German Power Grid Research Articles

Optimizing Power-to-Gas Technology for Efficient Renewable Energy Storage and Integration in Germany: a Review

This study explores the integration of renewable energy sources into the German power grid, with a specific focus on the application of Power-to-Gas (PtG) technology as a solution for energy storage and optimization. Amidst the growing penetration of renewables, characterized by their intermittent nature, the challenge of maintaining a stable and reliable energy supply becomes paramount. This research delves into the use of Polymer Electrolyte Membrane (PEM) electrolysis for hydrogen storage and biological methanation within the PtG process chain, aiming to enhance the efficiency of methane production and the operational performance of trickle-bed reactors. By developing an economically viable approach for PtG technology and suggesting future business models, this work contributes to the identification of the most suitable electrolysis technology for sector coupling and grid integration. The findings indicate that PtG not only offers a promising pathway for the sustainable integration of renewable energies but also underlines the need for novel, application-oriented storage solutions and the optimization of system components for better market penetration and efficiency. This research underscores the pivotal role of PtG technology in bridging the gap between renewable energy production and the existing energy infrastructure, paving the way for a more sustainable and resilient energy system in Germany.

Improved rule-based power distribution algorithm for hybrid battery storage systems and real-world validation

Large-scale battery energy storage systems (BESS) can serve many applications and are already widely used for grid services. The rapidly growing BESS market and the recent interest in their deployment accentuate the need for safe, reliable, and highly available energy management systems (EMS) for automated control. However, the EMS and their integrated power distribution algorithms (PDA) can still be optimized to adapt various characteristics of the BESS. This study investigates a new version of a PDA with a particular focus on battery aging and system efficiency. The rule-based PDA has been validated on a 6 MW/7.5 MWh BESS system with five battery technologies providing frequency containment reserve to the German power grid. The results underline the PDA's capability to exploit the individual strengths of each battery technology. The PDA sets objectives for the state of charge, energy throughput, and power of the batteries to extend battery life. The distribution of energy throughputs among batteries can be selected in advance through the new implementation of the PDA. At the same time, the inverters are significantly less often activated and used in the optimal efficiency range, increasing the overall system efficiency to approximately 82 %. The optimized switching behavior leads to less frequent power switching between individual battery units and longer phases with more constant power. In addition, the operational efficiency of BESS can be improved by the choice of battery technology and the overall system layout on the hardware side. The improvements on the software side are only possible by increasing the overall power requests through multi-use operation by about 6 % compared to our benchmark test. The results can be used by BESS operators to increase operational profits due to longer battery life and fewer efficiency losses.

Compounding or Curative? Investigating the impact of electrolyzer deployment on congestion management in the German power grid

Integrating large amounts of hydrogen production capacities for decarbonizing energy-intensive industries in Germany can be challenging for transmission system operators. This research investigates interactions of hydrogen production deployment pathways and associated congestion management policies with the operation of the German electricity transmission system for future market projections. Hydrogen electrolysis imputes additional electricity loads above conventional levels. A scenario framework is created representing different geographic electrolyzer deployment pathways and congestion management regulations for electrolyzer operation. Fundamental electricity market modeling and load flow optimization are proposed to evaluate resulting congestion management volumes to resolve grid bottlenecks associated with the market clearing dispatch. Overall results of this work highlight the importance of designing congestion management frameworks that enable efficient utilization of electrolyzers as a redispatch capacity, primarily if a demand-oriented deployment of electrolyzer installations near energy-intensive industries is assumed to support renewable energy integration. Differences in congestion management cost between demand- and supply-oriented deployment pathways of electrolyzer capacity lie in the range of 0.77–0.97 bn Euro if electrolyzers cannot be redispatched but almost diminish to 0.10–0.21 bn Euro in the scenarios that include electrolyzer as a redispatch capacity. The findings of this work assist policymakers and regulators with valuable insights into design options for future congestion management frameworks.

Operational Validation of a Power Distribution Algorithm for a Modular Megawatt Battery Storage System

AbstractLarge‐scale battery storage systems have become popular for various grid services in recent years. A worldwide market growth for battery storage has led to increased competition in several grid service markets. Modular large‐scale battery storage systems require a safe, highly available, and intelligent energy management system (EMS) in order to be economically competitive. One component of this EMS is the control for distributing the power requests between individual battery units of the large‐scale battery storage system. As the EMS is usually undisclosed intellectual property of the system manufacturers, there is only little information on real‐world operation available. To contribute, we present a rule‐based power distribution algorithm (SPDA) in this paper and validate it through field tests on a 6 MW/7.5 MWh system that is providing frequency containment reserve to the German power grid. The results show that especially when combining different battery technologies, the SPDA can exploit individual technological strengths. In this way, the state of charge of the batteries, energy throughput and power load of the batteries can be controlled to extend the lifetime. Moreover, the SPDA managed to shift nearly 80 % of the energy throughput to one battery unit to protect less cyclic stable batteries and make use of the advantage of cyclic stable battery technologies, while fulfilling all grid service requirements. By shifting those large quantities of the energy throughput to more cyclic stable battery units, the large‐scale battery storage system experienced in sum up to 45 % less cyclic aging with the SPDA than with a symmetrical power distribution algorithm. Furthermore, the operational efficiency of a large‐scale battery storage system can be significantly improved via additional software adaptations of the power distribution, depending on the system layout.

Measurement data‐driven investigation of the actual power grid resilience with increasing renewable energy feed‐in

AbstractThe transformation of the energy system towards a sustainable reduction of CO2 emissions and the consequently rising contribution of fluctuating energy sources to the German energy system leads to new challenges. In particular, the sufficiency of the present powerline system is of interest. To evaluate the German network sufficiency, a data‐based modelling is used to measure the number of intervals with insufficient transport capabilities as well as the yearly sum of infeasible power transports. In order to do so, the actual residual loads are calculated from the power data in the database “GEOWISOL” and the data on the German power grid are obtained from the project “SciGrid.” The temporal resolution of power data is 15 min, and the spatial resolution refers to the 2‐digit ZIP code regions. The present transmission network is shown to be insufficient in a linearly increasing number of intervals for scenarios with increasing renewable power production. The uncertainties of the results presented are also investigated by means of a Monte Carlo simulation with the known uncertainties of the power data. The simulation results in a relative uncertainty for the number of intervals with insufficient transport capabilities of the network of roughly 1%. Thus, it can be used in the future either to investigate network expansion plans or to validate network expansion studies with simulated data or synthetic networks.

How modular structure determines operational resilience of power grids

The synchronization stability has been analyzed as one of the important dynamical characteristics of power grids. In this study, we bring the operational perspective to the synchronization stability analysis by counting not only full but also partial synchronization between nodes. To do so, we introduce two distinct measures that estimate the operational resilience of power-grid nodes: functional secureness centrality and functional robustness centrality. We demonstrate the practical applicability of the measures in a model network motif and an IEEE test power grid. As a case study of German power grid, we reveal that the modular structure of a power grid and particular unidirectional current flow determine the distribution of the operational resilience of power-grid nodes. Reproducing our finding on clustered benchmark networks, we validate the modular effect on power grid stability and confirm that our measures can be the insightful tools to understand the power grids’ synchronization dynamics.

Power transport needs for the German power grid for a major demand coverage by wind and solar power

The contribution of fluctuating wind and solar energy sources to the German electrical energy demand has increased from 12% up to 40% within the last 10 years and leads to higher infrastructure requirements due to the different spatiotemporal characteristics of wind and solar energy generation. However, common investigations of the energy system exhibit a limited spatiotemporal resolution of power or are based only on simulation models. Therefore, real measurement data regarding the energy demand and the generated energy from 95 German ZIP code regions are investigated to support current infrastructure decisions for the power system. In particular, the residual regional power generation with different wind and solar shares and the resulting power flows are calculated as the solution of a cost optimization problem without energy storage. As a result, a heterogeneous power distribution is identified with a medium surplus in northern and eastern regions and deficits in western and southern Germany. Furthermore, maximum regional coverage of the energy demand by solar and wind energy exists with respect to the share of wind and solar energy generation. For an extrapolation scenario of the average renewable energy to 100% of the average demand, the optimal share is 53% solar and 47% wind power. As a conclusion, a balance of the spatiotemporal fluctuations between renewable energy generation and demand is feasible with appropriate changes in the power grid system, e.g., load management.

Optimal power and gas flow for large-scale transmission systems

The integrated modeling of power and gas systems gains importance as a result of increasing interdependencies due to bidirectional coupling in renewable energy systems through power-to-gas and gas-fired power plants. The optimal power and gas flow problem (OPGF) aiming to minimize system dispatch costs is mostly applied to small test systems. However, to investigate system-wide effects of sector coupling, large-scale transmission grids must be considered. Due to nonlinearities especially in the pressure loss equation, a nonlinear optimization problem results. This paper aims to demonstrate that successive linear programming, in contrast to other discussed approaches, is suitable for solving large-scale and multi-period OPGF-problems. The presented approach shows high solution quality despite short computing time even for large-scale systems such as the German power and gas transmission grid.

Optimization of energy storage and system flexibility in the context of the energy transition: Germany\u2019s power grid as a case study

In this work we explore the ramifications of incoming changes brought by the energy transition, most notably the increased penetration of variable renewable energy (VRE) and phase-out of nuclear and other conventional electricity sources. The power grid will require additional flexibility capabilities to accommodate such changes, as the mismatch between generation and demand is bound to increase. Through mathematical modeling and optimization, we simulate the German power grid and investigate the requirements of on-grid large-scale storage. Different scenarios are evaluated up to 2050, when 80% of the gross electricity consumption is planned to be provided by renewable energy. Dispatchable power plants will play a key role in the transition to an energy mix with high shares of VRE. Around 120 GW of additional large-scale storage are required until 2050. Between the electrochemical technologies evaluated, lithium-ion was the best candidate. A strong reliance on dispatchables was observed, in case the commissioning of VRE plants goes slower than planned. Energy curtailment increases with VRE shares, with up to 14 TWh curtailed in high VRE scenarios in 2050.

Household CO2-efficient energy management

Residential and commercial buildings are responsible for one third of the total (CO2) emissions in the European Union, which are the main cause of global warming. Although the thermal load has long been considered the primary reason of domestic energy consumptions, the increasing demand for electricity has a non-negligible environmental impact, given that about 40% of electricity is generated by burning fossil fuels. Moreover, the amount of CO2 emitted to produce one kWh can greatly vary in time, depending on the sources used to generate it. For instance, the German electricity emissions intensity factor varied in 2017 between 113 and 533 gCO2eq/kWh. This paper proposes a novel CO2-efficient energy management approach to schedule household appliances while minimizing carbon dioxide emissions, given the possibility to change energy carriers (i.e., natural gas and electricity) and to shift loads in time. Several common loads are considered, and their operation is scheduled according to the emission factor of the German power grid. The results show that switching energy carriers can successfully enable up to 40% emissions reductions while indicating that shifting loads in time has little impact.

Einfluss von Starkstromleitungen auf den GNSS-Empfang von automatischen Lenksystemen

Global Navigation Satellite Systems (GNSS) are widely applied for positioning and navigation. They play a vital role in the realm of precision farming. As an integral part of automatic steering systems they relieve the driver and reduce costs by increasing efficiency and saving input material such as diesel, fertilizer and chemicals. For some applications the highest achievable accuracy of 2 cm must be maintained permanently. Related to the renovation of the German power grid the influence of underground and above-ground power lines on the performance of GNSS receivers in agricultural applications has been investigated.

Are PV Battery Systems Causing Ramping Problems in the German Power Grid?

Because of their intermittency, renewable energies increase uncertainty in predicting the residual load in interconnected power systems. Decentralized Photovoltaic (PV) Battery Systems can help to stabilize the volatile behavior of renewable power generation to some extent. Being the world’s largest market for private PV Battery Systems, Germany offers outstanding opportunities to study the performance and grid interaction behavior of PV Battery Systems in existing applications. This publication utilizes unique high resolution measurements performed in 20 carefully selected households with a PV Battery System. By combining the measured power profiles with an ample market analysis the overall effect on the German power grid regarding high power gradients is examined.

Integration of renewable energies, flexible loads and storages into the German power grid: Actual situation in German change of power system

Starting from the late 1990’s, the German government decided to change the national electric power supply system dramatically. The main stimulating instrument was the German Law on Renewable Energies (Erneuerbare Energien Gesetz (EEG)), which guaranteed a fixed feed-in tariff to everyone who was willing to invest into renewable generation. Based on the year of commissioning, defined revenues per kWh were fixed for the next 20 years. Due to a very attractive over-funding, more than 1.5 million renewable generation units were connected to the German grid up to the end of 2015. According to the EEG, renewable generation units can feed to the grid wherever they are located and whenever they are able to produce. The old physical principle was and is still neglected, which clearly stated that generation always has to follow the demand—simply due to the limited availability of storages in the power system. Only in cases, when temporarily renewable overproduction exceeds the tolerable loading of lines or transformers respectively endangers the system stability in total, are German grid operators allowed to announce curtailments by emergency measures. Even in such cases, the “not produced energy” from renewable sources has to be funded. Although the installed capacity from renewables is much higher than the peak load in Germany, it contributes only about 32% to German average annual energy. Unfortunately, the regional distribution of renewable generation and load is very different, e.g. in the northeast of Germany, this Renewable Energy (RE)-ratio meanwhile exceeds 100% due to the high RE-penetration and low load. High transits of renewable overproduction from the north to the south will be necessary at nearly every day per year. Therefore, a tremendous change is needed within the German power grid. This paper will give a first overview followed by several others, describing possible solutions on how to overcome this critical situation.

The potential of public participation to facilitate infrastructure decision-making: Lessons from the German and European legal planning system for electricity grid expansion

The article examines the potential role that public engagement and participative pro-cesses to play a role in effective infrastructure planning in the context of energy policies. For example, by 2050, at least 80% of Germany’s electricity has to be derived from re-newable energy sources if Germany is to meet the goals of its own energy policy. This includes the comprehensive and accelerated extension of the electricity grid. As a result of the magnitude of these changes, the German energy transition is not proceeding without debate and controversy. Public engagement is certainly no panacea for en-hanced social acceptance, yet it offers substantial potential to facilitate the energy tran-sition. The paper draws together social science and legal expertise in order to investi-gate the role of public participation in legal planning processes concerning energy infra-structures. The paper not only focuses on the extension of the German power grid, but also deals with participative policy at the European level. To this end, the paper analyzes the potential role of the German legal planning system in grid expansion and in the Eu-ropean processes of nominating Projects of Common Interest (PCI) and of drawing up the Ten Year Network Development Plan (TYNDP).

An Internet Inspired Approach to Power Grid Stability / Internet-Konzepte für Stromnetzstabilität

Summary The German power grid is facing the disruptive challenge to integrate massively decentral infeed of renewable electric power. It is commonly agreed that information technology can help in managing this problem, mainly by tailoring communication protocols and interfaces, as well as data warehousing and information retrieval approaches to this problem domain. This paper advocates a radically different approach. We draw strong analogies between the operation of the Internet and the operation of a future power grid, and from that derive principles that inspire the design of a new generation of distributed and decentralised power grid control appliances. We report on some prototypical controller designs for photovoltaic generators, and contrast their reliable operation with critical shortcomings of controllers installed on hundreds of thousands of German rooftops to date.

Integrating Electric Vehicles into the German Electricity Grid – an Interdisciplinary Analysis

This study analyses the integration of electric vehicles (EV) into the German power grid including different demand side management (DSM) approaches from a technical, economical and user perspective. For this an overview of the future German electricity market with the focus on EV integration is given. It is shown that for conservative EV penetration rates the effect on the electricity generation is marginal while the shortage in the regional and local electricity grid could be already significant. DSM in combination with smart grids can help to tackle this issue by controlled charging of EVs. One simple concept is to postpone the charging process by offering incentives to vehicle users e. g. with dynamic electricity tariffs. The common Time-of-Use (TOU) tariff defines in advance a dynamic tariff scheme according to the load forecast for the following days. This allows to release the local electricity grid and to increase the share of renewable energies: In times of high electricity generation by renewable energies and low electricity demand the price is low and vice versa. The impact of these dynamic tariffs on the charging process of EVs is shown in a techno-economic analysis for an exemplary urban high voltage grid by an optimising energy model. These strong impacts are however somewhat reduced by the acceptance and the low profits for the single user. At least for the users in a German field trial, environmental aspects played a major role in influencing the charging behaviour – this gives still hope for the future.

Ballard system connected to German power grid

Ballard system connected to German power grid