Many research projects in the context of the electrification of mobility, heat and industry are investigating how new electrical consumers in combination with the ramp-up of renewable energies will affect electricity grids. A large share of the added electrical load is connected in low-voltage grids (LV grids). One approach for their integration is to make consumption behavior more flexible in order to avoid or eliminate congestions in the grid. To evaluate the concepts in terms of their impact on the grids, they are simulated with future load scenarios and grid operation strategies.
In total, there are over 500,000 LV grids in Germany, which are operated by around 800 distribution grid operators . In total, these result in a line length of over 1,200,000 km . It is hardly possible to simulate all grids individually. On the one hand, they are not available in a simulatable form, and on the other hand, this would require an enormous amount of computation capacity. In order to be able to make statements for different grid structures in Germany, reference grids are therefore used for simulations. These allow to draw conclusions about the grid infrastructure from geographical and structural parameters.
This series of articles shows which parameters and methods are used to create reference grids. Furthermore, data from literature is merged and a set of reference grids is created. Specifically, the following topics are addressed:
- Low-voltage grids in Germany
- Characterisation of low-voltage grids
- Identification of grid clusters in the low voltage level
- Identification of reference grids for the clusters
- Distribution grids in the Climate-Neutral Energy System – Scenarios for Consumption, Generation and Grid Operation
Change to a climate-neutral energy system
As described in article 1 of the series, the structure and behavior of consumers and generators connected to the low-voltage level is changing in the wake of the energy transition. In order to respond to the challenges, adjustments in grid operation, such as the use of flexibility, are among the issues being discussed. Therefore, the question arises which assumptions have to be made in order to realistically represent consumption and generation behavior on the one hand and future grid operation on the other hand in the simulation of future scenarios.
Scenarios for mapping generators and consumers in the distribution grid of the future
Assumptions for renewable energy (RE) expansion and the ramp-up of electrical loads – especially heat pumps and electric vehicle charging points – vary widely. Policy targets can be used as a guide, but these include the nationwide ramp-up. Due to the geographically very different RE potentials as well as structural differences in the ramp-up of electrical consumers, these must be broken down regionally.
According to §14d of the Energy Industry Act (EnWG), distribution system operators (DSOs) must submit a grid expansion plan to the Federal Network Agency (BNetzA) for the first time by April 30, 2024, and update it every two years from then on. The grid expansion plan is to be based on regional scenarios, which are to be prepared for planning regions at least 10 months in advance. All DSOs in a planning region must prepare this scenario in cooperation with the higher-level transmission system operator. The expansion plans on transmission grid level as well as climate and energy policy targets set by the German government are to be taken into account.  Germany was divided into 6 planning regions for this purpose: North, Central, West, East, Bavaria and South-West.
All regions have already published their regional scenario for 2023 . These include ramp-up numbers for individual sectors and consumer groups (e.g. household, transport, heat pumps, electrolysis, …) as well as for RE plants for individual years of consideration (2028, 2033, (2037,) 2045).
Scenarios for distribution grid operation in the climate-neutral energy system
The use of consumption-side flexibility is a much-discussed measure for future congestion management in low-voltage grids. In particular, the postponement of charging processes of electric vehicles as well as the electrical consumption of heat pumps is investigated and tested in many research projects of FfE. In the regional scenarios, the reporting DSOs take up the consideration of this possibility. In this context, there are partly different assessments regarding the future use of flexibility :
- Planning Region North: According to the DSOs, the potential of demand-side management cannot be estimated and is therefore not considered in the scenarios. However, some DSOs will consider this in the grid expansion planning. Overall, grid-serving flexibility is only used in individual cases, but represents a planning principle for the future energy system.
- Planning region East: Flexibility is mainly used in a system-oriented manner, whereby the type of use depends strongly on the market design still to be developed and on the regulatory framework conditions.
- Planning region West: No mention of the use of flexibility on the consumption side.
- Central planning region: Heat pumps and electric vehicles will be used in a grid- or market-oriented manner in the future. By “grid-oriented” is meant that flexible load is shifted to times with little load on the grid; “market-oriented” means that flexible consumption is shifted to time windows with a high RE share. The commercial-retail-service sector and industry are currently neglected.
- Planning region South-West: leveraging potential of load shifting (heat pumps and electric vehicle charging) is not considered.
- Planning region Bavaria: No consideration of flexibility and storage technologies in the next five years (“no significant grid expansion demand reducing effect through flexibilities and storage technologies”).
This makes it clear that the DSOs do not expect the use of consumption-side flexibility in the next few years. The design of §14a in the Energy Industry Act is mentioned but not taken into account by any of the planning regions due to the lack of concretization at the time the regional scenarios were created. For the implementation of grid operation strategies in simulations of the low-voltage grids, this means that grid-serving flexibility will hardly play a role until 2030. For the following years, it is still necessary to show the possibilities and efficiency potentials that the use of flexible consumers in the low voltage level can bring.
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 Länge des Stromnetzes in Deutschland nach Spannungsebene im Jahresvergleich 2010 und 2021. Hamburg: Statista, 2023
 Müller, Mathias et al.: Future grid load with bidirectional electric vehicles at home. Berlin: International ETG Congress 2021. VDE, 2021
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