Expansion of the charging infrastructure for electric vehicles

Maximum power is not always the right answer when charging on the factory premises

Fast for the few or slow for everyone? WS is pursuing its own concept when it comes to expanding the charging infrastructure for electric vehicles. In order to achieve a low-cost yet effective charging system on the factory premises, WS consistently relies on a low charging capacity.
Charging is also possible at a normal socket (Image source: WS)

Charging electric vehicles on the factory premises

When it comes to electromobility, a discussion about the associated charging infrastructure is usually not far away. Expectations are often based on the goal of achieving as little or no loss of comfort as possible compared to the usual status quo with combustion vehicles. In order to meet this requirement, the automotive industry is working flat out to enable particularly fast charging of electric vehicles, i.e. charging with the highest possible electrical power. In return, the industry is demanding that either the state or other companies (hotels, restaurants, industry & commerce, ...) provide the charging infrastructure. However, the fact that the necessary investments are considerable is all too often ignored. Particularly in existing buildings, neither the connected loads nor the electrical infrastructure are designed to supply additional large consumers with high simultaneity. Although intelligent control technology is theoretically available, it is also associated with high costs and additional installation and maintenance work.

A high charging capacity quickly pushes the electrical system to its limits

The requirement to be able to charge at almost any location as quickly as possible, i.e. with high power, is therefore potentially becoming an obstacle to the further spread of electromobility. Even a charging capacity of just 22 kW per charging point quickly pushes the electric system to its technical limits - particularly in existing industrial buildings - especially if several charging points are to be installed.

Assuming that around 20 charging points are already available at a site with around 150 employees, this results in a theoretical maximum load of 440 kW, which exceeds the usual connection values even for newer buildings. As a result, a complex load management system would have to be installed that balances the power distribution with the current capacities and, if possible, includes the local generation from PV systems that is frequently available today. After all, vehicles should preferably be refueled with real green electricity and not just electricity that has been colored on the balance sheet. As a 22 kW charging point, including the associated wiring, protection and installation work, often costs several thousand euros, this quickly results in a necessary investment in the six-figure euro range for the industrial company, including the necessary load management system.

"Slow charging stations" can be set up quickly (Image source: WS)

The WS approach to charging infrastructure

WS therefore chooses a different approach at its headquarters in Renningen, which is based on the following key premises:

  1. Electric vehicles are always particularly useful when they are used to cover local short-distance and commuter traffic. The daily mileage is therefore generally up to approx. 100 km, often even significantly less. This results in a daily energy requirement per vehicle of 15 to 20 kWh.
  2. In order to reap the full ecological benefits of electromobility, real green electricity should be used for charging, preferably generated locally in a decentralized manner
  3. The vehicles are parked for long periods during working hours, usually 9 hours, most of which are during the day when it is light at WS due to the single-shift operation, even in winter.
  4. The local generation of green electricity from our own PV systems (currently around 400 kWp in total at the WS headquarters) often exceeds the demand from production and office operations in the morning hours. The surplus generation can therefore be used to charge vehicles with a sufficiently high probability, even without dedicated control, as long as the cumulative charging power is low.
  5. Although it is theoretically possible to re-park vehicles during the day as required, in practice this is only compatible with internal company processes to a limited extent.

The required daily charging energy of up to 20 kWh per vehicle, based on the assumption of a maximum distance of approx. 100 km per day, can be achieved over a standing time of nine hours with a continuous charging power of 2.2 kW. On the connection side, special earthed sockets designed for continuous load are easily suitable for this. Such sockets can be installed relatively quickly in existing parking areas. Corresponding supply lines are fused separately in the sub-distributor and, depending on the objective, can be activated permanently or time-controlled using very simple means. Due to the comparatively low theoretical maximum total load of 20 * 2.2 kW = 44 kW, there is no need for a dedicated load management system. The total load is very likely to be less than the remaining surplus generation from the local PV systems. The need for re-parking of vehicles during the workday, which might be necessary with a few charging points with higher power, is completely eliminated. The existing electrical system also offers reserves for further expansion with low-power charging points in the future. If fast charging is still necessary in individual cases, reference is made to external charging infrastructure. The investment required for implementation for WS in the concept presented amounts to significantly less than 10% of the alternative proposals with higher charging capacities, with approximately the same target achievement, and can therefore be easily financed from own funds. 

Charging with max. 10A at a normal socket (Image source: WS)

Implementation is also possible without subsidies: Slow charging can be implemented all the faster 

The example presented here impressively demonstrates that a problem-adequate approach is indispensable, particularly in the area of electrical energy supply. The investments required for increasing electrification are considerable, especially in existing buildings, and can hardly be realistically implemented. However, with intelligent concepts which, in addition to the technical conditions, also include a precise limitation of the objectives pursued in each case, high costs can often be avoided without significantly reducing the achievement of objectives. Implementation is then easily possible without subsidies.

However, as unbiased and non-profit-driven external advice is particularly difficult to find in this area, entrepreneurs should endeavor to formulate clear objectives and demand implementation within previously defined framework conditions.

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