A modular open source framework to model energy supply systems

2025.09 dev meeting retrospective

For the last three days, we were meeting at HTW in Berlin for our semi-annual developer meeting. Here are some of the key results:

We plan to have an improved lecture/ tutorial session, that might eventually develop into a summer school.
There will be a release of oemof.solph mid November. It will include whatever is done until then.
Costs calculations in oemof.solph will be aligned with VDI 2067. We plan to distinguish between energy-related costs (€/kWh), capacity related operational costs (€/kW/a), fixed operational costs (€/a) for OPEX and capacity related investment costs (€/kW/a) as well as an investment cost offset (€/a) for CAPEX. At the moment, we group by units, and thus have CAPEX and OPEX mixed.
The SubNetworks, we decided to have at the oemof 2025.02 developer meeting are functional, an example is merged in dev.
There is a software implementing robust optimisation. We plan to release something along these lines (as rolph).
Some of use will create an awareness concept. For upcoming meetings, there will be an awareness team you can contact if you do feel uncomfortable because of other participants or externals. We will also try to organise ourselves so that you can feel save on your trip back to the hotel.

See you next time (in Nordhausen)!

First tespy community meeting to be hosted in Flensburg

The first ever in-person community meeting of tespy will be held in one month in Flensburg. From October 13. to 15. we will meet at the location of tespy’s origin, Flensburg University of Applied Sciences. There are many interesting topics on the agenda, suitable from very beginners to advanced users and potential future developers.

You can find all details and register here: https://github.com/oemof/oemof/wiki/Meeting-2025.10%3A-tespy-user-meeting

See you in Flensburg!

Premiere: oemof association as affiliation

This week, there was a premiere at the Conference of Northern German Heat Research (in German): When presenting TESPy, our module for thermodynamic simulation, Francesco named the oemof association as an affiliation of Malte, Jonas, and himself.

Thanks for the initiative!

Save the date: oemof user meeting 2026.02

Our next in-person user meeting will take place in Nordhausen from 11th to 13th of February 2026. It will be hosted by Nordhausen University of Applied Sciences partly parallel to the 9th Regenerative Energy Technology Conference (page in German).

We are posting this save the date already, as the parallel RET.Con also allows to submit contributions to its proceedings. If you wish to do so, please send an abstract (maximum two pages A4) to ret@hs-nordhausen.de. The deadline for abstracts to the RET.Con is the 15th of October. If accepted, full papers will be due at the 15th of January. Registration to the oemof track will be possible later, (as usual) without abstracts and proceedings.

2025.09 Developer Meeting in Berlin: Save the Date

We just got the feedback that the next oemof meeting will be hosted by Reiner Lemoine Institut from September 15th to 17th at HTW Berlin. Due to the limited room capacity it will come as a developer meeting. Save the date and contribute, if you are interested! (Beginners, in particular first-time contributors, will get guidance, of course.)

We created a wiki page for the Meeting 2025.09 to work on the agenda.
To register, you can either add your name to the linked Wiki page at GitHub, use the registration form, comment this post, or write an email to meetings@oemof.org.

TESPy version 0.9 released

Version 0.9 of TESPy is available!

A major refactoring of the presolving and solving architecture has been carried out. The changes will allow users to debug models much more efficiently, as it is possible to extract the list of variables and the list of equations that have been presolved as well as those that are finally passed to the numerical solver. In this context, the presolver now further reduces the model size by identifying linear relationships between variables and mapping such variables to a single one. PowerConnections and respective components like Motor, Generator and PowerBus replace the Bus architecture, for example enabling the modelling of single shaft gas turbines, where the generator efficiency will only affect the net shaft power of the gas turbine.

For the full changelog please check out the documentation website: https://tespy.readthedocs.io/.

Also, a new package in context of thermal engineering has been released under the oemof organization: ExerPy. The exergy analysis features of TESPy have been ported to the new package and it will be developed independently in the future to integrate more methods in the context of exergy analysis. ExerPy provides an easy to use API to read and process the results of your TESPy models.

OWEFE: integrated water, energy, food, and environment systems

As developers and users of the oemof software, we’re always interested in efforts that leverage its modular, open-source design for broader, cross-sectoral analyses. A recent paper, OWEFE, open modelling framework for integrated water, energy, food, and environment systems by J. Fleischmann et al. (2024), presents an “integrated-WEFE” layer that extends oemof’s energy system graph to encompass water, energy, food, and environmental systems in one unified model.

Feisty Friday: omeof.solph v0.6.0

Without any public announcement, we shadow-dropped oemof.solph v0.6.0 last Friday (solph package 0.6.0 at PyPI, solph 0.6.0 changelog at GitHub). As yesterday was a public Holiday in Germany, this was an extra-bold move, breaking the dogma “never release on Fridays” in an extreme way. Seems like it wasn’t extra-stupid: Until now, nobody complained.

We decided to do this, as we believe it to be a rather stable release. We have cool new features (time-series aggregation and new result handling), but we marked them as experimental. The most noticeable change probably is the completely revised and reshaped documentation, which we tried to be more beginner-friendly than ever. Other changes include removal of API wrappers that allowed to still use old class names and keywords. Highlights of the release include:

Demandlib 0.2.2: VDI and BDEW25

If a rough estimate for energy demands is just good enough, standard load profiles can be handy. To easily generate these kinds of profiles, we have the “demandlib” in the oemof cosmos. This week, we released a new iteration that includes profiles as defined by the VDI (Verband Deutscher Ingeneure, Association of German Engineers) and the updated profiles by the BDEW (Bundesverband der Energie- und Wasserwirtschaft, German Association of Energy and Water Industries).

2025.02 dev meeting retrospective

At the last developer meeting, in sunny Flensburg, we focused on decision making and drafting for the future development of solph. Here are the main results:

There is consensus that we should have common approach of facades or sub-networks. Currently, there are several similar implementations, namely facades in oemof.tabular, nested energy system object (used for cellular approaches, now removed), and node containers (in MTRESS).
We worked hands on at the documentation. Improvements will be merged to the v0.6 dev branch. We also have a suggested colour palette to use in examples:
Lapis Lazuli (#1F567D) , Cambridge blue (#8AA8A1), Pumpkin (#FA8334) , Rose (#FF006E), Icterine (#FFFD77)
We drafted a new class Results that will eventually replace the nested dict generated by solph.processing.results().
Before thinking about alternative back-ends to Pyomo, we should remove code duplication.

Group picture taken at the balcony of the FH Flensburg building near the habour.