Due to desirable emission reductions and population growth, increasing energy demand is identified as a dire issue for energy systems. The introduction of low-energy building districts enables increased energy system efficiency. This study’s aim is twofold. Firstly, an extensive urban building energy model is used to simulate the hourly use and geographic distribution of the heat demand for residential and commercial buildings that are to be supplied by a low-temperature district heating system. The simulated buildings are a part of a planned city district, located in Gävle, Sweden. Two building energy performance cases are studied; one where all buildings are assumed to be of Passive House standard, and one where the building energy performance is in line with conventional new-building regulations in Sweden. Secondly, one specific building is modeled in detail and simulated in the building energy simulation software IDA ICE to investigate what building heating system is best suited for low-temperature heat supply. The temperature demands of floor heating and ventilation with heat recovery are investigated and compared to conventional water-based radiators. The building’s temperature demand results can be used when designing a lowtempered district heating system which will provide the supply temperature to identify a compatible heating system technique. Varying supply temperature demand will enable optimization for choosing building heating systems and consequently, possible cost reductions. The results could be used as an example for future city district planning as well as presenting relevant heating systems for low-temperature district heating.

In this study, the performance of different cooling technologies from energy and economicperspectives were evaluated for six different prototype residential Nearly Zero Energy Buildings(NZEBs) within a planned future city district in central Sweden. This was carried out by assessingthe primary energy number and life cycle cost analysis (LCCA) for each building model and coolingtechnology. Projected future climate file representing the 2050s (mid-term future) was employed.Three cooling technologies (district cooling, compression chillers coupled/uncoupled with photovoltaic (PV) systems, and absorption chillers) were evaluated. Based on the results obtained fromprimary energy number and LCCA, compression chillers with PV systems appeared to be favorableas this technology depicted the least value for primary energy use and LCCA. Compared to compression chillers alone, the primary energy number and the life cycle cost were reduced by 13%, onaverage. Moreover, the district cooling system was found to be an agreeable choice for buildingswith large floor areas from an economic perspective. Apart from these, absorption chillers, utilizingenvironmentally sustainable district heating, displayed the highest primary energy use and life cycle cost which made them the least favorable choice. However, the reoccurring operational cost fromthe LCCA was about 60 and 50% of the total life cycle cost for district cooling and absorption chillers,respectively, while this value corresponds to 80% for the compression chillers, showing the high netpresent value for this technology but sensitive to future electricity prices.

In Europe, the prices of natural gas and electricity reached an all-time high in 2022. A way to mitigate high electricity costs is to expand district heating systems in urban areas, this will reduce electric load as well as increase the power generation possibilities in combined heat and power plants. District heating has been the dominant heat supply technology in urban areas in Sweden since the 1980s. However, as the energy efficiency in buildings increase, district heating distribution losses must be reduced to ensure a cost-efficient heat supply. This has led to the idea of the 4th generation district heating which is characterized by low distribution temperatures. In this study, low-temperature district heating distribution in a planned future city district is simulated using a Python-based tool. Two different low-temperature distribution systems are investigated: 1) 2-pipe low-temperature system, and 2) a cascading 3-pipe low-temperature system. The focus is on simulating the distribution losses, temperature drop, and mass flow in the pipe network. The scope of the analysis also includes an investigation of the effect of lower return temperatures on the central district heating network. The results indicate that the low-temperature distribution system with the 2-pipe system performs better than the cascading system when considering distribution losses and temperature drop. The mass flow depends on the temperature demand in the heating systems in the buildings and is considerably high for both low-temperature distribution systems investigated.

The use of strategic visions based on concepts like climate-neutrality, net-zero emissions and energy efficiency is important to align action and build momentum. The agency of transition actors requires clear definitions and explanations of visions, enabling operationalization for action, monitoring and measuring of results. This paper develops a maturity scale for climate-related strategic visions among local governments. Further, the maturity of Swedish municipalities’ climate-related strategic visions is reviewed. The results show that out of Sweden’s 290 municipalities, 256 shows overall low maturity in their strategic visions, not supporting their local, regional and national system actors sufficiently. Furthermore, results from workshops indicate that the roles, mandate and process for working with municipal strategic visions are not clear. There is an ambiguity around visions that is hindering aligned action and progress.

The traditional energy system as we know it today will change in the future. There is a worldwide concern about the global warming situation and there are different actions implemented to limit the consequences from, mainly, the use of fossil fuels.

In this thesis, multi-unit apartment buildings have been simulated according to how the global CO2 emissions change when different energy efficiency measures are implemented. The simulated buildings have also been used to investigate how the calculated energy efficiency of a building according to Swedish building regulations varies depending on which technology for heating is used in the building and if the building has a solar PV installation or solar thermal system. When the energy efficiency of a building is calculated accord-ing to Swedish building regulations, this thesis shows that heat pumps are a favored technology compared to district heating. Another result is that electric-ity use/production within the investigated district heating system is the most important factor to consider when minimizing global CO2 emissions.

This thesis also investigates how the configuration of electric meters owned by the distribution system operator affects the monitored amount of self-consumed and produced excess electricity. Finally, four local low-voltage distri-bution networks were simulated when a future charging scenario of electric vehicles was implemented.

If a single-family house installs a solar PV installation, this thesis reveals that the configuration of the electric meter is important for the monitored amount of self-consumed electricity. This thesis also shows that the investigated low-voltage distribution networks can handle future power demand from electric vehicles and a high share of solar PV installations, but rural low-volt-age distribution networks will need to be reinforced or rebuilt to manage the investigated future scenarios.

Sammanfattning Det traditionella energisystem som vi är vana vid idag kommer att förändras i framtiden. Oron för växthuseffekten och dess konsekvenser medför att olika åtgärder genomförs, framförallt för att minska koldioxidutsläppen från fossila bränslen.

I denna avhandling har flerfamiljshus simulerats med avseende på energi-användningen när olika energieffektiviseringsåtgärder implementeras. Resultatet av förändringarna i globala koldioxidutsläpp har sedan beräknats för de olika energieffektiviseringsåtgärderna. De simulerade resultaten har även använts för att analysera hur en byggnads energieffektivitet enligt Boverkets byggregler varierar med olika uppvärmningssätt och om byggnaden har en solvärme- eller solcellsanläggning installerad.

Denna avhandling visar att värmepumpar favoriseras jämfört med användning av fjärrvärme när en fastighets energieffektivitet beräknas enligt Boverkets byggregler. Samtidigt visas att den viktigaste åtgärden för att minska de globala koldioxidutsläppen är att minska elanvändningen eller att öka elproduktionen lokalt inom det studerade fjärrvärmeområdet.

Avhandlingen undersöker också hur konfigureringen av kundens elmätare i elnätet påverkar den uppmätta andelen egenanvänd och överproducerad el. Slutligen har fyra lokala lågvoltsnät simulerats då ett framtida scenario för laddning av elfordon adderats till fastigheternas nuvarande elanvändning.

Resultaten visar att om en villafastighet installerar en solcellsanläggning så påverkar konfigureringen av kundens elmätare den uppmätta andelen egenanvänd och överproducerad el och skillnaden kan vara relativt stor. Avhandlingen visar också att delar av lågvoltselnätet klarar en stor andel elfordon och en hög andel solcellsanläggningar men att landsbygdsnätet behöver förstärkas för att klara den ökade lasten i de antagna scenarierna.

When there are differences in economic value of self-consumed and exported electricity, profitable PV installations are dependent on accurate predictions of self-consumed electricity. In this study, minute-based data of PV production and electricity use were logged in a single-family house in Sweden. It is shown that when self-consumed electricity is measured, a low time resolution and different electric meter configurations can result in 60% lower registered self-consumed electricity than predicted. When feed-in tariffs or net metering schemes change to incentives dependent on the fraction of self-consumed electricity, the market and electric meter infrastructure must be prepared to avoid market disturbances.

This study evaluates how the principal function of bi-directional electric meters affects the monitored amount of self-consumed and produced excess electricity for dwelling buildings connected to the grid by three phases. The electric meters momentarily record the sum of the phases or the phases individually and then summarize the recorded values to a suitable time period and is then collected by the grid owner. In Sweden, both electric meter configurations fulfill laws and regulations.

The meter configuration affects the monitored distribution of self-consumed and produced excess electricity significantly for the investigated single-family house but is negligible for the investigated multi-dwelling buildings. The monitored self-consumed electricity produced by the PV installation for the single-family house varies between 24% and 55% depending on the configuration and how the inverter is installed for the investigated year. The difference in economic value for the produced electricity varies between 79.3 to 142 Euros.

Due to the electric meter configuration, the profitability of PV systems will be different for identical single-family houses with identical conditions. This should be corrected for a well-functioning market. It is also important to decide how the configuration should be designed to ensure that different incentives and enablers results in desired effects.

In the European Union's Energy Performance of Buildings Directive, the energy efficiency goal for buildings is set in terms of primary energy use. In the proposal from the National Board of Housing, Building, and Planning, for nearly zero energy buildings in Sweden, the use of primary energy is expressed as a primary energy number calculated with given primary energy factors. In this article, a multi-dwelling building is simulated and the difference in the primary energy number is investigated when the building uses heat from district heating systems or from heat pumps, alone or combined with solar thermal or solar photovoltaic systems. It is also investigated how the global CO₂ emissions are influenced by the different energy system combinations and with different fuels used. It is concluded that the calculated primary energy number is lower for heat pump systems, but the global CO₂ emissions are lowest when district heating uses mostly biofuels and is combined with solar PV systems. The difference is up to 140 tonnes/year. If the aim with the Swedish building code is to decrease the global CO₂ emissions then the ratio between the primary energy factors for electricity and heat should be larger than three and considerably higher than today.

Partial shading decreases the performance of PV modules due to the series connection between the solar cells. In the recent years, several new technologies have emerged within the photovoltaics field to mitigate the effect of shading in the performance of the PV modules. For an accurate assessment of the performance of these devices, it is required to evaluate them comparatively in different circumstances. Three systems with six series-connected PV modules (each containing 60 cells) have been installed at the University of Gavle. System One comprises a string inverter system with 6 PV modules; System Two features a DC-DC optimizer per panel and a string inverter; System Three incorporates three micro inverters for six modules. A major conclusion of this study was that under partial shading of one (or more) modules both System Two (DC-DC optimizers) and System Three (micro inverters) perform considerably better than System One (string inverter), as long as the Impp of the shadowed module is lower than the Impp of the unshaded string It is also important that the Vmpp in the shaded module is higher than the lowest allowed voltage of the DC-DC optimizer or module inverter. The economic implications of the usage of these devices were also analyzed.

When taking action to fulfill the directives from the European Union, energy conserving measures will be implemented in the building sector. If buildings are connected to district heating systems, a reduced heat demand will influence the electricity production if the reduced heat demand is covered by combined heat and power plants.

This study analyze five different energy conserving measures in a multi-dwelling building regarding how they affect the marginal production units in the district heating system in Gävle, Sweden. For CO₂ emission evaluations, two different combinations of heat and electricity conserving measures are compared to an installation of an exhaust air heat pump.

The different energy conserving measures affect the district heating system in different ways. The results show that installing an exhaust air heat pump affects the use/production of electricity in the district heating system most and electricity conserving measures result in reduced use of electricity in the building, reduced use of electricity for production of heat in the district heating system and an increase of electricity production.

The conclusion is that electricity use in the building is the most important factor to consider when energy conserving measures are introduced in buildings within the district heating system in Gävle.