It is challenging for China to achieve its long-term climate goals, of limiting temperature increase within 2 degrees C and reaching carbon neutrality by 2060, as the current energy supply is still dominated by fossil energy with 83 % in 2021. This study conducts a meta-analysis of 131 existing energy scenarios that achieve at least 70 % CO2 emission reduction by 2050 compared to 2020 levels, aiming to identify no-regret decarbonisation strategies under high future uncertainty. The analysis reveals a wide range of projected pathways, yet consistently highlights four no-regret actions: improving energy efficiency, expanding and integrating renewable energy, increasing electrification across end-use sectors and applying hydrogen and synthetic fuels in hard-to-abate sectors. On average, scenario projections indicate an Improved energy intensity of 1.9 MJ/USD2020 PPP, renewables supplying 49 % of primary energy and 65 % of electricity, end-use electrification rates of 52 %, and deployment of around 8 EJ of hydrogen and synthetic fuels by 2050. Compared with global indicators for the 1.5 degrees C target from IRENA, these projections remain conservative, suggesting the need for more ambitious actions. Scenarios achieving net-negative emissions require faster efficiency improvements, electrification approaching 90 % in industry, and large-scale deployment of bioenergy with carbon capture and storage. Overall, the results underline the importance of focusing on no-regret measures that remain effective across diverse futures, supported by timely infrastructure expansion, investment, investment, and institutional capacity.

AbstractThis article explores the evolution of research in the field of renewable energy over the past five decades, tracing its development through various phases. Initially sparked by the 1970s energy crises and growing environmental consciousness, the journey began with a focus on technological solutions for renewables. The article highlights the shift over time away from purely technology-driven research to a broader, interdisciplinary orientation. Following the first phase of exploring technology solutions, we discuss the market expansion phase of renewables, their market integration as well as the current speeding up of the transition towards a more and more renewable electricity system. We highlight the evolution of support mechanisms and concomitant scientific debate that accompanied the move from quota obligations to feed-in tariffs. With renewables now a key element in achieving climate neutrality, research has expanded to include market and system integration, the socio-economic impacts of the renewable energy expansion, and systems transformation perspectives. The article underscores the contribution of different types of institutions and players in shaping renewable energy research and policy, emphasising the increasing importance of a systemic and interdisciplinary approach to address current energy and sustainability challenges in a holistic manner.

With its ability to store and transport energy without releasing greenhouse gases, hydrogen is considered an important driver for the decarbonisation of energy systems. As future hydrogen import prices from global markets are subject to large uncertainties, it is unclear what impact different hydrogen and derivative import prices will have on the future German energy system. To answer that research question, this paper explores the impact of three different import price scenarios for hydrogen and its derivatives on the German energy system in a climate-neutral setting for Europe in 2045 using three different energy system models. The analysis shows that the quantities of electricity generated as well as the installed capacities for electricity generation and electrolysis increase as the hydrogen import price rises. However, the resulting differences between the import price scenarios vary across the models. The results further indicate that domestic German (and European) hydrogen production is often cost-efficient.

This study explores the integration of variable renewable electricity (VRE) sources, such as photovoltaic (PV) and wind power, into energy systems and the role of thermal storage within district heating networks to enhance system flexibility. Utilizing the Enertile model, a techno-economic linear optimization tool, we analyze the supply, transmission, and storage of energy across the EU, with a focus on Germany for the year 2050. We take a detailed look at the dispatch of the district heating supply and the usage of the thermal storage, both qualitatively and quantitatively. Our analysis reveals that thermal storages in district heating, together with high shares of heat pumps, significantly aid the integration of VRE by allowing for the storage of thermal energy during periods of high VRE availability. Future research should focus on different types of thermal storage and their distinct impact towards VRE integration.

Abstract Background The transition towards a sustainable energy system is reshaping the demand for final energy, driven by the diffusion of new end-use technologies. This shift not only impacts consumers’ energy expenses, but also holds implications for the public budget. Building on data from a German energy transition scenario, we analyse the direct impact of energy costs on industries, low-income households, and changes in government revenues from the taxes and levies on final energy carriers. Our analysis considers the impact of current policies and explores a scenario introducing additional excise tax rates to offset potential revenue losses. Results We found that substantial carbon price increases could generate revenues that offset the losses from excise taxes on fossil fuels while enabling the financing of renewable support from the public budget by the end of this decade. Nevertheless, a decline in government revenues from taxes and levies is anticipated after 2030 until the middle of the century due to the declining use of fossil fuels. Maintaining current excise tax revenues during the transition could be achieved by introducing additional excise taxes on fossil fuels and electricity. Lastly, our analysis indicated a continuous decline in household energy expenditures until 2050, whereas energy-intensive industries face adverse impacts due to decarbonisation. Conclusions This research provides valuable insights into the fiscal implications of the energy transition, shedding light on different industrial sectors and households while considering the evolving impact on the public budget. Policymakers may need to consider systemic reforms or alternative financing mechanisms outside the energy system to balance the books.

This paper takes a novel modelling approach by considering high spatial resolution heat generation potentials for district heating and integrating them into a European energy system model. Subsequently, a modelling analysis of an integrated energy system including district heating, electricity and hydrogen supply for 25 EU Member States and the year 2050 is carried out. In contrast to existing approaches, the modelling approach captures the heterogeneous resource availability in district heating. The results show multivalent district heating networks based on a wide range of renewable and excess heat sources used directly or in combination with large-scale heat pumps. The high spatial resolution of the heat generation potentials allows a detailed cost comparison of different possible future technology mixes in district heating. The paper finds that the use of heat pumps, geothermal energy and industrial excess heat offer slight cost advantages for the energy system as a whole. Geothermal heat can also provide cost advantages for district heating generation.

Heat pumps and battery electric vehicles play a crucial role in achieving a climate-neutral economy and integrating the Energy Efficiency First Principle into the building and transport sectors, rendering the overall energy system more efficient. To achieve cost competitiveness of these new technologies compared to conventional ones, investments, operating costs and conversion efficiencies are important. We conducted micro-simulations of the development of levelised cost of heat and transport for these sector coupling technologies to assess the direct cost impact of these parameters. With a broad and in-depth analysis of economies of scale, we determine future bandwidths of investment development. Based on this data, we compared implications of two policy scenarios of taxes and levies on final energy prices using a German case study. The first scenario considers recently adjusted taxes and levies: the national emissions trading system in 2021 and the abolishment of the electricity levy to finance renewable energy support in 2022. A counterfactual scenario includes previous framework conditions. Our results show that rising carbon and lower electricity prices already economically favour heat pumps from 2020 onwards. In contrast, taxes and levies do not decisively impact the cost competitiveness of battery electric vehicles, but expected reductions in manufacturing cost do.

A carbon price on heating fuels aims to reduce the use of fossil energy in the heating sector. However, it has a greater effect on tenants than on landlords. The heating transition requires adequate building insulation for efficient use of low-temperature technologies. To encourage this particular kind of investment, German landlords are given the option to apply a modernisation levy of up to 8% on top of rents. Similar to carbon pricing, rent increases cause distributional effects. The net effect of these measures on tenants has not been analysed so far. Using a micro-simulation integrating representative empirical data on tenant households in Germany from KOSMA and the detailed building database TABULA, we analyse direct distributional effects of a carbon price (euro55/t and euro250/t), a per-capita redistribution of carbon price revenues and the modernisation levy (8% and 2% rent increases). The analysis shows that carbon prices and modernisation levies have strong regressive effects. These can be mitigated by the per-capita redistribution. However, the effect on tenants within a given income decile varies largely due to the diversity of buildings. Thus, when designing and evaluating policies, looking at average effects is not sufficient to assess economic impacts for individual households.

This chapter provides a comprehensive approach to assessing costs and benefits for the past and future development of the energy transition in the EU. It briefly outlines the analytical framework to assess the impacts of the energy transition and describes the framework by using RET deployment in general as well as examples. It describes different types of costs and benefits, applies a unified and consistent terminology for the costs and benefits of the energy transition and provides guidance for their assessment. It identifies which types of effects arise in line with the energy transition in general, in different economic sectors, regions or technology fields and how they can be assessed on a regular basis, e.g. life cycle or annual. In addition, it discusses the system boundaries of impact assessments, which impacts can be quantified and expressed in terms of indicators and their potential monetarisation, which information and methodological approach is most suitable to get an appropriate picture of the costs and benefits of the system that are the focus of the analysis and how to critically assess results in terms of indicators and be aware of limitations.

Zusammenfassung Steuern und Abgaben auf Produkte oder Verbrauch mit gesellschaftlichen Folgekosten (externe Kosten) – sogenannte Pigou- oder Lenkungssteuern – sind ein gesellschaftliches „Win-Win-Instrument“. Sie verbessern die Wohlfahrt und schützen gleichzeitig die Umwelt und das Klima. Dies wird erreicht, indem umweltschädigende Aktivitäten einen Preis bekommen, der möglichst exakt der Höhe des Schadens entspricht. Eine konsequente Bepreisung der externen Kosten nach diesem Prinzip könnte in Deutschland erhebliche zusätzliche Einnahmen erbringen: Basierend auf bisherigen Studien zu externen Kosten wären zusätzliche Einnahmen in der Größenordnung von 348 bis 564 Milliarden Euro pro Jahr (44 bis 71 Prozent der gesamten Steuereinnahmen) möglich. Die Autoren warnen allerdings, dass die Bezifferung der externen Kosten mit erheblichen Unsicherheiten verbunden ist. Damit Lenkungssteuern und -abgaben ihre positiven Lenkungs- und Wohlstandseffekte voll entfalten können, seien zudem institutionelle Reformen notwendig.

Im Kern eines Instrumentenmixes fur die deutsche Energie- und Klimapolitik sollte nach Ansicht von Andreas Loschel, Universitat Munster, eine allgemeine CO2-Bepreisung stehen, die einen okonomisch sinnvollen und langfristigen Rahmen fur die umfangreiche Transformation setzt. Bei marktwirtschaftlichen Preis- oder Mengeninstrumente genuge zur kosteneffizienten Erreichung der Ziele, klimaschadlichen Aktivitaten einen angemessenen einheitliches CO2-Preis zu geben. Zudem generiere die CO2-Bepreisung Einnahmen, die eine gerechte Transformation ermoglichen. Till Baldenius, Tobias Bernstein, Matthias Kalkuhl, Maximilian von Kleist-Retzow und Nicolas Koch, MCC, diskutieren die Verteilungswirkungen von Preis- und ordnungsrechtlichen Instrumenten fur mehr Klimaschutz im Verkehrssektor. Sie zeigen, dass sowohl CO2-Effizienzstandards als auch Subventionen und Fahrverbote problematische Verteilungswirkungen haben und regulatorische Masnahmen nicht durch vorteilhafte Verteilungswirkung gegenuber Preisinstrumenten gerechtfertigt werden konnen. Anke Bekk, Anne Held und Jan George, Fraunhofer Institut fur System- und Innovationsforschung, zeigen, dass eine Abschaffung der EEG-Umlage Verzerrungen im Wettbewerb zwischen konventionellen Technologien und Sektorkopplungstechnologien verringern wurde. Eine Refinanzierung uber eine hohere CO2-Bepreisung des EEG-Finanzierungssystems konnte somit einen wichtigen Beitrag zur weiteren Marktdurchdringung von Sektorkopplungstechnologien leisten und zur Beschleunigung der Dekarbonisierung der Energiewende beitragen. Allerdings seien damit Verteilungseffekte verbunden, fur die ein Ausgleichsmechanismus implementiert werden sollte, beispielsweise eine Pro-Kopf-Ausschuttung zur Entlastung einkommensschwacher Haushalte. Doina Radulescu, Universitat Bern, stellt die Probleme vor, die entstehen, wenn mehrere Ziele – Umwelt-, Verteilungs- und Wettbewerbspolitik – mit einem einzigen Instrument adressiert werden. Umweltziele sollten uber CO2-Steuern, Verteilungsziele uber progressive Einkommensteuern und Industriepolitik uber weitere Masnahmen erreicht werden. Unterschiedliche Vorstellungen von Gerechtigkeit spielen fur die Zustimmung zu klimapolitischen Masnahmen eine grose Rolle. Michael Pahle, Potsdam-Institut fur Klimafolgenforschung, Stephan Sommer, RWI, und Linus Mattauch, University of Oxford, untersuchen, unter welchen Aspekten die Bevolkerung einem CO2-Preis zustimmt und ihn als fair wahrnimmt. Sie zeigen, dass zur Verbesserung der gesellschaftlichen Unterstutzung eine direkte Ruckverteilung, bevorzugt mit einer Pro-Kopf-Pramie, erfolgen sollte. Eine Studie von Daniela Setton und Ortwin Renn, IASS, kommt zu dem Ergebnis, dass die Energiewende von der Mehrheit der Bevolkerung als ungerecht eingestuft wird, insbesondere im Hinblick auf die Kostenverteilung. Quer durch alle Bevolkerungsgruppen zeige sich bei den gewunschten Kostenverteilungsregeln eine klare Praferenz fur Verursachergerechtigkeit, dabei stehe jeweils die Klimaverschmutzung oder die Hohe des Energieverbrauchs im Vordergrund. Wer viel verbraucht oder hohe CO2-Emissionen verursache, solle mehr, nicht weniger fur die Energiewende zahlen. Es sei vor diesem Hintergrund nicht verwunderlich, dass eine breite Mehrheit der Bevolkerung die EEG-Ausnahmeregeln fur die stromkostenintensive Industrie ablehne. Hartmut Kahl, Stiftung Umweltenergierecht, pruft, ob das Modell der Schweiz, die eine CO2-Abgabe auf fossile Brennstoffe erhebt und deren Aufkommen zu zwei Dritteln an die Bevolkerung ruckerstattet, als Vorbild fur Deutschland dienen konnte. Im Ganzen zeige sich, dass die Pro-Kopf-Ruckerstattung einer CO2-Bepreisung in Deutschland rechtlich umsetzbar sei. Ob diese Verwendung der eingenommenen Mittel sinnvoll sei oder die Gelder an anderer Stelle eine ungleich starkere Hebelwirkung in Sachen Klimaschutz entfalten konnten, sei aber eine andere Frage. Karen Pittel, ifo Institut, diskutiert die Frage der Verteilung der Lasten aus der Klimapolitik auf verschiedene Generationen. Eine Politik, die zu kurzfristig ausgelegt sei, konne die Kosten der Erreichung langfristiger Klimaziele erheblich erhohen. Die Formulierung von jahresgenauen Zielen fur die Emissionsminderung leiste einer solch inkrementellen Denkweise weiteren Vorschub und konne sich negativ auf die Erwartungen und Innovationstatigkeit von Unternehmen auswirken.

[Summary and conclusions] A stronger integration across energy sectors can contribute to achieving climate targets, provided that fossil fuels are substituted by renewable energy sources. One analysis for the German energy market estimates the potential GHG-emission savings due to sector coupling to 50 Mio t of CO2 emissions by 2030 (see Wietschel et al. 2017). A high potential to reduce GHG-emissions in the short and medium term is provided by direct electrification options: e-mobility, heat pumps and electric blast furnace. In the longer term, trolley trucks may also contribute to GHG-emission reductions, but the technology is not yet mature and it will depend on the achievable technology and cost development. There are also options in the industry sector, including methanol, ammonium or refineries, but these options are still far from being economically efficient. Producing electricity mainly based on RES is crucial for exploiting the GHGemission reduction potential of sector coupling technologies. However, we believe that a timely market entry of sector coupling technologies is required in order to exploit potentials on a longer term. The current electricity mix still shows considerable shares of fossil fuels, but a further increase of the RES-E share is a precondition for exploiting the GHG-emission reduction potential of sector coupling technologies. Wietschel et al. (2017) suggest using options with high efficiencies and a high GHG-emission reduction potential in the early phase of the transformation mainly for reasons of public and social acceptance. Sector coupling technologies may also contribute to increasing energy efficiency (e.g. e-mobility, electric steel) and thus reduce GHG-emissions due to efficiency improvements. For example, heat pumps make use of the ambient heat and can therefore improve efficiencies. Wietschel et al. (2017) have estimated for Germany that final energy consumption can be reduced by 180 TWh due to the efficiency effect by 2030, whilst electricity demand of new applications would increase by 50 TWh. Finally, sector-coupling technologies can increase the flexibility of the power system, which can be particularly relevant for systems with high shares of variable RES-E. However, the flexibility potential of different options and technologies strongly differs. According to Wietschel et al. (2017) there are high potentials for e-mobility and electrode boilers in heating networks.

The discussion on whether and bow to continue support for almost mature renewable electricity (RES-E) technologies, such as onshore wind and PV, has recently intensified. In this paper we analyze arguments in the literature in favor and against the phase-out of renewables support in the context of increasingly competitive RES-E tecbnologies. We conclude that there are good reasons to continue dedicated RES-E policies beyond 2020 for those technologies. Dedicated RES-E support can provide a predictable, secure investment framework that lowers the risk premiums required by investors and therefore reduces the capital costs of RES-E. In addition, there are still significant cost reduction potentials for these technologies. The increased use of renewables has multiple socio-economic benefits in addition to climate change mitigation. These arguments are still valid when looking at the current market situation characterized by oversupply and low prices on both the CO2 market and some power markets in Europe. Since renewables are not the main reason for the current oversupply, it would not be effective to take actions towards restoring market equilibrium in the form of radical or overall phase-out of RES-E support.

Increasing the share of renewable energy sources in the electricity sector (RES-E) contributes to achieving the European energy and climate targets including a 27% share of renewables in final energy consumption by 2030. We assess the future costs of the power sector for different RES-target levels and support schemes including generation costs, system operation costs and transmission grid development costs based on three power sector models. The results show similar power system costs for different target levels. RES-E shares below 70% involve limited infrastructure costs that are below 2.6% of the overall system costs. The impacts of the modelled RES-E policies, an EU quota and national feed-in premiums on transmission costs are ambiguous: Contrary to expectations, the costs of transmission network development under quota obligations are lower than under technology-specific feed-in premiums for RES-E penetration levels up to 50%. The drivers of transmission costs include not only a concentration of renewable capacity, but also the exact location of RES-E capacity with respect to existing power plants and the strength of the existing infrastructure. Quota obligations lead to higher grid costs than feed-in premiums if the RES-E share amounts to 70% due to the stronger regional concentration of RES power plants.

This paper assesses challenges arising for renewable energy technologies that have achieved a certain maturity level in terms of technology development, costs and market penetration. We identify these challenges, which diverge from challenges for less mature technologies and, based on three case studies, we analyse how some of the challenges have materialised and have been dealt with in practice. Case studies include experiences with the occurrence of negative prices in Germany, the question of how to deal with a market situation characterised by overcapacity in Spain and the problem of social opposition towards the construction of renewable power plants in the UK. Finally, we suggest solutions to deal with these issues in order to ensure the 2030 target is achieved, taking into account the changing framework conditions.

This paper describes a concept for the detailed assessment of the costs and benefits of renewable energy technologies deployment. A first quantitative impact assessment of German renewable energy technologies use is conducted from a historical perspective based on this comprehensive method. It includes costs and benefits at three different levels – energy system, micro- and macro-economic. The findings suggest that, at the system level, the generation costs in the electricity and heat sector are partly compensated by positive effects mainly from avoided emissions due to the use of renewable energy technologies in the electricity and heat sector. On the electricity market, small power consumers bear a very large share of the policy costs, while others might even profit from renewable energy technologies use. However, a comprehensive assessment that accounts for all the different negative and positive effects in the long term, including distributional effects, is more challenging. The concept applied here allows a differentiated comparison of a wide range of effects including aggregated costs and benefits as well as how these are distributed across different economic actors.