OpenSimula

OpenSimula is a component-based time simulation environment in Python, focused on the thermal and energy simulation of buildings and their HVAC installations — though it can be used to simulate any system whose state evolves over time. It implements the ASHRAE 140 standard test suite to validate its building load and HVAC calculations.

Documentation · Getting started · User guide · Component list

What it does

A project is built from components — spaces, walls, windows, constructions, schedules, HVAC equipment, weather files — wired together and simulated hour by hour (or at any other time step). OpenSimula takes care of:

• Building thermal simulation: multi-space heat balance, constructions with thermal mass, windows and solar gains, ground-coupled surfaces, internal gains and schedules.
• HVAC systems: from an ideal loads system (HVAC_perfect_system) to direct-expansion and water-based single- and multi-zone systems, coils, fans, pumps, chillers and heat pumps.
• Solar geometry and shadows: direct and diffuse shadow calculations between the surfaces of a project, with an interactive 3D Plotly view — including an animated view of shadows changing throughout the day.
• Everything else a simulation needs: psychrometrics (via PsychroLib), day/week/year schedules, arbitrary math expressions as inputs, and reading weather data (TMY3, MET) or generic data files (CSV, Excel).
• Validation against ASHRAE 140: the ASHRAE_140/ folder in this repository reproduces the standard's load, heating, cooling, air-side HVAC and weather test cases as runnable notebooks, comparing OpenSimula's results against the reference values.

Projects can be defined as plain Python dictionaries, JSON or Excel files, and results come back as component Variable time series or pandas DataFrames, ready to plot or export.

Installation

pip install opensimula

Requires Python 3.12 or later.

Quick example

import opensimula as osm

project_dict = {
    "name": "First example",
    "time_step": 3600,
    "n_time_steps": 24 * 7,
    "initial_time": "01/01/2001 00:00:00",
    "components": [
        {
            "type": "Day_schedule",
            "name": "working_day",
            "time_steps": [8 * 3600, 5 * 3600, 2 * 3600, 4 * 3600],
            "values": [0, 100, 0, 80, 0],
            "interpolation": "STEP",
        },
        {
            "type": "Day_schedule",
            "name": "holiday_day",
            "time_steps": [],
            "values": [0],
            "interpolation": "STEP",
        },
        {
            "type": "Week_schedule",
            "name": "office_week",
            "days_schedules": ["working_day"] * 5 + ["holiday_day"] * 2,
        },
    ],
}

sim = osm.Simulation()
pro = sim.new_project("First example")
pro.read_dict(project_dict)
pro.simulate()

sim.plot(pro.dates(), [pro.component("office_week").variable("values")])

This is deliberately minimal — the Getting started guide walks through a full building, and the jupyter_test/ and ASHRAE_140/ folders in this repository contain complete, runnable building and HVAC examples.

Working in Jupyter

OpenSimula ships an interactive project editor as a Jupyter widget (pro.editor()), built on anywidget so it works the same in Jupyter, JupyterLab, VS Code notebooks and Marimo. It shows every component's parameters as a form generated from each component's own schema, together with an interactive 3D view of the building.

Component types

Components are grouped by what they define:

• Building: Building, Space_type, Space, Building_surface, Opening, Solar_surface.
• Constructions: Material, Construction, Glazing, Frame, Opening_type.
• HVAC (air side): HVAC_perfect_system, DX_unit, HVAC_DX_system, Water_coil, Fan, HVAC_SZW_system, HVAC_MZW_system.
• HVAC (water side): Pump, Chiller_heat_pump, HVAC_water_system.
• Schedules: Day_schedule, Week_schedule, Year_schedule.
• Files: File_met, File_data.
• Utilities: Calculator.

See the Component list for every parameter and variable of each one.

Package dependencies

• numpy
• pandas
• scipy
• shapely
• psychrolib
• plotly
• matplotlib
• anywidget
• jsonschema
• nbformat
• openpyxl
• tqdm

These are installed automatically with pip install opensimula.

Documentation and support

Full documentation, including the getting started guide, user guide and component reference, is at jfcoronel.github.io/OpenSimula. Bugs and feature requests are tracked on GitHub Issues.

Main Developers

• Juan F. Coronel, Universidad de Sevilla

License

OpenSimula is released under the MIT License.