Netze BW charging project in underground parking garage: It doesn't need that much electricity at all

Contrary to the general assumption, the underground parking garage of a multi-family house can be used for the energy supply of electric cars without major network reinforcements. This is the conclusion of a pilot project by distribution network operator Netze BW in Tamm. The charging requirements in an electrified underground parking garage were met with a fraction of the maximum available charging power that the e-cars could theoretically draw. The maximum charging power of 124 kW in the building was not called upon even once.

The project by EnBW's subsidiary complements the theoretical models of the network operator in reality, in so-called NETZlaboratories. A 16-month field test, the E-Mobility-Carré in Tamm near Ludwigsburg, investigated whether the previous connection capacity is still sufficient for charging stations installed later in the underground garage, or how one can get by with the existing house connection without additional network reinforcement measures – and without compromising the comfort of the residents.

Running smoothly: All users switched to e-cars for the project

For the project in Tamm, Netze BW equipped the underground parking garage of the Pura Vida residential complex with 58 charging points and provided participants with 45 e-cars for daily use. The user profile ranged from families with children, to couples and retirees, covering both occasional and frequent drivers. They had temporarily decommissioned their gasoline or diesel vehicles and were only electrically mobile in a very short time, with growing enthusiasm, as the network operator happily reports. On average, participants in the trial reached a monthly mileage of 1,100 kilometers, an impressive figure despite home office and corona-related restrictions. Although the project vehicles have now been collected, many of Tamm’s "e-pioneers" are now considering purchasing an electric car, summarizes the operator.

Intelligent charging management smooths peak loads

The project also focused on how to optimize the house connection of multi-unit residential properties for the additional consumption by charging stations. An ideal connection provides sufficient power without being oversized, the findings suggest. This would be the case if it were assumed that all e-cars would be charged at the same time.

However, the E-Mobility-Carré showed that no more than 13 charging processes took place in parallel – out of a total of 58 available charging points. Thus, the "simultaneity" affecting the network was only 22 percent. This value was significantly lower than the 50 percent measured in a similar field test in Ostfildern. During almost half the time, no car was being charged at all.

"This shows the potential of flexibilized charging processes. The most important tool for this was an intelligent charging management system installed for the project," said the operator.

This allowed the connection power of the charging points to be reduced and peak loads to be minimized. Existing network connections of multi-family houses could thus be optimally utilized. Additionally, an intelligent charging management system gives network operators time for meaningful, efficient, and sustainable network reinforcement in the future. This would merely require accepting slightly longer charging times temporarily. However, over 90 percent of the project's participants did not feel restricted at all, another key insight from the E-Mobility-Carré, the operator concludes.

Collaboration between politics, science, and the energy sector

For the transformation, politics and science are required equally, as well as other economic sectors such as the energy industry, explained Martin Konermann, Technical Managing Director of Netze BW.

"We are gladly willing to collaborate to make a significant contribution to the mobility transition," he affirmed. 

Projects like the one in Tamm are laying the foundation for this. For electromobility to become a success story in this country, a powerful and still reliable electricity network is needed, Konermann continued.