2026.1 Release

Update 2026-MAR-12

General availability: Modelon Cloud UX version 4.104.10

We're excited to introduce the 2026.1 release of Modelon Impact, bringing powerful improvements across our Modelon Library Suite, the Modelica Standard Library integration, and our compiler and simulation engine. This release focuses on new model content, simulation robustness and performance gains that help teams model, simulate, and deploy faster than ever.

Highlights

• New Modelon Library Suite 2026.1
  • New content, simulation speed and robustness improvements.
• Modelica Standard Library 4.1
  • Modelica Standard Library 4.1 is now standard when creating a new workspace
• Improved post-processing
  • Improved icon animation, and added support for SVG, BMP and JPEG file types.
• New execution environment
  • Compiler and solver improvements

Note

Since we have continuously been rolling out new features and fixes, we also encourage you to look into the previous release notes here.

Modelon Libraries

The Modelon library suite has been improved and contains following highlights:

Modelon Base

• New weather data components: A Weather component and accompanying WeatherDataConversion model provide an easy workflow for reading and converting Excel based weather datasets.

• Dual state wall modeling: The DynamicWall model now uses two temperature states per segment, reducing or eliminating the need for iterative solving in heat exchanger models.

• Relaxation option for two-phase heat transfer coefficients: All two-phase heat transfer correlations now support optional coefficient relaxation, enabling smoother transient simulations and improved numerical stability.

• Refined two-phase flow channel transient behavior: Minor equation improvements enhance transient robustness without affecting steady state results.

• Libraries affected by these shared two-phase improvements: Air Conditioning, Vapor Cycle, Liquid Cooling, Heat Exchanger, Thermal Power, and any models using Modelon.ThermoFluid two-phase components benefit from these enhancements.

Breaking changes:

• Requires conversion script

Air Conditioning

• Smarter refrigerant flow modeling: Valve components now automatically detect and handle reverse flow, enabling more realistic behavior in systems with dynamic or bidirectional operation.

• Improved controller and TXV initialization: SimpleTXV and the LimPI controllers provide expanded integrator initialization options, delivering smoother startup, better stability, and more predictable transient behavior.

• Trace component tracking in air handling systems: All air side components now support trace component flow, enabling deeper insights into mixing, ventilation efficiency, and air quality behavior.

• Enhanced diagnostic summaries: Flow component summaries have been unified and expanded with pressure, temperature, and enthalpy information for clearer system analysis.

Breaking changes:

• Requires conversion script

Energy Systems

• Easier debugging of optimization workflows: The Optimizer now includes a showValuesInDiagram option to display key constraint values directly in the diagram, simplifying the analysis of infeasible problems.

• Enhanced HeatPump performance modeling: The HeatPump model now supports two COP formulations (CarnotEfficiency and CoefficientOfPerformance), each configurable as constant or variable for realistic part load and custom performance curves.

• Improved usability and documentation: Several models feature refreshed parameter dialogs and clearer documentation for a smoother modeling experience.

Breaking changes:

• Requires conversion script

Heat Exchanger

• More accurate flat tube heat exchanger modeling: Refrigerant–air flat tube heat exchangers now support orthogonal discretization within each pass, enabling nonuniform temperature profiles across parallel flat tubes for improved accuracy in uneven airflow conditions.

Breaking changes:

• Requires conversion script

Liquid Cooling

• More intuitive and informative visualization: All components now include a display_name option for showing component names in the diagram layer. Visualization has been enhanced with new colormaps, including CoolWarm and TrafficlightColor, for clearer thermal representation.

• Standardized interfaces for easier configuration: A new Interfaces package standardizes all two-port components, improving replaceability, redeclaration workflows, and overall model consistency.

• Faster simulations with visualization disabled: Unused rendering code is removed when visualization is off, improving simulation runtime. Visualization can be controlled globally via ExperimentBase or individually per component.

Breaking changes:

• Requires conversion script

Vapor Cycle

• New SBTL Isobutane medium: A high performance SBTL based Isobutane medium is now available for faster and more robust simulations.

• More accurate thermal behavior in CapillarySuctionLine: The soldered wall heat capacity calculation now uses a weighted average of capillary tube, suction line, and soldering material properties.

• Improved component startup handling: SimpleTXV offers improved integrator initialization control, and compressors now handle zero speed startup more reliably.

• Consistent default airside medium: All airside components now default to MoistAirIce for consistent behavior across heat exchangers, sensors, flow modifiers, and sources. Users may revert to MoistAir if necessary.

Breaking changes:

• Requires conversion script

Build

Improvements:

1. Modelica Standard Library Default version has been updated to 4.1.0 and the compiler now supports this version.
   • When creating a new workspace, the version 4.1.0 is used by default.
   • The version 4.1.0 is available as a choice in the workspace configuration UI for existing workspaces.
   • The entire 2026.1 Modelon Library Suite is built against and delivered using 4.1.0.

Analyze

Improvements:

1. Improved calculated variable filtering performance by limiting results to 500 visible matches.

2. Time slider range controls remain enabled while a simulation is running.

3. Added support for moving connection lines defined within a for-loop.
4. Added support for rendering SVG (converted to PNG), BMP, and JPEG files in dynamicSelect expressions.

Bug fixes:

• Fixed incorrect icon colors on the model selection page.
• Fixed scatter plot tooltips when multiple results are selected and during live plotting.
• Prevents components with dynamicSelect annotations from resetting to their default value when selected.
• Fixed unintended navigation to the diagram view when saving changes in the code editor.
• Fixed an issue where creating plots by dragging and dropping properties fails in some cases.
• Corrected handling of the rotation attribute in annotations using dynamicSelect.

Modelica Compiler

Improvements:

1. Simulation log - Now warns about usage of high log levels (INFO, VERBOSE, DEBUG) in Dynamic simulation. High log levels can cause simulation slowdown.
2. Improved simulation performance - For high log levels (INFO, VERBOSE, DEBUG).

Bug fixes:

• Fixed incorrect unit offset for degrees Fahrenheit in exported FMUs.
• Fixed issue so it is possible to suppress multiple different warnings using compiler option filter_warnings. Specify multiple warnings separated by spaces.
• Fixed issue where simulation logs sometimes got incorrectly cut-off before actual cut-off size limit.

Platform information

Execution environment

This release includes the following execution environments.

Note, self-managed only include the latest version of the execution environment.

Execution environments	v2026.1	v2025.2
Optimica Compiler Toolkit	v1.66	v1.64
Modelica compliance	v3.4 of Modelica Language specification1	v3.4 of Modelica Language specification1
FMU compliance	v2 (default) and v1	v2 (default) and v1
Operating system	Ubuntu v22.04	Ubuntu v22.04
Python environment	v3.11	v3.11
C compiler	GCC v11.4 and glibc v2.35	GCC v11.4 and glibc v2.35

¹ See Optimica Compiler Toolkit User's guide for further information about Modelica compliance and limitations.

Libraries

This release includes the following library versions for Modelon Cloud. Columns indicate the release when a version was made available.

Library		2026.1	2025.2	2025.May
Air Conditioning		3.0	2.0	1.30
AirConditioningAdapters		3.0	2.0	1.30
Electrification		2.2	2.1	2.0
Energy Systems		2.0	1.4	1.3
Fuel Cell		3.0	2.0	1.21
Heat Exchanger		5.0	4.0	3.0
Hydraulics		4.25	4.24	4.23
Industry Examples		1.9	1.8	1.7
Liquid Cooling		4.0	3.0	2.15
Modelon Base		7.0	6.0	5.0
Thermal Power		4.0	3.0	2.0
Vapor Cycle		5.0	4.0	3.0
Vehicle Dynamics		4.9	4.8	4.7
Modelica Standard		4.1	4.0	4.0
Buildings		12.1.1	12.1.1	12.0

Breaking Changes

Execution environment

• Removed non-linear block solver Minpack (was deprecated).
• Added additional error checks, see oct_release_notes for more details

Libraries

2025.1 library distribution

The 2025.1 distribution of libraries has been removed from Modelon Cloud. The following library versions are therefore not longer available on Modelon Cloud.

Libraries	2025.1
AirConditioning	1.29.0
AirConditioningAdapters	1.29.0
Electrification	1.13.0
EnergySystems	1.2.0
FuelCell	1.20.0
HeatExchanger	2.14.0
Hydraulics	4.22.0
IndustryExamples	1.6.0
LiquidCooling	2.13.0
Modelon	4.6.0
ThermalPower	1.29.0
VaporCycle	2.14.0
VehicleDynamics	4.6.0

See Library Conversion for how to migrate workspaces to newer library versions.

We hope you like the new functionality and improvements and look forward to your input!