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The goal of the European energy policy is to achieve climate neutrality. The long-term energy strategies of various European countries include additional targets such as the diversification of energy sources, maintenance of security of supply, and reduction of import dependency. When optimizing energy systems, these strategic policy targets are often only considered in a rudimentary manner and thus, the understanding of the corresponding interdependencies is lacking. Moreover, hydrogen is considered as a key component of a fully decarbonized energy system, but its role in the power sector remains unclear due to the low round-trip efficiencies.This study reveals how fully decarbonized European power systems can benefit from hydrogen in terms of overall system costs and the achievement of strategic policy targets. We analyzed a broad spectrum of scenarios using an energy system optimization model and varied model constraints that reflect strategic policy targets. Our results are threefold. First, compared to power systems without hydrogen, systems using hydrogen realize savings of 14–16% in terms of the total system costs. Second, the implementation of a hydrogen infrastructure reduces the number of infeasible scenarios when structural policy targets are considered within the power system. Third, the role of hydrogen is highly diverse at a national level. Particularly, in countries with low renewable energy potential, hydrogen plays a crucial role. Here, high levels of self-sufficiency and security of supply are achieved by deploying hydrogen-based power generation of up to 46% of their annual electricity demand, realized via imports of green hydrogen.

This Virtual Special Issue collects the results of six research projects conducted under the umbrella of the MODEX network. MODEX stands for Model Experiments and refers to the combination of qualitative and quantitative model comparisons, the latter based on a harmonized model application. While all projects focused on the comparison of energy system models, the experiments covered a broad range of different areas. Thus, the experiments address different model types, such as vehicle diffusion models, power system models, distribution grid models, and transmission grid models, but also different thematic scopes, such as policy instruments, decentralized flexibility, and sector coupling. In total, the projects involved 40 models. The experiments were based on a harmonization of models and data, which was realized to the degree possible and useful in the respective project context. Complementary to the harmonized model application, the methods and tools for the systematic comparison of energy system models were further developed within the MODEX projects. The results of the MODEX projects significantly expand the spectrum of systematic comparisons of energy system models. The added value compared to previous model experiments consists particularly in the profound characterization of the models involved, the consistent linking of model differences with outcome differences, and the transparent description of appropriate methods and challenges of comparing energy system models. Due to a high degree of transparency, the project findings can be used directly by developers and users of other models

In which way, and in which sectors, will renewable energy be integrated in the German Energy System by 2030, 2040, and 2050? How can the resulting energy system be characterised following a −95% greenhouse gas emission reduction scenario? Which role will hydrogen play? To address these research questions, techno-economic energy system modelling was performed. Evaluation of the resulting operation of energy technologies was carried out from a system and a business point of view. Special consideration of gas technologies, such as hydrogen production, transport, and storage, was taken as a large-scale and long-term energy storage option and key enabler for the decarbonisation of the non-electric sectors. The broad set of results gives insight into the entangled interactions of the future energy technology portfolio and its operation within a coupled energy system. Amongst other energy demands, CO2 emissions, hydrogen production, and future power plant capacities are presented. One main conclusion is that integrating the first elements of a large-scale hydrogen infrastructure into the German energy system, already, by 2030 is necessary for ensuring the supply of upscaling demands across all sectors. Within the regulatory regime of 2020, it seems that this decision may come too late, which jeopardises the achievement of transition targets within the horizon 2050.

Renewable & sustainable energy reviews 158, 111995 (2022). doi:10.1016/j.rser.2021.111995 special issue: "MODEX: energy system model comparisons through harmonized applications / Edited by Hans Christian Gils, Jochen Linßen, Dominik Möst, Christoph Weber", Published by Elsevier Science, Amsterdam [u.a.]

Renewable & sustainable energy reviews 159, 112177 (2022). doi:10.1016/j.rser.2022.112177 special issue: "MODEX: energy system model comparisons through harmonized applications / Edited by Hans-Christian Gils, Christoph Weber, Dominik M��st, Jochen Lin��en", Published by Elsevier Science, Amsterdam [u.a.]

As electric vehicle fleets grow, rising electric loads necessitate energy systems models to incorporate their respective demand and potential flexibility. Recently, a small number of tools for electric vehicle demand and flexibility modeling have been released under open source licenses. These usually sample discrete trips based on aggregate mobility statistics. However, the full range of variables of travel surveys cannot be accessed in this way and sub-national mobility patterns cannot be modeled. Therefore, a tool is proposed to estimate future electric vehicle fleet charging flexibility while being able to directly access detailed survey results. The framework is applied in a case study involving two recent German national travel surveys (from the years 2008 and 2017) to exemplify the implications of different mobility patterns of motorized individual vehicles on load shifting potential of electric vehicle fleets. The results show that different mobility patterns, have a significant impact on the resulting load flexibilites. Most obviously, an increased daily mileage results in higher electricty demand. A reduced number of trips per day, on the other hand, leads to correspondingly higher grid connectivity of the vehicle fleet. VencoPy is an open source, well-documented and maintained tool, capable of assessing electric vehicle fleet scenarios based on national travel surveys. To scrutinize the tool, a validation of the simulated charging by empirically observed electric vehicle fleet charging is advised.

To assess the resilience of energy systems, i.e., the ability to recover after an unexpected shock, the system’s minimum state of service is a key input. Quantitative descriptions of such states are inherently elusive. The measures adopted by governments to contain COVID-19 have provided empirical data, which may serve as a proxy for such states of minimum service. Here, we systematize the impact of the adopted COVID-19 measures on the electricity demand. We classify the measures into three phases of increasing stringency, ranging from working from home to soft and full lockdowns, for four major electricity consuming countries of Europe. We use readily accessible data from the European Network of Transmission System Operators for Electricity as a basis. For each country and phase, we derive representative daily load profiles with hourly resolution obtained by k-medoids clustering. The analysis could unravel the influence of the different measures to the energy consumption and the differences among the four countries. It is observed that the daily peak load is considerably flattened and the total electricity consumption decreases by up to 30% under the circumstances brought about by the COVID-19 restrictions. These demand profiles are useful for the energy planning community, especially when designing future electricity systems with a focus on system resilience and a more digitalised society in terms of working from home., German Federal Ministry of Economic Affairs and Energy, German Federal Ministry of Education and Research

The transition towards decarbonized energy systems requires the expansion of renewable and flexibility technologies in power sectors. In a model comparison, we examine the optimal expansion of such technologies with six capacity expansion power system models. The technologies under investigation include base- and peak-load power plants, electricity storage, and transmission. We define four highly simplified and harmonized use cases that focus on the expansion of only one or two specific technologies to isolate their effects on model results. We find that deviating assumptions on limited availability factors of technologies cause technology-specific deviations between optimal capacity expansion in models in almost all use cases. Fixed energy-to-power-ratios of storage can entirely change model optimal expansion outcomes, especially shifting the ratio between short- and long-duration storage. Fixed initial and end storage levels can impact the seasonal use of long-duration storage. Models with a pre-ordered dispatch structure significantly deviate from linear optimization models, as limited foresight and flexibility can lead to higher capacity investments. A simplified net transfer capacity approach underestimates the need for grid infrastructure compared to a more detailed direct current load flow approach. We further find deviations in model results of optimal storage and transmission capacity expansion between regions and link them to variable renewable energy generation and demand characteristics. We expect that the general effects identified in our stylized setting also hold in more detailed model applications, although they may be less visible there.

Der vorliegende zweite Teil - Sektorenkopplung und Wasserstoff: Zwei Seiten der gleichen Medaille knüpft an diesem Punkt an. Er befasst sich detailliert mit möglichen Nutzungspfaden von Wasserstoff in den Sektoren Verkehr, Industrie und Wärme sowie mit dem systemisch wichtigen Aspekt der Rückverstromung. Am Beispiel aktueller Forschungsarbeiten im DLR wird dargestellt, welche Potenziale sich durch die Kopplung der verschiedenen Energieverbrauchssektoren bei der Erzeugung und Nutzung von Wasserstoff ergeben. Diese Synergien ebnen den Weg zu einer effizienteren und flexibleren Nutzung von erneuerbarer Energie. Neben den technologischen Einsatzmöglichkeiten spielen darüber hinaus die Infrastruktur sowie dazugehörige Sicherheitsaspekte bei der Nutzung von Wasserstoff eine gewichtige Rolle. Weiterhin wird im DLR auf dem Gebiet der Energiesystemanalyse an der Einschätzung der Auswirkungen großskaliger Wasserstoffinfrastrukturen auf das bestehende und zukünftige Energiesystem geforscht. Dies beinhaltet auch die Fragestellungen, ob ein klimaneutrales Energiesystem aus heutiger Sicht überhaupt ohne Wasserstoff denkbar ist, bzw. wie groß der Wasserstoffbedarf und das -angebot in solchen Zielszenarien ausfällt. Zudem werden Umwelteinwirkungen untersucht und Lebenszyklusanalysen erstellt.

Background Energy system models (ESM) are widely used in research and industry to analyze todays and future energy systems and potential pathways for the European energy transition. Current studies address future policy design, analysis of technology pathways and of future energy systems. To address these questions and support the transformation of today’s energy systems, ESM have to increase in complexity to provide valuable quantitative insights for policy makers and industry. Especially when dealing with uncertainty and in integrating large shares of renewable energies, ESM require a detailed implementation of the underlying electricity system. The increased complexity of the models makes the application of ESM more and more difficult, as the models are limited by the available computational power of today’s decentralized workstations. Severe simplifications of the models are common strategies to solve problems in a reasonable amount of time – naturally significantly influencing the validity of results and reliability of the models in general. Solutions for Energy-System Modelling Within BEAM-ME a consortium of researchers from different research fields (system analysis, mathematics, operations research and informatics) develop new strategies to increase the computational performance of energy system models and to transform energy system models for usage on high performance computing clusters. Within the project, an ESM will be applied on two of Germany’s fastest supercomputers. To further demonstrate the general application of named techniques on ESM, a model experiment is implemented as part of the project. Within this experiment up to six energy system models will jointly develop, implement and benchmark speed-up methods. Finally, continually collecting all experiences from the project and the experiment, identified efficient strategies will be documented and general standards for increasing computational performance and for applying ESM to high performance computing will be documented in a best-practice guide.

Battery electric vehicles (BEV) provide an opportunity to balance supply and demand in future power systems with high shares of fluctuating renewable energy. Compared to other storage systems such as pumped-storage hydroelectricity, electric vehicle energy demand is highly dependent on charging and connection choices of vehicle users. We present a model framework of a utility-based stock and flow model, a utility-based microsimulation of charging decisions, and an energy system model including respective interfaces to assess how the representation of battery electric vehicle charging affects energy system optimization results. We then apply the framework to a scenario study for controlled charging of nine million electric vehicles in Germany in 2030. Assuming a respective fleet power demand of 27 TWh, we analyze the difference between power-system-based and vehicle user-based charging decisions in two respective scenarios. Our results show that taking into account vehicle users’ charging and connection decisions significantly decreases the load shifting potential of controlled charging. The analysis of marginal values of equations and variables of the optimization problem yields valuable insights on the importance of specific constraints and optimization variables. Assumptions on fleet battery availability and a detailed representation of fast charging are found to have a strong impact on wind curtailment, renewable energy feed-in, and required gas power plant flexibility. A representation of fleet connection to the grid in high temporal detail is less important. Peak load can be reduced by 5% and 3% in both scenarios, respectively. Shifted load is robust across sensitivity analyses while other model results such as curtailment are more sensitive to factors such as underlying data years. Analyzing the importance of increased BEV fleet battery availability for power systems with different weather and electricity demand characteristics should be further scrutinized.

Im Projekt MuSeKo wird der kombinierte Einsatz unterschiedlicher Flexibilitäten und Sektorenkopplungen in einem künftigen Energiesystem mit einem hohen Anteil erneuerbarer Energien modellbasiert untersucht. Die Analyse erfolgt mit einem zeitlich und räumlich aufgelösten, techno-ökonomischen Ansatz. Anhand dessen Ergebnissen werden unterschiedliche energiewirtschaftliche Rahmenbedingungen im Hinblick auf Investitionen und den Anlageneinsatz bewertet. Der Neuheitswert des Projekts liegt einerseits in der Fokussierung auf die Ausgestaltung der Kopplung von Strom- und Gassystem und andererseits auf der Kombination der gesamtwirtschaftlichen mit der betriebswirtschaftlichen Perspektive. Die Projektergebnisse zeigen einerseits die Chancen einer engeren Verzahnung der Strom-, Wärme- und Gasversorgung, und andererseits die damit einhergehenden regulatorischen Herausforderungen für die Anreizung systemdienlicher Investitionen und Anlageneinsätze. Die Arbeiten bieten in den erweiterten Methoden und erhobenen Daten eine wichtige Grundlage zur weiteren Erforschung der Umsetzung der flexiblen Sektorenkopplung in der Energiewende.

The expected increase in battery electric vehicles poses both, opportunities and risks for the decarbonisation of future power systems. While electric mobility may technically serve as a source of flexibility, it increases the overall power demand and may as well increase the demand for power in peak load hours. While electric mobility in national and continental scale energy system optimization is often treated in an aggregated fleet, user behaviour and charging decisions play a crucial role in the availability of vehicles' batteries for balancing electric load and renewable energy feed-in. Michaelis, Gnann & Klingler (2018) find that reduction of peak load and RE surplus electricity stemming from plug-in vehicles in Germany may be as high as 2.2 GW and 1.8 TWh respectively for 2030. However, they assume constant charging stations' power of 3.7 kW that seem conservative. Also, the authors don't explicitly describe to what effect user behaviour limits vehicle charging. By linking the modular energy system optimization model REMix with the vehicle stock model VECTOR21 and the charging decision simulation tool CURRENT, we aim to determine a more realistic demand response potential for future electric vehicles compared to previous studies. All three models are developed at the German Aerospace Center (DLR) and have been applied and validated in different project contexts. We for the first time integrate hourly profiles determined by individual charging decisions as input for an energy system optimization model. We determine the reduction potential of peak load, renewable energy (RE) curtailment as well as RE capacity expansion for the different cases of controlled charging versus uncontrolled charging for Germany for 2030. Thus, we provide both methodological and quantitative insights into the effects of coupling power and transport sector that are of value to the scientific discussion.