---
title: 'Interview: Libre Solar'
author:
- Open make interview team
- Michel Langhammer
date: '2023-09-29'
slug: interview-libre-solar
categories: [interview]
banner: img/banners/libresolar_logo_small.png
tags:
- technology
- open hardware
- personal story
editor_options:
markdown:
wrap: 80
---

# Interview: Libre Solar

*By the Open make team and Michel Langhammer. Copyright to the authors,
distributed under a CC-BY 4.0 licence.*

**Sections:**

- [The project](#the-project)
- [The hardware](#the-hardware)
- [The research outputs](#research-outputs)
- [The participants](#participants)

*Banner image: libre solar logo, distributed under a CC-BY-SA 4.0*

> Date: 2022-08-02
>
> Interviewee: Michel Langhammer
>
> Interviewers: Robert Mies (TU Berlin) & Moritz Maxeiner (FU Berlin)
>
> Transcription and editing: Diana Paola Americano Guerrero, Robert Mies, Fabio
> Reeh, Moritz Maxeiner & Julien Colomb

<img src="images/screenshot.png" alt="screenshot of the interview" width="60%"/>

*Screenshot of the interview.*

{{< card "The Libre Solar in a nutshell">}}


*Image of the BMS circuit, by libresolar, distributed under a CC-BY-SA license.*

- Main website: <https://libre.solar>
- Project start: 2015/2017
- Core development team size: 7 people

### Hardware products

The project propose hardware and software building blocks for DC (direct current) Energy Systems: DC/DC Charge Controllers, Battery Management Systems, Communication Interfaces and other elements.
The libre solar is a set of (mostly electronic) products like a portfolio.
You have different components for different system requirements and can mix them to build up a system.

### Hardware maturity

Different products are at different development stage, it is declared for each
product on [the website](https://libre.solar/hardware/) with a badge: alpha, beta, eval, and release.

### Rebuilds

We have test fields of friends who are living in rural areas or trailer parks. They build up the off grid energy system completely by themselves. Additionally via the [forum website](https://talk.libre.solar/search?q=rebuild) some more rebuilds are visible but as it is open-source we cannot track the exact number of rebuilds.

{{< /card >}}

## The project

{{< card2 "Project start">}}
It was developed in Hamburg by Dr.-Ing. Martin Jäger, who’s the main developer and founder of the Libre Solar project.
Martin Jäger is a mechanical engineer. For him, it was tinkering around and learning about power electronics and software development. In 2017, people started to kick in, mainly in the firmware development and documentation.

When I jumped in concerning the educational resource, the benefit was to have open source resources for redesigning new systems like the solarbox.
{{< /card2 >}}

> How did the project Libre Solar started?

{{< expand "Show answer">}} The Libre Solar project started in 2015.
It all started with an Arduino based charge controller for photovoltaic
systems. With Arduino there was a low entry point. Later developed to a
next generation of charge controller with a STM32 microcontroller. The higher demand
regarding resolution and calculation time required the upgrade of the hardware
component.

There were different prototyping phases of different components.
It was always developing one component and testing it. Based on the
test we implemented new requirements. An example would be power classes and how
to get a higher current out of the system. There were different development
stages from the component. Now it's a set of hardware components such as charge
controllers and battery management systems (BMS) which allows a modular setup, in case you want to use different types of batteries.
For example, a battery management system is needed
for lithium batteries, if you want to use them. {{< /expand >}}

{{< card2 "Project process">}}

There were different prototyping phases of different components. It was always
developing one component, letting the PCB manufactured and soldering it at the Fab Lab and then testing it. Based on the test we implemented new
requirements.

We didn't write down everything in github issues, we just make an iteration of the documentation.

As we were some more people mainly from the university, we did an entry workshop about how to use Git. As the Libre Solar repositories were stored on GitHub, we used Github which is really comfortable because you have beside the version controlling, all this DevOps
functionalities behind it. {{< /card2 >}}

> Where was this developed?

{{< expand "Show answer">}} It was developed in Hamburg by Martin Jäger, who's
the main developer and founder of the Libre Solar project. He mainly developed
this by his own in the beginning. Later, people started to kick in, mainly in
the firmware development for example restructuring the codebase to add modularization of the
software. There is one firmware repository for all supported charge controllers so you can modularly choose the
different type of chargecontroller hardware and the firmware adapts to that. Same for the BMS firmware. {{< /expand >}}

> What was the core benefit of this project? How does the hardware fit in the
> overall project?

{{< expand "Show answer">}} The main benefit from the Libre Solar project was
learning about power electronics. Martin Jäger doesn't come from the field
of electronic development, he's a mechanical engineer. For him, it was tinkering
around and learning about power electronics and software development for renewable energy systems. It's
mainly the benefit for him as a developer. When I jumped in concerning the
Open Educational Resources (OER), the benefit was to have open source resources for
redesigning a Solar Box where we could develop an
application out of the electrical components from the Libre Solar project. This
was the benefit from my point of view as a student in that time. The benefit for the people
who are using the component is the possibility to build a renewable energy system by themselves. We have test fields of
friends who are living in rural areas. They build up the off grid energy system
completely by themselves. For example, there were users in South Germany who
rebuilt a the charge controller for supplying a environmental sensor node in a rural area. Besides, we have research
projects. As example, in Rwanda in Africa, we built up a test system with these
components. The benefit there for the people is that they can run an energy grid
system with open source hardware components. They are now able to redesign it by
themselves. But the knowledge level is still needed to know how to adapt and how
to redesign it. There're different layers of benefits. {{< /expand >}}

{{< card2 "Funding">}}
The first hardware and software development stage was made without funding by Martin.
The Open Educational Resources development was funded by the city of Hamburg via the Hamburg Open Online University (HOOU).
(All the money wasn’t spend on people but on external resources. For eaxmple the university didn't have the infrastructure for us. That's why we went to a local Fab Lab in Hamburg.)

A research fund from Scotland helped with hardware development and implentation together with partner startups.

{{< /card2 >}}

> How were the different parts funded?

{{< expand "Show answer">}} The first development stage was voluntary funded.
All the development was made free. At the education project we derived open
educational resources out of the existing design documents. This was funded by
the city of Hamburg by the Hamburg Open Online University. This was one funding
pot mainly for creating educational resources. And then the research projects.
Another funding was a research project from Scotland together with partner
startups who are interested in this field. This was financed by a research fund
from Scotland. {{< /expand >}}

> Did the Rwanda project come from Scotland as well?

{{< expand "Show answer">}} I think this was from Scotland. {{< /expand >}}

> How much money did you receive overall? Can you provide some ballpark numbers?

{{< expand "Show answer">}}

I don't know the size of the overall funding on the project. I have numbers for
the educational part. It was around 70,000 € in sum. There were two funding rounds where we
got money. For the Rwanda project I have no numbers. {{< /expand >}}

> Could you describe the overall process? How did you organize it?

{{< expand "Show answer">}} For the development of the Libre Solar Box and the OERs we created a student group which was accepted by our Professor for Automation Systems. With this student group, we replicated the Libre
Solar PCBs in a community-based workshop run in the FabLab St.Pauli. In the
planning process, we got a bill of materials (BOM) and saw what components we needed.
We divided the replication into PCB replication and the actual solar box
replication. Within PCB replication, we decided between to order a full assembled
PCB or to order just the printed circuit board without electronic parts on it. It was like the PCB
without components. With the ordered components we went to the Fab Lab and did
the usual process steps to do for electronics (putting soldering paste, pick&place the parts manually by hand and then baking it in a reflow oven). Afterwards it was about testing to see if all the components were assembled in the right direction and currency.
Then we flashed the PCB. Finally, we had a ready to use charge controller.
{{< /expand >}}

> How did you organize the development process?

{{< expand "Show answer">}} So the development process for the PCB mainly takes place in GitHub, as a collaboration platform. The repository is placed in GitHub. For the electric design, KiCAD is used as a development tool, to design the components. And then, you place ready design files in Github, and make some comments. We used the Git workflow, you have there and yeah. So this about development, using the tools on GitHub and then iterating.
{{< /expand >}}

{{< card2 "Work Coordination">}}
It’s like the usual software development workflow where you have other people who contribute, make a pull, push or merge requests or create issues and give comments.

Different people are working with different styles and the documentation gets a little bit unstructured and messy,
contribution guidelines help mitigate these issues.

If you don't have proper and easy understandable documentation, people don't have a good starting point where they can jump in the development.

Within the forum, you can see a lot of people who are interacting and making questions because they replicate the components by themselves.

For the local student group, we had a telegram channel where we had ad hoc communication. We built up a GitHub repository for the Libre Solar Box development where we had issue-based coordination. And we had weekly meetings at the Fab Lab St.Pauli.

About contributors: A review of the electronics was there but it was from friends. So we
had the direct contact. It wasn't on a GitHub sphere or distributed community
sphere.
{{< /card2 >}}

> Would you do this from different locations?

{{< expand "Show answer">}} The electronic design is mainly developed by Martin.
I have to look up if there're some other contributers. Especially in electric
designing, hardware is designed without many contributors because you need very specific
technical knowledge. It's like the usual software kit workflow where you have
other people contribute, make a pull, push or merge requests or give comments.
That's a typical good workflow. {{< /expand >}}

{{< card2 "Major issues">}}
From the development and production side the main issues were safety, quality and secureness. Especially when you work with batteries some people have been insecure how to handle the safety issues: You can’t shortcut them otherwise they will explode.

[Getting feedback was difficult]: A review was there because it was from friends. We
had the direct contact. It wasn't on a GitHub sphere or distributed community
sphere.
{{< /card2 >}}

> During that process or the project overall, what major issues have you come
> across and how did you resolve them?

{{< expand "Show answer">}} About development process issues, I can't tell much
because Martin is the main developer. I know there are issues regarding
contribution guidelines. Especially for the firmware, you stick to a code style
but different people are working with different styles and the code gets a
little bit unstructured and messy. For people to learn the code, it's important
to have a common structure. This was one case of a contribution guideline for
the software/ firmware design, but I can't say too much because I'm not too much
contributing in it. If you don't have proper documentation, people don't have a
good starting point where they can jump in the development. A proper
documentation is crucial.

The same counts for modular development that people
can contribute to specific modules or sub-modules of your hardware. From the
development and production side, the main issues was safety, quality and
secureness. When you work with batteries some people have been insecure on how to
handle the safety issues. You can't shortcut them otherwise they will explode.
There you need expertise and a guide how to trust the people you're working
with. Some of us had an electrical background. The people, who didn't have the
background in electrical engineering were more insecure about handling
batteries. {{< /expand >}}

> Did you them some idea what not to do?

{{< expand "Show answer">}} This was one issue besides the quality testing. For
quality parameters, there was not so much documentation done. About this, we depended on
expertise. {{< /expand >}}

> Did you receive some outside expertise from people?

{{< expand "Show answer">}} We had Martin as the main developer with the main
expertise. If he wasn't there, it would have been harder to do the quality test.
{{< /expand >}}

{{< card2 "Decision making">}}
Martin made most of the decisions in the hard- and software design of the electronics because he had the main expertise.

For the educational part and the Libre Solar Box application, it was made in a group of seven people by consensus.
{{< /card2 >}}

> How were the decisions made within the project all the time?

{{< expand "Show answer">}} Martin made most of the decisions because he had the
main expertise. What he said should fit. Other people had expertise which been
discussed. For the educational part, I was the project leader on the
administration side but I didn't make any decisions. It was made in a group of
seven people by consensus.{{< /expand >}}

## The hardware

> What hardware components have you developed in this project?

{{< expand "Show answer">}} It's been mainly power electronics (PCBs). {{< /expand >}}

> Were those PCBs parts of multiple products or were they all part of the same
> product?

{{< expand "Show answer">}} I would call it more a set of products like a
portfolio. You have different components for different requirements. You can
mix them to build up a system out of it. {{< /expand >}}

> Could you give maybe a quick overview over those products or are there too
> many?

{{< expand "Show answer">}} One type of product
are DC-DC converters for charging batteries so called charge controllers with different types depending
on power class and voltage levels. The second type is a battery management system which have
different types depending on how many cells you want to connect and the maximum current. The third are
communication gateways to connect to server-based applications via LoRa or Wifi . {{< /expand >}}

> How would you classify the products in terms of mechanical, electrical
> and software?

{{< expand "Show answer">}} First the electrical classification. Firmware would be another one.
{{< /expand >}}

> Did you have some mechanical issues, e.g.with the panels?

{{< expand "Show answer">}} No, the panels, batteries, cable and plugs were
sourced and out-of-self products. There are no mechanical components for the electronics just a 3D printed housing. But for Libre Solar Box application we use a mechanical frame from aluminium profiles.
class. {{< /expand >}}

> How would you rate the maturity from prototype, demonstrator to market ready?

{{< expand "Show answer">}} We declared on our website the different development
stages. I don't have it all in my head. If you look there, you can see the
development stage declared for each product. {{< /expand >}}

> Have these hardware components been built, produced or modified by others
> outside of the project independently?

{{< expand "Show answer">}} Yes, definitely. We had a makerspace in South
Germany who replicated one charge controller completely by themselves, we didn't
even know about. Afterwards they sent us a link to the forum when he discussed
it. They replicated it and used it to supply a sensor node. This is one
independent replication of the component.

We have a forum in the project. Within the forum, you can see a lot of people
who are interacting and asking questions, because they replicate the components
by themselves. I don't have an exact number. {{< /expand >}}

> Is the project still ongoing and you're working together in a group?

{{< expand "Show answer">}} The hardware development of the electrical layout is
mainly done by Martin Jäger. I have to look in the GitHub[*] if there are more
contributors. I'm doing the educational part. I'm designing the resource
contents for education. Kathrin, who was in the Open Hardware Summit, works in
the educational part because she's in the library and does a little bit of
software for data visualization. On the data software side are contributors, but
we aren't in a local student group here in Hamburg any more. It's distributed in the world.

[* Notes from the open make team: not many more contributors spotted on GitHub, although the projects are often forked.]
{{< /expand >}}

> Are you all working on the same hardware what can be found on the repository?

{{< expand "Show answer">}} Yes, everything around the hardware components
within the Libre Solar project. {{< /expand >}}

## Research outputs

> What were or still are the envisioned outputs of the hardware development in
> terms of publications, the hardware itself, documentation, learning and
> experience?

{{< expand "Show answer">}} My wish is to build up Libre Solar as the Arduino
for renewable energy systems. I always wanted to have an open hardware base for
learning and building up its own renewable energy system for everyone. It's for
industrial, private or educational use. We aim for a ready to sell product and
we are nearly there. It's just because of the CE certification. We already did a
few tests in the laboratory for measuring the CE standards but we were out of
range and didn't get the CE certification. That's why we can't legally sell the
products, but it's a goal.

Right now we have the supply shortage of
micro-controllers which causes the prototyping process to hold, because we can't
source STM 32 micro-controllers. In the beginning, the goal is to have a set of
hardware components ready to sell with a portfolio for educational reasons and
research institutes. There was a connection with the University of Freiburg and different
other universities are interested. This is a low entry point because you
don't need the proper certification if you just use it in research environment.
{{< /expand >}}

> Would those be your customers?

{{< expand "Show answer">}} This would be one channel. For example, we think of
sensor nodes for agricultural applications. It's electrical energy supply, we can use it for nearly
everything which needs electrical current. {{< /expand >}}

> Do you combine the Libre Solar with other hardware?

{{< expand "Show answer">}} We combined the UniProKit project which is a set of aluminium profiles and fitting 3D printed junction parts. So we combined this hardware project with the Libre Solar electronics to build the Libre Solar Box.

{{< /expand >}}

{{< card2 "Academic outputs">}}
It’s not the main goal.
{{< /card2 >}}

> What do you think about publications in scientific journals or in hardware
> journals?

{{< expand "Show answer">}} It's not the main goal. I'm a researcher now. I
talked with Martin about the publication of one paper, for example, from Joshua
Pierce on Hardware X. There you can publish open source hardware projects, but
it's not the main focus. {{< /expand >}}

> Did you publish project findings in relation to the hardware like issues you
> faced in the development process and what you learned in the development
> process along with the individual bill of materials, CAD files, assembly
> instructions, guidelines, essentially and everything you found out during the
> process of development?

{{< expand "Show answer">}} Not specifically, our feedback or the issues is that
we make an iteration of the documents and republish the documentation. If we see
that there is something missing within the documentation, we redevelop the
documentation and publish it. But it's not explicitly a publication about the
issues. We're thinking about a blog. If you have a blog post, you can say: 'here
is something we made'. It's a little bit like issue tracking using GitHub. While
we were in a replication workshop, we didn't write down the issues. We just make
an iteration of the documentation. {{< /expand >}}

> The research output was the hardware itself and not any publications around
> it?

{{< expand "Show answer">}} Yes, no publications. {{< /expand >}}

> What kind of information have you shared in terms of the bill of materials,
> CAD files, assembly instructions, warning and safety guidelines.

{{< expand "Show answer">}} I could have a look in the repository. It's mainly
for the hardware with common information like design files, CAD files and
interactive bill of materials. We didn't provide an assembly guideline for
electronics but we made a guideline how to source the components. It's like our
educational resource website where we put in everything concerning assembly
processes. {{< /expand >}}

{{< card2 "Publication strategy">}}
We published it only on GitHub. There’re some linking to the wiki from Open Source Ecology in Germany.

Open Source Ecology helped to disseminate or promote the project in a way.
We provide information on different platforms to draw more people for us and the Open Source Ecology.
{{< /card2 >}}

> How did you publish the hardware?

{{< expand "Show answer">}} We published it only on GitHub. There is
linking to the wiki from Open Source Ecology in Germany. The key entry in this
platform is describing a so called Open Nano Grid. This would be another
application you can make with hardware components from the Libre Solar project.
{{< /expand >}}

> Why did you choose GitHub and the Open Source Ecology?

{{< expand "Show answer">}} GitHub was like the poster in this time, Martin
Jäger choose it. I think it was the most common collaboration platform for
software development and electronics. It's really comfortable because you have a
version controlling and all this DevOps functionalities behind it.
{{< /expand >}}

> Was using this platform for development easy or have you faced any barriers?

{{< expand "Show answer">}} The starting point is a little bit tricky. For
people, who come from outside and aren't aware of software, it's hard to
interact with GitHub or Git-based repositories. {{< /expand >}}

> Why didn't you publish issues you came across? Was there any active decision
> making?

{{< expand "Show answer">}} No, I think it wasn't a high quality notes document
that we had. We didn't have the time to make it in a qualitative documentation
to publish. {{< /expand >}}

{{< card2 "Core team and community">}}
The creating of more content is limited by the amount of people, time and financial resources. Everything is on a voluntary basis.

With master students from electrical engineering, renewable energy systems and mechanical engineering, we mainly replicated the Libre Solar hardware and redesigned the solar box.
I was introducing it to all the courses. They wrote me they were interested.

We used a typical forum where people can add questions and threads.
It’s very good because you see people contributing in this topic.
This shows that different people come with different requirements.

{{< /card2 >}}

> Is there something else besides the time constraints?

{{< expand "Show answer">}} Yeah, that's one of the main main components and
maybe the amount of contributors. If you have more contributors who feel more
safe with the thing you develop, you will get more feedback and you can optimize
the product better. When Martin Jäger is the only developer here, he always
doesn't know if the design is the best design. The feedback on hardware design
is crucial besides a lot of contributors.

It would be easier because now you're developing and you maybe know that the
quality is quite good but you don't have the direct feedback. Because we don't
sell the product, we don't have a customer environment feedback process. For
now, there's not so much qualitative feedback for the design. {{< /expand >}}

> Since the project has been reproduced in independently, did they need to
> reinvent anything or did they have all the information they needed to
> reproduce it?

{{< expand "Show answer">}} From the independently replicated parts we don't
have any qualitative feedback. I can just assume and you can analyze the forum.
{{< /expand >}}

> How did you handle problems with GitHub?

{{< expand "Show answer">}} It's easy for people who have a technical or
software development background. We did the entry workshop about how to use Git.
(Yeah, okay.) A colleague of ours did a little workshop. The graphical interface
of GitHub makes it much more easy using it and it was like trial and error or
working with it together. It helped to focus on the main features. With time the
people got used to it. It's like a learning curve for platforms. {{< /expand >}}

> Could you explain the connection to Open Source Ecology Germany?

{{< expand "Show answer">}} Yeah, it wasn't directly to GitLab from Open Source
Ecology but to the wiki from Open Source Ecology. (Open Source Ecology
Germany is running a wiki). There they can maybe just search for the entry. It
was like one article where they mentioned the Libre Solar project. But we are
documenting it mainly on GitHub. Other people, who are reusing the component,
are documenting it and the key focus was ecology. They helped to disseminate or
promote the project in a way. Some people informed others that there's this
component you can use to build up an open nano grid. This was the system they
introduce. Therefore, they link to the Libre Solar project and say that this is
the open hardware component you can use for building up such a system.
{{< /expand >}}

> All right. And so you you use these pages as well, I mean, I see I see your
> name here. You use this to and to draw more people, I guess, at least a couple
> of people.

{{< expand "Show answer">}} We provide information on different platforms to
draw more people for us and the Open Source Ecology. That project pays to show
the interlinking or the collaboration between the organizations. Indirectly,
it's to draw more people and to reach out from the different organizations.
{{< /expand >}}

> Could you explain the connection with the POC 21 of Libre Solar?

{{< expand "Show answer">}} I wasn't involved there, this was before my time.
Martin Jäger attended at the POC 2021 meeting in Paris. I don't know how he got
there and under which circumstances. He was asked for something that I don't
know. He got to know different people from this from the Open Source Hardware
community and they're still connected there. {{< /expand >}}

{{< card2 "Local production">}}
I think because the documentation is there. They're replicating it.

The second part in the educational part is the production.
We have development and production stage and now the usage stage. Each component has a user manual.
It would contain the data acquisition, data analyzes of energy systems and improvements.
The fourth stage would be recycling or upcycling of such components.
{{< /card2 >}}

> How would you classify the overall information you've put out?

{{< expand "Show answer">}} The main clustering was the hardware, education and
maybe the website. Then it's three or four if you want to consider the forum as
an information base. It's like the hardware information. This was mainly the
repository you have on GitHub. The hardware information is consisting of the
design files, BOM file, readme file and an overview. This is the technical
documentation of the hardware. It's one main information cluster. For all the
components, a separate or a dedicated repository exists with these informations.

The second information cluster is the learning cluster. It's the
open education resources. The main idea behind it is to give a basic information
about the used technologies within a system. It's divided in two chapters. One
is a system view to have an overall view of what we are here talking about
regarding the nano grid system, renewable energy and PV battery. The second part
is the component part. It's to dive in into the components. For example, how is
a charge controller built up? What does a charge controller contain? It has a
power electronics, measuring and communication stage. I'm clustering it in the
sub-components of the hardware. The idea behind it was that people who want to
contribute in the development have a starting point of what do they want to
develop. If you have an electrical engineering background, you don't need this
because this what you learn in university. But if you don't have and you're
interested in renewable energies, you can use the educational resources to get
the basic overview.

The second part in the educational part is the production.
It's about how to replicate and produce such components. I'm oriented on the
life cycle process. We have development and production stage and now the usage
stage. Each component has a user manual. For learning environment, user usage
and documentation it would contain the data acquisition, data analyzes of energy
systems and improvements. But this isn't yet developed. The fourth stage would
be recycling or upcycling of such components. {{< /expand >}}

> All right, yeah.

{{< expand "Show answer">}} The forum was a typical forum where people can add
questions and threads. It's very good because you see people contributing in
this topic. There is one about the development of a new charge controller and
this was a very active thread where people give their feedback to it. It went on
for some time. It results in a new development of a hardware. This shows that
different people come with different requirements and make up their mind for the
development of a new 20 ampere maximum power point checker. {{< /expand >}}

> Is this on your own website again? It's like a repository blog.

{{< expand "Show answer">}} It's made with static site generator called
viewpress and a git repository. There's a framework and broad usage. Within
viewpress are different content blocks. This forum is based on this course an
open source forum platform. {{< /expand >}}

> Do you publish everything there?

{{< expand "Show answer">}} GitHub is the main backbone of all information and
data. It's linked to two other front end websites. {{< /expand >}}

> Did you publish everything you have?

{{< expand "Show answer">}} Yeah, everything is published. For example, the main
development of the battery management system, which got funded by energy access,
is within one repository. Energy access funds open hardware project in the field
of renewable energy.

The creating of more content is limited by the amount of people, time and
financial resources. Everything is on a voluntary basis. {{< /expand >}}

{{< card2 "Successes and failures">}}

Successful is the ready to use prototype we developed.

In my opinion, it's a very high quality documentation of all the components,
it's very structured. We were able to develop educational resources within such
a hardware project which isn't typical.

The idea behind the open education resources was that people who want to
contribute in the development have a starting point of what do they want to
develop.

The feedback on hardware design is crucial. It would be easier with a lot of
contributors. For now, there's not so much qualitative feedback for the design.
It would be nice to have more contributors dedicated on the electrical hardware
design.

If we would have people who manage the feedback and community work, we could get
more qualitative feedback out of it.

{{< /card2 >}}

> What was successful and what wasn't about the project?

{{< expand "Show answer">}} Successful is the ready to use prototype we
developed. I would declare it a prototype because of this legal issue of the CE
certification and not call it a product. It's ready to use and people are using
it with off grid applications all around the world. We have a feedback loop from
the research project how the system is running: It's running. This is the main
success. The documentation is a success, too. In my opinion, it's a very high
quality documentation of all the components, it's very structured. We were able
to develop educational resources within such a hardware project which isn't
typical. The contribution in the hardware design is improvable. This is still a
gap. It would be nice to have more contributors dedicated on the electrical
hardware design. We had some reviewers which was good. We need to know how to
improve the EMC within the electrical component. There was a review but not an
active contribution to this. {{< /expand >}}

> What kind of contributions are you looking for?

{{< expand "Show answer">}} A review was there because it was from friends. We
had the direct contact. It wasn't on a GitHub sphere or distributed community
sphere. It would be nice to have a review and improvement suggestions for the
design. A complete redesign isn't the goal behind it. If someone would redesign
it and make a suggestion, that would be very cool. But it's not the main goal.
{{< /expand >}}

> Do the universities and others, who are using it already, contribute ?

{{< expand "Show answer">}} They don't contribute in the electrical electrical
layout. I think, the users are mainly people who need the current and want to
have renewable energy. The main reason is always the software part. You have
open interfaces where you can extract data out of it and you can control data
out of it. You have the operating power for the system. You can use it for your
requirements. If the current flow is not 99%, these users doesn't care about if
they see a failure. Till now, they wouldn't contribute to erase this failure to
improve function. {{< /expand >}}

> How do people use it? Do you sell it and they put it together? How far is the
> reach of the hardware?

{{< expand "Show answer">}} They're building it by themselves. I think because
the documentation is there. They're replicating it. We had one hardware where we
made a little batch of 100 components and this was sold. Now the batch is empty.
We had no CE certification for one component, therefore it was only for
educational and tinkering purpose. Another example, at the CCC Congress we had
around 10 and we sold three out of it. It were Universities from France and UK.
The third I don't know anymore, but there were people who were interested and
said to buy a new one, because they have a research topic and it costs like 50
or 60€. There were distributed server applications and they wanted to test how
servers can run on renewable energy systems. This was the perfect use case for
them because they can extract all data out of the charge controller and they can
correlate with their process data. They are still running on those parts and
sharing with us information.

If we would have people who manage this feedback and community work, we could
get more qualitative feedback out of it. {{< /expand >}}

## Participants

> What brought you to this project?

{{< expand "Show answer">}} At this time, I was a member of the Open Source
Ecology association in the field of open source hardware community. I was
attending some lab meetings. I was definitely convinced by the idea of open
source hardware and I was intrinsically motive interested in renewable energy
systems. I studied electrical engineering with the focus on automation systems
and therefore my interest are energy systems and the automation aspects behind
it. When I moved to Hamburg, there was one member of Open Source Ecology who
said to me that there is the Libre Solar project and Martin Jäger, the
developer, lives in Hamburg. This was a coincidence. Besides I found a call from
the open Hamburg online university to contribute to a project of open education
resources. Afterwards I made a concept to build a box which I've seen in the
Open Source Ecology wiki. It was a solar box. But it used different types of
PCBs of solar charges. At this time, it was a solar charger developed by a
Canadian developer. So my idea was to take this solar box and take the Libre
Solar components out of it. I already had the electrical expertise to design
this a little bit in my head.This was when I called Martin Jäger and introduced
him to this idea and he was interested. That's how I jumped in. It was mainly
within the development of open educational resources. {{< /expand >}}

> Was this like a thesis or how did this project start?

{{< expand "Show answer">}} It was a funding project of the Hamburg Open Online
University. They had a funding round and they were very interested of students
who contribute. At this time it was mainly professors, researcher and staff. I
was like a student which they were very interested in. This time I got funded.
It was like 25,000 Euro. It was like the first funding project for me. I was a
completely inexperienced with such things. I was just a student.

My professor was the mentor because that was needed from the Hamburg open online
university. I was a student and the project leader of this funding project.
That's how we started. In this project we didn't pay any people. This was my
idea to have people who are intrinsically motivated who would join without
money. We took all the money for buying hardware, to rent fab labs and the
machines and producing a promo video. It's a little YouTube video of introducing
open source hardware. All the money wasn't spend on people but on external
resources. {{< /expand >}}

> Have other grants been used to pay people?

{{< expand "Show answer">}} The second grant we get was used to pay student
assistants. They created the content. Our idea was bigger and it was to much to
write this content all in our free time. {{< /expand >}}

> What were the occupations of the people who contribute?

{{< expand "Show answer">}} It wasn't directly to the Libre Solar project. With
the beginning of this open educational resource, I started a student group with
my professor as a mentor and we called the student group "collective open source
hardware". „Cosine eight" was the name behind it. We were the seven people in
the student group. We mainly replicated the Libre Solar hardware and redesigned
the solar box. {{< /expand >}}

> Were all of you students? Could elaborate if there're other postdocs or
> professors.

{{< expand "Show answer">}} My old supervisor, or professor, wasn't in the
content. He wasn't really part of it. He was very interested and he gave me all
the possibilities. I started to introduce this project in all courses within the
university. I jumped in 20-25 courses and introduced it to the students with his
help because he introduced myself. It made it a little bit easier to introduce
my project because he said it's a good project and you should listen to it. In
the group we were students and Martin Jäger has a PhD degree. He worked part
time in the automotive industry and part time developed the Libre Solar project.
The others were all mainly master students from electrical engineering,
renewable energy systems and mechanical engineering. In the Hamburg open online
university we had some communication designers who did the logo and other icons.
They designed it for us or helped us to design it. They were employed at the
Hamburg Open Online University. It was a service they gave us for free.
{{< /expand >}}

> How did you find all these people?

{{< expand "Show answer">}} I was introducing it to all the courses. It acquired
them by myself and some of them I knew already. With two of them I had direct
contact and the others were interested after introducing it. They wrote me an
email and told to be interested.

We had two students who made their student project work in this area. They took
a solar box and made the testing. They tested all the parameters of the solar
box, for example current versus saturation. But it didn't went so good to be
honest because they didn't document anything. It was for them to do it but not
on a qualitative level. They just did it for getting the credit points without
the open source community documenting. It was a project work they had in one
course. {{< /expand >}}

> Did all students receive credit points for the work?

{{< expand "Show answer">}} No, it were only two of them. They said they had to
do a project work. They asked if they can do this project work in this field.
For myself, I didn't get any credit points because we didn't have a project work
where we could use this for. But I did my master thesis in the Libre Solar
project. I asked my professor if I can do my master thesis there. I introduced
the topic, it was about control systems {{< /expand >}}

{{< card2 "Personal gain">}}
Some students perceived a benefit, they could get credit points. For the others, it was fun. You're playing football and others are tinkering in a Fab Lab.
It provided a learning effect. Application oriented learning I would call it now.
{{< /card2 >}}

> How did the different members benefited from the work?

{{< expand "Show answer">}} I think, Martin Jäger's was happy that people were
interested in his project. In terms of community reach out, this supported
community building for him. The main idea of the student group was to get more
students in the field of open source hardware. In 2017, no students knew what
open source hardware is. This was in my field, I was very pity that no one knew
what open source hardware is, especially engineering students, because there's
so much potential behind. It's still the case. I think, this was for Martin a
motivation because we talked about it. He said that's a good idea to disseminate
the idea of open source hardware within engineering students. Some students
perceived a benefit, they could get credit points because they had this project
work where they got credit points. For the others, it was fun. You're playing
football and others are tinkering in a Fab Lab. For some, it was the first time
of manufacturing. For example, I studied electrical engineering and I've never
picked and placed a PCB. I've never saw a PCB production. It was in theory
taught but we never experienced it in the laboratory. It provided a learning
effect. Application oriented learning I would call it now. {{< /expand >}}

> Who got paid from the grants?

{{< expand "Show answer">}} Martin Jäger got a little bit of this money because
he has this high education level and he put a lot of time in it. We said to
Martin to write a receipt because he's working so much in this field. Even
though he didn't want it to but we said that's money for your work. Besides we
did the video I mentioned. It was a video creator who got paid for doing
information videos. {{< /expand >}}

> Didn't anyone receive payment for a longer period?

{{< expand "Show answer">}} In the second phase we got students paid as student
assistants and paid students for creating the content. {{< /expand >}}

> How many student assistants did you have?

{{< expand "Show answer">}} We had two. I think they worked for a year or a year
and a half. There was Corona and maybe it was extended by half a year.
{{< /expand >}}

> Was all of this still at the Hamburg Open Online University situated?

{{< expand "Show answer">}} All of this was at the Hamburg Open Online
University. {{< /expand >}}

> How did you coordinate the work?

{{< expand "Show answer">}} The coordination of the development was quite easy
because Martin was the only developer at this time. The software development
coordination went through Git. The research projects had a typical research
project coordination with Martin as a partner. But I don't know the exact
constellation of the research project he worked with. For our student work the
coordination was made by me. We had a telegram channel where we had ad hoc
communication. We built up a GitHub repository where we had issue-based
coordination. This was a little bit of our project management behind it.
Besides, we had weekly meetings at a Fab Lab. This was every Thursday, it was
meeting in the evening with discussing and thinking about the design and
requirements. It was in the Fab Lab St. Pauli.

Martin was there before us. His first prototype and first testing system was
build in the Fab Lab St Pauli. At the Fab Lab St. Paul was a solar panel
charging a battery. This is why we went to the Fab Lab St Pauli, too.
{{< /expand >}}

> Why didn't you meet at the University?

{{< expand "Show answer">}} The university didn't gave us a room. We asked for
it. They brought us then in an old laboratory, where we could hang around. But
this isn't a good place to work. Then they build up a Fab Lab but it wasn't open
for students. We asked for it but it's just for start-ups and some ecosystem
share stakeholders.Further, there was a Fab Lab with 3D printers. But it wasn't
a Fab Lab where you can like tinker around, it was just for 3D printing. The
university didn't have the infrastructure for us. That's why we went to a Fab
Lab. {{< /expand >}}

> How many members were in the project?

{{< expand "Show answer">}} We were seven people.