Source code for RCAIDE.Library.Methods.Powertrain.Systems.compute_ecs_power_draw
# RCAIDE/Library/Methods/Powertrain/Systems/compute_ecs_power_draw.py
#
# Created: May 2026, M. Clarke, S. Sharma
# ----------------------------------------------------------------------------------------------------------------------
# IMPORT
# ----------------------------------------------------------------------------------------------------------------------
# package imports
import RCAIDE
import numpy as np
[docs]
def compute_ecs_power_draw(environmental_controls,vehicle,state,bus):
"""
Computes the power draw of an environmental control system.
Parameters
----------
environmental_controls : Environmental_Controls
The ECS component object containing efficiency and thermal attributes
- power_draw : float
Power consumption of the environmental control component [W]
vehicle : Vehicle()
The vehicle object, used to extract the total passenger capacity
state : State
Object containing the dynamic mission state arrays (altitude, Mach, pressure, temperature)
bus : Electrical_Bus
The electrical bus that powers the cabin system
Returns
-------
None
This function modifies the environmental_controls_conditions.power array in-place.
Notes
-----
This function dynamically calculates the ECS power draw in two parts:
1. Electric Cabin Air Compressors: Evaluated dynamically across the mission profile
based on the pressure differential between the freestream ram air and the
required cabin pressurization schedule.
2. Vapor Cycle Cooling: Evaluated as a steady-state load based on the coefficient
of performance (COP) required to dissipate passenger, system, and solar heat.
For more complex environmental controls models, this function could be extended to calculate
power draw based on operating mode, altitude, or other mission parameters.
See Also
--------
RCAIDE.Library.Methods.Powertrain.Systems.append_environmental_control_conditions
"""
N_pax = vehicle.number_of_passengers
m_dot_per_pax = 0.00416 # kg/s (0.25 kg/min per passenger)
Q_per_pax = 70 # W (70 W per passenger, 100 W per flight crew member, 200 W per cabin crew member)
Q_sys_per_pax = 40 # W (IFE/Avionics/Galley heat)
COP = 2.5 # Coefficient of Performance for the cooling system, MEA Vapor Cycle Systems typically have a COP between 2.0 and 3.0
Q_sun = 1367 # W/m² (The paper uses a solar constant of 1367 W/m²)
A_window = 0.08 # m² (The paper assumes 0.08 m² per window)
N_windows = 0 # Number of Windows (Number of rows in cabin * 2)
# Step 1: Compute Compressor Power
altitude = state.conditions.freestream.altitude
Mach = state.conditions.freestream.mach_number
Cp = state.conditions.freestream.constant_pressure_specific_heat
T1 = state.conditions.freestream.temperature
P1 = state.conditions.freestream.pressure
gamma = state.conditions.freestream.specific_heat
m_dot = m_dot_per_pax * N_pax
eta_c = environmental_controls.cabin_compressor_efficiency
# Compute the ram pressure at the inlet of the compressor
P_ram = P1 * (1 + ((gamma - 1) / 2) * Mach**2)
# Determine Design Cabin Pressure based on altitude threshold
P_cabin = np.where(
altitude < 2438.4, # If below 8,000 ft
P_ram + 20000, # Ram pressure + 0.2 bar (in Pascals)
78000 # Else: Constant 0.78 bar (in Pascals)
)
P2 = P_cabin
# Calculate isentropic compressor power
P_comp = (m_dot * Cp * T1 / eta_c) * ((P2/P1)**((gamma-1)/gamma) - 1)
# Step 2: Compute Vapor Cycle Cooling
Q_pax = N_pax * Q_per_pax
Q_sys = N_pax * Q_sys_per_pax
Q_solar = Q_sun * A_window * N_windows
P_cool = (Q_pax + Q_sys + Q_solar) / COP
# Step 3: Compute total power
P_evs = P_comp + P_cool
bus_conditions = state.conditions.energy.busses[bus.tag]
environmental_controls_conditions = bus_conditions[environmental_controls.tag]
environmental_controls_conditions.power[:,0] = P_evs[:,0]
bus_conditions.power_draw += environmental_controls_conditions.power*bus.power_split_ratio /bus.efficiency
return
