Tour de Sol – Pioneer Era of Solar Vehicles

The buzzword electromobility is now on everyone's lips, and solar panels on rooftops are no longer anything special. However, the times when these technologies were still in their infancy are almost forgotten. Switzerland played a significant role in promoting these innovations.

The oil crisis in 1973 highlighted that fossil fuels are not inexhaustible. Following the crisis, several companies in Switzerland began focusing on the use of solar energy [1]. But soon the energy crisis was forgotten, and a decade later, the last remaining companies from that time were struggling to survive. One of these companies was Jenni Energietechnik AG, founded by Josef Jenni. To promote the company and the use of solar energy, the idea was born to drive through Switzerland with a solar-powered lightweight vehicle. Jenni was inspired by Australians Larry Perkins and Hans Tholstrup, who had crossed Australia in 1982 with their solar car "The Quiet Achiever" [2]. This idea eventually developed into a friendly solar car race, and the "Tour de Sol" was born. Josef Jenni, together with his brother Erwin Jenni, built a prototype of a solar car. This was to test the feasibility of a solar-powered vehicle and simultaneously serve as a promotional tool for the endeavor.

The interest and media response to the Tour de Sol were already very high in advance, attracting many participants for this adventure. The first Tour de Sol took place at the end of June 1985 and covered five stages and 368 km from Romanshorn to Geneva. It was the world's first solar car race. In the first edition, there were three categories: [1]

• Category I: Solar cars without auxiliary drive – These solar cars could only draw their energy from the sun. The conditions were a PV area of a maximum of 6 m², a maximum generator power of 480 W, and at least three wheels.

• Category II: Solar cars with auxiliary drive – These solar cars had to meet the same conditions as category one but could also be powered by muscle power via pedal drives.

• Category III: Colorful variety – The vehicles in this category were not subject to any restrictions, but it was naturally understood that they had to be environmentally friendly means of transport.

Since some of the solar cars without auxiliary drive had to be charged from the grid during the race, a separate category was created for these vehicles so they could continue to participate in the race. The solar modules used in the first vehicles cost about 1000 Swiss francs each at the time and were used accordingly carefully. To reduce costs, some participants of the Tour de Sol resorted to creative solutions: they used mirrors to direct sunlight specifically onto a few solar cells to maximize their efficiency [3].

These ingenious methods demonstrated the inventiveness and commitment of the early pioneers of solar mobility. Despite the high costs and technical challenges, they did everything they could to make their vehicles as efficient and cost-effective as possible. The Tour de Sol thus became not only a competition of technology but also a showcase for innovative ideas and solutions in the field of renewable energies. This is why media interest was high during the solar race, and the Tour de Sol was featured on television every day. Entire school classes waited on the roadsides for the solar racers. Of the 73 solar cars that started at Lake Constance, 58 reached the finish line in Geneva. The winner in Category I "Solar cars without auxiliary drive" was the vehicle from alpha-real/Mercedes Benz.

After the success of the first Tour de Sol, eight more editions of the race took place until 1993. The conditions and vehicle categories were repeatedly adjusted to the current state of development. Inspired by the Tour de Sol, similar races emerged worldwide, and since 1987 there has been the World Solar Challenge in Australia. The Tour de Sol was a pioneering project that significantly advanced the development of solar mobility.

The development of solar technology continued

Solar technology has greatly improved since the first Tour de Sol. Compared to 1974, the modules have not only become more efficient, but the prices of solar modules have also fallen to less than one percent of the costs at that time [4]. Before the start of the first Tour de Sol, participants with their "tinkered" vehicles were taken only partially seriously, the technology was too new, and its potential too unknown [1].

In terms of advertising, the Tour de Sol proved to be a complete success. Nevertheless, solar vehicles remain distant from the mass market to this day. Why is that?

For a race like the Tour de Sol, which is entirely powered by solar energy, high efficiency was essential. This meant that the vehicles had to be as light and aerodynamic as possible. Today's production vehicles, however, range from 1.5 to 3.5 tons, and good looks are more important than good aerodynamics – a combination not suitable for efficient solar operation [5].

Nevertheless, there have been repeated attempts in recent times to fuse solar cells with electric cars. However, these have mostly failed due to financial difficulties. To be attractive to the mass market, solar vehicles need to offer more than just energy efficiency and sustainability [5]. Josef Jenni, a pioneer of solar technology, criticizes that today money often takes precedence over environmental protection [6]. As long as we have a strong power grid that allows us to easily operate even battery-powered 3.5-ton luxury electric vehicles, it will be difficult to successfully market a solar-powered vehicle [5].

Development of electromobility in Switzerland

Switzerland has always been a significant player in the development of electromobility since the early 1900s. Even then, renowned companies like Tribelhorn and Ciem built electric vehicles. Despite the dominance of the combustion engine, the idea of electric propulsion largely persisted in various market niches [7].

In the 1970s, electromobility in Switzerland received a strong boost through various environmental movements and innovations. The Tour de Sol generated great media interest and became a symbol of alternative drives and environmental awareness of that time. This movement was also promoted by Swiss politics, which increased the significance of the Tour de Sol. The potential of electromobility was recognized and then promoted [7]. Many pioneers who participated in the Tour de Sol played an important role in the further development of the electric vehicle. Two of these pioneers were Erwin and Josef Jenni, who demonstrated with their contribution to the Tour de Sol what was possible with electric drives.

A large-scale experiment with electric vehicles in Mendrisio revealed the potential of electric bicycles. Support programs and financial incentives for e-bikes became apparent and ultimately led to a significant market share of electric bicycles in the Swiss economy. This made Switzerland an important contributor to the success of e-bikes throughout Europe [7].

Today, electromobility in Switzerland is well advanced. Almost half of the newly sold vehicles run on alternative drives, and about a third of them run purely on battery power. E-bikes have also sold well and make up about a third of the bicycles sold. Switzerland is considered a model example for the use of electric drive technologies and follows global movements [7].

A well-known Swiss company that emerged from the Tour de Sol is Biketec AG (later known as Flyer) from Huttwil. This company set early standards in the field of electric bicycles with the "Flyer Classic" in 1995. The model was known for its reliability and quality and significantly contributed to the spread of e-bikes in Europe [8]. Kyburz Switzerland AG, founded in 1991, is also known for its electric utility vehicles and is closely linked to the Tour de Sol. The three-wheeled Kyburz DXP is used by the Swiss Post and is thus also a model in terms of electromobility [9].

What impact has the Tour de Sol had on the development and acceptance of electromobility and solar technology today?

The Tour de Sol was undoubtedly a promotional success. It showed the broad Swiss population the potential of both solar technology and electromobility. Several successful companies emerged from this group of tech enthusiasts. Although lightweight solar vehicles are not yet rolling on the streets today, we see a strong expansion of renewable energy technology and a boom in the e-car industry. E-bikes are very popular, and small, efficient vehicles like the Microlino or the Twike are occasionally seen on the roads. The influence of the Tour de Sol is still recognized in publications today and is considered the starting point for the connection between photovoltaics and vehicles [10].

Interview with Erwin Jenni

Erwin Jenni is the engineer, builder, and driver of the vehicle exhibited at Enter.

How did you come to organize the first Tour de Sol and what was your goal?
We wanted to find out if it was possible to operate a vehicle solely with solar energy or even to construct such a vehicle. This experiment resulted in a bicycle-like vehicle that served as a prototype. After we managed to get it running and found that it worked, the idea for such a race was born. The goal was to promote solar energy and show people the possibilities it offers.

What was the state of technology when planning the first Tour de Sol? Did you have to invent components?
The individual components were available, but there was no plan on how to combine them into a vehicle. Of course, much of the vehicle was homemade, such as the chassis. The solar modules used came from the USA and supplied the vehicle's batteries with energy.

What were the costs for the prototype?
I can't give an exact number, but it was probably over 10,000 CHF. About half of the costs were due to the solar modules, which were still quite expensive at the time. The small modules attached to the vehicle cost about 1,000 CHF each. Some participants came up with special constructions with mirrors to get by with as few solar cells as possible.

How did the search for participants for the first Tour de Sol go?
It went very well. We held a promotional event with our prototype, which already attracted a surprising number of people. We also advertised in the magazine of the Swiss Association for Solar Energy SSES, which made us known beyond the country's borders. The participation of Mercedes-Benz with its apprentice workshop was a stroke of luck and of great importance for public perception.

What experiences were made with the first vehicle and what changes were made based on those experiences? The variety of vehicles was enormous, as there was nothing comparable until then. For most participants, the first event was also the first test of their vehicles, which led to some breakdowns. It turned out that suspension was very important for the vehicles. It not only improved road holding by preventing the vehicle from lifting off at every bump but also contributed to the stability of the components. Burst tires, too weak wheels, and brakes were common. These problems were continuously addressed in the following years. Overall, enormous progress was made in development in later tours.

Did patents or new technologies emerge from the Tour de Sol?
No, I am not aware of any patents. But there was a lot of development and inspiration. Companies like Flyer, KYBURZ Switzerland AG, or Twike, which are connected to the Tour de Sol, later emerged. Many tinkerers from back then were also brought into the industry.

What kind of audience did the event attract?
Was it mainly tech enthusiasts, or was there broader interest? The first Tour de Sol attracted a lot of interest, much more than expected. We almost rivaled the Tour de Suisse. Besides the numerous tour participants, we had many spectators along the roadside. The media at home and abroad reported on the event, and we were also noticed in politics.

Was there increased enthusiasm or acceptance for the new technology among the population due to the Tour de Sol? Our perception was very positive. The technology was so new that there were hardly any critics. Probably because of this novelty, the interest was so great. Of course, some people saw the whole thing as a gimmick. But we managed to attract enormous attention and prove that it works. That was our success.

Looking back: Was the development of solar technology after the Tour de Sol gratifying or too slow? Basically successful, the company Jenni Energietechnik still exists (laughs). The Tour de Sol clearly showed what is possible with solar technology in Switzerland. We also hoped for a trend towards small electric vehicles, but the auto industry showed little to no interest in this. In general, the development of electric vehicles stalled until the current boom we are experiencing.

Are there moments or anecdotes from the first Tour that you particularly remember?
For me, the first Tour de Sol was the most beautiful. Besides the attention from outside, I found it great how people in the driver field supported each other. There was very little competitiveness because everyone followed the same ideology.

Authors:
Florian Hochstrasser
Benjamin Wicki
Jonas Pechlaner
David Braitsch