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Installers & partners

Charge with green electricity while you shop

26/05/2023 / Mainz-Kostheim, Germany
Extraordinary solar charging park constructed with Fronius project inverters.
SUN2CHARGE GmbH operates a solar charging park in Mainz-Kostheim (D), Hesse, which generates 100% of its own solar power. This means that customers of the local shopping center next door can conveniently and inexpensively charge their electric cars with green electricity while they shop. This large-scale project is a truly pioneering project and was implemented exclusively with our Fronius Tauro and Fronius Symo project inverters.

900,000 kWh of solar power for electric mobility

This project is quite singular and has never been built this way before in Germany,” explains Christoph Hesselmann of Opel Energy GmbH, which built the charging park. To generate the solar power, a photovoltaic system with 2,300 modules and an annual output of approximately 900,000 kWh was built on the roofs of the surrounding buildings. This amount would enable a single electric car to travel 5 million emission-free kilometers per year. 

The core of the approx. 1,000 kWp PV system comes from Fronius: nine 50 kW Fronius Tauro inverters along with three 100 kW Fronius Tauro inverters and two 15 kW Fronius Symo inverters are installed on the roofs and, together with 16 km of PV cable and 1,000 meters of data cable, combine to make the solar power available for further use.

kWh solarpower
kW peak
million emssion-free kilometers with an electric car

High capacity in any situation

Our robust project inverters are the ideal choice for this exceptional large-scale project. They not only offer maximum flexibility for system design but also withstand even the most adverse environmental conditions. At the same time, they consistently provide stable, high output and don’t require overhead protection, even outdoors. 

The Fronius inverters used are quick to install and easy to maintain. With the Fronius Tauro, only the replacement components need to be exchanged when servicing is required, instead of the entire inverter. This saves time and resources, minimizes overall system costs, and makes operating the commercial PV system with the solar charging park even more economical. 

Solar power – green, economical, stored

What makes the concept for the Mainz-Kostheim solar charging park exceptional: instead of feeding surplus electricity into the grid, it is stored at the site in 560 kWh batteries. “This way we can make sure that more than 80% of the electricity we put into the cars is generated by the sun,” Hesselmann explains. In the next few years, this is expected to increase to a full 100%. The cost for charging the electric cars depends on the amount of solar power produced: when the storage units are full and the sun is shining, the charging price for customers is significantly lower.

» After 45 minutes of shopping, the electric vehicle is charged on average from 20% to 80%. This makes these charging points ideal for using the time spent shopping to charge the electric vehicle. Systems with higher charging capacity would require significantly more investment but would not provide an equivalent increase in the added value. «

Says Hesselmann, explaining the choice of charging infrastructure. 

Optimal charging capacity

A total of 10 charging stations are available with 2 charging points each and a charging capacity of 22 kW AC and 50 kW DC. These have been selected with the aim of optimizing the cost-benefit ratio and with consideration of customer charging behavior. 


Solar power + storage = 100% independence

Since the electricity generated can only leave the property in Mainz-Kostheim in the charged car, and public infrastructure is used for this project only to a minimal extent, the charging park is truly a prime example of a completely self-sufficient micro-power solution. This shows once again that our vision of 24 hours of sun can be achieved. The system only has to fall back on electricity from the public grid when the PV system is not producing anything and the battery storage is also empty. “But thanks to our intelligent power management, we don’t expect this to happen, especially in the first few years. So we’re basically functional even if the infrastructure around us collapses,” Hesselmann says confidently. This means the issue of grid congestion, which is regularly discussed in connection with electric mobility, does not play a role in Mainz-Kostheim.

» The contacts at Fronius were the first to say, ‘We think that's exciting; we can make it work.’ «

Christoph Hesselmann, Opel Energy GmbH – charging park construction

“Flawless cooperation with Fronius”

While other companies were skeptical about the challenging and pioneering project, the courage and openness to new ideas shown by Fronius convinced the builders of the solar charging park from the very start. Our Fronius project team demonstrated their impressive level of expertise and focus on service during the 14-month planning phase. “The cooperation was flawless. All of the technology worked without a hitch and the support was excellent. I have had very different experiences in the past with much smaller projects,” says Christoph Hesselmann enthusiastically, recounting his first project working together with Fronius. Regionality and the entirely European manufacture of our products and product components were also relevant aspects for the builders in their decision to work with Fronius.

Visionary answers for future large-scale projects

The EUR 1.8 million project in Mainz-Kostheim was just the starting point for many more charging parks of this kind: with valuable experience and positive feedback, the builders are now considering further expansion of the infrastructure for electric mobility. “We’ve found conclusive answers to all the things currently seen as challenges in connection with electric mobility – answers we believe are absolutely visionary.,” Hesselmann says. 

As a project partner, we are proud of the successful implementation of this extraordinary project and the central role our Fronius inverters are playing in it. We look forward to more collaborations of this kind for electric mobility that will help us all move forward.

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