Sweden has an ambitious plan to fully decarbonise district heating by 2030 and to contribute with negative emissions of greenhouse gases in 2050. The vagaries of the energy market associated with climate, political, and social changes entail cross-sectoral integration that can fulfill these national targets. Fifth-generation district heating and cooling (5GDHC) is a relatively new concept of district energy systems that features a simultaneous supply of heating and cooling using power-to-heat technologies. This paper presents best practices for developing 5GDHC systems in Sweden to reach a consensus view on these systems among all stakeholders. A mixed-method combining best practice and roadmapping workshops has been used to disseminate mixed knowledge and experience from middle agents representing industry professionals and practitioners. Four successful implementations of 5GDHC systems are demonstrated and the important learned lessons are shared. The best practices are outlined for system planning, system modeling and simulation, prevailing business models for energy communities, and system monitoring. A roadmap from the middle agents’ point of view is composed and can be utilised to establish industry standards and common regulatory frameworks. © 2023 The Author(s)

To meet the new regulation for the deployment of alternative fuels infrastructure which sets targets for electric recharging and hydrogen refuelling infrastructure by 2025 or 2030, a large infrastructure comprising truck-suitable hydrogen refuelling stations will soon be required. However, further standardisation is required to support the uptake of hydrogen for heavy-duty transport for Europe’s green energy future. Hydrogen-powered vehicles require pure hydrogen as some contaminants can reduce the performance of the fuel cell even at very low levels. Even if previous projects have paved the way for the development of the European quality infrastructure for hydrogen conformity assessment, sampling systems and methods have yet to be developed for heavy-duty hydrogen refuelling stations (HD-HRS). This study reviews different aspects of the sampling of hydrogen at heavy-duty hydrogen refuelling stations for purity assessment, with a focus on the current and future specifications and operations at HD-HRS. This study describes the state-of-the art of sampling systems currently under development for use at HD-HRS and highlights a number of aspects which must be taken into consideration to ensure safe and accurate sampling: risk assessment for the whole sampling exercise, selection of cylinders, methods to prepare cylinders before the sampling, filling pressure, and venting of the sampling systems. 

Corrosion of aluminium anode in alkaline solution is a challenging matter for the development of a long-life aluminium anode in Al–air battery. This research focuses on grain size reduction by equal channel angular pressing (ECAP) of Al, Al–Zn, and Al–Zn–In samples. The average grain size of all samples after ECAP is lower than 1μm. Open circuit potential, potentiodynamic polarisation, electrochemical impedance spectroscopy, and self-corrosion test were carried out to study the effects of alloying elements (Zn, In) and grain size reduction by ECAP on the electrochemical behaviours of aluminium alloy anodes. The results show that alloying element, zinc, can improve the stability of ion dissolution by porous Al2ZnO4 film formation. Indium can activate ion dissolution that causes enhanced electrochemical activities for Al–Zn–In sample. Moreover, increasing grain boundaries through grain size reduction can enhance more negative potential and cause a uniformly corroded surface of Al–Zn–In sample, leading to a longer anode life in alkaline solution. © 2022 The Authors

Despite the apparent usefulness of prosumers in the DH grid, there has not been a systematic investigation into why Sweden has not seen a general uptake in prosumer integration in the district heating (DH) sector. The transition to 4th generation district heating (4GDH) and smart energy system concepts are conducive to prosumer integration. Nonetheless, the integration of heat prosumers has been slow in Sweden. Our current study investigates the drivers and barriers for prosumer integration in the Swedish DH sector and looks at if and how rules, regulations and policies may affect the enabling of prosumer integration. The research questions posed in this study are: what are the drivers and barriers for prosumer integration in the DH sector in Sweden, and, what are the rules, regulations and policies that can affect the enabling of prosumer integration in the DH sector in Sweden. A directed Content Analysis of systematically selected scientific and industry-related literature is analyzed to investigate the drivers and barriers for prosumer integration in the Swedish DH sector. The drivers for prosumer integration can be broadly categorized as DH-side drivers, prosumer side drivers and macro-trend drivers. In terms of the DH-side, costs savings, more flexibility, increasing the environmental and commercial profile of the company and increasing the effective use of energy are the main drivers. Similarly, for the prosumers, it is additional income, increased self-sufficiency and raising the environmental profile which are the main drivers. In the barriers side, not up-to-date policies and regulations about the energy use and required energy efficiency for buildings, and conflicting regulations about accounting of energy use disincentivize prosumer integration in the Swedish DH sector. There are barriers on both the DH-side and prosumers’ side hindering the integration of prosumers in the DH sector. These barriers are also enhanced by ambiguous policies, which hinder the prosumer integration in the Swedish DH sector.

Flexibility in the energy system has been studied previously but few results have been implemented in district energy (DE) pricing models. This means that pricing models are not accounting for existing information making them less efficient than they need to be. We have studied if and how business models of DE firms capture flexibility in the DE grid and suggest price model updates to harvest flexibility. A systematic literature search with content analysis of resulting scientific peer-reviewed publications and project reports has been performed. Thereby, the different business models which have been described in the literature have been categorized. Based on literature, efficient price models have been identified. Another source of information is six demonstrators aiming at generating knowledge about DE flexibility. They are part of the Flexi-sync Project (ERA-Net). Findings show that most DE grids are slow to recognize and capture flexibility that can be catalyzed through end-users, thermal inertia, heat pumps and other. Similarly, DE firms employ a marginal cost logic to determine whether flexibility should be operationalized, and often their business models and price models are not oriented towards expressing that value logic to their customers. We identify that there is a potential for DE companies to further capitalize on flexibility in the energy system. By inclusion of flexibility incentives in price models a win-win can be established by cutting operational costs for the DE provider and energy consumption of the end-user.

The apparent usefulness of prosumers in the district energy (DE) grid, with the transition to 4th generation district heating (4GDH) and smart energy system is beginning to be realized. Similarly, there is a burgeoning interest in the exploitation of flexibility in the DE grid. But, whether the business models for prosumers also capture the flexibility provided by the prosumers is doubtful. Our current study ponders on: what are the business models for prosumers in the heating sector? do they capture flexibility? And, if so, how do they capture flexibility? A directed Content Analysis of systematically selected scientific literature is analyzed to investigate the business models for prosumer integration in the DE sector, and how they capture flexibility. Fifteen scientific articles were chosen through a systematic selection process. The selected literature was analyzed under the following categories: research objectives or research questions, methodology used, key actors considered, key technologies, pricing logic of heat, control of the prosumer system, computation of benefits and flexibility consideration. The findings from the selected articles show that when looking at how prosumers can supply peak heat, most studies consider the marginal cost of heat supply as an important parameter in the price logic. Similarly, the benefits are computed in a system-wide manner as the difference between the marginal cost of heat either through production from DE system or through production from the prosumer. In calculating the marginal cost of heat investment costs are not considered, which is not conducive for positive decision-making by the potential prosumer looking to invest in heat pumps or excess-heat exploiting technologies. © 2021 The Authors

Thermal ageing at elevated temperatures is the standard method to determine the service life of pre-insulated district heating pipes nowadays. However, DH pipes are also subjected to axial movements which can affect the adhesion strength between the polyurethane foam and the service pipe. This contact surface is usually exposed to the highest temperatures. In this project, DH pipes were aged at elevated temperatures and at the same time cyclic axial loads were applied. Two DH pipes were only exposed to thermal ageing at 130 and 140 °C, while two other similar pipes were also exposed to cyclic axial loads. The adhesion strength was evaluated as the function of ageing time using the RISE plug method. Any changes in the chemical structure of the PUR samples were also observed using Fourier transform infrared spectroscopy. Comparing the results in this investigation, we found that the degradation of the mechanically loaded pipes was significantly faster than the degradation observed in non-loaded pipes at the same ageing temperatures. The FTIR study revealed that cyclic mechanical loads accelerated the chemical degradation of the PUR foam during thermal ageing. This study shows how important it is to consider all influencing factors in accelerated ageing. The methods presented here should be considered as an alternative to thermal ageing at high temperatures because the combination of mechanical and thermal loads reproduces better the real operating conditions. It is even of bigger interest when energy from different sources will be connected to the fourth generation of DH networks, which can cause more temperature fluctuations.

For local governments and municipalities, both urban and energy planning are required to make the transition to more energy efficient cities with lower carbon emissions. However, energy planning and urban planning are usually under the responsibility of different departments and have their own planning processes. When dealing with energy plans, this separation could lead to a less effective impact on cities in reaching climate goals since a lack of coordination may result in different strategies set out by the two plans. In consideration of the fact that space heating dominates the energy use in buildings, this study has a focus on urban heating systems in the building sector. We propose an integrative municipal heat planning methodology investigating which features of the urban planning process that could be integrated into a spatially explicit energy systems model and how. The proposed methodology is then applied to a specific case: the heating system in the municipality of Lyngby-Taarbæk, Denmark. The inclusion of stakeholders from both the heat and urban planning departments in the case study enabled us to reflect on their preferences and expectations for the future heating system. Finally, the applicability of the methodology and the application results are discussed and compared to other methods.