # 7.5 hours
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min_up_time: 172800 # 48 hours
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min_down_time: 172800 # 48 hour
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hhv: 29310000000 # J/m³ for bituminous coal (29.31 MJ/m³) [4]
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fuel_density: 1000 # kg/m³ for bituminous coal
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efficiency_table:
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power_fraction:
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- 1.0
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- 0.50
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- 0.30
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efficiency: # HHV net plant efficiency, fractions (0-1)
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- 0.35
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- 0.32
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- 0.32
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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
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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. IRENA (2019), Innovation landscape brief: Flexibility in conventional power plants, International Renewable Energy Agency, Abu Dhabi.
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3. T. Schmitt, S. Leptinsky, M. Turner, A. Zoelle, C. White, S. Hughes, S. Homsy, et al. “Cost And Performance Baseline for Fossil Energy Plants Volume 1: Bituminous Coal and Natural Gas Electricity.” Pittsburgh, PA: National Energy Technology Laboratory, October 14, 2022b. https://doi.org/10.2172/1893822.
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4. 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

‎examples/08_hard_coal_steam_turbine/hercules_input.yaml‎

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# Input YAML for hercules
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# Explicitly specify the parameters for demonstration purposes
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# Name
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name: example_08
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###
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# Describe this simulation setup
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description: Hard Coal Steam Turbine (HCST) Example
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dt: 60.0 # 1 minute time step
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starttime_utc: "2020-01-01T00:00:00Z" # Midnight Jan 1, 2020 UTC
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endtime_utc: "2020-01-10T00:00:00Z" # 10 days later
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verbose: False
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log_every_n: 1
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plant:
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interconnect_limit: 500000 # kW (500 MW)
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hard_coal_steam_turbine:
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component_type: HardCoalSteamTurbine
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rated_capacity: 500000 # kW (500 MW)
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min_stable_load_fraction: 0.3 # 30% minimum operating point
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ramp_rate_fraction: 0.03 # 3%/min ramp rate
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run_up_rate_fraction: 0.02 # 2%/min run up rate
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hot_startup_time: 27000.0 # 7.5 hours
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warm_startup_time: 27000.0 # 7.5 hours
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cold_startup_time: 27000.0 # 7.5 hours
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min_up_time: 172800 # 48 hours
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min_down_time: 172800 # 48 hour
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efficiency_table:
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power_fraction:
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- 1.0
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- 0.50
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- 0.30
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efficiency: # HHV net plant efficiency, fractions (0-1)
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- 0.35
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- 0.32
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- 0.32
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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: 500000 # Start ON at rated capacity
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controller:

‎examples/08_hard_coal_steam_turbine/hercules_runscript.py‎

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"""Example 08: Hard Coal Steam Turbine (HCST) simulation.
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This example demonstrates a simple hard coal steam turbine (HCST) that:
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- Starts on at rated capacity
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- Receives a shutdown command and begins ramping down
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- Transitions to off
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- Receives a turn-on command with a setpoint of 100% of rated capacity
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- Minimum down-time requirement is reached and the turbine begins ramping up
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- Ramps up to 100% of rated capacity
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- Receives a command to reduce power to 50% of rated capacity
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- Receives a command to reduce power to 10% of rated capacity
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(note this is below the minimum stable load)
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- Receives a command to increase power to 100% of rated capacity
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- Receives a shutdown command
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- Simulation runs for 10 days total with 1 minute time steps
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"""
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from hercules.hercules_model import HerculesModel
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from hercules.utilities_examples import prepare_output_directory
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prepare_output_directory()
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# Initialize the Hercules model
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hmodel = HerculesModel("hercules_input.yaml")
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class ControllerHCST:
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"""Controller implementing the HCST schedule described in the module docstring."""
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def __init__(self, h_dict, component_name="hard_coal_steam_turbine"):
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"""Initialize the controller.
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Args:
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h_dict (dict): The hercules input dictionary.
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"""
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self.component_name = component_name
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self.rated_capacity = h_dict[self.component_name]["rated_capacity"]
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simulation_length = h_dict["endtime_utc"] - h_dict["starttime_utc"]
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self.total_simulation_time = simulation_length.total_seconds()
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def step(self, h_dict):
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"""Execute one control step.
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This controller is scaled by the total simulation time, pulled from the h_dict
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This preserves the relative distance between control actions, but changes the
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simulation times that they are applied.
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Args:
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h_dict (dict): The hercules input dictionary.
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Returns:
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dict: The updated hercules input dictionary.
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"""
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current_time = h_dict["time"]
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# Determine power setpoint based on time
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if current_time < 0.05 * self.total_simulation_time:
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# First 5% of simulation time, run at full capacity
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power_setpoint = self.rated_capacity
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elif current_time < 0.15 * self.total_simulation_time:
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# Between 5% and 15% of simulation time: shut down
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power_setpoint = 0.0
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elif current_time < 0.45 * self.total_simulation_time:
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# Between 15% and 45% of simulation time: signal to run at full capacity
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power_setpoint = self.rated_capacity
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elif current_time < 0.65 * self.total_simulation_time:
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# Between 45% and 65% of simulation time: reduce power to 50% of rated capacity
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power_setpoint = 0.5 * self.rated_capacity
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elif current_time < 0.75 * self.total_simulation_time:
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# Between 65% and 75% of simulation time: reduce power to 10% of rated capacity
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power_setpoint = 0.1 * self.rated_capacity
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elif current_time < 0.9 * self.total_simulation_time: #
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# Between 75% and 90% of simulation time: increase power to 100% of rated capacity
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power_setpoint = self.rated_capacity
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else:
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# After 90% of simulation time: shut down
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power_setpoint = 0.0
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h_dict[self.component_name]["power_setpoint"] = power_setpoint
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return h_dict
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# Instantiate the controller and assign to the Hercules model
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hmodel.assign_controller(ControllerHCST(hmodel.h_dict))
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# Run the simulation
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hmodel.run()
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hmodel.logger.info("Process completed successfully")

‎examples/08_hard_coal_steam_turbine/plot_outputs.py‎

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# Plot the outputs of the simulation for the OCGT example
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import matplotlib.pyplot as plt
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from hercules import HerculesOutput
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# Read the Hercules output file using HerculesOutput
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ho = HerculesOutput("outputs/hercules_output.h5")
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component_name = "hard_coal_steam_turbine" # Change to "open_cycle_gas_turbine" if needed
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# Print metadata information
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print("Simulation Metadata:")
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ho.print_metadata()
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print()
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# Create a shortcut to the dataframe
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df = ho.df
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# Get the h_dict from metadata
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h_dict = ho.h_dict
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# Convert time to hours for easier reading
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time_hours = df["time"] / 60 / 60
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print("TONNES OF COAL USED:", df[component_name + ".fuel_volume_rate"].sum() * h_dict["dt"])
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fig, axarr = plt.subplots(4, 1, sharex=True, figsize=(10, 10))
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# Plot the power output and setpoint
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ax = axarr[0]
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ax.plot(time_hours, df[component_name + ".power"] / 1000, label="Power Output", color="b")
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ax.plot(
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time_hours,
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df[component_name + ".power_setpoint"] / 1000,
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label="Power Setpoint",
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color="r",
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linestyle="--",
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)
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ax.axhline(
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h_dict[component_name]["rated_capacity"] / 1000,
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color="gray",
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linestyle=":",
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label="Rated Capacity",
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)
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ax.axhline(
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h_dict[component_name]["min_stable_load_fraction"]
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* h_dict[component_name]["rated_capacity"]
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/ 1000,
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color="gray",
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linestyle="--",
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label="Minimum Stable Load",
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)
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ax.set_ylabel("Power [MW]")
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ax.set_title("Open Cycle Gas Turbine Power Output")
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ax.legend()
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ax.grid(True)
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# Plot the state
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ax = axarr[1]
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ax.plot(time_hours, df[component_name + ".state"], label="State", color="k")
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ax.set_ylabel("State")
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ax.set_yticks([0, 1, 2, 3, 4, 5])
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ax.set_yticklabels(["Off", "Hot Starting", "Warm Starting", "Cold Starting", "On", "Stopping"])
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ax.set_title(
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"Turbine State (0=Off, 1=Hot Starting, 2=Warm Starting, 3=Cold Starting, 4=On, 5=Stopping)"
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)
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ax.grid(True)
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# Plot the efficiency
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ax = axarr[2]
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ax.plot(
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time_hours,
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df[component_name + ".efficiency"] * 100,
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label="Efficiency",
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color="g",
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)
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ax.set_ylabel("Efficiency [%]")
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ax.set_title("Thermal Efficiency")
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ax.grid(True)
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# Plot the fuel consumption
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ax = axarr[3]
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ax.plot(
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time_hours,
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df[component_name + ".fuel_volume_rate"],
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label="Fuel Volume Rate",
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color="orange",
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)
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ax.set_ylabel("Fuel [m³/s]")
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ax.set_title("Fuel Volume Rate")
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ax.grid(True)
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ax.set_xlabel("Time [hours]")
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plt.tight_layout()
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plt.show()

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