How useful is the free, open source Scilab/Xcos vs Matlab/Simulink?

One of my clients has requested a dynamic fuel cell power system model, so I investigated both Matlab/Simulink and Scilab/Xcos modelling environments.  These packages are able to model complex electrical power and control systems using a graphical block diagram modelling tool.  Here is an example of Xcos’ DC DC Boost Converter:

Xcos DC DC Boost Converter

Xcos DC DC Boost Converter

To model the fuel cell power system in Matlab/Simulink requires the addon toolboxes SimPowerSystems and SimScape.  This raises the license price to about $12,000 USD plus further yearly license fees (~20%).  An advantage of Scilab/Xcos is that the software is free.  Simulink/SimPowerSystems has a more extensive library of predefined component or subsystem models than Xcos, yet Xcos has the most important components defined.  Simulink/SimPowerSystems has much better documentation, which is typical of commercial software vs open source software.  There are some Xcos documentation and tutorials available, covering the most important topics.

I had difficulties getting both packages up and running on my Windows 7 computer as in both cases there were problems in getting external C compilers connected.  With Matlab, I was able to go back and forth with their helpful customer support to resolve the issue.  With Scilab, I had to do internet searches for forum posts by other users with the similar problems.  In both cases I was able to get the packages running with some delay.  Matlab has better user support as it is easier to call someone for help, but Scilab has a fair number of users posting problems and solutions, and with a bit of sleuthing, resolving my problem was not too difficult.

Working inside the environments is pretty similar. Simulink/SimPowerSystems has the most capability, yet Xcos is impressively capable, with more and more tools being published by their user community.  Perhaps Xcos is roughly 80-90% of the capability of Simulink/SimPowerSystems for my application, and good enough for what I need at this time.

One further advantage of Xcos is that it is much easier to share models, as it is easy to get access to the modelling environment.  With Matlab/Simulink, you really need your other collaborators and clients to have Matlab/Simulink available, and that is an expensive proposition, especially being tied to yearly maintenance fees.

Xcos is steadily improving in capability, documentation, tutorials, and links to other programs.  It has come a long way in the last three years.  By being free, it is more accessible to a larger community, which will help accelerate its development and usefulness through the network effect.  For many practitioners, it is a great choice.

Matlab/Simulink will have some threat from Scilab/Xcos in the lower end of the market, yet I expect it to lead the high-end market as it continues to add capability, modules, applications, and linkages to other programs.  For larger institutions, it is a good choice.

Product Comparison

Product Comparison for my application

Overall I am pleasantly surprised and impressed with Scilab/Xcos, and while it takes a little more time and effort to be productive with it than Matlab/Simulink, for my application, it is worth it.


Open Source Thermodynamic Process Simulator Review – DWSIM

Many complex energy systems use thermodynamic process simulators for systems design, especially if fueled by oil, natural gas, methanol, hydrogen or landfill gas.   The leading industry simulators are Aspen HysysProSim, and VMGSim.   These simulators are very powerful, as they can model very complex chemical and biological reactions, networks of unit operations with many interactions requiring multivariable convergence, and both steady-state and dynamic control systems.  As they provide significant value, especially to Oil and Gas, the license fees per seat are on the order of $10,000/year.

Open Source software continues to gain traction with consumers; for example OpenOffice has approximately between 10-20% of the market, with Microsoft Office being most of the rest.   Could there be a viable Open Source alternative for thermodynamic process simulators, given the smaller market and similar software complexity?

DWSIM is the only real Open Source thermodynamic simulator with a very similar capability to the steady-state versions of Hysys, ProSim or VMGSim, including a graphical flowsheet and integrated spreadsheet.

Figure 1: DWSIM User Interface

Figure 1: DWSIM User Interface


I have recently used both the latest versions of a leading industry thermodynamic process simulator and DWSIM.  I am impressed with DWSIM, and I am currently productive with this tool.  It has the core functionality for steady-state mass and energy balances, and is powerful enough to examine part power and start-up states.  It is easy to use, easy to report, and convergence times are good.  While it does not have dynamic capability, nor is that capability on the author’s roadmap, the vast majority of studies for most users are done in steady-state mode.  The overall support materials are good.  One advantage of being open source is that the underlying engine and calculations can be more transparent to the user, so for some that can be good for learning and checking.

Every process simulator has its own learning curve because they all have somewhat different convergence routines and architecture, and especially for converging very complex networks, so to become truly productive will require some time investment.  I have simulated high complexity systems in DWSIM so far, and overall it works fine.

The author, Daniel Medeiros, is currently active and planning further releases, which means the product will continue to improve.

For many users, such as students, or some small businesses, part-time practitioners, or those that need primarily the core functionality only, DWSIM is a great choice.  So far the big industry players with proprietary software do not offer light versions of their software for lower costs, so there is a demand for packages like DWSIM for this end of the market.  DWSIM has the “first-mover” Open Source advantage, and can set the standard in this segment of the market, and will take some of this market from the big players.

Overall, I am pleased with the product for what it is.  For most large companies, the industry leading simulators are an overall better value proposition, because of the higher power and features.  For the other end of the market, DWSIM is well worth trying, or may be the only economic option.