This work is an example of a CFD-assisted design and characterization process for thermal energy storage vessels. A general modeling technique for future works is also proposed. The Short-Term Thermal Storage (STTS) tanks at the Drake Landing Solar Community (DLSC) were used as the principal case study. The performance characterization of the STTS tanks and the evaluation of other tank designs were made under solar charging conditions and for the STTS “Hot Tank” only. Three sets of simulations were undertaken for each tank design, each representing a different state of inlet conditions reflected in the DLSC’s operational manual. Characterization of the STTS tanks was done mainly by applying a set of 2nd Law characterization indices, both existing and new, using exergy as the primary Figure of Merit. It was evident that significant mixing occurs in the current STTS tanks due to the ineffective placement of the inlet ports and the lack of an appropriate flow diffuser to prevent mixing. For example, at the end of the simulations exhibiting constant inlet temperature and flow rate, the total exergy in the original STTS tank was only 68% of a perfectly-stratified vessel. A modified design of the STTS tanks, which only shifted the position of the inlet port and center baffle, significantly improved this value to over 90%. Additional analysis also indicated that the STTS tanks would benefit from a simple flow distributor or inlet manifold that would address stratification issues inherent to variable temperature inlet conditions. However, further analysis on this particular design configuration is needed. The characterization methods employed in this work represent an effective means to differentiate between the stratification effectiveness of various thermal storage vessel designs. This work would further benefit from a future study that compares changes to the STTS tanks’ stratification efficiency with changes to the DLSC’s overall performance, including a cost-benefit analysis. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2009-09-18 05:50:58.362

Fjärrvärme är idag den vanligaste formen av fastighetsuppvärmning i Sverige. Förutom värmeanläggningar som byggts just för ändamålet att leverera fjärrvärme har pappers- och massaindustrin blivit en betydande aktör på marknaden i de orter där industrin finns. BillerudKorsnäs massa- och pappersbruk på Gruvön i Grums kommun levererar fjärrvärme till kommunen och till det intilliggande sågverket.   Syftet med projektet är att genom kartläggning av Gruvöns sekundärvärmesystem på barrsulfatlinjen belysa effektiviseringsmöjligheter med en ökad fjärrvärmeleverans som följd.   Målet är att upprätta en simuleringsmodell i programmet Wingems och med hjälp av den se vad dessa effektiviseringsmöjligheter kan leda till i form av ökad fjärrvärmeleverans.   Metoden i arbetet har utgått från att kartlägga energiflöden till två vattencisterner på barrsulfatlinjens sekundärvärmesystem. Driftdata för vattenflöden i sekundärvärmesystemet har inhämtats i form av flödesstorlek och temperatur, vilka har legat till grund för en simuleringsmodell i Wingems.   Sekundärvärmesystemet på barrsulfatlinjen består av en ljumvatten-cistern, en hetvatten-cistern och ett antal värmeväxlare och kondensorer. Ett av de identifierade problemenen med systemet är att temperaturen i ljumvatten-cistern är högre än den borde. Anledningen till detta är ett vattenflöde från en värmeväxlare som kyler svartlut och leds in till cisternen. Vattenflödet håller en temperatur mellan 70-75°C. Huvudkonsumenten till cisternen är en förindunstare som förses med kylvatten. Temperaturen på vattnet bör ligga på 23°C. Vid en lägre temperatur skickas hetvatten från lövsulfatlinjen att värma vattnet till 23°C, på vägen passerar hetvattnet två värmeväxlare som överför energi till fjärrvärmenätet. Med en högre temperatur i cisternen krävs ett mindre flöde att förvärma kylvattnet, vilket leder till en minskad effekt ut på fjärrvärmenätet.   Resultatet visar att genom omledning av kylvattenflödet från svartlutkylaren till hetvatten-cistern på barrsulfatlinjen kan effektöverföringen till fjärrvärmenätet öka med 3,1 MW. En alternativ lösning skulle kunna vara att kyla svartluten med 74°C vatten från hetvatten-cisternen på barrsulfatlinjen. Kylvattnet kan sedan ledas in tillbaka till hetvatten-cisternen, svartlutkylaren skulle då bli en betydande energiproducent till systemet. Simuleringar visar att denna åtgärd skulle kunna ge en potentiell ökad effektöverföring till fjärrvärmenätet med 9 MW. / District heating is the most common form of house heating in Sweden today. Apart from heating plants that has been built to the purpose, the paper and pulp industry has become a significant contributor. BillerudKorsnäs paper and pulp mill at Gruvön in Grums municipality delivers district heating both to the residents in Grums and the nearby sawmill.   However it has been observed that the amount of energy transferred to the district heating network has been reduced after several redevelopments and new installations at the mill. The purpose with this report is through mapping of the mills secondary heating system find efficiency opportunities that will lead to an increased delivery of district heating. The goal is to develop a simulation model with the software Wingems and with the model make simulations to see the amount of increased district heating the efficiency opportunities may lead to.   To achieve this, the method has been to map the energy flow to and from two water tanks in the secondary heating system in the mills softwood line. Input data for streams in the secondary heating system has been gathered, and these have then been used to construct the simulation model.   The part of the secondary heating system that is located at the mills softwood line consists of one lukewarm water tank, one tank that contains hot water and several heat exchangers and condensers. One of the identified problems with the system is that the temperature in the lukewarm water tank is higher than it should be. The main consumer of the water tank is a pre-evaporator that is using water at the temperature of 23°C to condense some of the flash steam it produces. If the temperature of the water in the tank is below 23°C, hot water from the hardwood line is being pumped to heat the water to the pre-evaporator. The hot water passes two heat exchangers that transfer some of the energy to the district heating system. A higher temperature of the water in the lukewarm tank leads therefore to a smaller flow through the heat exchangers that in turn leads to a lower delivery of district heating.   The reason to the higher temperature in the lukewarm tank is a heat exchanger that cools black liquor from the pre-evaporator. The heated water used to cool the black liquor has a temperature between 70°C to 75°C. This water is being led to the lukewarm tank and is the main reason that the temperature in the tank is higher than designed. The results show that a rerouting of the heat exchangers cooling water to the tank containing hot water could lead to a 3,1 MW increased power transfer to the district heating network. Redesigning the heat exchanger to use water from the hot water tank to cool the black liquor and then lead the even hotter water back to the tank could lead to a 9 MW increased power transfer.

The aim of this study was to develop a load prognosis model for Uppsala district heating system to be used as a tool for heat production optimization. The methodwas to build three models for the different customer types; housing, industry andoffices and then scale them for the total system using data from Uppsala districtheating system. The heat load consists of two parts, one that is temperaturedependent and one that is dependent of the social behavior of the customers. Thetemperature part was modelled with an ARX model using an outdoor temperatureprognosis as input signal. The social behavior part was modelled using the mean ofthe social behavior from some days before and additionally by distinguishing betweenweekdays and weekends. The outcome was a model that would produce a prognosisfor the heat load for each customer type. The total model for the whole districtheating system was less accurate, but still usable. All models developed are howeverrelying on the quality of the available weather prognosis. The benefit of a precise loadprognosis is to facilitate production planning and optimization. Accurate predictions ofthe heat demand, especially in the case of peak load, will result in better productionplanning and thus cost efficiency.

District heating has a long standing tradition in Sweden and today it is the most common way of producing and transporting heat. A District heating system (DH system) is divided into three parts: a production facility, distribution network (DH network) and one more heat stations. The heat produced in the facilities is distributed to the customers via a heat transfer medium, usually water (DH water), in piping networks that make up the DH network. The heat is transferred to the customers via the heat exchanger at which point they can use it as heated tap water or for heating purposes. The DH networks are often constructed in steel as it is cheap and a relatively resistant material. However it has the disadvantages of corrosion and expansions when it is exposed high temperatures which lead to damages in the DH network resulting in loss of the DH water, this is an unavoidable occurrence in any DH network. This results in addition of pollutants by leakages into the DH network or with the water that is used to compensate for the losses. The pollutants cause further corrosion, leading to metal contamination, and more damages on the DH network meaning there is a continuous degradation. Therefore various treatments are used to clean and ascertain an acceptable chemical environment in the DH systems. These treatments are effective but not at a level which is required so many chemicals are used to enhance the treatment of the water. Some of these are known to be toxic to humans and water ecosystems. As leakages are abundant and often end up in the WWTPs of the concerned municipality, which often have troubles with disturbances of the biological treatment, it was decided that an assessment of the toxic effects that DH water pose on activated sludge was to be investigated. This was done by testing water from two DH networks, Växjö and Kalmar, on the same activated sludge obtained from Tegelviken WWTP in Kalmar. A respirometric bioassay approach established by the Organization for Economic Co-operation and Development (OECD), OECD standard 209; OECD Guidelines for the Testing of Chemicals was used with changes made to exposure and measuring time as this decrease the risk of misinterpretation of the results. A dilution series using different concentrations (6.25%, 25% and 100%) of DH water was tested and compered to a blank control samples containing only activated sludge. Assessment of toxicity on total oxidation, oxidation carbon and oxidation of nitrogen was made. To get some idea of what might cause toxic effect samples of the waters was sent to outside laboratories for analyses of metals. The result from the bioassay and metal analysis was used to formulate risk factors associated with a DH water spill and exposure to WWTPs. It was found that both DH waters have a significant inhibition on nitrification in WWTPs. The DH water from Kalmar exhibited similar toxicity dynamics, roughly 20% inhibition, despite large differences in concentration. The DH water from Växjö showed a negative correlation between an increase in concentration of DH water and toxicity, 74% for the lowest concentration and 11% for the highest. The metal analysis concluded that there was no abundance of metal contamination which led to the inference that toxicity is probably caused by the chemicals used for treatment. This poses a great risk for the Baltic Ocean as many WWTPs release their treated water directly into water courses with a short detention time before reaching the sea.

Med ett energikombinat vid Lillesjöverket vill Uddevalla Energi energieffektivisera samt sänka temperatur på återkommande fjärrvärmevatten, för att kunna utnyttja rökgaskondensorn effektivare. Uppdraget var att utreda mängden tillgänglig energi under sommarhalvåret och utföra en matematisk kalkyl som ska ligga till grund för val av tork. Valet stod mellan två alternativ av tork där storlek på värmeväxlararea och investeringskostnad skilde dem åt. Sedan följde dimensionering av fjärrvärmeledning samt cirkulationspump från fjärrvärmenätet till tork. Syftet var att ge Uddevalla Energi ett tekniskt beslutsunderlag för val av storlek på tork samt dimensionering av energiöverföring till densamma. Som metod användes flera olika beräkningsmodeller vid kalkylering av resultaten. Vid jämförelse mellan de två torkalternativen visade det sig att med en ökad investeringskostnad med 2,18 %, för en större värmeväxlararea i tork, ökade mängden energi som fanns tillgänglig till tork under sommarhalvåret med 16,7 %. Detta medförde att kostnaderna för tillskjuten energi sänktes med 65,9 % för att Uddevalla Energi skulle nå sitt mål på 60 GWh. För att nå målet krävdes enligt kalkyl en installation av torkalternativ 2 samt en sänkning av antalet dagar då verket står still på grund av underhåll. / With an energy combine at Lillesjöverket, Uddevalla Energi wants to improve energy efficiency and lower the temperature of the returning district heating water in order to utilize the flue gas condenser more effectively. The assignment was to investigate the availability of power during the summer months and perform a mathematical calculation that will form the basis for the selection of dryer. The selection stood between two options of dryer where the size of the heat exchanger area and investment costs separated them. Also performed were sizing of the district heating water pipeline and the circulation pump from the district heating water network to the dryer. The purpose was to present Uddevalla Energi with a technical basis for selection of the size of the dryer and sizing of energy transfer to the dryer. As method several different calculations were used when calculating the results. When comparing the two options, it turned out that with an increased investment cost of 2.18%, for a larger heat exchange area in the dryer, the amount of energy available to the dryer during the summer months increased by 16.7%. This meant that the cost for energy contributed, for Uddevalla Energi to achieve their goal of 60 GWh, is reduced by 65.9%. To achieve their goal it was required by calculations to install dryer option number two and a reduction in the number of days in which the work is at a standstill due to maintenance.

One application of the Internet of Things that is currently developed is the collection of data from district heating systems. This development leads to the problem of how the collected data should be used to operate the systems in a manner that reduces the dependency on fossil fuels. This thesis proposes a characterization of this problem into visualization tasks and requirements, as well as a visualization application, based on the tool Power BI, for gaining insight into how to operate a district heating system. The tasks and requirements were elicited during collaborative meetings and prototyping together with district heating experts. The perceived effectiveness of the visualization application was validated with a usability evaluation, including the usability metric for user experience questionnaire, with four district heating experts. The perceived efficiency was, however, found to be lacking compared to the other usability aspects. A redesign of one of the Power BI components, which according to the evaluation should improve the application, is also suggested.

Many machines in these days have sensors to collect information from the world they inhabit. The correctness of this information is crucial for the correct operation. However, at times sensors are not so reliable since they are sometimes affected of some type of noise and thus give incorrect information. Another drawback might be lack of information due to shortage of existing sensors. Sensor fusion is trying to overcome these drawbacks by integrating or combining information from multiple sensors. The heating of a building is a slow and time consuming process, i.e. either the flow or energy consumption are object to drastically changes. On the other hand, the tap water system, i.e. the heating of tap water can be the source to severe changes in both flow and energy consumption. This because of that the flow is stochastic in the tap water system, at any given time a tap may be opened or closed and therefore drastically change the flow. The purpose of this thesis is to investigate if is it possible to use sensor fusion to get accurate continuous flow values from a district heating substation. This is done by integrating different sensor fusion algorithms in a district heating substation simulator.

The main research goal is to identify specifics of energy utilities generating electricity and heat from a valuation perspective. To fulfill this goal, the electricity and district heating sector, their characteristic, economic aspects and related regulation have been described. Having weighted possible valuation approaches, the author has decided to opt for both the DCF method and the method using market multiples. The former has been extended by Monte Carlo simulation. The financial and strategic analysis, analysis of key value drivers, financial plan and valuation itself has been thoroughly done. There have been 7 values of equity derived according to a method used and assumptions considered. The variability of outcomes indicates the need for a correct consideration of relevant factors while compiling valuation. These factors are as follows: costs of inputs and their impacts on the entity's operation, price of electricity and heat, life cycle, technological parameters and ecological regulation.

The goal of the thesis is identification and analysis of key risks for Czech district heating sector with focus on coal availability and impact of the EU regulatory measures. In the Czech Republic district heating sector is an important part of energy industry. It serves heating needs of 1.5 million households and substantial amount of industry needs. Currently the question of possible brown coal shortage is becoming urgent. Dynamically changing regulatory framework generating requirements for additional investments is destabilizing. The sector is defined, its competitiveness is evaluated and further the risks are analyzed. Based on brown coal market analysis it is concluded that the current market situation can be considered as stabilized. In the long term perspective the question of possible lifting of the coal mining limits remains crucial. It is concluded that impacts of the EU regulatory measures can't be objectively evaluated at the moment. But it can be assumed that most of district heating companies will be finally able to meet the requirements.

District heating delivers more than 70% of the energy used for heating and domestichot water in Swedish buildings. To stay competitive, district heating needs toreduce its losses and increase capabilities to utilise low grade heat. Finding faultysubstations is one way to allow reductions in supply temperatures in district heatingnetworks, which in turn can help reduce the losses. In this work three suggestedsymptoms of faults: abnormal quantization, drifting and anomalous values, are investigatedwith the help of hourly meter data of: heat load, volume flow, supplyand return temperatures from district heating substations. To identify abnormalquantization, a method is proposed based on Shannon’s entropy, where lower entropysuggests higher risk of abnormal quantization. The majority of the substationsidentified as having abnormal quantization with the proposed method has a meterresolution lower than the majority of the substations in the investigated districtheating network. This lower resolution is likely responsible for identifying thesesubstation, suggesting the method is limited by the meter resolution of the availabledata. To improve result from the method higher resolution and sampling frequencyis likely needed.For identifying drift and anomalous values two methods are proposed, one for eachsymptom. Both methods utilize a software for predicting hourly heat load, volumeflow, supply and return temperatures in individual district heating substations.The method suggested for identifying drift uses the mean value of each predictedand measured quantity during the investigated period. The mean of the prediction iscompared to the mean of the measured values and a large difference would suggestrisk of drift. However this method has not been evaluated due to difficulties infinding a suitable validation method.The proposed method for detecting anomalous values is based on finding anomalousresiduals when comparing the prediction from the prediction software to themeasured values. To find the anomalous residuals the method uses an anomalydetection algorithm called IsolationForest. The method produces rankable lists inwhich substations with risk of anomalies are ranked higher in the lists. Four differentlists where evaluated by an experts. For the two best preforming lists approximatelyhalf of the top 15 substations where classified to contain anomalies by the expertgroup. The proposed method for detecting anomalous values shows promising resultespecially considering how easily the method could be added to a district heatingnetwork. Future work will focus on reducing the number of false positives. Suggestionsfor lowering the false positive rate include, alternations or checks on theprediction models used.