Expert Interview – "Grid-Serving Charging Is Crucial"

Expert Interview – June 27, 2022

Interview with Markus Wunsch, head of e-mobility grid integration at Netze BW

Will we have to choose between switching on the light and charging our e-cars in future? This is a scenario many people worry about. Markus Wunsch from Netze BW talked to us about whether these concerns are justified, and how distribution grid operator Netze BW wants to ensure that the power grid keeps pace with the rapid expansion of electromobility.

Markus Wunsch, head of e-mobility grid integration at Netze BW

Netze BW is the largest grid operator in the state of Baden-Württemberg. What are your estimates for the expansion of e-mobility, and what actions need to be taken to meet the resulting demand?

Netze BW bases its estimates on target figures such as those set by the German government, which wants to see 15 million additional electric vehicles on the roads by 2030. We use algorithms and socio-demographic data to create forecasts that allow us to apply and adjust these figures to our own grid territory and to identify hotspots. At the same time we need to assess the charging infrastructure in these territories. Are we dealing with publicly accessible charging stations or private ones, and what is their capacity? Will they be enough or do we need to install more?

How do you keep track of the number of charging stations, and does this differ between public and private infrastructure?

All new charging points must be registered and approved, provided they have an output of 12 kilovolt ampere (kVA) or more. This means that even though anything below 12 kVA – for example an 11 kW wallbox – needs to be registered, only charging stations that exceed this threshold require a permit. This applies to all 22 kW wallboxes and upwards.

When charging points that are just subject to registration are installed, we, as grid operator, are informed after the fact, while new charging stations that are subject to approval require such approval prior to installation. This enables us to assess whether the existing grid connection will be able to cope, or if the grid needs to be expanded or reinforced. As grid operator we are then able to predict the impact on the power grid and balance peak loads. One of our biggest challenges is avoiding electricity bottlenecks.

Several Netze BW projects have assessed the impact of e-mobility on power grids in order to develop possible solutions. What are some of these solutions?

Our solution consists of four different spheres of action. Firstly, on the customers’ side, the approval and registration process needs to become faster and simpler. Secondly, we need a clear picture of grid utilization at any given time – which only digital measurement technology can achieve. Thirdly, we need to optimize the existing grid infrastructure through intelligent charge management, which once again requires digitalization. And lastly, we need to expand the power grid to enable it to meet demand and become future-proof. In each of these fields of action, we have conducted field experiments to determine the impact of electromobility on the grid and what we need to do to be ready for the ramp-up of electromobility.

Can you tell us more about these field experiments? Did you ever experience one of the much-dreaded blackouts?

No, there was never a blackout, but we did come close to the limit. Our first project was the NETZlabor E-Mobility-Allee initiative in Ostfildern near Stuttgart in 2018, for the grid integration of electromobility in suburban areas. It was our assumption that the commuters living here would be the first adopters of e-mobility. Based on this initiative and the valuable and differentiated results of this first study more NETZlabor projects were started, including NETZlabor E-Mobility-Carré: a multi-family dwelling with 58 charging points powered by a grid connection in the underground car park. And let’s not forget NETZlabor E-Mobility-Chaussee, a project which assessed the impact of e-mobility on the power grid in rural areas.

How important is grid-serving charging – i.e. external control – for the mobility transition?

We have a robust power grid to work with. But this in itself will not prevent grid congestion every so often if the market penetration of e-mobility happens quickly. We consider grid-serving charging to be a crucial approach to meeting the electricity demand if the expansion of e-mobility continues at the current pace. Smart and digitalized solutions will help us integrate charging into the grid in a way that benefits users. In the NETZlabor projects, we were able to develop suitable technology and put various approaches to the test together with the project participants. This way, we could assess the relevance and value of this technology – i.e. to what extend it can actually serve the grid and support us as grid operator.

Grid-serving charging requires a tool that enables customers’ wallboxes to communicate with the grid operator. How do you process this data and how do you ensure everything works as it should?

From a technical point of view, the grid operator requires access to the charging stations. This means that we need to set up a communication and actuator connection to an smart metering system via a control box. We will continue to roll out smart metering systems over the next few years to build on the existing, scalable infrastructure.

The idea of grid-serving charge management is benefit from flexible charging at home or at work. In these scenarios, cars generally stay in the space after being fully charged, providing a “flexibility delta” we can make use of. For example, we can prevent grid congestion by reducing the power if several cars are charged simultaneously from one grid connection point or secondary substation feeder. This slows down charging a little, but the cars will still be fully charged over night. People don’t need to change their habits, but reducing the power levels out peak loads during those critical times when other consumers also draw on the grid.

By what percentage can grid-serving charging level out peak loads?

This depends on how much you reduce the power. Theoretically, you could go from 100% to 0%, but effectively we never completely switch off supply, so will never reach 0%. 50% has proven to be a effective reduction, meaning that an 11 kW wallbox will charge with a reduced output of 5.5 kW for two to four hours. The vehicles continued to charge but in each instance the peak load was reduced by half. We can roll out this process for all e-vehicles that are charged via a grid connection point or cable outlet.

One of the worrying scenarios often painted is that everyone will want to charge their e-car at the same time. Was this confirmed in your projects?

Simultaneous charging can be an issue. But our calculations need to go beyond just e-mobility and account for all consumers drawing on the grid at any one time, such as heat pumps, which have also seen widespread adoption. The expectations for grid feed-in also needs to factor in the ongoing expansion of PV systems and the resulting recovery. However, we focus on electromobility because it has the greatest potential. In consequence, we mainly assess what happens when several e-vehicles charge at the same time. Our NETZlabor projects include very different levels of simultaneous charging, with 22% for the E-Mobility-Carré initiative with 48 charging points to one grid connection, or as much as 75% for the E-Mobility-Chaussee project, which only covered eight vehicles. So this varies depending on how many vehicles were supplied and assessed.

Is bidirectional charging an option given that grid infrastructure is still lacking in parts?

Bidirectional charging, i.e. the two-way flow of energy to stabilize the power grid, is a hot topic at the moment. We need to make a distinction between Vehicle2Home and Vehicle2Grid. In Vehicle2Home set-ups, electricity is fed into a closed system behind a grid connection point – for example a single-family home – where it can be used to optimize self consumption. Vehicle2Grid set-ups feed electricity back into the public grid, meaning that the capacity of vehicle batteries can contribute to stabilizing the grid. For this to work, you need a sufficient number of vehicles and you can influence consumption and generation at transmission system level by initiating or stopping parallel charging processes. (SP)

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