Researchers developing DC micro smart grid for charging EV fleets; Li-ion, redox flow batteries and renewables
7 March 2014
|Up to 30 electric vehicles at a time can recharge in Fraunhofer IAO’s parking garage. Click to enlarge.|
A team from Fraunhofer Institute for Industrial Engineering IAO, together with Daimler AG and the Institute for Human Factors and Technology Management at the University of Stuttgart, is developing both the charging infrastructure and the energy management systems required to manage large fleets of EVs in a project called charge@work.
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 Fraunhofer Institute Center Stuttgart IZS, where up to 30 electric vehicles at a time can recharge at AC charge spots in the Fraunhofer Campus parking garage.
|EV charging at IZS|
|Up to 340 kW are consumed when all 30 charging spots are occupied—equivalent to ~20% of the load of the Institute Center, with 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.”|
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. A 30-meter-tall wind turbine delivers 10 kW. Since it operates on a vertical rather than a horizontal axis, it does not have to be oriented to wind direction. The MSG can be run in island mode in parallel to the grid operated by the local energy provider.
The MSG is designed as a direct current (DC) grid.
Photovoltaic facilities and battery storage devices both use direct current. We settled on a DC design for our micro smart grid to avoid the losses that occur when transforming alternating current (AC) into DC.— Dipl.-Ing Hannes Rose, head of the Mobility Innovation Lab at the Fraunhofer Institute for Industrial Engineering IAO
In addition to the energy management software, the IAO scientists are also setting up a simulation environment in which to lay out their MSG and play out various scenarios, such as different weather conditions.
Rose sees a host of advantages in decentralized power generation, but none more significant than being able to secure supply.
As Germany continues to move toward a new energy economy, increasing demand is being placed on the country’s power grids. Wind and photovoltaic facilities generate electricity intermittently, which doesn’t always match customer demand. The grid has to compensate for these fluctuations, increasing the risk of power outages. We can counteract this risk by establishing decentralized supplies of electricity and by optimizing the way we manage our energy. And doing so also serves to increase our independence from energy price trends by largely eliminating the need to import electricity.—Hannes Rose
The IAO scientists now plan to create a testing environment that will allow industrial companies, systems providers, public utility companies, communities and distributers to explore the potential of micro grids.
Over the next two years, the Micro Smart Grid innovation network is to provide interested parties with an opportunity to work up new kinds of smart grid configurations and operating strategies. Using the Fraunhofer micro smart grid demonstrator, the project partners can test their hardware and software components. They can also investigate options for allowing other consumers to connect to the MSG—whether, for example, to run a building’s air conditioning system or to integrate other production facilities.
Our long-term goal is to bring individual local grids together to form a large smart grid.—Hannes Rose
Researchers will be presenting a virtual model of the smart grid at the Hannover Messe from 7-11 April 7-11 at the joint Fraunhofer booth in Hall 2, Booth D18.
The project "charge@work" is one of more than 40 initiatives in the “LivingLab BWe mobil” program to demonstrate the merits of electric mobility. It is being sponsored by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety as part of the federal government’s agenda to promote electric mobility in Germany.
Supported by the state of Baden-Württemberg and the Stuttgart region, more than 100 partners from business, science and public sectors are conducting practical research into electric mobility under the auspices of the state government of Baden-Württemberg as part of the LivingLab BWe mobil promotion program. Daimler AG is involved in ten such promotion projects.
As part of its efforts in charge@work, Daimler is making 260 electric vehicles available to employees, with more than 170 charging points at five Daimler plants in Stuttgart.
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