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To better facilitate renewable energy systems, the district heating sector is currently changing towards lower temperatures and increased cross-sectoral integration. Seasonal thermal energy storage systems alongside heat pumps have received an increasing attention. However, the operation of a seasonal thermal energy storage system alongside a heat pump is more complex than a short-term thermal energy storage system, and as such, several complex simulation models have been developed. These models have shown to be usable for simulating the operation, but due to their complexity are difficult to implement in simulation models that focus on overall energy system analyses. Based on the operation of an existing seasonal thermal energy storage system, this paper provides a simulation method for a seasonal thermal energy storage system with a heat pump that can be utilized in overall energy system simulation models. The simulation method is based on the proven different operational situations of the seasonal thermal energy storage system. The method is shown to be able to approximate the actual operation on an hourly basis and the yearly thermal losses. [ABSTRACT FROM AUTHOR]

This paper identifies the energy system benefits of transitioning district heating infrastructure from current 3rd generation district heating (3GDH) to 4th generation district heating (4GDH) with lower grid temperatures and more integration with other energy sectors. Previous papers have investigated the effect of going from 3GDH to 4GDH on a local perspective. In this paper it is investigated how this transition affects the energy system on a national level, where both the costs and energy effects are evaluated based on national hourly energy systems simulations including all energy sectors in a climate neutral energy system scenario. Moreover, the paper identifies the effects of different cooling solutions in datacentres. The analyses include effects on heat sources as well as the effect on the cost and losses in the district heating grid. This is done for the case of Denmark. In the case of Denmark, it is found that transitioning from 3GDH to 4GDH decreases the system cost by 220 M EUR/year, corresponding to 7 M EUR/TWh delivered heat at the end-user. Increasing the temperature outlet of datacentre waste heat has a value for the system as high as 52–59 M EUR/year, corresponding to 1.7–1.9 M EUR/TWh delivered heating at the end-user. • Evaluates the national energy system effects of 4th generation district heating. • The paper also evaluates the effects of different cooling solutions in datacentres. • The evaluation is done using a carbon neutral scenario for Denmark. • Going to 4th generation district heating reduces the system cost by 220 M EUR/year. • Higher temperature of waste heat from datacentres reduces the energy system cost. [ABSTRACT FROM AUTHOR]

Intermittent renewable energy sources (RES) are increasingly used in many energy systems. The higher capacity of intermittent RES increases the importance of introducing flexible generation units into the electricity system balancing. Distributed district heating plants with combined heat and power (CHP) can provide this flexibility. However, in electricity systems with a high penetration of intermittent RES, CHP units are currently experiencing decreasing hours of operation, making it likely that existing CHP capacity will be phased out from the energy system. Furthermore, when the plants provide balancing for the electricity system, the complexity of their daily operation planning is increased. This article analyses and discusses how these units can improve their economic feasibility by providing balancing services to the electricity system, benefitting both each individual plant and the system as a whole. This is done by using the case of the Danish district heating plant, Ringkøbing District Heating, which has a relatively high capacity of solar heating installed and is located in an area with a high penetration of wind power. It is found that the plant can increase the economic feasibility of the CHP unit by participating in the electricity balancing tasks; however, it is uncertain whether the benefits are substantial enough to keep the distributed CHP capacity in operation. [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]

The decentralization of energy production and recovery of excess heat (EH) to reach climate targets is essential for renewable and fully decarbonized heating systems. This paper identifies current and potential industrial EH sources providing baseload capacity for district heating (DH) systems. These sources are evaluated by sector and process for supplying baseload capacities explored for current 3rd generation district heating (3GDH) and 4th generation district heating (4GDH) systems with lower grid temperatures and losses, with and without expansions. The method combines geographical analysis and available baseload capacity estimations for 360 Danish DH systems scenario-making and an additional sensitivity analysis evaluating baseload capacity full-load hours. It is found that 80 % of Danish DH systems have an unmet baseload capacity of 50 % or higher. Half of the systems have geothermal capacity available and up to 20 % of industrial EH baseload capacity potential, which sums up to 5 PJ of EH potential within a 2 km distance. The findings also suggest that there is an additional opportunity for the placement of future energy infrastructure able to supply EH, which is highly contextual and strategic in heat planning, particularly considering the future development of sustainable and energy-efficient DH systems. • Maps 360 Danish DH systems with expansion potentials for 3GDH and 4GDH. • Identifies 9235 sources and 19.8 PJ of exploitable industrial excess heat. • Spatially evaluates 3 PJ and 5 PJ of EH for supplying 3GDH and 4GDH baseload capacity. • Locates 5–10 GW of total available baseload capacity in Danish DH systems. • Provides placement opportunities for future excess heat sources. [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]

Research into new advanced district heating concepts has increased since the first four generations of district heating were defined in 2014. This definition created a common framework for research and industry alike, and pointed to potential futures for district heating which could benefit from low-temperature heating in buildings. The fully developed fourth-generation district heating includes the cross-sectoral integration into the smart energy system. This paper defines four generations of district cooling to make a similar useful framework for district cooling. The first generation being pipeline refrigeration systems that were first introduced in the late 19th century, the second generation being mainly based on large compression chillers and cold water as distribution fluid, the third generation having a more diversified cold supply such as natural cooling, and the fourth generation combining cooling with other energy sectors sometimes into a renewable energy-based smart energy systems context, including combined heating and cooling. • Definition of four generations of district cooling. • District cooling systems from first developments to contemporary state-of-the-art. • District cooling and energy system integration. [ABSTRACT FROM AUTHOR]