• Energy Research

Abstract A promising tool to achieve more flexibility within power systems is demand response (DR). End users in many strands of industry have been subject to research regarding the opportunities for implementing DR programmes. We review recent DR modelling approaches in the realm of energy systems models and industrial process models. We find that existing models over- or underestimate the available DR potential from an industrial end user for two main reasons. First, the interaction between power system operation and industrial process operation caused by DR is not taken into account. Second, models abstract from critical physical process constraints affecting the DR potential. To illustrate this, we discuss the wastewater treatment process as one industrial end user within the energy-water nexus, for which the lack of suitable modelling tools is affecting the accurate assessment of the DR potential. Case studies indicate the potential for wastewater treatment plants to provide DR, but no study acknowledges the endogeneity of energy prices which arises from a large-scale utilisation of DR. Therefore, we propose an integrated modelling approach, combining energy system optimisation with the level of operational detail in process simulation models. This will yield a higher level of accuracy regarding the assessment of DR potential from a specific process, such as wastewater treatment.

The use of green hydrogen can support the decarbonization of sectors which are difficult to electrify, such as industry or heavy transport. Yet, the wider power sector effects of providing green hydrogen are not well understood so far. We use an open-source electricity sector model to investigate potential power sector interactions of three alternative supply chains for green hydrogen in Germany in the year 2030. We distinguish between model settings in which Germany is modeled as an electric island versus embedded in an interconnected system with its neighboring countries, as well as settings with and without technology-specific capacity bounds on wind energy. The findings suggest that large-scale hydrogen storage can provide valuable flexibility to the power system in settings with high renewable energy shares. These benefits are more pronounced in the absence of flexibility from geographical balancing. We further find that the effects of green hydrogen production on the optimal generation portfolio strongly depend on the model assumptions regarding capacity expansion potentials. We also identify a potential distributional effect of green hydrogen production at the expense of other electricity consumers, of which policy makers should be aware.

Die verstärkte Nutzung von Wärmepumpen ist eine wichtige Maßnahme zur Senkung der CO2-Emissionen im Wärmesektor. Zudem können Wärmepumpen dazu beitragen, die Importe von Erdgas zu reduzieren. Mit Hilfe eines Stromsektormodells werden die Auswirkungen eines beschleunigten Ausbaus von Wärmepumpen auf den deutschen Stromsektor untersucht. Knapp sechs Millionen zusätzliche Wärmepumpen würden den Strombedarf im Jahr 2030 um neun Prozent erhöhen. Um diesen mit Solarenergie zu decken, wäre eine Erweiterung der Photovoltaik-Kapazitäten um 23 Prozent notwendig. Die Erdgasimporte könnten dadurch um 15 Prozent gesenkt werden. Aus gesamtwirtschaftlicher Sicht wird eine deutlich stärkere Nutzung von Wärmepumpen immer vorteilhafter, je höher der Erdgaspreis ist. Ein schneller Umstieg auf Wärmepumpen erfordert allerdings die Unterstützung durch ein ambitioniertes und koordiniertes Programm der Politik, das auch den Ausbau von Produktionskapazitäten für Wärmepumpen und die Qualifizierung von Fachkräften im Blick hat – eine Art „Apollo-Programm“ für Wärmepumpen. DIW Wochenbericht, 89 (2022), 22, S. 311-320

AbstractHeat pumps play a major role in decreasing fossil fuel use in heating. They increase electricity demand, but could also foster the system integration of variable renewable energy sources. We analyze three scenarios for expanding decentralized heat pumps in Germany by 2030, focusing on the role of buffer heat storage. Using an open-source power sector model, we assess costs, capacity investments, and emissions effects. We find that investments in solar photovoltaics can cost-effectively accompany the roll-out of heat pumps in case wind power expansion potentials are limited. Results further show that short-duration heat storage substantially reduces the need for firm capacity and battery storage. Larger heat storage sizes do not substantially change the results. Increasing the number of heat pumps from 1.7 to 10 million units could annually save more than half of Germany’s private and commercial natural gas consumption and around half of households’ building-related CO2 emissions.

AbstractAs power systems evolve towards integrating higher shares of renewables, the demand for additional levels of flexibility is increased. Meanwhile, o‐ther energy consuming sectors, such as transport and heating, could provide flexibility when they move from fossil fuels to electricity. In this paper, the impact of a range of flexibility measures is assessed for the island system of Ireland, with a high share of renewable energy, particularly wind and solar. Flexibility measures studied include hybrid heating in domestic and industrial processes, smart charging of electric vehicles, renewable hydrogen, power to ammonia, peak shaving demand response and batteries. The novelty of this paper lies in directly quantifying the interactions and dependencies between different flexibility measures, with the objective of increasing the operational flexibility of an increasingly renewable energy‐dominated power system. Four different scenarios are modeled to explore this interplay between the different flexibility measures. The costs and benefits of several sector‐coupling measures. The scenarios have also been compared in terms of their influence on system inertia, renewable energy curtailment and non‐synchronous penetration levels. The results indicate the potential importance of electricity‐based heating in the industrial sector, smart charging of electric vehicles, batteries and power‐to‐ammonia, as part of achieving future targets

Conventional wastewater treatment plants consume significant amounts of electricity. The constant aeration of the wastewater in order to foster the growth of microorganisms or the pumping of wastewater are two examples for energy-intensive processes within a plant. Case studies have shown that switching off blowers and inlet pumps for a certain period of time is possible without a loss in water quality. This yields a potential for wastewater treatment plants to provide demand response (DR) to the power system and thereby increase overall system flexibility. So far, the DR potential has only been quantified for individual plants, while the effects of large-scale DR provision by the wastewater treatment sector for the power system have not yet been studied. One reason for this is the lack of optimisation models which include both the wastewater treatment process and the power system operation in sufficient detail. Our model tackles this gap in the literature by providing a reduced-order linear biochemical model for the activated sludge process within a WWTP that can be incorporated into an operational energy system model. The results show that the effluent concentrations are predicted well by the linear reduced-order model in comparison to the results of the Standard Activated-Sludge model No. 1 (ASM1). Potential model applications are the variation of the airflow rate within a certain range and the variation of liquid influent flow rate to the system, which is a result of electricity load shedding of the inlet pumps and the blowers connected to the activated sludge tank.

Grüner Wasserstoff aus erneuerbaren Energien soll künftig fossile Energieträger in bestimmten Anwendungen in der Industrie und im Verkehr ersetzen, die nicht direkt elektrifizierbar sind. Laut Nationaler Wasserstoffstrategie soll ein Teil des künftigen Wasserstoffbedarfs inländisch durch Elektrolyse mit erneuerbarem Strom erzeugt werden. In dieser Studie wird mit einem Stromsektormodell untersucht, welche Auswirkungen dies auf den deutschen Stromsektor hätte. Dabei werden unterschiedliche verbrauchsnahe oder -ferne Speicheroptionen für Wasserstoff berücksichtigt: in Hochdrucktanks oder in unterirdischen Kavernen. Deutlich wird, dass die Produktion von grünem Wasserstoff in jedem Fall einen zusätzlichen Ausbau der erneuerbaren Energien erfordert. Die Nutzung zentraler Kavernenspeicher führt in der Modellierung zu den geringsten Gesamtkosten der Stromversorgung. Dies gilt dann, wenn sowohl die Wasserstoffherstellung als auch der Wasserstoffverbrauch nah am Kavernenspeicher liegen oder ein leistungsfähiges Wasserstoffnetz vorhanden ist. Muss der Wasserstoff dagegen nach einer zentralen Kavernenspeicherung per Lastwagen zum Verbraucher transportiert werden, kann eine verbrauchsnahe Produktion mit kleineren und teureren Tankspeichern günstiger sein. Die Ergebnisse der Modellierung legen nahe, dass Politik und Infrastrukturplanung auf eine möglichst flexible Wasserstoffproduktion unter Nutzung großer Speicher hinwirken sollten. Dabei können sich allerdings die Strompreise für alle anderen Verbraucher leicht erhöhen. DIW Wochenbericht, 90 (2023), 41, S. 573-580