The ability to charge up to 30 electric cars at once requires some ingenious energy management, which is why researchers in Germany are incorporating a mix of renewables into the design of a smart grid for Germany's largest charging station.
Fraunhofer Institute for Industrial Engineering IAO scientists working with Daimler AG and the Institute for Human Factors and Technology Management at the University of Stuttgart, are developing a charging infrastructure and the energy management in a project called charge@work.
The network of charging stations for electric vehicles is becoming more tightly meshed. In Germany, the ratio of electric cars to charging stations is currently two to one and utility companies are pushing forward expansion of charging opportunities, especially in cities and metropolitan areas.
More than 2,000 charging spots have already been installed nationwide and Germanys largest charging infrastructure is at the Fraunhofer Institute Center Stuttgart IZS where up to 30 electric vehicles (EVs) at a time can re-charge at AC charge spots in the Fraunhofer Campus parking garage.
A German charging station in Fraunhofer IAO’s parking garage.
There is also one DC fast charging spot that has a charging capacity of up to 50 kW and can fully charge a cars battery in just 20 minutes. Up to 340 kilowatts of electricity are consumed when all charging spots are occupied equivalent to around 20% of the load of the entire Institute Center, which has a staff of 1,500.
Charging an electric vehicle fleet poses high requirements on the energy system. Setting up an EV charging infrastructure of this kind is impossible without smart charging and load management, explained Dipl.-Ing Hannes Rose, head of the Mobility Innovation Lab at the Fraunhofer Institute for Industrial Engineering IAO. Rose and his team are currently using their living lab to investigate the technology required to manage EV fleets.
The lab will aim to address a whole host of questions which include: How do you maximize operational efficiency? How do you avoid short circuits occurring during peak load times? How do you design a smart grid that can meet all these requirements?
The aim of charge@work is to design a micro smart grid (MSG) capable of supplying the EV fleet with electricity produced exclusively from renewable sources. This year will see the installation of a photovoltaic unit and a small wind power system at the IZS to provide power to the fleet. In addition, a lithium-ion battery storage unit will be added to the basement and a redox flow battery to the roof as temporary storage of energy.