This repository contains small, explainable Python notebooks for exploring auxiliary thermal loads and their impact on EV energy consumption and range.
The goal of these notebooks is to build transparent, physics-inspired system models that help visualize how thermal systems (HVAC, cabin cooldown, battery heat generation) interact with overall vehicle energy usage.
These models are intentionally simplified and designed as concept-level engineering tools rather than full OEM simulation environments.
hvac_energy_budget.ipynb
Introductory notebook estimating how steady auxiliary HVAC loads influence overall EV energy consumption and range.
Focus:
- Auxiliary load estimation
- Range sensitivity to HVAC power
- Basic energy accounting
hvac_battery_combined_energy_thermal.ipynb
Explores the interaction between traction energy usage, HVAC loads, and battery thermal behavior.
Focus:
- Combined traction and HVAC energy consumption
- City vs highway driving comparisons
- Simplified battery thermal coupling
battery_thermal_trade_study.ipynb
Physics-based estimation of battery heat generation using a lumped thermal model.
Focus:
- (I^2R) heat generation
- Lumped battery thermal capacitance
- Sensitivity analysis to current and cooling effectiveness
closed_loop_hvac_battery_conditioning_hot_cold.ipynb
Concept-level exploration of how HVAC systems may interact with battery thermal management during hot and cold conditions.
Focus:
- Coupled thermal loads
- Cabin conditioning vs battery conditioning interactions
- Simplified control behavior
01_aux_thermal_transient_model.ipynb
A simplified transient model that simulates hot-soak cabin cooldown and auxiliary energy consumption during the first minutes of vehicle operation.
Focus:
- Cabin air and interior thermal mass modeling
- Transient HVAC cooling load
- Compressor power estimation using COP
- Battery thermal node interaction
- Ambient temperature sensitivity study
Example insight:
| Ambient | Cooldown Time | Compressor Energy |
|---|---|---|
| 30°C | 6.47 min | 0.517 kWh |
| 35°C | 8.70 min | 0.604 kWh |
| 40°C | 11.57 min | 0.710 kWh |
| 45°C | 15.40 min | 0.826 kWh |
This illustrates how environmental conditions alone can increase auxiliary energy consumption by ~60% during cabin cooldown events.
These notebooks prioritize:
- Transparency over complexity
- Physics-based intuition
- Clear engineering assumptions
Rather than replicating detailed OEM simulation environments, the goal is to build lightweight models that clearly illustrate system-level trade-offs.
Across the notebooks, several simplifying assumptions are commonly used:
- Lumped thermal masses
- Simplified heat transfer relationships
- Constant or simplified drive load assumptions
- Simplified HVAC COP models
- No detailed refrigerant cycle modeling
- No solar radiation or infiltration modeling (in Version 1 studies)
Future versions may expand the models to include:
- Temperature-dependent HVAC efficiency
- Air infiltration and cabin leakage effects
- Battery thermal derating interactions
- Transient drive cycles
- Cabin preconditioning scenarios
This repository serves as a collection of engineering exploration notebooks for:
- EV thermal system intuition
- Auxiliary energy impact analysis
- Simple system-level modeling
The notebooks are intentionally written to remain readable, modifiable, and explainable, allowing engineers to quickly explore "what-if" thermal scenarios.
Srikantan Natarajan
Automotive Systems Engineer – Thermal Systems / HVAC Development