Interviewer: Hello Ravi, thanks for meeting with us! Tell us a bit about yourself and your role in ATELIER.
Ravi Singh: I am Ravi Singh and I work for DNV – one of the partners in ATELIER. The department I’m part of focuses particularly on energy systems. We are situated in Arnheim in the Netherlands and I joined DNV in September 2021. Since then, I have also been part of this ATELIER project.
DNV is involved in the demonstration of positive energy districts. Part of our work for ATELIER is to simulate and analyse the electric power flows, and study the impact of electric vehicles on the electricity grid. I recently presented the work DNV has done so far on the assessment of electric vehicle charging strategies and their effect on residential grids using co-simulation on the SEST Conference in Eindhoven.
Interviewer: Tell us more about that. How will electric vehicles (EVs) impact PEDs?
Ravi Singh: When we have mass integration of EVs in any geographical area (that means for example an energy or electricity network in that area), it takes huge amounts of power and energy from the grid. Basically, you could say that further in the future, if you have a house and an EV, it means you have two houses because EVs can put a lot of strain on the electricity network or if you see in totality the energy.
We analyze the demand of energy from mass integration of EVs, but also what impact it will have. (It will take the energy from the electricity grid which can be problematic for the grid.) Let’s take a look at an example to illustrate that: Let’s say, you have a transformer that is rated for a certain amount of power. You have high household loads and in addition to that, there are a lot of EVs set to charge at a certain time in the evening because many people come home from work at that time. This can result in an overload of the network because there is a high demand in total and EV owners put strain on the network at the same time. Therefore, it is also important to consider how EV owners charge their vehicles to assess the impact on the network. That’s what we do in our research work.
Interviewer: Speaking of how people charge their EVs: what potential issues can occur for them?
Imagine you own an EV, more and more of your neighbours buy EVs, but there are not enough public chargers. This is bad for you as EV owner because you will not be able to prioritize your charging or you might have to wait if there are other EVs in line to charge. You’ll probably be very dissatisfied as customer but it’s good for the grid and grid operators because only a certain amount of EVs are able to connect to the grid and the energy demand will not exceed the maximum grid capacity. On the other hand, if multiple EVs start to charge at the same time, this can lead to congestion in the grid.
Interviewer: What aspects do you take into account when analyzing the impact of EV charging on grids?
There are two main aspects we consider: First, we consider the behaviors of EV users because there are different types of EV users. Then, there are different charging schemes.
Let’s talk about the schemes first: Most people connect the EV to the charger, charge it while it’s connected and stop charging when they disconnect it. But now there are also more advanced technologies with which you connect the EV to the charger and charge it in a smart way when the prices are low. This is called Smart Charging. There is also a more advanced version to that called Vehicle2Grid: the EV can charge when prices are low and when prices are high, it can give energy back or sell it back. These advanced schemes have impacts on the grid. The grids will be kept busy for a longer time, especially in Vehicle2Grid since now the EV is not only charging but discharging as well. Also, if the transformer is overloaded once during the normal EV charging process, it might be overloaded again in reverse direction during the discharging process.
Interviewer: What about the different types of EV users?
In our analysis there are nine different types of EV users. Each user type has a portfolio of different EV charging sessions. The two main parameters that define the user types are the time and the duration of your charging sessions. If I’m a user type A, I might for instance charge mostly at night, but sometimes also during the day for longer or for shorter periods of time. User type B might charge mostly during the day for short periods of time and only occasionally during the night, and so on.
Interviewer: How do you integrate the different EV user types and charging schemes in your work?
We include them in our simulations. For the aspect of different EV user types our tool automatically decides, based on probability, what kind of EV users are represented among a certain number of EV owners and therefore what portfolio of charging sessions to expect. We also include the three different charging schemes, so the simple plug-and-play charging scheme, Smart Charging when prices are low and Vehicle2Grid – charging when prices are low and discharging when prices are high. For our simulations, we also vary the number of EVs and the number of chargers in the network to find out what impact this has on the grid.
Interviewer: How is this part of your work connected to Positive Energy Districts?
As discussed, the number of EVs is growing and they have a huge impact of electricity grids. So when planning PEDs, their role has to be taken into account. We can provide advice during the design phase of the PEDs based on our simulations, so for instance on the state of the electricity grid under various scenarios, effect of different pricing strategies on the grid, number of chargers required, etc.
Interviewer: What about the ratio of EVs to chargers? What is the current situation and how could this change in the future?
We have to consider that the ideal ratio is also influenced by the size of EV batteries. Right now we see battery sizes of around 60-70 kWh. In the future, we could have batteries with a size of 100 kWh. Then the current ratio of EVs to chargers which is currently in many countries about 9 to 10 should be lowered in order for the grid to accommodate these bigger batteries.
Interviewer: So many variables to think about! Is there an aspect that you feel could be considered a lot more in the research on the EV charging infrastructure?
The modeling of EV behaviours is a tricky thing. When doing analyses as described before, we assume quite simplistic behaviours of EV users that are not always realistic. So this definitely deserves attention. Also, in a grid or in a residential grid, we don’t only have EVs – we also have solar or smart household loads that are quite influential. For instance, smart heating and cooling technologies that cool down the house only when prices are low. To include all these detailed aspects and make a holistic kind of study is in my view very important.
Interviewer: Thank you for introducing us to this fascinating topic, Ravi!
Thanks a lot!