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The use of pit thermal energy storages (PTES) enables higher solar fraction in district heating networks by counteracting the mismatch between heat demand and production in solar district heating (SDH) installations. Capital costs linked to land areas with site-specific geological conditions are the deciding factors for PTES constructions. This study investigates non-technical and technical factors for the implementation of PTES in Swedish district heating networks. Having several SDH and PTES installations in operation the country of Denmark is used as a reference. This study, based on literature review, discusses the drivers and challenges for the use of PTES in district heating networks.

Recent advancements in occupancy and indoor environmental monitoring have encouraged the development of innovative solutions. This paper presents a novel approach to room occupancy detection using Wi-Fi probe requests and machine learning techniques. We propose a methodology that splits occupancy detection into two distinct subtasks: personnel presence detection, where the model predicts whether someone is present in the room, and occupancy level detection, which estimates the number of occupants on a six-level scale (ranging from 1 person to up to 25 people) based on probe requests. To achieve this, we evaluated three types of neural networks: CNN (Convolutional Neural Network), LSTM (Long Short-Term Memory), and GRU (Gated Recurrent Unit). Our experimental results show that the GRU model exhibits superior performance in both tasks. For personnel presence detection, the GRU model achieves an accuracy of 91.8%, outperforming the CNN and LSTM models with accuracies of 88.7% and 63.8%, respectively. This demonstrates the effectiveness of GRU in discerning room occupancy. Furthermore, for occupancy level detection, the GRU model achieves an accuracy of 75.1%, surpassing the CNN and LSTM models with accuracies of 47.1% and 52.8%, respectively. This research contributes to the field of occupancy detection by providing a cost-effective solution that utilizes existing Wi-Fi infrastructure and demonstrates the potential of machine learning techniques in accurately classifying room occupancy.

This study investigates primary energy use and CO₂ emission reduction potential resulting from the integration of solar thermal heating in biomass-based district heating systems in high-latitude regions. A newly commissioned solar thermal system based on parabolic trough collectors for an existing district heating network in Häarnösand, Sweden, is used as a case study, and its hourly one-year measured data are used as inputs for the analysis. The changes in operation and fuel use for local district heat production are extended to a regional context, considering the short- and long-term perspectives of the energy system. The results show that during the studied period, the solar water heating system provided 335 MWh of heat to the existing district heating system with a supply/return temperature of approximately 80/45 °C. Consequently, 339–382 MWh of biomass fuel consumption could be reducedannually with such an installation, depending on the district heat production technologies being substituted. An annual CO₂ reduction of 65.3–189 tons can be achieved in an overall energy system perspective when the saved biomass substitutes fossil fuels. The reduction of CO₂ emission depends on the fuels being substituted and energy conversion technology.

In 2018, EU launched the programme “Positive energy districts and neighbourhoods for sustainable urban development” with an aim to support the planning, deployment and replication of 100 Positive energy districts (PEDs) by 2025. This is an ambitious target considering the various challenges on implementing PEDs. This paper, based on literature review, provides an overview on the challenges and possibilities on the three main components of PEDs; energy production, energy efficiency and energy flexibility.

This study investigates the influence of a microencapsulated Phase Change Material (mPCM) on building systems in a subarctic climate which is not commonly studied for PCM applications. The mPCM is incorporated into gypsum to make a composite board with a volume fraction of 30 vt%. The fabricated composite board is then used to make a box model. This model along with a reference model built only with gypsum boards are placed inside a climate chamber where temperature is regulated to a summer day of a subarctic country, where large temperature variation exists between day and night. In addition, a Finite Element Method (FEM), is also used for the validation of the experimental data. The thermal-physical properties of the mPCM gypsum board including the specific heat capacity and thermal conductivity are measured. The microscopic features of the composite board are also studied. In addition, the temperature variation and the thermal energy storage of the boards of the two models have been studied. Results indicate that incorporation of mPCM into gypsum will change the thermal properties of the material. PCM can work as an additional insulation layer due to its low thermal conductivity. Further, the temperature fluctuation inside of the model with mPCM is reduced. In addition, the energy stored in the mPCM composite is around 3 times higher than that of gypsum board, making it promising for building energy improvement and load shifting.

Currently, companies in the solar heating sector may choose from a wide range of tools for modelling and simulating solar thermal power. However, due to the deviant design of some collectors, conventional simulation tools may be inadequate in correctly assessing the performance of such collectors. This study aims to test and validate an in-house simulation model for T160 PTC collectors developed by the company Absolicon Solar Collector AB by comparing measured data with simulated results. A solar district heating (SDH) plant in Härnösand, Sweden featuring 192 parabolic trough collectors (PTC) is used as a case study for the validation. Operational data such as weather data,solar heat production and collector loop/ambient temperatures were collected from the facilities of Absolicon. The data was compiled and simulated using a Python model developed for the T160 collectors. The study shows anacceptable correlation between simulated and measured data during periods with high DNI where a relatively highamount of heat is delivered to the district heating. Deviations are present during periods of low DNI and can bederived from inadequate assessments of heat losses from the piping of the installation in addition to inaccurate measurement data. 

Life cycle analysis (LCA) can be utilized to evaluate environmental impacts from the construction sector. In Sweden, from January 2022, climate declarations are mandatory when constructing new buildings. This report provides a literature review on various aspects related to LCA inbuilding, with focus on challenges and possibilities. Major challenges with LCA conductance are that buildings have long life-spans which introduce uncertainties in the LCA calculations since parameters may change over time. Choice of calculation tool, system boundaries for the LCA analysis and deviations between databases are further challenges that affect LCA results. Problems with data quality are another issue since usage of generic data may lower the accuracy of LCA studies on local level. Transparency of calculation tools, LCA methods, approximations and complexity of analysis are further challenges. Furthermore, when different LCA methods and calculation tools have been used, comparability between LCA studies can be compromised. To counteract the challenges voices have been raised to create national and even global databases to homogenize the data. Thorough and transparent communication of scope, method and system boundaries in LCA studies can counteract the problem with low transparency, deviating results and comparability issues. Using local data instead of generic data can increase data quality and therefore the quality and accuracy of the results.  

Positive energy district (PED) is a novel idea aimed to have an annual surplus of renewable energy and net zero greenhouse gas emissions within an area. However, it is still an ambiguous concept, which might be due to the complexity of city district projects with interconnected infrastructures and numerous stakeholders involved. This study discusses various aspects of PED implementation and presents practitioners’ experiences with the PED concept, challenges, and facilitators they have faced with real projects. The study is based on interviews with ten Swedish professionals. The major challenges reported for PED implementation were local energy production and energy flexibility, sub-optimization, legislation, suitable system boundaries, and involvement of stakeholders. Most of the interviewees mentioned improved collaboration, integrated innovative technology, political support, and climate change mitigation goals as important facilitators. The interviewees highlighted the importance of a local perspective and considered each city’s preconditions when developing a PED project. The study emphasizes that to facilitate PED implementation and replication in cities, more knowledge and clarity is required about PED such as on the definition and system boundaries.

The energy use of buildings is almost one-third of the global final energy use. Phase change Materials (PCMs) are substances that undergo phase transition when the surrounding temperature reaches their phase transition temperature. PCMs are reported to be a good candidate as a thermal storage buffer in building systems. Accordingly, PCMs may be able to regulate the indoor temperature while using less energy and thereby contributing in improving the energy performance of the building. In this project a trail to analyse the effect of PCMs in indoor temperature was carried out, in an experimental set-up, using a climate chamber. The chamber temperature is regulated as a sinusoidal profile with a cycle of 24 hours, with a maximum of 40 °C and a minimum of -10 °C. A cubic-box, is placed at the centre of the chamber, and is used as a representation of “building”. A board was made by encapsulating PCMs, with a melting temperature of 24 °C, to gypsum with a fraction of 20 wt%. The influence of PCM added gypsum board on inside temperature of the box is studied. Temperatures at different locations have been measured by thermocouples. The results indicated that the presence of PCM resulted in less temperature variation inside the box with the temperature holding close to the PCM transition temperature for a long period. Also, the PCM boards shifted the temperature profile. Further results are expected to determine the location of the PCM board that is most suitable to reduce the temperature variation inside the building.

Positive energy districts (PED) are neighborhoods with a net positive energy balance with the main goal to create sustainable districts that contribute to the energy transition. The three pillars energy efficiency, renewable energy, and energy flexibility forms the foundation of PEDs, and ‘Quality of life’ is one of the key principles.

Indoor swimming facilities for recreation and sports, also called aquatic centers or swimming halls, are important for healthy lifestyles. They are highly energy-demanding facilities due to the large volumes and strict heating- and ventilation requirements to ensure the health of staff, visitors, and bathers. The large energy consumption indicates good potential to reduce their energy use. One possibility might be to include aquatic centersin PEDs: the district could support the facility with locally produced renewable energy. There are also studies that investigates innovative solutions regarding aquatic centers that might have potential to increase resilience and flexibility in the district.

However, one important aspect in studies on energy use in aquatic centers that is often neglected is the presence of disinfection by-products (DBP), which are found in the air and water of chlorinated swimming pools. Several DBPs can lead to health issues, such as asthma, eye irritation, and even cancer. There are often conflicting goals in studies on swimming halls. The connection between DBP and energy is currently missing, and it could lead to projects compromising health over energy savings. Based on a literature review, this study highlights the research gap between DBPs and energy use in swimming facilities. A suggestion is also presented to integrate swimming halls into PEDs with the aim of increasing possibilities for a healthy lifestyle, supporting the aquatic center’s energy demand with renewable energy, and exploring new solutions for flexibility and resilience in the district