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In 100% renewable energy systems, the requirements for flexibility will be greater than for traditional carbon-based energy systems. New technologies and system setups are needed to provide flexibility for balancing the system. Implementing electricity storages in the energy system could provide parts of the required flexible demand and production, though most of these storage solutions have been shown to have relatively high costs. So-called Carnot batteries have been shown to have a relatively lower cost than traditional batteries, but at a reduced electric efficiency. This paper investigates to what extent large-scale integration of Carnot batteries has a role in the transition to and the operation of 100% renewable energy systems. By implementing Carnot batteries in a 100% renewable energy scenario for Denmark, the energy system effects are identified. The results indicate that the potential economic benefit could be as high as 60.5–66.2 EUR/MWh e discharged, not including costs related to investment as well as operation and maintenance of the Carnot batteries. Thus, large-scale integration of Carnot batteries must perform below this economic threshold to be economic relevant. Existing concepts for stand-alone Carnot batteries are not able to achieve these costs today, therefore solutions for cost reductions should be investigated. • Electricity storages could provide parts of future required system flexibility. • Most of these storage solutions have been shown to have relatively high costs. • Carnot batteries have a relatively lower costs but at reduced electric efficiency. • Large-scale integration of Carnot batteries is tested in a renewable energy system. • Carnot battery concepts should aim for a cost lower than 60.5–66.2 EUR/MWh e. [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]

Abstract: In most countries markets for electricity are divided into wholesale markets on which electricity is traded before the operation hour, and real-time balancing markets to handle the deviations from the wholesale trading. So far, wind power has been sold only on the wholesale market and has been known to increase the need for balancing. This article analyses whether wind turbines in the future should participate in the balancing markets and thereby play a proactive role. The analysis is based on a real-life test of proactive participation of a wind farm in West Denmark. It is found that the wind farm is able to play a proactive role regarding downward regulation and thereby increase profits. [Copyright &y& Elsevier]

Abstract: The long-term goal for Danish energy policy is to be free of fossil fuels through the increasing use of renewable energy sources (RES) including fluctuating renewable electricity (FRE). The Danish electricity market is part of the Nordic power exchange, which uses a Marginal Price auction system (MPS) for the day-ahead auctions. The market price is thus equal to the bidding price of the most expensive auction winning unit. In the MPS, the FRE bid at prices of or close to zero resulting in reduced market prices during hours of FRE production. In turn, this reduces the FRE sources’ income from market sales. As more FRE is implemented, this effect will only become greater, thereby reducing the income for FRE producers. Other auction settings could potentially help to reduce this problem. One candidate is the pay-as-bid auction setting (PAB), where winning units are paid their own bidding price. This article investigates the two auction settings, to find whether a change of auction setting would provide a more suitable frame for large shares of FRE. This has been done with two energy system scenarios with different shares of FRE. From the analysis, it is found that MPS is generally better for the FRE sources. The result is, however, very sensitive to the base assumptions used for the calculations. [Copyright &y& Elsevier]

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]

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]

The transition towards carbon-neutral energy systems requires the identification of solutions that are optimal at a societal level, however, market actors operate under a different logic where each individual investment option is required to show business-economic feasibility. Thus, while there are energy system analysis modelling tools that can help identify optimal transition paths for a given society in general through the minimisation of national or regional energy system costs, there is also a need for modelling tools that take a closer focus on how energy system actors and their investment considerations perceive and are affected by the economic and technical environment. The modelling tool energyPRO is of the latter type developed and evolved over the last decades to assist in the assessment of the feasibility of different energy units in the energy systems, but which can also model larger complex systems. This article presents energyPRO with a focus on its system understanding and general model characteristics and a thorough view into its two optimisation approaches based on analytical programming or mixed integer linear programming. Finally, a comparison with other models as well as a review of its characterisation and application in the academic literature is supplied. • Introducing the energyPRO model for business economic analyses of energy investments. • Full model description of energyPRO. • Systematic review of energyPRO in the journal literature. • EnergyPRO has been instrumental in the development of district heating in Denmark. • EnergyPRO has helped assess technology options and economic conditions worldwide. [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]