Smart charging sounds cool but what is it really?

24 October 2021

Some concepts mean different things to different people. The buzzword “smart charging” seems to be particularly prone to confusion. You would think that the word “charging” is as clear as water but it is actually ambiguous as it is sometimes used for bidirectional charging or V2G, vehicle to grid, which actually means discharging. Let’s have a closer look at the “smart” part of the compound. 

Most people understand it as a charging strategy that provides added value, either in terms of the environment, revenue, costs or time saved. Given the broad scope, it is interpreted then differently in practice.

Some people use the term to refer to connected and controllable chargers from the cloud. Others use it for automatic billing using “Plug & Charge”.  

To save costs it is worth going beyond just starting to charge as soon as a charging cable is plugged in a socket and as fast as the power electronics or electrical circuit of the vehicle, charger or site allow it. 

As you see, the devil lies in the detail of what the “smart charging” strategy is exactly. Let’s dig a bit deeper.

Chargers, are they smart?
Chargers, are they smart?

Most “smart charging” strategies today just provide peak shaving. This means trying to minimize the local power demand at the grid connection point. The price per kW of power increases linearly with the maximal power level consumed in a year. So what peak shaving does is, even if chargers could be charging vehicles faster, the speed is reduced. What is sometimes added to this is the consideration of the load of the building, as this influences the overall power level of the site. 

Another strategy consists in maximizing local solar PV (photovoltaics) production, i.e. charging mostly during solar production.

Other strategies include the prioritization of certain vehicles compared to others at the same connection based on simple heuristics. For instance charge vehicles first because of a certain business rule or lower battery states of charge (SoC).

Additionally, it is common to optimize for battery lifetime. Batteries have a longer lifetime if kept within 20 and 80 % SoC and if not recharged at full speed. Consequently charging is stopped when 80% SoC is reached.

What becomes more interesting is when “smart charging” strategies become more sophisticated and do not consider only local parameters but systemic ones. 

For example, when strategies consider power markets and power grids that contain many more variables, are much more dynamic and request more short-term reactions. Local distribution grids for example might have excess solar PV and need the local demand to ramp up to keep stable. Or on the contrary, a production shortage requires the demand to drop. In both cases, EV (electric vehicle) charging could take it into account. Similarly, the national grid could compensate for solar and wind volatility at a systemic level with EVs down to the level of seconds.

Power market prices take into account all national production and demand. Here as well it makes more sense to adjust the demand to the production time than to waste the peak electricity or to store it in expensive extra stationary storage. EVs are perfectly suited to also engage at the power market level, having a big battery that is already paid for when purchasing the vehicle and having reasonable flexibility to decide when to charge. 

To conclude, the most efficient and real smart charging is best understood as an optimal combination of the above-mentioned local and systemic strategies. Some strategies can be in conflict with each other. For instance, it might make sense to charge the battery to 100% if prices to charge are particularly low at the expense of a slightly lower battery lifetime. Or do a bit less peak shaving and more trading at the systemic level. Power markets might signal that charging is very convenient yet local grids might need less load. Ultimately, the best overall "smart charging" strategy involves comparing the trade-offs of the individual approaches to maximize the combined benefits.

Ultimately, the best overall "smart charging" strategy involves comparing the trade-offs of the individual approaches to maximize the combined benefits.

At RiDERgy we call this mode efficient charging. If you want to discuss it further or ensure an optimal strategy for your company, don’t hesitate to reach out to us.