Energy Simulation

Overview

This skill implements building energy simulation and analysis. Calculate thermal loads, evaluate building envelope performance, and optimize systems for energy efficiency and code compliance.

Capabilities:

• Heating/cooling load calculations
• Envelope thermal analysis
• HVAC system sizing
• Energy code compliance
• Renewable energy integration
• Life cycle cost analysis

Quick Start

python
from dataclasses import dataclass, field
from typing import List, Dict, Optional, Tuple
from enum import Enum
import numpy as np

class WallType(Enum):
    CONCRETE = "concrete"
    BRICK = "brick"
    WOOD_FRAME = "wood_frame"
    STEEL_FRAME = "steel_frame"
    CURTAIN_WALL = "curtain_wall"

@dataclass
class BuildingEnvelope:
    wall_area_m2: float
    wall_u_value: float  # W/m²K
    roof_area_m2: float
    roof_u_value: float
    floor_area_m2: float
    floor_u_value: float
    window_area_m2: float
    window_u_value: float
    window_shgc: float  # Solar Heat Gain Coefficient

@dataclass
class ClimateData:
    location: str
    heating_degree_days: float  # HDD base 18°C
    cooling_degree_days: float  # CDD base 18°C
    design_temp_winter: float
    design_temp_summer: float

def calculate_heat_loss(envelope: BuildingEnvelope, climate: ClimateData,
                       indoor_temp: float = 21) -> float:
    """Calculate design heat loss (W)"""
    delta_t = indoor_temp - climate.design_temp_winter

    # Transmission losses
    wall_loss = envelope.wall_area_m2 * envelope.wall_u_value * delta_t
    roof_loss = envelope.roof_area_m2 * envelope.roof_u_value * delta_t
    floor_loss = envelope.floor_area_m2 * envelope.floor_u_value * delta_t * 0.5  # Ground factor
    window_loss = envelope.window_area_m2 * envelope.window_u_value * delta_t

    total_loss = wall_loss + roof_loss + floor_loss + window_loss

    # Add infiltration estimate (simplified)
    volume = envelope.floor_area_m2 * 3  # Assume 3m height
    infiltration = volume * 0.5 * 0.33 * delta_t  # 0.5 ACH, 0.33 Wh/m³K

    return total_loss + infiltration

# Example
envelope = BuildingEnvelope(
    wall_area_m2=500, wall_u_value=0.35,
    roof_area_m2=200, roof_u_value=0.25,
    floor_area_m2=200, floor_u_value=0.30,
    window_area_m2=100, window_u_value=1.4, window_shgc=0.4
)

climate = ClimateData(
    location="Moscow",
    heating_degree_days=5000,
    cooling_degree_days=300,
    design_temp_winter=-25,
    design_temp_summer=30
)

heat_loss = calculate_heat_loss(envelope, climate)
print(f"Design heat loss: {heat_loss/1000:.1f} kW")

Comprehensive Energy Analysis

Building Thermal Model

python
from dataclasses import dataclass, field
from typing import List, Dict, Optional, Tuple
from enum import Enum
import numpy as np
from datetime import datetime

@dataclass
class MaterialLayer:
    name: str
    thickness_m: float
    conductivity: float  # W/mK
    density: float  # kg/m³
    specific_heat: float  # J/kgK

    @property
    def resistance(self) -> float:
        """Thermal resistance R (m²K/W)"""
        return self.thickness_m / self.conductivity if self.conductivity > 0 else 0

@dataclass
class WallAssembly:
    name: str
    layers: List[MaterialLayer]
    inside_surface_resistance: float = 0.13  # m²K/W
    outside_surface_resistance: float = 0.04

    @property
    def total_resistance(self) -> float:
        return (self.inside_surface_resistance +
                sum(layer.resistance for layer in self.layers) +
                self.outside_surface_resistance)

    @property
    def u_value(self) -> float:
        return 1 / self.total_resistance if self.total_resistance > 0 else 0

@dataclass
class Window:
    name: str
    u_value: float
    shgc: float
    visible_transmittance: float = 0.6
    frame_fraction: float = 0.2

@dataclass
class Zone:
    zone_id: str
    name: str
    floor_area_m2: float
    volume_m3: float
    occupancy: int
    lighting_power_density: float  # W/m²
    equipment_power_density: float  # W/m²
    ventilation_rate: float  # L/s per person
    setpoint_heating: float = 21
    setpoint_cooling: float = 24

@dataclass
class BuildingGeometry:
    zones: List[Zone]
    walls: List[Dict]  # {zone, orientation, area, assembly}
    windows: List[Dict]  # {zone, orientation, area, window_type}
    roofs: List[Dict]  # {zone, area, assembly}
    floors: List[Dict]  # {zone, area, assembly, is_ground}

class ThermalCalculator:
    """Calculate building thermal loads"""

    # Standard climate data (simplified)
    CLIMATE_DB = {
        'moscow': {
            'hdd': 5000, 'cdd': 300,
            'design_winter': -25, 'design_summer': 30,
            'latitude': 55.75
        },
        'new_york': {
            'hdd': 2500, 'cdd': 800,
            'design_winter': -12, 'design_summer': 33,
            'latitude': 40.71
        },
        'dubai': {
            'hdd': 50, 'cdd': 3000,
            'design_winter': 15, 'design_summer': 45,
            'latitude': 25.20
        }
    }

    def __init__(self, building: BuildingGeometry, location: str):
        self.building = building
        self.location = location.lower()
        self.climate = self.CLIMATE_DB.get(self.location, self.CLIMATE_DB['moscow'])

    def calculate_design_heating_load(self) -> Dict:
        """Calculate design heating load for each zone"""
        delta_t = 21 - self.climate['design_winter']
        results = {}

        for zone in self.building.zones:
            # Transmission losses
            wall_loss = 0
            window_loss = 0
            roof_loss = 0
            floor_loss = 0

            for wall in self.building.walls:
                if wall['zone'] == zone.zone_id:
                    u_value = wall['assembly'].u_value
                    wall_loss += wall['area'] * u_value * delta_t

            for window in self.building.windows:
                if window['zone'] == zone.zone_id:
                    window_loss += window['area'] * window['window_type'].u_value * delta_t

            for roof in self.building.roofs:
                if roof['zone'] == zone.zone_id:
                    u_value = roof['assembly'].u_value
                    roof_loss += roof['area'] * u_value * delta_t

            for floor in self.building.floors:
                if floor['zone'] == zone.zone_id:
                    u_value = floor['assembly'].u_value
                    factor = 0.5 if floor.get('is_ground', False) else 1.0
                    floor_loss += floor['area'] * u_value * delta_t * factor

            # Infiltration
            infiltration_loss = zone.volume_m3 * 0.5 * 0.33 * delta_t

            # Ventilation (if mechanical)
            ventilation_loss = zone.occupancy * zone.ventilation_rate * 1.2 * delta_t

            total = wall_loss + window_loss + roof_loss + floor_loss + infiltration_loss + ventilation_loss

            results[zone.zone_id] = {
                'zone_name': zone.name,
                'wall_loss_w': wall_loss,
                'window_loss_w': window_loss,
                'roof_loss_w': roof_loss,
                'floor_loss_w': floor_loss,
                'infiltration_w': infiltration_loss,
                'ventilation_w': ventilation_loss,
                'total_w': total,
                'total_kw': total / 1000,
                'w_per_m2': total / zone.floor_area_m2
            }

        return results

    def calculate_design_cooling_load(self) -> Dict:
        """Calculate design cooling load for each zone"""
        delta_t = self.climate['design_summer'] - 24
        results = {}

        for zone in self.building.zones:
            # Transmission gains
            transmission_gain = 0
            for wall in self.building.walls:
                if wall['zone'] == zone.zone_id:
                    u_value = wall['assembly'].u_value
                    # Apply sol-air temperature correction for orientation
                    sol_air_delta = delta_t + self._get_sol_air_correction(wall['orientation'])
                    transmission_gain += wall['area'] * u_value * sol_air_delta

            # Window solar gains
            solar_gain = 0
            for window in self.building.windows:
                if window['zone'] == zone.zone_id:
                    shgc = window['window_type'].shgc
                    irradiance = self._get_solar_irradiance(window['orientation'])
                    solar_gain += window['area'] * shgc * irradiance

            # Window conduction
            window_conduction = 0
            for window in self.building.windows:
                if window['zone'] == zone.zone_id:
                    window_conduction += window['area'] * window['window_type'].u_value * delta_t

            # Internal gains
            lighting_gain = zone.floor_area_m2 * zone.lighting_power_density
            equipment_gain = zone.floor_area_m2 * zone.equipment_power_density
            people_gain = zone.occupancy * 75  # W per person sensible

            # Ventilation
            ventilation_gain = zone.occupancy * zone.ventilation_rate * 1.2 * delta_t

            total = (transmission_gain + solar_gain + window_conduction +
                    lighting_gain + equipment_gain + people_gain + ventilation_gain)

            results[zone.zone_id] = {
                'zone_name': zone.name,
                'transmission_gain_w': transmission_gain,
                'solar_gain_w': solar_gain,
                'window_conduction_w': window_conduction,
                'lighting_gain_w': lighting_gain,
                'equipment_gain_w': equipment_gain,
                'people_gain_w': people_gain,
                'ventilation_gain_w': ventilation_gain,
                'total_w': total,
                'total_kw': total / 1000,
                'w_per_m2': total / zone.floor_area_m2
            }

        return results

    def _get_sol_air_correction(self, orientation: str) -> float:
        """Get sol-air temperature correction by orientation"""
        corrections = {
            'north': 0, 'south': 8, 'east': 4, 'west': 6,
            'northeast': 2, 'northwest': 3, 'southeast': 6, 'southwest': 7
        }
        return corrections.get(orientation.lower(), 3)

    def _get_solar_irradiance(self, orientation: str) -> float:
        """Get design solar irradiance W/m² by orientation"""
        # Simplified peak values
        irradiance = {
            'north': 150, 'south': 450, 'east': 350, 'west': 350,
            'northeast': 200, 'northwest': 200, 'southeast': 400, 'southwest': 400
        }
        return irradiance.get(orientation.lower(), 300)

HVAC System Sizing

python
class HVACSizer:
    """Size HVAC systems based on loads"""

    def __init__(self, calculator: ThermalCalculator):
        self.calculator = calculator

    def size_heating_system(self, safety_factor: float = 1.15) -> Dict:
        """Size heating system"""
        heating_loads = self.calculator.calculate_design_heating_load()

        total_load = sum(z['total_kw'] for z in heating_loads.values())
        sized_capacity = total_load * safety_factor

        # Recommend system type
        if sized_capacity < 15:
            system_type = "Split system heat pump"
        elif sized_capacity < 50:
            system_type = "Packaged rooftop unit"
        elif sized_capacity < 200:
            system_type = "Central boiler with radiators"
        else:
            system_type = "Central plant with multiple boilers"

        return {
            'total_load_kw': total_load,
            'sized_capacity_kw': sized_capacity,
            'safety_factor': safety_factor,
            'recommended_system': system_type,
            'zone_loads': heating_loads
        }

    def size_cooling_system(self, safety_factor: float = 1.1) -> Dict:
        """Size cooling system"""
        cooling_loads = self.calculator.calculate_design_cooling_load()

        total_load = sum(z['total_kw'] for z in cooling_loads.values())
        sized_capacity = total_load * safety_factor

        # Convert to tons
        capacity_tons = sized_capacity / 3.517

        # Recommend system type
        if capacity_tons < 5:
            system_type = "Split system DX"
        elif capacity_tons < 20:
            system_type = "VRF system"
        elif capacity_tons < 100:
            system_type = "Chilled water with AHUs"
        else:
            system_type = "Central chiller plant"

        return {
            'total_load_kw': total_load,
            'total_load_tons': capacity_tons,
            'sized_capacity_kw': sized_capacity,
            'sized_capacity_tons': capacity_tons * safety_factor,
            'safety_factor': safety_factor,
            'recommended_system': system_type,
            'zone_loads': cooling_loads
        }

    def estimate_annual_energy(self) -> Dict:
        """Estimate annual energy consumption"""
        climate = self.calculator.climate

        heating_loads = self.calculator.calculate_design_heating_load()
        cooling_loads = self.calculator.calculate_design_cooling_load()

        total_heating_load = sum(z['total_kw'] for z in heating_loads.values())
        total_cooling_load = sum(z['total_kw'] for z in cooling_loads.values())

        # Simplified degree-day calculation
        # Heating energy = load * HDD * 24 / delta_t_design
        delta_t_heating = 21 - climate['design_winter']
        heating_kwh = total_heating_load * climate['hdd'] * 24 / delta_t_heating / 1000

        delta_t_cooling = climate['design_summer'] - 24
        cooling_kwh = total_cooling_load * climate['cdd'] * 24 / delta_t_cooling / 1000 if delta_t_cooling > 0 else 0

        # Apply efficiency factors
        heating_fuel_efficiency = 0.9  # Gas boiler
        cooling_cop = 3.5  # Chiller COP

        heating_consumption = heating_kwh / heating_fuel_efficiency
        cooling_consumption = cooling_kwh / cooling_cop

        return {
            'heating_load_kw': total_heating_load,
            'cooling_load_kw': total_cooling_load,
            'annual_heating_kwh': heating_kwh,
            'annual_cooling_kwh': cooling_kwh,
            'heating_fuel_kwh': heating_consumption,
            'cooling_electricity_kwh': cooling_consumption,
            'total_hvac_energy_kwh': heating_consumption + cooling_consumption
        }

Energy Code Compliance

python
@dataclass
class EnergyCodeRequirements:
    code_name: str
    climate_zone: str
    wall_u_max: float
    roof_u_max: float
    floor_u_max: float
    window_u_max: float
    window_shgc_max: float
    lighting_lpd_max: float  # W/m²

class ComplianceChecker:
    """Check energy code compliance"""

    CODES = {
        'ASHRAE_90.1_2019_4A': EnergyCodeRequirements(
            code_name="ASHRAE 90.1-2019",
            climate_zone="4A",
            wall_u_max=0.45,
            roof_u_max=0.27,
            floor_u_max=0.32,
            window_u_max=2.0,
            window_shgc_max=0.40,
            lighting_lpd_max=9.0
        ),
        'IECC_2021_5A': EnergyCodeRequirements(
            code_name="IECC 2021",
            climate_zone="5A",
            wall_u_max=0.35,
            roof_u_max=0.20,
            floor_u_max=0.30,
            window_u_max=1.7,
            window_shgc_max=0.40,
            lighting_lpd_max=8.5
        )
    }

    def __init__(self, code_key: str):
        self.requirements = self.CODES.get(code_key)
        if not self.requirements:
            raise ValueError(f"Unknown code: {code_key}")

    def check_envelope(self, building: BuildingGeometry) -> Dict:
        """Check envelope compliance"""
        results = {
            'code': self.requirements.code_name,
            'climate_zone': self.requirements.climate_zone,
            'compliant': True,
            'issues': []
        }

        # Check walls
        for wall in building.walls:
            u_value = wall['assembly'].u_value
            if u_value > self.requirements.wall_u_max:
                results['compliant'] = False
                results['issues'].append({
                    'element': f"Wall {wall['zone']} {wall['orientation']}",
                    'actual': u_value,
                    'required': self.requirements.wall_u_max,
                    'issue': 'Exceeds maximum U-value'
                })

        # Check windows
        for window in building.windows:
            u_value = window['window_type'].u_value
            shgc = window['window_type'].shgc

            if u_value > self.requirements.window_u_max:
                results['compliant'] = False
                results['issues'].append({
                    'element': f"Window {window['zone']} {window['orientation']}",
                    'actual': u_value,
                    'required': self.requirements.window_u_max,
                    'issue': 'Exceeds maximum U-value'
                })

            if shgc > self.requirements.window_shgc_max:
                results['compliant'] = False
                results['issues'].append({
                    'element': f"Window {window['zone']} {window['orientation']}",
                    'actual': shgc,
                    'required': self.requirements.window_shgc_max,
                    'issue': 'Exceeds maximum SHGC'
                })

        # Check roof
        for roof in building.roofs:
            u_value = roof['assembly'].u_value
            if u_value > self.requirements.roof_u_max:
                results['compliant'] = False
                results['issues'].append({
                    'element': f"Roof {roof['zone']}",
                    'actual': u_value,
                    'required': self.requirements.roof_u_max,
                    'issue': 'Exceeds maximum U-value'
                })

        return results

    def check_lighting(self, zones: List[Zone]) -> Dict:
        """Check lighting power density compliance"""
        results = {
            'compliant': True,
            'issues': []
        }

        for zone in zones:
            if zone.lighting_power_density > self.requirements.lighting_lpd_max:
                results['compliant'] = False
                results['issues'].append({
                    'zone': zone.name,
                    'actual_lpd': zone.lighting_power_density,
                    'required_max': self.requirements.lighting_lpd_max
                })

        return results

Quick Reference

| Component | Good U-Value | Code Maximum | |-----------|--------------|--------------| | Wall | < 0.25 W/m²K | 0.35-0.45 | | Roof | < 0.15 W/m²K | 0.20-0.27 | | Floor | < 0.20 W/m²K | 0.25-0.32 | | Window | < 1.2 W/m²K | 1.7-2.0 |

Resources

• ASHRAE 90.1: Energy standard for buildings
• IECC: International Energy Conservation Code
• EnergyPlus: DOE building simulation
• DDC Website: https://datadrivenconstruction.io

Next Steps

• See co2-estimation for carbon analysis
• See cost-prediction for energy cost modeling
• See bim-validation-pipeline for model integration