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Future renewable energy systems with high shares of variable renewable energy production must also include technologies and measures to balance these production fluctuations. This could be in the form of electricity storage, energy demand adaptation (also known as demand-side management), or sector coupling. Industry electrification couples electricity and industry sectors by replacing the fossil fuel demand with electricity demands, thus enabling further integration of renewable electricity and transitioning the hard-to-abate energy sector. The effects of electrification on 100% renewable energy systems are rarely investigated. When investigated, one 100% renewable energy system scenario is used, which is often created by the same author, actor or organisation and may result in a narrow view of the possibilities for future energy systems. This study quantifies the role of industry electrification in the context of different 100% renewable energy system scenarios created by different relevant actors, to identify how its role may differ based on the scenario investigated. It is found that direct electrification of industrial process heat demands should be favoured over, e.g., a fuel shift to hydrogen-based process systems, even when these provide more flexibility. • Future renewable energy systems must balance variable production fluctuations. • Industry electrification enables integration of renewable electricity. • Industry electrification is analysed in three renewable energy system scenarios. • Direct electrification should be favoured over hydrogen-based process systems. [ABSTRACT FROM AUTHOR]

District heating is a well-established system for providing energy efficient space and domestic hot water heating in dwellings in particularly in temperate and cold climate zones. Research has shown that going from the current 3rd generation district heating (3GDH) systems towards 4th generation district heating (4GDH) systems can facilitate a better integration between energy sectors, reduce grid losses and assist the integration of renewable energy sources. This article investigates the economic and energy effects of going from 3GDH to 4GDH for the specific case of Aalborg Municipality, Denmark based on overall hourly energy systems simulations. The analyses include effects from changes in excess heat potentials, changes in grid losses, and changes in efficiencies of conversion units in the district heating. Altogether, the analyses of the Aalborg case reveal that going from 3GDH to 4GDH decreases the primary energy consumption of the entire energy system by around 4.5% and the costs of the system by 2.7%. • District heating is well-established for providing energy efficient heating. • 4th generation district heating (4GDH) is expected to provide increased efficiency. • The effects of going to 4GDH is analysed for Aalborg Municipality, Denmark. • Going to 4GDH decreases the primary energy consumption and the energy system costs. • The benefits were especially due to increased utilisation of industrial excess heat. [ABSTRACT FROM AUTHOR]

As Europe moves towards renewable energy, hydropower stands out as a renewable technology that can provide supply side flexibility through dispatchable electricity production. Several studies have investigated the flexibility hydropower can provide with a particular focus on the Nordic hydropower resources. Of all European countries, Norway has the largest hydropower resources and storage capacity. However, Norway also has a highly electrified heating sector, which means high electricity demand during winter when reservoirs are low. This paper uses EnergyPLAN to analyse how a shift from individual electric heating to district heating affects the flexibility the Norwegian energy system can provide to Europe. The analysis develops a 2015 reference scenario and two scenarios that introduce district heating based on biomass and heat pumps, respectively. Results show that district heating can decrease the maximum load on dammed hydropower facilities, thus freeing up capacity for potential export. Furthermore, the dammed hydropower facilities are able to balance the electricity demands in all hours of the year. However, the shift to district heating also increases forced export to drain reservoirs as domestic electricity demand is reduced. Also, the amount of import the system is able to handle is decreased under the modelled conditions. • A shift from electric heating to district heating frees up generation capacity. • A decrease in electricity demand leads to excess electricity production. • The amount of import the energy system can handle decreases with district heating. [ABSTRACT FROM AUTHOR]

Abstract The transition to a 100% renewable energy system based on variable renewable energy raises technical but also institutional questions. The smart energy system concept integrates variable renewable energy by addressing the technical challenges through the integration of different energy sectors, but integration of variable renewable energy also entails a change in the cost structures, especially related to electricity. The effect of this change in cost structures on market prices is investigated. This is done through simulation of a 100% renewable energy system that utilises a large degree of cross-sector integration but maintaining the current electricity market structure. The paper uses a 100% renewable energy system scenario for a 2050 Danish energy system. This is reflected in the use of wind energy as the primary renewable energy source. It is concluded that the current electricity market structure is not able to financially sustain the amounts of wind power necessary for the transition to a 100% renewable energy system. Since earlier research shows that neither electricity production costs nor the total system costs is higher for the renewable path than the fossil-based alternatives, the conclusion in this paper points towards a need for reshaping the institutional structure of electricity trade. Highlights • Calculates electricity prices in a renewable energy system with current market design. • Calculates private profitability of wind power investments within such system. • The market design cannot financially sustain wind power in a renewable energy system. [ABSTRACT FROM AUTHOR]

This paper presents a strategy for achieving a fully decarbonized Danish energy system (including transport and industry) in 2045. The strategy could also be relevant for most countries at a global level. The energy system analysis includes hour-by-hour computer simulations leading to the design of a Smart Energy System with the ability to balance all sectors of the complete energy system. In the analysis, issues such as international shipping and aviation, the sustainable use of biomass, and the exchange of electricity and gas with neighbouring countries are all considered. Moreover, the energy system is coordinated with other sectors to achieve a fully decarbonized society. Finally, the size of the employment impact of investing in decarbonizing the Danish economy is discussed. • A strategy for a fully decarbonized Danish society in 2045. • The inclusion of international shipping and aviation in a country strategy. • A Smart Energy Systems approach modelled by EnergyPLAN. • Detailed calculations of different elements of the strategy in 2030 and 2045. [ABSTRACT FROM AUTHOR]

Decarbonising the heating sector is one of the key elements to realizing the ambitious dual carbon goals of China, which is the largest carbon emitter and energy consumer globally. Currently, district heating (DH) systems have penetrated approximately 88% of the urban heating areas in Northern China. Nevertheless, around 90% of the heating demand in China still relies on fossil fuels. A larger scale integration of renewable energy and waste heat sources into the DH systems is critical for decarbonising the entire heating sector in China. However, a deeper level of comprehension is required to harness its full potential. This paper provides a thorough investigation of the status, potential, and national policy schemes of renewable energy and waste heat recovery in the DH systems of China. Combined with a critical review of recent literature on relevant areas published in both international and Chinese domestic sources, the trends, challenges, and future perspectives are discussed from scientific research and practical implementation aspects. This paper highlights the synergy of the integration of renewable energy and waste heat sources in DH, the energy efficiency improvements as well as the use of thermal storage technologies through the implementation of 4th generation district heating and smart energy systems that could offer a more economically viable pathway forward. • Focus on renewable energy and waste heat (REWH) in the district heating (DH) systems in China. • A systematic review of REWH in Chinese DH systems from status, policy, and literature aspects. • Identification of research gaps based on the review of both international and Chinese journals. • Policy recommendations proposed to promote REWH in Chinese DH systems. • The introduction of international experiences on REWH in DH for analysis in the Chinese context. [ABSTRACT FROM AUTHOR]

• Focusing on the trade-off problem between industrial excess heat and heat pumps in DH system. • A novel hybrid framework for optimal DH strategy in 100% renewable smart energy systems. • The real energy system of Aalborg, Denmark is employed for technical–economic analysis. • Sector synergies between the DH network, power grid, and gas grid are revealed. • 40% IEH and 20% HP in DH bring Aalborg a balanced near carbon–neutral system with minimum cost. The literature emphasizes the important role of industrial excess heat (IEH) and heat pumps (HP) in future 4th generation district heating and smart energy systems. However, they can potentially have negative or positive effects on the integration of renewable energy sources (RES). It is necessary to find a trade-off between IEH and HP in the transition towards a 100% renewable energy system yet has not been discussed in the literature. This paper presents a comprehensive techno-economic analysis for the optimal district heating (DH) strategy in a 100% renewable energy system. It is conducted based on a novel hybrid methodology framework that couples hourly smart energy system simulation, multi-objective optimization, and multiple-criteria decision making. The optimal share between IEH and HP and associated RES capacity can be determined considering the preferences of policymakers. A scenario for 2050 for Aalborg Municipality in Denmark is used as a case study. Results show that an appropriate mix of IEH and HP, 40% and 20% respectively in the DH supply, should be employed to obtain a balanced near carbon–neutral system with the least cost. Also, the cross-sector effective interactivities between the DH network, power grid, and gas grid are revealed in the smart energy system context. The proposed framework is designed in a general way that can be used in other cities, regions, or countries. [ABSTRACT FROM AUTHOR]

Abstract This review article presents a description of contemporary developments and findings related to the different elements needed in future 4th generation district heating systems (4GDH). Unlike the first three generations of district heating, the development of 4GDH involves meeting the challenge of more energy efficient buildings as well as the integration of district heating into a future smart energy system based on renewable energy sources. Following a review of recent 4GDH research, the article quantifies the costs and benefits of 4GDH in future sustainable energy systems. Costs involve an upgrade of heating systems and of the operation of the distribution grids, while benefits are lower grid losses, a better utilization of low-temperature heat sources and improved efficiency in the production compared to previous district heating systems. It is quantified how benefits exceed costs by a safe margin with the benefits of systems integration being the most important. Highlights • Provides a review of 4th Generation District Heating (4GDH) in scientific papers. • Shows how 4GDH is an important integrated part of future sustainable energy systems. • Quantifies costs and benefits of 4GDH in a future sustainable energy system. • Shows how benefits exceed costs by a safe margin. • Shows the significant benefits of systems integration. [ABSTRACT FROM AUTHOR]