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A bus trailer using solar technology in Munich

MVG trailer no. 5912 with Sono Motors solar panels mounted on the roof | © Sono Motors

A bus train operated by the Munich Transport Company (MVG) will in future be on regular service with solar cells on the roof. MVG officially presented the vehicle on Thursday, March 31, 2022 together with the start-up Sono Motors, which developed the photovoltaic system, and Katrin Habenschaden, Deputy Mayor of the City of Munich. MVG wants to use the solar system to investigate which auxiliary systems on board can be reliably supplied with solar energy.

The solar system that MVG ordered from the Munich company Sono Motors covers an area of ​​around 12 square meters. The available space on the roof of ​​the trailer corresponds to that of a standard 12-metre bus – the test results can be transferred to the use of electric normal buses. The experimental setup is funded by the City of Munich as part of the “Integrated Action Program to Promote Electromobility in Munich”. 

Katrin Habenschaden, Deputy Mayor of the City of Munich: “We need a change of course in the transport sector. The traffic still falls far short of the climate protection goals, and this also has a direct impact on the air quality in the city of Munich. The solar buses can be a building block in this urgently needed change towards climate-friendly mobility. The idea convinces me, because a lot of fuel can be saved here and CO2 emissions can be significantly reduced.”

“We are already working with MVG to convert our bus fleet completely to electric drives. Using the power of the sun is of course much more sustainable and I hope that this pilot project shows that we can also extend the range of the e-buses with solar energy. What makes me particularly happy about this cooperation with our MVG is that such an innovative idea comes from a Munich-based company,” she said. 

© Sono Motors
Roof-mounted solar panels | © Sono Motors
Katrin Habenschaden, Deputy Mayor of the City of München, together with Veit Bodenschatz, MD and Division Head Bus of MVG and Laurin Hahn, Founder and CEO of Sono Motors, during the presentation | © MVG

Die Photovoltaik-Anlage ist auf dem Anhänger eines sogenannten „Buszugs“, also einem Gespann aus Omnibus und Busanhänger, installiert. Der Anhänger vom Hersteller Göppel vom Typ G13 ist seit mehreren Jahren im Münchner Stadtverkehr unter der MVG-Nummer 5912 im Einsatz. Buszüge sind in München sehr verbreitet, 57 besitzt die MVG selbst, weitere 56 kommen bei Auftragsunternehmern auf MVG-Linien zum Einsatz. In Extremsituationen, zum Beispiel an besonders heißen Sommertagen unter vollem Einsatz der Klimaanlage, verbraucht der Anhänger mehr Strom als das Zugfahrzeug liefern kann. Die MVG will nun herausfinden, wieviel Energie die Solarzellen auf den Linienwegen produzieren können.

The photovoltaic system is installed on the trailer of a so-called “bus train”, i.e. a combination of towing motorbus and bus trailer. The trailer built by manufacturer Göppel, model G13 and numbered 5912, has been in use on Munich’s city bus lines for several years already. Bus trains are very common in Munich, with 57 owned by MVG itself and a further 56 operated by sub-contractors on MVG routes. Under extreme climate conditions, for example on particularly hot summer days with full use of the air conditioning, the trailer consumes more electricity than the towing vehicle can supply. MVG now wants to find out how much energy the solar cells can produce on the routes. 

Veit Bodenschatz, Managing Director and Bus Division Manager of the Munich Transport Company (MVG): “With the photovoltaic system on our bus trailer, we can now test under real conditions how well the power generation works in the Munich summer and whether there are routes in our network that are better than others are suitable for this type of power generation. The question of what energy savings can be achieved by using solar energy is of course particularly exciting given the current fuel and energy prices.”

It is also being examined whether the photovoltaic system can compensate for the additional energy demand of the heat pump in air conditioning mode in summer when electric buses are used in the future. This could keep the ranges of the e-buses at a stable value all year round. 

Bodenschatz: “In the case of vehicles with electric drive, each additional consumer is at the expense of the range. In the project, we now want to investigate whether the photovoltaic system can supply enough energy to reliably operate the heat pump of the air conditioning system. The results of the test are particularly interesting with regard to the electrification of our bus fleet, which should be completed by 2032.” 

Laurin Hahn, founder and CEO of Sono Motors: “The partnership with the Munich transport company illustrates the enormous potential of our unique solar technology, which is now being used in local public transport for the first time in the company’s history. For Sono Motors this is a milestone in the mission to equip every vehicle with solar cells”. 

“Especially in times of rising energy prices and increasing emission regulations in urban areas, our solar technology offers great added value for public transport companies. City buses and coaches – regardless of whether they have an electric or diesel drive – offer a lot of space and are out and about every day,” Hahn continues. 

Sono Motors’ Innovative Solar Technology for buses Is used for the first time in real operating conditions in Munich. It is expected that it helps to reduce local CO2 emissions per vehicle by over 6.5 tonnes per year, supporting the City of Munich’s clean air targets. Other benefits include fuel savings of up to 2,500 litres of diesel per year, stabilisation of the energy supply and extension of the 24V battery’s lifetime, as well as reduced maintenance costs.

The bus train trailer starts regular service after technical approval by the supervisory authorities. 

MAN Lion’s City diesel bus + Göppel G13 trailer with solar panels mounted on the roof | © Sono Motors
Göppel trailers no. 5901 and 5912 prior to conversion of 5912 at Munich’s Depot West | © Dirk Budach
© Sono Motors
The newly converted trailer in comparison with others of the same model | © Sono Motors
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