An autharchic concept for EV charging

Thanks to the integration of different elements in just one comprehensive system, SUN2WHEEL provides the best technical and economic solution


SUN2WHEEL is the most recent project of Protoscar, the e-mobility specialist based in Ticino, Switzerland. The system fully integrates building technology and electric mobility. In order to achieve the clean and independent energy supply of the vehicles, SUN2WHEEL perfectly combines the following elements: photovoltaic production, buffer batteries, regulated and/or bidirectional charging of the car and connection to the house for delivering excess electricity. It is a self-sufficient garage for electric vehicles with secondary use buffer batteries and allows a repayment of the investment in less than 10 years.


The goal of SUN2WHEEL is to create a rapidly growing synergy between the electrical system of the building and the electric vehicle, considering also the grid and the power utilities. Besides consuming clean energy through the private photovoltaic system, this configuration also enables and improved return on investment for the end user. Furthermore, the power peaks for industrial customers can be reduced. Thanks to the SUNTOWHEEL concept that integrates smart meter signals, power utilities can raise customer loyalty in this increasingly independent market by sending their regulation wishes to the system.


The technical functionalities are depicted in the graph bellow. The unique technical feature of SUN2WHEEL is that the process is actively monitored and the load management can be regulated by the control and distribution box (D). The needs of the grid can also be considered through the ripple control receiver. Because of the cost of the components SUN2WHEEL today considers a mixed AC/DC network whereas tomorrow all the components related to the garage will be DC driven. Only the excess energy provided to the home (and to the grid) will be transformed to AC power.

S2W Today
S2W Tomorrow

The energy produced by the photovoltaic roof is stored in the buffer battery for charging the cars. In fact only the excess is used for the consumptions in the house and what is still left is fed into the grid. The car first charges its battery with the photovoltaic energy that has been produced locally and stored in the buffer battery. Only when the buffer battery is empty, the car charges from the grid.


The communication between PV modules and electric vehicle through buffer batteries allows to manage and control the energy flows
SUN2WHEEL allows the direct use of the locally produced photovoltaic energy for the mobility instead of feeding the energy into the grid
SUN2WHEEL is independent from the grid for the use of self-produced clean energy
The use of field proven secondary life car batteries as a buffer allows to maximally exploit the bi-directional function

SUN2WHEEL Solution

Advantages for end user
Independent production of green clean energy through the photovoltaic roof
Direct use of the photovoltaic energy, without selling it at a low cost (during the day) and buying it from the grid (while charging)
Shorter payback of the photovoltaic, since the green energy is used to replace the most expensive energy of a family bill: the one for mobility
Reduce cost of peak-power
Benefit from a personal blackout-safe power backup (for several hours)

Advantages for power utilities involved in distribution of SUN2WHEEL
Offer new services and products mainly to private customers and small enterprises
Create customer loyalty in an increasingly free and independent market
Reduce peaks and optimize the grid through power management


The first prototype was installed in Rovio (TI) in autumn 2016. The architect Federico Testa designed the modern architecture. The building consists of a concrete base and a wooden facade. The 60m2 roof provides space for photovoltaic panels from DESIGNENERGY and produces more than 7’000kWh a year, enough for 40’000 km. Two further SUN2WHEEL installations are already in construction (in Luzern and Stuttgart).


If you are interested in the SUN2WHEEL concept, please contact us any time. Currently we are looking for additional pioneers willing to install SUN2WHEEL and test its advantages. Don’t hesitate to contact Milton Barella.

Milton Barella

Milton Barella
Business development
El.-Ing. dipl. ETHZ, MBA
T +41 (0)91 / 649 60 60




SUN2WHEEL Rovio: timelapse top/bottom

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