The German government’s deployment plans for green power plants are ambitious. Most of the country’s electric power system must be climate-neutral by 2035 to enable all other sectors such as heat, mobility and industry to be green by 2045. PV systems, heat pumps and e-cars are all connected at the distribution grid level. The challenges are enormous.
The German government plans to add 360 GW of green power to the grid by 2030, with 215 GW coming from PV systems alone. This change in the generation structure will have an enormous impact on grid operation: Compared to conventional power plants, the majority of green power plants are connected to the grid at the distribution grid level via an inverter. “This results in novel requirements for ensuring secure and robust grid operation,” emphasizes Alexander Folz, Senior Government Official at the German Federal Ministry for Economic Affairs and Climate Action (BMWK) during the Future Power Grids Conference, which took place at the end of January 2024 in Berlin. Folz collaborated with 80 institutions and attended about 70 meetings in order to develop the System Stability Roadmap, which was published in December 2023.
System services are key to stable grid operations. These services include frequency support through operating reserves or power system inertia, and AC voltage support through the provision of reactive power. Besides electricity, the synchronous machines in conventional power plants provide inertia, which has a stabilizing effect on frequency changes in the electricity system. As conventional coal and gas-fired power plants are being phased out, their stabilizing properties need to be replaced by other means.
Renewable power generation plants and other systems, such as storage and charging systems for e-cars or grid operator systems, will need to be advanced to perform these functions. Tenders for reactive power are expected to be published as early as next year. For power system inertia, however, the plan is to introduce a fixed remuneration similar to the feed-in tariff under the original Renewable Energy Sources Act (EEG for short), says Folz.
Amprion, a transmission system operator, launched a pioneering system stability project in late August 2023. At the Opladen switchgear and substation site near Cologne, Germany, a reactive power compensation system has been put into operation. The system consists of inverters, choke coils and battery storage systems with supercapacitors.
Thanks to the system’s power electronic components, the reactive power can be adjusted quickly and continuously so that Amprion can immediately respond to changes in the grid and stabilize the voltage. Reactive power helps to keep grid voltage stable when high capacities are transmitted over long distances, for instance wind power from the north of Germany to the south – a scenario which will become more frequent in the future.
Amprion’s system also has grid-forming properties – a complete novelty in German grids. This special power converter regulation will also be programmed into solar and wind power sites so that they act like a voltage source. Similarly to conventional power plants, they would then provide power system inertia. The Amprion pilot plant, for example, can provide 300 megaVAr of reactive power. The transmission system operator is currently planning several more systems with battery storage for the supply of power system inertia, and for a quick response to disruptions such as when grids are split into sub-grid areas, preventing power failures.
This year, the Future Power Grids Conference has chosen partner country Austria. The energy system of the future will be complex, but the ZusammEn 2040 cooperation project is ready to tackle this challenge. It involves calculating the vision of a climate-neutral Europe using a mathematical model. Complex relationships in the energy system are presented by a cross-sector optimization model. The entire value-added chain will be illustrated with an open source software with high spatial resolution for individual regions.
It also includes a platform where stakeholders can compare their results. Austrian Power Grid (APG), a transmission system operator, has developed this model together with TransnetBW and AGGM.
Based on the provided baseline scenario, the model can define many different visions of the future. APG experts assist other grid operators in defining assumptions and parameters and in interpreting results to ensure that the vision is aligned to the European and Austrian climate targets. The model takes into account all relevant sectors – from electricity, gas, heat, transportation to industry. The purpose of the tool is to identify no-regret actions, and the associated demand. This includes setting up an infrastructure that won’t be regretted even if requirements or goals change in the future. The use of a common model increases transparency and interaction between grid operators from different EU countries.
Grid transformation cannot be stopped – and the consumers are changing, too. Our centralized, unidirectional power supply will become a decentralized and bidirectional, and integrate with many power generation systems. Of the planned 215 GW of PV capacity in Germany, almost all systems will feed into the distribution grid at lower grid levels. “By 2030, the number of charging stations for electric cars will increase 30-fold to between 15 and 20 million,” explains Professor Jochen Kreusel, who works at Hitachi Energy (formerly Hitachi ABB Power Grids) as Global Head of Market Innovation.
Heat pumps are also set to increase to between 12 and 15 million. This represents an installed capacity of around 700 to 900 GW for these two consumption groups alone. To put this into perspective, only 45 gigawatts are currently installed. This is a good illustration of the challenges facing distribution grid operators, says Kreusel. In addition, there is a lack of transparency and digitalization at this grid level.
The System Stability Roadmap provides a good foundation for the rest of the process. First, however, the flexibility in the grid that paragraph 14a of the Energy Industry Act EnWG allows for must be put into practice. This paragraph provides rules for grid operators to quickly integrate controllable consumers, such as heat pumps and EV-chargers, into the power grid. At the same time, grid expansion needs to be accelerated. The risk of falling behind in grid expansion is greater than the risk of over-investing in this transformation, Kreusel reminds. “We must act now to build the grids we will need in 2030.”