When several production units provide a district heating network, water is pumped from different directions. When the flows from the plants finally meet in the network, the water can be completely still. These places are called zero flow zones. In district heating networks with several plants, which also have different supply temperatures, large and frequent temperature fluctuations can occur when the zero flow zones move. This may cause wear on the pipes, a phenomenon called low cycle fatigue. For this reason it is important to examine where and when zero flow zones that cause temperature changes occur. The purpose of this thesis was therefore to investigate how temperature changes caused by zero flow zones influence Fortum’s district heating network. Simulations in the software TERMIS and literature reviews regarding temperature variations in district heating pipes were used. The results showed that low cycle fatigue in district heating pipes is rare. The design criteria that the European standard, EN13941, contain are well proportioned. However, pipe manufacturers agree to that temperature changes should not occur too quickly to minimize potentially harmful bending moments. Most of the surveyed manufacturers recommend that temperature changes should not be faster than 10°C/h. The simulations showed that temperature variations occurred exclusively in an area where the flows from two different production units with a significant difference in supply temperature met. The conclusion is thus that no specific actions need to be implemented to prevent the temperature variations. This is because they are not considered as a major issue.

Fortum has in a pilot project installed metering equipment with wireless communication in secondary substations in Stockholm. So far, the collected data are used only in specific projects. This master thesis was carried out at Fortum Distribution AB in Stockholm during 2013. The purpose of this study is to simplify and enhance the use of data in for example network planning process, by giving suggestions on how data can be managed and giving examples of analyzes that collected data can be used for. The electricity meter which Fortum has installed is a EDMI-Mk10A which is set to measure max/average/min values with a one hour time resolution of the following parameters: voltage (per phase), current (per phase) andactive power and active and reactive energy. In order to analyze the collected data an analysis tool is required. During this thesis two customized tools in Microsoft Excel have been developed, one for sorting data and one for analyzing. One aim of the thesis is to show examples of what collected measurement data can be used for. This work shows an example of analysis of active power, power factor, voltage, occurrence of interrupts and the relationship between outdoor temperature and power. This master thesis has among others resulted in the following advice: Expand the number of secondary substations with measuring equipment. Higher time resolution. Measure apparent power and temperature.

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With development within district heating leading to more incorporation of decentralized production, lowered temperature levels are required to enable these possibilities. Therefore, this study was conducted in collaboration with Fortum with the purpose of investigating and quantifying the effects of lowered delivery temperatures on mass flow and return temperatures. When these effects had been determined, the limiting factors were identified as well as the adjustments needed to enable the lowering delivery temperatures. This study is divided into two sections: a modeling of four type buildings and two case studies of specific areas of the Stockholm district-heating grid. The two sections of the study both use an Excel constructed model to examine the effects of the new proposed delivery temperature levels. The first section uses four type buildings with varying internal temperature levels to display how different secondary systems react to the changes in delivery temperature. The second section contains two case studies of outer parts of the grid where actual buildings are modeled. In the case studies the pipes speeds and secondary systems are analyzed to determine limiting factors for the lowering of the delivery temperatures. Overall this study contributes with quantified results of the effects of four lowered delivery temperature profiles on different customer systems. Analysis of the delivery temperatures showed that the largest change was shifting from the actual delivery temperatures of 2011 to the delivery profile that Fortum currently promised to deliver. The pipes of the studied areas were found not to be a limiting factor even in cases where the when mass flows increased three fold. The greatest limiting factor was determined to be the internal temperatures of the buildings, which set a strict limit and cannot be altered by Fortum without the customers’ cooperation. In conclusion a range of limiting factors were identified that proved to be potential limitations depending on the circumstances of a specific case. Depending on the investment needs in a specific case the economic viability was deemed to most likely be positive. When implementing lowered delivery temperatures in reality it is vital to acquiring data on secondary systems in order to identify the specific limitations of the proposed area. In addition an area of more research on the effects of lowered temperatures on the entirety of the grid as this study only investigates isolated sections.

To ensure that production is equivalent to consumption, hydro power units are used becauseof their high reliability as a regulation power source.Regulation is used due to the unbalance in the power grid between the production and con-sumption, for which reserved hydro power units for Primary and Secondary regulation areused. Primary regulation is done to balance the frequency in the grid by automatically ad-justing the water flow that runs through such units.Secondary regulation units are used for compensation of lost power production or for takingaway the surplus of power production and has become more intermittent today, which re-sults in more starts and stops of units. The increased intermittency of the units causes strainson the various components especially the generators. Therefore it is of great interest to knowthe total start-stop cost of the secondary regulated units. The theoretically calculated costsmay not coincide with the actual costs, as there are many parameters and complex calcula-tions that are included in the start-stop costs.A revised version of a calculation model was done for the secondary regulated units, basedon an earlier work, and showed higher start-stop costs compared to the earlier study, mostlybecause of these parameters:• Start and stop frequency for each unit has increased because of a higher flexibility in theelectrical market prices.• Age of the generators and turbines. Many of these components are near their time forrehabilitation which results in a higher maintenance cost.• The average failure frequency for each hydropower unit was thoroughly investigated andshowed to be higher than earlier estimated. A more individually calculated failure fre-quency for each unit showed to be higher than the earlier used standard average values.One important result is that the units with the lowest start and stop costs are preferred to beused, with the exception that the units with high start and stop cost, because of considerableleakage cost, should be used as much as possible. / För att säkerställa att elproduktionen är likvärdig med konsumtionen, används vattenkraf-ten för reglering eftersom den är lätt att reglera; såväl i det omedelbara tidsperspektivet (s)som i det lite längre (minuter/timmar/dagar). Reglering i kraftnätet krävs på grund av attobalans i elnätet mellan produktion och konsumtion hela tiden uppstår. Aggregat reserverade för primär- och sekundärreglering används för detta syfte. Primärreglering sköts auto-matiskt efter hur nätfrekvensen varierar genom att snabbt justera vattenflödet som går ge-nom ett aggregat. Sekundärreglerade aggregat används för kompensering av förlorad elleröverskott av effekt och används mer intermittent, vilket innebär många start och stop avdessa aggregat. Den mer intermittenta användningen av enheterna har blivit vanligare desenaste decennierna och orsakar påfrestningar på de olika komponenterna i aggregatet, särskilt generatorn. Det är därför av stort intresse att veta den tillkommande kostnaden somuppstår p.g.a. start-stopp av sekundärreglerade enheter. De teoretiskt beräknade kostna-derna sammanfaller ibland inte med de faktiska kostnaderna, eftersom det finns många pa-rametrar och komplicerade beräkningar som ingår i start-stopp-kostnaderna.I denna studie har det tagits fram en reviderad beräkningsmodell för de sekundärregleradeaggregaten. Resultatet visar på högre start-stopp-kostnader jämfört med en tidigare studie,främst på grund av dessa parametrar• Start- och stoppfrekvensen för varje enhet har ökat på grund av den ökade flexibilitetenpå elpriserna i elmarknaden.• Åldern på generatorer och turbiner. Många av dessa komponenter är nära deras tid förrehabilitering vilket resulterar i en högre underhållskostnad.• Den genomsnittliga felfrekvensen för varje vattenkraftaggregat undersöktes grundligtoch visade sig vara högre än tidigare bedömt. En mer individuellt beräknad felfrekvensför varje aggregat visade sig vara högre än det tidigare använda genomsnittliga värdetför alla aggregat. Ett viktigt resultat är att detta examensarbete visar tydligt på att aggregaten med Ett viktigt resultat är att detta examensarbete visar tydligt på att aggregaten med lägst start-och stoppkostnader bör väljas för drift i första hand. Undantag från detta är de aggregat medhöga start- och stoppkostnader som en följd av betydliga läckagekostnader, som bör köras så mycket det går.

The combination of Biomass Energy with Carbon Capture and Storage (BECCS) can reduce the level of CO2 in the atmosphere. It is, therefore, seen as an interesting tool in the CO2 abatement portfolio. In a Swedish context, BECCS could contribute to the goal of CO2 neutrality by 2045. This thesis aims to investigate the application of BECCS in the district heating system of Stockholm region with a case study at the energy utility Fortum Värme. The focus of the study is the technical and economic feasibility of such an application. The applicability of Fortum Värme´s plants to implement carbon capture is investigated together with costs and technical implications on each applicable plant and the district heating system as a whole. Three plants are deemed feasible for carbon capture with a cost of about 45€/tonne of captured CO2 (not including transport or storage). A model for transport of CO2 to promising storage sites in Sweden, Norway, and Denmark is constructed for transport by pipeline and ship. Ship transport is estimated to be the most cost-efficient option in all scenarios. The total cost for BECCS is calculated at 70-100€/tonne depending on size of emissions and distance to storage locations. Furthermore, the total cost is calculated to decrease by 10-25% if some current promising technologies for carbon capture reach maturity, a market for transport services of CO2 evolves, and a number of actors are sharing the costs for storage.Calculated costs are on a similar price level as other CO2 abatement strategies such as CCS in industries, biogas, and biodiesel in the vehicle fleet. If the cost is applied directly to the heat price, without any subsidies, it would increase the price of heat by 14-21%.The major challenge of BECCS in combined heat and power production, compared to other studies based on power production, is the seasonality of heat demand. The capacity of the carbon capture system will be oversized during the summer, or undersized during the winter. This is an optimization challenge which has to be further studied.