How to charge electric vehicles – an opportunity and dilemma for distribution grids

Distribution system operators face a dilemma. They want to accommodate the growth of electric mobility and adapt the charging station network to rising demand. At the same time, however, they must take into account the practical possibilities for reinforcing grids and the associated costs. As Stanislav Votruba, head of Network Planning at PREdistribuce, points out, it is not possible to dig up entire cities to lay new cables.

The solution lies in appropriate management of the charging station network and incentives for electric vehicle owners to spread their vehicle charging efficiently over time. Preferential tariffs could help encourage charging during time intervals that are most beneficial for the distribution system. “If electric vehicle charging becomes more predictable for distribution companies, costs can be saved for everyone,” Stanislav Votruba stressed in an interview with oEnergetice.cz. In his view, electric mobility is an opportunity to improve and reduce the cost of using the distribution grid. However, the challenges of the transition period must be managed.

Stanislav Votruba will be one of the main speakers at the Energy infrastructure development projects seminar held as part of the conference on digitalisation in construction. The conference will be held in hybrid format on 9-10 February 2022 at the Czech Technical University in Prague.

The aim of the energy infrastructure seminar is to identify priority tasks in this area and formulate proposals for legislative changes. Representatives of ministries and municipalities will also discuss them with representatives of energy distribution companies.

An electric vehicle as a household

Stanislav Votruba illustrates the complex task facing distribution companies with a simple example. The annual consumption of an electric car driven 10 to 12 thousand kilometres reaches 2-2.5 MWh and is roughly equal to the consumption of an average household. However, a household's consumption is spread far more evenly over time.

Moreover, distribution companies can estimate household behaviour very well – they have gained experience in this area over many decades. By comparison, electric vehicles are still a “newcomer”, and their owners' preferences may continue to evolve dynamically in the coming years.

The success of electric mobility in individual countries will therefore be determined not only by the number of vehicles and charging stations, but also by how efficiently the services of the power system can be used. The idea that distribution companies should prepare for a situation in which electric vehicle owners start charging all vehicles simultaneously, regardless of place and time, is unrealistic. “Not only would it require enormous investment, but such a vision is practically unfeasible. Just look at how urban pavements are full of infrastructure and how long it takes to obtain a permit to build a new cable line,” says Stanislav Votruba.

After all, even today nobody expects all cars with internal combustion engines to refuel at the same time.

No blanket bans

According to the PREdistribuce expert, however, the aim is certainly not to reduce customer comfort or impose blanket charging bans. Electricity distributors could offer preferential pricing conditions to electric vehicle owners willing to adjust the timing of their charging needs. On the basis of a mutual agreement, electric vehicle charging could then be locally restricted during certain intervals.

Distribution companies are discussing innovative tariffs with the Energy Regulatory Office and the Ministry of Industry and Trade. Since this year, for example, preferential electricity prices have applied in the evening and night hours for supply points in apartment buildings intended exclusively for charging electric vehicles. In return, the operator of such a charging station ensures that it can be temporarily blocked in exceptional cases and solely during the period when the high tariff applies. Stanislav Votruba noted that more than 1.5 million households in the Czech Republic already have experience with dual-tariff rates, as they benefit from more favourable electricity prices for electric heating, heat pumps or water heating.

It is important that, thanks to smart grids, distributors are able to communicate with individual charging stations. They will thus have all information on current electricity consumption available in real time. The construction of charging stations goes hand in hand with the rollout of smart metering, which distribution companies are required to implement under current legislation. And online management of distribution grids will increasingly resemble the regulation of the backbone transmission system.

Cooperation with cities

The development of the charging station network will not be possible without effective coordination between distribution companies and municipal authorities. If, for example, a pavement needs to be dug up to lay stronger cables, the city should have a clear idea of electricity demand in the area over the coming years – including for public lighting and charging stations. “It would be very unfortunate if, in a few years' time, we found that we had to dig up the same place again,” Stanislav Votruba remarks.

At a time of growing electric mobility, however, estimating future needs is becoming quite a complicated puzzle. When upgrading grids today, distribution companies allow for capacity reserves for future chargers, but these reserves cannot be too large, so that financial costs do not rise unnecessarily to disproportionate levels. Underestimating or overestimating the pace of electric mobility development could, in individual cases, throw budgets badly off course.

Cooperation with cities is already often working well. Thanks to it, Prague can, for example, gradually increase the number of lamp posts that serve both public lighting and as locations for chargers. “This synergy will deliver significant savings in the future when building charging infrastructure. Last but not least, it will also save considerable time and implementation capacity, as there will no longer be a need to dig up the ground again,” Stanislav Votruba adds.