Charging infrastructure
Electromobility has developed into a dynamic field of the energy transition - both in terms of political requirements and new registrations of electric vehicles. As a result, the charging infrastructure is increasingly becoming the focus of public discussion. Its performance not only determines charging comfort, but is also an important factor for grid expansion planning. The use of battery storage can make a significant contribution to minimising the necessary grid expansion and at the same time improving charging comfort.
References
Relevance of this field of application
The National Charging Infrastructure Control Centre has developed scenarios for Germany for the market ramp-up and the demand for charging infrastructure until 2030. The reference scenario assumes a demand for charging stations of 10.4 million units, with an expected stock of 14.8 million battery electric and plug-in hybrid vehicles. The amount of energy charged is estimated at 30,000 GWh per year.1
For grid planning purposes, each charging station represents a new consumer whose supply must be guaranteed by the grid. If the reference scenario is followed, this results in an additional capacity of 162 GW across Germany by 2030. The actual grid expansion requirement results from the balance of the required capacity and the available grid reserve at the respective grid level. For example, a household connection in the standard load profile (SLP) is calculated with 14.5 kW, the low-voltage grid is designed for 30 kW per household - the grid reserve at household level is thus 15.5 kW. On average, there are 100 households per grid section as the smallest grid level. If the connected load reaches the capacity of the affected grid level, the integration of further charging stations requires a grid expansion.1
The distribution of charging points across different types of locations is a key lever here. In the reference scenario, private households bear the main burden in 2030 with 7.1 million charging points and 41 % of the amount of energy charged. Employers represent the second pillar of supply with 2.6 million charging points and 27 % of the charging volume. The third pillar is the public space, which, with 711,000 charging points, however, covers the considerable amount of 32 % of the electricity supply. In the public space, there is a further subdivision into inner-city charging hubs, charging hubs on axes, customer car parks and the street space. While a connected load of 11 kW is assumed for private households, the load for employers, customer car parks and the street space is 22 kW. Charging hubs are calculated with a connected load of 150 kW in urban areas and even 350 kW at axles. A lower availability of private charging stations would have to be compensated above all in the public space: first and foremost in customer car parks (+25%) and inner-city charging hubs (+22%) as well as charging points in the road space (+16%).1
1 Nationale Leitstelle Ladeinfrastruktur (2020): Ladeinfrastruktur nach 2025/2030: Szenarien für den Markthochlauf. Studie im Auftrag des BMVI.
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Use of battery storage
In Germany, charging columns with a capacity of 3.6 kW or more are subject to registration with the grid operator concerned.2 Private households usually receive a permit for a charging station with a capacity of 11 kW, which is within the 15.5 kW grid reserve at household level. A maximum of 11 kWh of energy can thus be charged per hour. The charging time for fully electric cars with batteries of 40-100 kWh capacity thus takes several hours and usually takes place at night. In the meantime - also in the sense of an investment in the future - charging columns with a capacity of up to 22 kW are being installed at private households, but initially throttled back to 11 kW. For households, this not only offers the advantage of having to fulfil fewer regulatory conditions. It would also make it possible to integrate a home storage system, which would enable double the charging capacity with an unchanged household connection power.
The connected load at customer car parks and employers could also be significantly reduced by integrating battery storage - and thus also the need for grid expansion. Additional utilisation potentials arise when self-generated renewable energies are integrated and offered for off-grid refuelling. This is accompanied by an increasing demand for storage capacity, with the opportunity for efficient peak load management. The exploitation of such potential must be taken into account in battery design.
The use of buffer storage at charging hubs and in the road space can offer relief at peak times in particular and in turn reduce the connected load relevant to grid expansion. It is not for nothing that some of the so-called "superchargers" are not powered by the electricity grid, but by generators based on fossil or renewable fuels.3,4
2 Bonn Netz (2021): Anschluss von Ladeeinrichtungen für E-Fahrzeuge. Ladeeinrichtung für E-Fahrzeuge an Haushaltszählern (Aussetzbetrieb).
Link ↗ (accessed 28.01.2021).
3 Wiesinger, Günther (2019): MotoE-Premiere: Ladestationen mit Diesel-Generatoren.
Link ↗ (accessed 28.01.2021).
4 Ecomento.de (2019): Berliner Startup entwickelt Methanol-Schnellladestation.
Link ↗ (accessed 28.01.2021).
Performance requirements
An essential requirement for battery storage as a component of a charging infrastructure is a pronounced fast-charging capability. This enhances charging comfort and takes the load off the grid. The higher the charging performance is to be, the more important the fast-charging capability becomes for the same storage unit size. Using a fast-charging home storage unit with a usable capacity of 10.4 kWh, an output of 41.6 kW could be realised when discharging at 4C for 15 minutes. With the corresponding fast-charging capability of the receiving traction battery, 10.4 kWh could thus be charged within 15 minutes. Depending on the type of vehicle, this amount is sufficient for almost 100 km of driving.
Due to the connection of the charging infrastructure to the living and working areas, the safety of the batteries used is of particular importance. Flammability and explosion risks should therefore be minimal. Furthermore, the use of buffer storage should contribute to improving the environmental balance in the mobility sector both by avoiding grid expansion and by using resources sparingly. The better the eco-balance and service life of battery storage systems, the greater their contribution. The latter also has a significant influence on investment security.
Market outlook
The market volume for battery storage in the area of charging infrastructure results from the required charging power, the expected charging quantity and the buffering target. In addition, the charging speed possible on the vehicle side determines the extent to which fast charging can actually be used.
The market in the field of charging infrastructure is two-sided: the battery buffer mediates between the needs of the producer side and the consumer side in a similar way to a platform. Accordingly, different customer relationships must be taken into account. While on the grid side it is about avoiding expansion and improving the integration of renewable energies, on the consumer side a high level of comfort plays the main role. The charging infrastructure as a whole can play a significant role in this balance.
With 10.4 million charging points, each buffering of an average of 1 kWh is associated with a storage requirement of 10.4 GWh. For 2030, the average amount of energy charged per day and charging point in the reference scenario is assumed to be as follows: 5.2 kWh in private parking spaces, 9.3 kWh at the employer's, 172.5 kWh at charging hubs in towns, 200.6 kWh at charging hubs on axes, 33.4 kWh at customer parking spaces and 28.5 kWh on the road. If this amount of energy were to be buffered for one day, a storage requirement of 90 GWh would result. Private charging stations would account for 36.8 GWh, employers for 24.3 GWh and public spaces for 29.1 GWh.1
Estimating the market volume for other countries requires setting premises at a comparable level. In this context, grid quality is a key driver for buffer demand: the lower the grid quality, the more the increasing connection line for electromobility has to be absorbed by battery storage.