Blog of Urs Riggenbach

First Wood-Based Lytefire 5 Unit to Make Pizzas in the Swiss Alps!

Posted Wednesday 9 September 2020 by Urs Riggenbach.

Since a few weeks we have the first wood-based solar concentrator installed at Heuberge Mountain Resort in Switzerland, where we have also installed our Solar Sauna. As reported earlier, in April 2020 we held an online design course with the Berne University of Applied Sciences to create wood-based solar designs.

So, when we were in the process of designing the Lytefire 5 unit to power a Solar Oven for Pizza and Bread making at Heuberge, we took inspiration from the students’ work and quickly moved to build the first wood-based prototype.

The solar concentrator is basically an adaptation of the solar concentrator for which we sell construction plans, but instead of using metal for the basic frames, here we use wooden beams. From our experience building this unit for the first time, the basic frame is assembled really quickly. We still followed the original construction guide steps for all the other parts, such as the mirror rows which still require a bit of welding.

Actually, the welding that needs to be done on the mirror rows is the perfect way to learn welding – during the course of the fabrication, solar pioneers Jiri Ucen from Heuberge and Lucas Castro from Solothurn came visiting and we instructed them in the welding process – and by the end of the mirror-row welding the quality of their welds was good enough to take on the more critical welds, such as the two supports that hold an entire mirror row – here we have to make sure the welds are structurally sound, and they were! It’s really exciting to see people pick up welding skills just like that to build a solar concentrator.

And that’s how the first solar pizzas on with the wood-version of the Lytefire 5 turned out (impossible to get a picture before people started eating the delicious pizzas!):

Online Interdisciplinary Design Course on Solar Thermal Energy

Posted Tuesday 9 June 2020 by Urs Riggenbach.

As reported earlier, together with Bern University of Applied Sciences (BUAS) we launched a education course on design and development of wood-based solar thermal designs for our Lytefire solar concentrators. Due to covid, we moved the course online. In this post we’ll go over the structure of this first online course.

Our online-course was fully booked and the 24 participating students came from the fields of wood-engineering, architecture and design. The interdisciplinary group had no prior experience working together and no experience working with solar. On GoSol’s site the project was lead by Judith Bernet and Urs Riggenbach. On BUAS’s site the project was facilitated by teachers Franz-Josef Niederwolfsgruber and Markus Zimmermann.

Screenshot from the interdisciplinary design course with BUAS.

Design Thinking

The main goal for us was to instil in the students our design-thinking which is based on developing practical solutions to the world’s most pressing problems.

“Practical” means it works in the real-world, meaning that a crazy amount of design parameters need to be met: It can’t be too costly, it has to be powerful, it needs to have high usability, it needs to be fabricatable with available materials and simple to maintain – and it should be built to last.

One key aspect is cost-efficiency versus efficiency. Western schools often teach efficiency assuming that efficiency is also reducing cost. This was true in a fossil-fuel powered world, where every percent gained in efficiency would represent huge fuel-savings over time. However, in renewable energies increase in efficiency do not result in increased cost-efficiency per default and often just create higher cost of equipment. Since the energy is there for free and is abundant and not finite, you can just make the solar concentrator a percent bigger if you want that extra percent energy. Our aim at cost-efficiency for the Lytefire product-line was a pay-back in less than two years and we hit 18 months in some cases and we are striving to get the payback down to one season which would be the best for many farmers and small-scale entrepreneurs in low-income countries.

Apart from cost-efficiency, the concept of simplicity is also key to develop innovation. We explained the team a lot about the context of where a solution is needed, and that for example eliminating moving parts can be a big gain as it reduces wear and tear and need to maintain systems – and at the same time has also cost-reduction potential. So a big part of the design-thinking we wanted to instill in the students was to seek for simplicity. It’s a difficult process, because to get to a simpler design requires more thinking and the result is – well, simpler! It took us years to develop a simple and cost-efficient way to concentrate the mirrors but in the end it is actually a very simple and elegant solution – and from looking at it these hours are not visible. On the other hand, it really takes a while for the simplicity of the design to sink in and sometime people say, Wow – it’s “just” that? But that’s so simple! – Yes it is, and that’s part of good design.

Preparation Sessions

To get things started we held preparation sessions. 2.5h hours each week were dedicated to this to get the students up to speed with the subject matter and prepare them for the practical intensive-week following the preparation sessions.

Before the first session we asked the students to familiarize themselves with the technology. We compiled a list of resources, mainly videos from our Youtube channel featuring the Lytefire 4, Lytefire 5 and Solar Sauna products. That way they were already able to get a first impression on the concept of solar concentration.

In the first session we held a presentation on the history of Solar Fire / GoSol / Lytefire, we covered the different applications running in the field and we did a technical walk-though of the different aspects of the technology. We ended with a Q&A session. Due to covid we were unable to bring the students to have a hands-on visit on one of the machines in Switzerland.

In the next session we presented the specific goals of the project. The students were to develop wood-based alternatives to our solar concentrator designs mainly built from steel. They were to design and create instructional content about the fabrication process. Due to covid we were unable to do a physical build-project, normally we would then also build the developed designs. We shared on the context of real-world entrepreneurs such as David in Kenya who bakes daily with the solar oven. The design would have to be fabricate with simple tools and skills so it can easily be maintained locally even in contexts like Kenya.

By the third session we had split the students into 4 sub-groups, and each group had started to develop drafts of wood-based designs. We spent the bulk of this session reviewing the different design-proposals from the group, we encouraged the groups to be creative and gave technical feedback. Each group was able to develop their own design, and as long as it fit the basic requirements and could technically work we left them free hands. The student groups were very creative and we encouraged them to discuss and agree as much as possible internally. In our experience it’s precisely this kind of internal design-discussion that results in great design. In the end every group got to refine one design proposal and create the instructional content for it. Some groups also prototyped their ideas in simple ways, which brought a lot of input to the preparation-sessions.

In the fourth session each group presented their design proposal along with first drafts of that the instructional content would look like. We provided feedback on both and gave inspirations where needed.

Project -Week

In the intensive week the students now worked in their group (all-though remotely due to covid), to refine their designs and create the instructional content and project deliverables such as the engineering calculations for strength/sizes of materials chosen.

We provided fixed times for coaching sessions with individual groups. All groups progressed steadily and on Friday of the week we held a presentation-session to which we also invited some guests from the Lytefire-Team which were not familiar with the project and could give an outsider’s perspective.


The project proved that it is really possible to teach the design-principles of solar concentration online and get the students to apply their design-skills to a completely new technology.

We were excited by the student’s creativity and energy. One group developed a design fully built in Bamboo, others impressed with great simplifications, such as removing wheels or creating wood-based pivot points requiring no metal screws. Another group developed a wood-based mirror holder. The groups also delivered great instruction content in the form of construction guides. Unfortunately we were not able to fabricate their solutions due to covid, but subsequent project-weeks could focus more on the practical aspects of wood-fabrication – the designs are ready!

Interdisciplinary Education Project to develop wood-fabrication methods of Lytefire Solar Concentrators

Posted Tuesday 12 May 2020 by Urs Riggenbach.

We are excited to announce that together with Berne University of Applied Sciences we facilitated an interdisciplinary design/build course in solar thermal energy. The course was held as part of their project-week format, where interdisciplinary groups of students get to apply their skills in design, architecture and wood-engineering to real world problems.

A Lytefire 5 solar concentrator.

At Lytefire we’re all about enabling people to have their own energy access. Powered by the sun, the Lytefire 5 for example helps entrepreneurs cut down on fuel costs. In many developing countries, and most recently also in France and Switzerland, our units often replace charcoal and firewood, and thus help preventing deforestation at the same time as increasing people’s incomes – by now we are 100% sure that there is a huge untapped impact potential in solar concentration.

One key aspect our our technology is that it is built using simple materials that are available locally practically anywhere on earth. The mirror material we use, for example, can be purchased from any glass-store found in larger towns (and we have worked in Kenya, Burkina Faso, Brazil, Philippines, Switzerland to verify that). The structural parts of the solar units is normally made from steel, and requires welding to complete. A welding machine costs 100 dollars and all-tough they say welding takes a lifetime to perfect we have trained people to weld the structural parts of the Lytefire 4 unit (for which there are construction plans available) in less than an hour. The Lytefire 4 is actually a perfect way to learn welding, as you an start with the minor parts and do the key welds at the end once your welding is solid. Nonetheless, welding does create barriers as generally there are fewer people with experience in working with metal than there are people working with wood.

Thus came about our collaboration with BUAS – the Bern Bern University of Applied Sciences. Together with an interdisciplinary group of students from the fields of wood-engineering, architecture and design, we have launched a project to develop wood-based fabrication methods and designs.

In 2012 we already prototyped the key parts of our solar technology in wood, to verify that there are no technical limits to building our technology in wood or bamboo long-term. With this project we are now able to bring in a group of motivated students eager to apply their skills to a real-world problem and develop solutions that can have an impact. The wood-version could be even easier to maintain locally, it could be more low-cost in some contexts and make fabrication easier for people already familiar with wood rather than metal.

Stay tuned for updates on this track and check the project page for more information:

Our Gift to the World:
The Lytefire Construction Guide Available Now!

Posted Tuesday 24 December 2019 by Urs Riggenbach.

Today we release the Lytefire 4 Construction Guide to help solve the climate change crisis. It is immediately available for free on the Website.

Available for download now on

After years behind the screen, in the field, working with entrepreneurs to develop solar technology that brings value to people and impact to the planet, we are really happy and grateful we can share this gift with you.

We invite you to build, use, and share. We are here and we will continue on this path, working with users, entrepreneurs, investors, sponsors and education partners - it will take all of us to spread solar energy in the limited time we have to avoid catastrophic climate change.

With the Lytefire 4 construction guide available for free, we allow anyone in the world to build our technology and start using solar energy at a fraction of the cost of other energy sources. We intend to release a lot more construction guides and educational material for entrepreneurs as we continue on this path.

But that’s not all! With the release of the Lytefire 4 construction guide we are also launching the Lytefire campaign to bring to market the Lytefire 5, our most powerful solar concentrator for entrepreneurs. We are also calling on investors and sponsors to join the effort to spread solar energy through product sales, open source construction guides and education. If you want to collaborate with us - check out the different options on and get in touch with us!

We are immensely grateful to have reached this point. Our belief that solar energy could not only be good in itself but inspire a more sustainable society as a whole is what brought our team together. Knowledge is the most fundamental approach to empowering people, and free knowledge means it can spread wide and fast. We want to thank all our partners, supporters and investors who have supported us over the years. Without you, we would not have reached this milestone. Thank you all!

GoSol Partners, Clients and Sponsors

Learn more and get involved:

GoSol Event on 14th of November at ResponsAbility, Zurich

Posted Sunday 3 November 2019 by Urs Riggenbach.

Swiss Impact Investing Network (SIIN) and GoSol are welcoming you to join us for an impact talk on the topic of How to Build a Business Model for Maximum Impact. The event is happening on 14th of November at ResponsAbility headquarters in Zurich, at 18:30.


Register here:


More about this Event

Join us for the "Impact Talk" Event about "How to Build a Business Model for Maximum Impact:" with the founders of


18:15 Registration

18:30 "How to Build a Business Model for Maximum Impact:" with the founders of

Followed by Q&A

19:30 Socializing at Café Gloria, Hohlstrasse 59, 8005 Zürich


Making a business profitable is difficult enough, having impact even harder. GoSol’s co-founders share their history of building and rebuilding a business model that puts impact first.

We’ll discuss challenges and strategies for finding an impact maximizing mission, developing impact-oriented technology and products, building the right team and why raising impact finance is important.

We’ll also share from our personal experience of staying motivated and persistent in face of the ever growing challenge of climate change and poverty and hope to motivate others to do the same.

About the Speakers

Urs Riggenbach, Chief Operating Officer, Switzerland

"A sustainable society needs a sustainable source of energy."

Urs has an international Baccalaureate from the United World College, India and BA in Human Ecology from the College of Atlantic, US. As chief operating officer, Urs follows closely all projects, financials and administration processes and supports the team in management and planning. As full-stack web developer he manages the company’s IT infrastructure, security policy and software development, always striving to optimize workflows. Urs has developed solar concentrators in Nepal and EU. Always willing to challenge himself, he can’t rest until the world is a better place for all.

Eerik Wissenz, Executive Director & CEO, Finland

"An energy solution must be low capital (the lower the better), yet power a viable economy, and be locally buildable and maintainable with little or no imports."

Co-founder and CEO of Solar Fire Concentration Oy. Finn and Canadian, Eerik studied mathematics at Ottawa and Carleton University. Quickly took a hiatus to dedicate himself to developing solar thermal technologies. Eerik developed solar concentrators in Mexico, Cuba, India and EU. Eerik has the vision of a fair solar thermal economy and he’s in charge of the strategy and the development of the company. He gave lectures at Tampere Applied Science University in Finland, Autodesk University in Los Angeles, Johannesburg, London, and Berkely University.

This event is organized in collaboration with SIIN - Swiss Impact Investing Network. More about SIIN here

Several GoSol Events are happening in Switzerland this September

Posted Wednesday 4 September 2019 by Urs Riggenbach.

Read in German

We are excited to extend our invites for two events that will happen in Switzerland this September.

Since a few days we have an additional Team Member with us here in Solothurn, Switzerland, and we’re busy completing a SOL5 solar concentrator .

After recent projects started up in East Africa, the Philippines and Brazil, we now also want to start in Switzerland roasting, drying, cooking and baking with direct solar energy!

Join us:

  • Saturday, 14. September for a live demo event at the Rosegghof Farm, starting at 14:00.
  • Tuesday, 24. September we are holding an evening event in the city of Solothurn, presenting on how direct solar energy can pave the way into a climate neutral future. With us will be Beto Borges of Forest Trends to present our work in the Amazon, as well as Lorin Symington from our team sharing on his experience in the Philippines and East Africa.

We look forward to starting many good discussions at our events. The events will be partly German, partly English. Please see the individual event infos below.

GoSol Experience Event - Experience the Direct Solar Energy!

Saturday, 14. September 2019 at Rosegghof,
14:00 to 17:30 Uhr

We are visited from Canada by Lorin Symington, who tells us about the beginnings of GoSol and makes several live demos with our solar units.


  • 10am: Start of setup of the solar units at the Rosegghof farm, interested people are welcome to join
  • 14:00: Welcome-Apéro with Solar Snacks, short presentation about GoSol by Urs Riggenbach and Lorin Symington,
  • 14:30: Live-Demos of the SOL4 und SOL5 solar concentrators for baking, roasting, drying and cooking
  • After 15:00 Uhr: Workshops with solar energy: Solar roasting, distillation of essential oils, pizza baking, etc
  • until 17:30 / Open End

Location: Rosegghof, Weissensteinstrasse 76, 4500 Solothurn

Signup/RSVP: Please fill our form or send an email to

(This event happens only with sunny conditions, the alternative date is Sunday, 15th of September. Please RSVP to the event.)


GoSol Impact Event - Direct Solar Energy and the Path toward a Climate Neutral Future!
Tuesday, 24. September 2019
18:30 - 20:30, Kino im Uferbau, city of Solothurn, Switzerland

GoSol combines vision, technology, education, collaboration and entrepreneurship. In this event we have visitors from Brazil and Canada and present our work, especially our project in the Amazon. How can we enable sustainable economies even in poorer countries in the age of climate change? How can direct solar energy also spread in Switzerland? Using concrete examples, we share our experiences and present our plan for a climate-neutral future.

Time and Date

Tuesday, 24. September 2019, 18:30 - 20:30 Uhr

Place and Schedule
im Uferbau
, Ritterquai 10, 4500 Solothurn, Switzerland

  • at 18:15 - Doors open
  • 18:30 - Presentations and interactive Parts
  • ca. 20:00 Uhr - GoSol: What’s next? Summary and start of Apéro
    Riche with Solar Snacks


  • Judith Bernet, Geographer and Moderator, Solothurn


  • Urs Riggenbach, Chief operating officer GoSol,
  • Lorin Symington, Chief Fabricator GoSol, Canada
  • Beto Borges, Director, Communities Initiative, Forest Trends, Brazil
  • Kurt Baumann, teacher and artist, Aarwangen

We look forward to to the event!


This was TBLI Conference Zurich 2019

Posted Saturday 20 July 2019 by Urs Riggenbach.

Last month I attended the TBLI Conference in Zurich. The conference brought together impact investors and companies with a commitment for real impact.

This was certainly one of the best conferences I’ve attended. Many participants shared in the impact-maximizing spirit, ready to learn about scalable impact solutions, have their own views challenged and motivated to figure out how we can use the ressources at hand to avoid climate and economic collapse. I look forward to collaborating with the many new contacts made.

TBLI stands for tripple bottom line, the concept of measuring a business not only on financial, but also on social and environmental returns. Learn more on TBLI here

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