The interest in using finite element analysis (FEA) as a product development tool is present within IKEAof Sweden (IoS). To gain additional support from within IoS a project was issued to identify the meritsand demerits of FEA. This was done by applying FEA to optimise an existing product, namely theEktorp sofa frame. Three important questions are addressed in this report: • How can the finite element method efficiently and reliably be applied to improve an existingproduct? • What types of improvements can be anticipated from using the finite element method andhow can these be achieved? • What products are suitable to be developed with the use of FEA? As the sofa frame mainly consists of wood a literature study is conducted to answer several questionsregarding the use of wood in conjunction with FEA. Real life tests are performed to verify acquiredmaterial data. The original design is analysed with FEA to act as reference for newer concepts and also to identifyareas of improvement. Additional design tools are also applied to complement the FEA. Concepts are generated to improve a number of factors such as weight, number of components andcost. These concepts are analysed with FEA to be compared to the original design and incrementallychanged until meeting set requirements. A final concept where the cost, weight and number of components are reduced is thoroughlydescribed and presented as a CAD model. The final result is the Ektorp sofa frame with its weightreduced by 10.9%, number of components reduced by 18.2% and material cost reduced by 13.4%. The conclusion from this process is that FEA can efficiently and reliably be applied to improve anexisting product. This, however, requires thorough knowledge in FEA. Strength, weight and cost arethe most obvious factors that can benefit from the use of FEA while almost all design changes canbenefit indirectly as well. Almost any product can benefit from the use of FEA; however, severalfactors decide the efficiency and reliability of these analyses, such as analysis experience and productcomplexity. / Det finns ett intresse för att använda finita element analyser (FEA) som ett produktutvecklingsverktygpå IKEA of Sweden (IoS). För att få ett ökat stöd inom IoS skapades ett projekt där för och nackdelarnamed FEA kan identifieras. Detta projekt baserades på att optimera en existerande produkt, nämligenEktorp soffans ram. Tre viktiga frågor behandlas i och med detta projekt: • Hur kan finita element metoden appliceras på ett effektivt och tillförlitligt sätt för att optimeraen existerande produkt? • Vilka typer av förbättringar kan man förvänta sig genom att använda finita element metodenoch hur uppnås dessa? • Vilka produkter lämpar sig att utvecklas med hjälp av FEA? Eftersom soffans ram till större delen består av trä inleds en litteraturstudie för att besvara frågor somberör användandet av trä i samband med FEA. Verkliga tester utförs för att verifiera insamladematerialdata. Originalkonstruktionen analyseras med FEA för att skapa en referens till kommande koncept och ävenför att identifiera möjliga förbättringsområden. Flera designverktyg används för att komplettera FEA. Koncept genereras för att förbättra en rad faktorer såsom vikten, antalet komponenter och kostnaden.Dessa koncept analyseras med FEA och jämförs mot originalkonstruktionen för att förbättrasinkrementellt tills det att fastställda krav uppfylls. Ett slutgiltigt koncept där kostnad, vikt och antalet komponenter är minskat beskrivs i detalj ochpresenteras som en CAD modell. Det slutgiltiga resultatet är Ektorp-soffans ram där vikten ärreducerad med 10,9%, antalet komponenter reducerade med 18,2% och materialkostnadernareducerade med 13,4%. Slutsatsen från projektet är att FEA kan appliceras på ett effektivt och tillförlitligt sätt för att förbättraen existerande produkt. Detta kräver dock omfattande kunskap inom FEA. Hållfasthet, vikt ochkostnad är de mest uppenbara parametrar som kan tjäna på användandet av FEA medan nästan allakonstruktionsändringar kan dra nytta av FEA indirekt. Nästan alla produkter kan dra nytta av FEA, detfinns dock en rad faktorer som avgör hur pass effektiva och tillförlitliga analyserna blir. Exempel pådessa är användarerfarenhet och produktkomplexitet.

<p>Inom grossistbranschen associeras distributionen med svårigheter så som många kunder, små godsvolymer per kund och krav på korta ledtider. Många kunder kräver dessutom leveranser inom vissa tidsfönster. Dessa faktorer ställer höga krav på logistiken och skapar behov om hög leveransservice.</p><p>Inom transportbranschen råder idag generellt en relativt låg datormognad. Sedan tidigare finns avancerade digitala informationssystem tillgängliga för inköp, ordermottagning och lagerkontroll. Utvecklingen går dock mot att även logistik- och transportavdelningarna i större utsträckning börjar använda sig av mer avancerade transporttekniska hjälpmedel. Exempel på sådana är ruttoptimeringsprogram som kan användas för att beräkna optimala körvägar.</p><p>Servera R&S är en restauranggrossist som har ett antal lager utspridda i Sverige. Då deras kundkrets i stockholmsområdet under senare år blivit allt större har även antalet lossningsplatser ökat drastiskt. Godset till dessa förses från lager placerade i Norrköping och Västerås. Godset från Norrköping samlas och packas om i en terminal i Årsta innan det transporteras vidare till kunderna i Stockholm.</p><p>Servera R&S efterfrågade en analys av deras distribution i Stockholm. Detta för att undersöka om nuvarande distributionsstrategier är kostnadseffektiva. Syftet var att finna möjliga förändringar i verksamheten som skulle kunna medföra förbättringar för distributionen till kunder i Stockholm. Målet innefattade att finna förbättringsförslag som skulle innebära ett bättre användande av distributionsnätverkets resurser, minskade transportkostnader och ökad leveransservice.</p><p>Inledningsvis genomfördes en nulägesanalys för att kartlägga arbetsmetoder och tillvägagångssätt vid distributionen. Utifrån intervjuer och enkätundersökningar skapades sedan en modell av distributionen i vilken det verkliga trafikarbetet efterliknades. Denna användes vid simuleringar i ett ruttoptimeringsprogram med syftet att påvisa förbättringsmöjligheter. Under analysfasen studerades distributionsprocessen och simuleringsresultaten med målet att ta fram förslag på förbättringar och annorlunda tillvägagångssätt vid terminalhantering och transport.</p><p>Studien visar att det i distributionsprocessen finns stora möjligheter för förbättringar gällande terminalhantering och godstransporter. Ruttoptimeringen påvisar stora besparingsmöjligheter gällande transporttid, antalet körda kilometer och antalet använda fordon i distributionsarbetet. Simuleringsresultaten visar exempelvis en minskning av den totala transportsträckan med upp till 30 procent. Då transportsträckan står i direkt relation till transportkostnaderna skulle en sådan minskning innebära reducerade kostnader för distributionen.</p> / <p>Within the wholesale sector, the distribution is often associated with difficulties, such as many customers and a requirement for short lead times. A lot of customers also demand delivery within certain time windows. These factors all contribute to a high level of strain on the logistics.</p><p>In general, the amount of computer usage within the transportation industry is relatively low. However, advanced information systems are available for order handling and inventory management, and a lot of software for distribution planning and vehicle routing have surfaced as of recently. These often combine digital maps and optimization algorithms, and can be used for calculating optimized routes within the distribution.</p><p>Servera R&S is a wholesale company with a number of warehouses in different parts of Sweden. As of lately, their clientele in Stockholm has expanded, and the number of delivery points have increased drastically. The customers in Stockholm are provided with goods from warehouses in Norrköping and Västerås. The goods from Norrköping passes through a transfer terminal in Årsta before it is delivered to the customer in Stockholm.</p><p>Servera R&S is requesting an analysis of their distribution in Stockholm. They want to determine whether their distribution strategies are economically effective or not. Within this study, we aim to analyze different distribution strategies, which may or may not result in improvements of the efficiency of the distribution process. The purpose is to find solutions that better use the recourses of the distribution network (i.e. vehicles and personnel etc.), increase the level of delivery service and reduce the transportation costs.</p><p>A survey analysis was carried out to map work methods and procedures within the distribution process. Interviews and surveys were used in the process of creating a basis for the optimization tool. Simulations were performed in an attempt to demonstrate the possibilities for decreasing distribution costs through the use of a vehicle routing program. During the analysis, the distribution process and the results from the simulations were studied with an aim to find possible improvements in the way that goods and information are handled within the warehouses and during the transports.</p><p>The study shows a lot of possibilities for improvements within the distribution process. The route optimization prove a potential for decreasing costs regarding transportation time, distances and the number of vehicles used within the distribution. For example, the simulations show that the distances can be decreased with as much as 30 percent.</p>

In this study, the effect of implementing Network Coding on the aggregated throughput in Wireless Mesh Networks, was examined. Wireless Mesh Networks (WMNs) are multiple hop wireless networks, where routing through any node is possible. The implication of this characteristic, is that messages flow across the points where it would have been terminated in conventional wireless networks. User nodes in conventional wireless networks only transmit and receive messages from an Access Point (AP), and discard any messages not intended for them. The result is an increase in the volume of network traffic through the links of WMNs. Additionally, the dense collection of multiple RF signals propagating through a shared wireless medium, contributes to the situation where the links become saturated at levels below their capacity. The need exists to examine methods that will improve the utilisation of the shared wireless medium in WMNs. Network Coding is a coding and decoding technique at the network level of the OSI stack, aimed to improve the boundaries of saturated links. The technique implies that the bandwidth is simultaneously shared amongst separate message flows, by combining these flows at common intermediate nodes. The number of transmissions needed to convey information through the network, is decreased by Network Coding. The result is in an improvement of the aggregated throughput. The research approach followed in this dissertation, includes the development of a model that investigates the aggregated throughput performance of WMNs. The scenario of the model, followed a typical example of indoors WMN implementations. Therefore, the physical environment representation of the network elements, included an indoors log–distance path loss channel model, to account for the different effects such as: power absorption through walls; and shadowing. Network functionality in the model was represented through a network flow programming problem. The problem was concerned with determining the optimal amount of flow represented through the links of the WMN, subject to constraints pertaining to the link capacities and mass balance at each node. The functional requirements of the model stated that multiple concurrent sessions were to be represented. This condition implied that the network flow problem had to be a multi–commodity network flow problem. Additionally, the model requirements stated that each session of flow should remain on a single path. This condition implied that the network flow problem had to be an integer programming problem. Therefore, the network flow programming problem of the model was considered mathematically equivalent to a multi–commodity integer programming problem. The complexity of multi–commodity integer programming problems is NP–hard. A heuristic solving method, Simulated Annealing, was implemented to solve the goal function represented by the network flow programming problem of the model. The findings from this research provide evidence that the implementation of Network Coding in WMNs, nearly doubles the level of the calculated aggregated throughput values. The magnitude of this throughput increase, can be further improved by additional manipulation of the network traffic dispersion. This is achieved by utilising link–state methods, rather than distance vector methods, to establish paths for the sessions of flow, present in the WMNs. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2012.

In this study, the effect of implementing Network Coding on the aggregated throughput in Wireless Mesh Networks, was examined. Wireless Mesh Networks (WMNs) are multiple hop wireless networks, where routing through any node is possible. The implication of this characteristic, is that messages flow across the points where it would have been terminated in conventional wireless networks. User nodes in conventional wireless networks only transmit and receive messages from an Access Point (AP), and discard any messages not intended for them. The result is an increase in the volume of network traffic through the links of WMNs. Additionally, the dense collection of multiple RF signals propagating through a shared wireless medium, contributes to the situation where the links become saturated at levels below their capacity. The need exists to examine methods that will improve the utilisation of the shared wireless medium in WMNs. Network Coding is a coding and decoding technique at the network level of the OSI stack, aimed to improve the boundaries of saturated links. The technique implies that the bandwidth is simultaneously shared amongst separate message flows, by combining these flows at common intermediate nodes. The number of transmissions needed to convey information through the network, is decreased by Network Coding. The result is in an improvement of the aggregated throughput. The research approach followed in this dissertation, includes the development of a model that investigates the aggregated throughput performance of WMNs. The scenario of the model, followed a typical example of indoors WMN implementations. Therefore, the physical environment representation of the network elements, included an indoors log–distance path loss channel model, to account for the different effects such as: power absorption through walls; and shadowing. Network functionality in the model was represented through a network flow programming problem. The problem was concerned with determining the optimal amount of flow represented through the links of the WMN, subject to constraints pertaining to the link capacities and mass balance at each node. The functional requirements of the model stated that multiple concurrent sessions were to be represented. This condition implied that the network flow problem had to be a multi–commodity network flow problem. Additionally, the model requirements stated that each session of flow should remain on a single path. This condition implied that the network flow problem had to be an integer programming problem. Therefore, the network flow programming problem of the model was considered mathematically equivalent to a multi–commodity integer programming problem. The complexity of multi–commodity integer programming problems is NP–hard. A heuristic solving method, Simulated Annealing, was implemented to solve the goal function represented by the network flow programming problem of the model. The findings from this research provide evidence that the implementation of Network Coding in WMNs, nearly doubles the level of the calculated aggregated throughput values. The magnitude of this throughput increase, can be further improved by additional manipulation of the network traffic dispersion. This is achieved by utilising link–state methods, rather than distance vector methods, to establish paths for the sessions of flow, present in the WMNs. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2012.

The dissolved silicon (DSi) has a crucial role for growth of a large group of primary producers – diatoms and, hence, impact on functioning of the aquatic food web. This thesis contributes to an increased understanding of the modifications of the DSi cycling in the Baltic Sea. The results provide new information about spatial and temporal changes in DSi concentrations and nutrient ratios for the period 1970-2001 as well as during the 20th century. For the period 1970-2001, the declining DSi trends were found at the majority of monitoring stations all over the Baltic Sea. This decrease is assumed to be mainly due to the ongoing eutrophication. It is supported by the increasing trends of inorganic nitrogen and phosphorus. The trends have implications for the nutrient ratios, DSi:DIN and DSi:DIP, which are important indicators of the state of an ecosystem. The long-term retrospective DSi budget has shown that the DSi concentrations before major hydrological alterations and eutrophication were about twice the present ones. This decrease is related to both eutrophication and anthropogenic perturbations in the catchment. The occurrence of DSi concentrations close to the potentially limiting levels has been also analysed. While DSi concentrations are still high in the northern regions of the Baltic, other areas may be at risk of developing Si limitation if the decrease in DSi concentrations persists. The results depict the Baltic Sea journey from being water body with DSi levels sufficient to support diatom production to one that may experience Si limitation and its adverse ecological consequences. / Löst kisel (DSi) har en viktig roll för tillväxten av en stor grupp av primärproducenter – kiselalger, och därmed även påverkar hela den akvatiska näringskedjan. Denna avhandling bidrar till en ökad förståelse av förändringarna i DSi kretsloppet i Östersjön. Resultaten tillhandahåller ny information om rumsliga och tidsmässiga förändringar i DSi koncentrationer såväl för perioden 1970-2001 som för hela 1900-talet. För perioden 1970-2001 återfanns minskade DSi koncentrationer på mätstationer över hela Östersjön. Minskningen antas främst bero på den pågående övergödningen. Detta antagande stöds av stigande halter av oorganiskt kväve och fosfor. Sammantaget har dessa trender en inverkan på ekosystemets tillstånd och näringsämnenas kvoter, DSi: DIN och DSi: DIP. Ur ett längre tidsperspektiv kan man se att innan övergödningen och de stora hydrologiska ombildningar i Östersjöområdet var DSi koncentrationerna ungefär dubbelt så höga som idag. Dagens förekomst av DSi koncentrationer som ligger nära de potentiellt begränsande nivåerna har också analyserats. DSi koncentrationerna är fortfarande höga i norra delar av Östersjön, men är i andra områden i riskzonen för att utveckla Si begränsning om minskningen av DSi koncentrationer fortsätter. Resultaten skildrar Östersjöns resa från att vara ett havsområde med DSi halter som är tillräckliga för att understödja kiselalgernas produktion till ett sådant som kan uppleva Si begränsning och dess negativa ekologiska konsekvenser.

Detta examensarbete har utförts som en del av högskolutbildningen Maskinteknik vid Linköpings universitet. Rapporten är skriven på uppdrag av Blomberg &amp; Stensson AB i Katrineholm som ingår i en företagsgrupp med företaget X-modul samt Engströms Verkstäder. Företaget erbjuder produkter i stor variation som verktygsvagn, renhetsskåp, arbetsbänk och en flexibel barack som kan byggas som ett boende, fältsjukhus, toaletter med mera. Produktionen i Katrineholm består främst av plåt- och rörbearbetning.Blomberg &amp; Stensson har på våren 2017 flyttat in i nya lokaler och ska därför optimera sina arbetsområden. Området som fokuseras i detta arbete är kapningsområdet där rör- och balkmaterial kapas. För närvarande finns det inget sätt att kapa material längre än sju meter vilket är grundproblemet i detta arbete, eftersom material måste kapas för hand innan den kan tas in i lokalen. Syftet är att skapa en ny layout för kapningsområdet, samt eliminera säkerhetsrisker, ergonomirisker, slöseririsker och miljörisker. Lösningsförslag ska presenteras på en ny layout samt lösningsförslag på åtgärder för eventuella risker som uppkommer.Genom en övergripande kartläggning av området och dess avgränsningar samt datainsamling genom intervjuer, observationer och litteraturstudier har förståelsen av kapningsproduktionen ökat. Tillgång till egen arbetsplats hos företaget har också varit betydande för arbetets resultat. Med närhet till produktionen och kunnig personal har lett till ett effektivare arbete och ökat förståelsen för arbetsprocessen.När kunskap hade samlats in analyserades området och lösningsförslag på layouts skapades. Layouten fokuseras på att utformas med Lean production, bra ergonomi och bra arbetsmiljö. Lösningsförslag skapades och gick igenom en process där de ansvariga på företaget fick säga sina åsikter och kritisera förslagen. Det tredje förslaget blev godkänt och bestämdes som den layout kapningsområdet skulle ha och en renovering tog fart. Under arbetsgången påpekades flertal gånger om att det behövdes ett koncept för att ta upp vätska som spills under rullbanorna. Ett lösningsförslag till detta skapades samtidigt som en riskanalys utfördes med ansvarig operatör när kapningsområdets design var bestämt.Resultatet presenterar layoutens design som gör det möjligt att kapa material på tolv meter vilket löser problemet. Dessutom presenterar den lösningsförslaget på problemet där vätska som spills samt resultatet från en framgångsrik riskanalys.I diskussionskapitlet har jämförelser före och efter arbetet på layouten och hur förändringarna har tillämpats på arbetsstationen dessutom har frågorna från syftet besvarats. I slutsatsen presenteras bidraget som detta arbete har gett. / This project has been carried out as part of the college education Mechanical Engineering at Linköping University. The report is written on behalf of Blomberg &amp; Stensson AB in Katrineholm and who is a part of a company group with the company named X-module and Engströms Verkstäder. The company offers products in a wide variety such as utility wagon, cleaner cabinet, workbench and a flexible shed that can be built as accommodation, field hospital, toilets and more. Katrineholm’s production consist mainly of sheet- and pipe processing.Blomberg &amp; Stensson has in spring 2017 moved into new facilities and therefore shall optimization be done on their work areas. The work area focused on in this paper is the cutting area where pipe- and beam materials are cut. At present time there is no way to cut materials longer than seven meters which is the basic problem in this paper, as materials must be cut by hand before it can be transported inside the facility. The purpose is the create a new layout for the cutting area and to eliminate any security risks, ergonomics, waste risks and environmental risks. Solution proposals will be presented on a new layout and solution proposals for measures on possible risks that have arisen through the steps of the work.Through an overall mapping of the area and its delimitations and data collection through interviews, observations and literature studies, the understanding of the production increased. With access to an own workspace at the company has also been significant for the work’s results. With close proximity to the production and knowledgeable personnel, has led to more efficient work and has increased understanding of the work process.Once knowledge had been gathered the area was analyzed and layout solutions were created. The layout focuses on being designed with Lean production, good ergonomics and good working environment. Solutions proposals were created and went through a process whereby the personnel in charge in the company were allowed to say their opinions and criticism of the proposals. The third proposal was approved and determined as the layout the cutting area should look like and a renovation took off. During the work of the paper, it was pointed out several times that there was a concept needed for taking up liquid that was spilled out under conveyor belts. A solution proposal for the liquid situation was created while a risk analysis was carried out with the main operator when the design of the area was determined.The result presents the layout design that enables cutting of twelve-meter materials which solves the main problem. In addition, it also presents the solution proposal for the problem where liquid spills as well as the result of the successful risk analysis.In the discussion chapter have before and after comparisons of the differences of the layouts and how changes have been applied to the workstation and answers the questions from the purpose. In conclusion, the contribution of the paper is presented.

The thesis has been performed in cooperation with a Swedish manufacturing company. The manufacturing site of the company is currently implementing a new machine layout in one of its workshops. The new layout will increase the product flow to another workshop on the site. The goal of the thesis was to evaluate the current transportation system and suggest viable alternatives for the future product flow. By means of discrete event simulation these alternative solutions would be modelled and subsequently optimized to determine if their performance is satisfactory. An approximated investment cost of the solutions would also be estimated. By performing a literature review and creating a frame of reference, a set of relevant methodologies were selected to provide a foundation to the project. Following these methodologies, the current state of transportation was identified and mapped using Value Stream Mapping. Necessary data from the current flow was identified and collected from the company computer systems. This data was deemed partly inaccurate and further verification was needed. To this end, a combination of Genchi Genbutsu, assistance from onsite engineers and a time study was used to verify the unreliable data points. The data sets from the time study and the company data which was deemed valid were represented by statistical distributions to provide input for the simulation models. Two possible solutions were picked for evaluation, an automated guided vehicle system and a tow train system. With the help of onsite personnel, a Kaizen Event was performed in which new possible routing for the future flow was evaluated. A set of simulation models portraying the automated guided vehicle system and the tow train system were developed with the aid of simulation software. The results from these models showed a low utilization of both systems. A new set of models were developed, which included all the product flows between the workshops. The new flows were modelled as generic pallets with the arrival distribution based on historical production data. This set of models were then subject for optimization with regard to the work in process and lead time of the system. The results from the optimization indicates the possibility to reduce the overall work in process by reducing certain buffer sizes while still maintaining the required throughput. These solutions were not deemed to be ready for implementation due to the low utilization of the transportation systems. The authors instead recommend expanding the scope of the system and including other product flows to reach a high utilization.

Den här rapporten behandlar ett system som använder en databas som lagringsplats för loggar. En bra metod för att hämta ut dessa loggar saknades och databasdesignen behövde förbättras för sökningar i loggarna. En applikation för att hämta och söka i loggposter från databasen skapades. En undersökning om hur databasdesignen kunde förbättras genomfördes också. Båda delarna gjordes i ett projekt för att de hörde ihop. Applikationen skulle använda databasen. Då jag inte kunde göra vilka ändringar jag ville i databasen gjordes relativt begränsade ändringar i den. Större ändringar utreddes teoretiskt. Applikationen gjordes mot den existerande databasdesignen, med ett undantag: en vy lades till. Rapporten undersöker index och andra metoder att göra sökningar i en databas snabbare. En metod för att hämta data inom ett intervall i en databas utvecklades och den beskrivs i rapporten. Metoden söker efter all data som har värden på en kolumn som faller inom ett intervall och där databasen är ordnad, eller nästan ordnad, på den kolumnen. Metoden ger oexakta svar om databasen är nästan ordnad på den kolumnen. Den är snabbare än en motsvarande exakt sökning. / This report considers a system where a database is used as the back-end storage for logging. A suitable method for extracting information from the logs was missing and the database design needed an improvement for log searching. An application for extracting and filtering the logs was created. An evaluation of how the database could be improved was also performed. Both parts were done in one project since they were heavily connected. The application would use the database. Since I couldn’t make arbitrary changes to the database only relatively limited changes were made in practice. Larger changes were evaluated theoretically. The application was made against the existing database, with one exception: a view was added. The report handles indexes and other methods for speeding up database searches. A method for fetching data inside an interval in a database was developed and is described in the report. The method searches for all data where the value of a column is inside an interval and the database is ordered, or almost ordered, on that column. The method gives inexact answers if the database is almost ordered on that column. It is faster than a corresponding exact search.

Biogas is an expanding sector within the broad field of agriculture and animal production. Small-scale biogas offers local combined power and heating production and the substrate is transformed into high-quality biological fertilizer. This bachelor thesis focuses on a pig farm in south-western Sweden, where biogas is produced from pig manure, evaluates and suggests ways of optimizing the process and investigates whether investing in an upgrading plant would be a feasible and more cost-efficient option. The results show that the biogas plant is working well, although the production differs from the original plans. This shows in turn that planning and examining the basic conditions before making the investment is of great importance, as well as monitoring and keeping detailed statistics of the running process. Logistical factors make optimizing the process through additional substrates difficult. The thesis shows that investing in a Biosling upgrading plant would be a profitable option, supposing that the upgraded gas is sold via the natural gas infrastructure. Furthermore, many farmers are interested in producing their own fuel for tractors and other machines, which offers more future alternatives for the upgraded biogas. However, biogas producers in Sweden today are not offered any particular subsidies, which makes it especially hard for small-scale producers.

The aeration step is the most energy consuming process in the wastewater treatment plant, i.e. making the energy usage in this step more efficient is of great concern both in Sweden and world wide. There are some examples of previous studies investigating ways to make the ae- ration control more efficient, though most of these have focused on for example ammonium feedback control rather than blower control which is the main focus of this study. Bromma wastewater treatment plant installed three new blowers in december 2016 functioning as suppliers of air to the aeration step in the bioreactor. Since there are still three old blowers operating at the WWTP, there is a need to control two different types of blowers efficiently. This is challenging since the two blower types have different capacities, efficiency and maxi- mum/minimum air flows and a control strategy that optimizes the operation of these two blower types combined needs to take this into account. Operational data for the blowers was used to generate a second grade polynome for each blower type which gives the efficiency as a function of produced air flow. These polynomes were further utilized to build a script in MATLAB that chooses the most efficient number of blowers operating and at what air flows for a certain total aeration need. The least square method was used to calibrate a model for calculating energy consumption for the simulated control strate- gy. Calculations for energy consumption from the current control strategy and another strategy proposed by the blower deliverer Sulzer were made in order to decide whether the optimized control strategy was an improvement or not. The simulation results and the calculations for energy consumption indicates that the current control strategy at Bromma WWTP is almost as effective as the optimized control strategy. Both strategies sets the new blowers at the first places in the queue. The optimized strategy appears to be more efficient for flows that requires both new and old blowers operating. From the calculations of energy consumption, it was shown that the control strategy from Sulzer de- mands an energy consumption on levels in between the one for the current control strategy and the optimized control strategy. / Luftningssteget är den mest energikrävande processen i ett avloppsreningsverk. Det finns därför incitament till att effektivisera energianvändningen då en minskad elförbrukning är positivt både ur ett ekonomiskt perspektiv och ur ett resursmässigt perspektiv. Energibesparingar från luftningssteget har undersökts tidigare genom att främst studera optimering av syreregleringen och luftregulatorn. Det här projektet syftar till att uppnå en minskad effektförbrukning på Bromma reningsverk genom att optimera blåsmaskinsregulatorn, ett mer outforskat forskningsfält.  På Bromma reningsverk installerades den 16 december 2016 tre nya blåsmaskiner som ska försörja luftningssteget i den biologiska reningen med luft. Det innebär att det finns två olika typer av blåsmaskiner som är i drift på Bromma: den gamla modellen (HST9000) och den nya modellen (HST40). Då dessa två olika typer av blåsmaskiner har olika kapacitet och verkningsgrad är det viktigt att blåsmaskinsregulatorn använder en styrstrategi som ställer dessa maskiner i kö på ett optimalt energieffektivt sätt. Det är även viktigt att i så stor utsträckning som möjligt låta maskinerna generera luftflöden nära sin högsta verkningsgrad.  Driftinformation för blåsmaskinerna användes för att med hjälp av beräkningar i MATLAB kunna välja ut det effektivaste antalet maskiner i drift, avgöra vilken typ av maskiner som ska användas samt vilket luftflöde respektive maskin ska generera vid ett specifikt luftflödesbehov. Målet var att hitta en optimal styrstrategi för Bromma reningsverk, samt att undersöka om det fanns möjligheter till energibesparingar jämfört med nuvarande implementerade styrstrategi. Effektförbrukningsberäkningar gjordes för både den simulerade optimerade styrstrategin och den nuvarande. Ytterligare en styrstrategi, föreslagen av blåsmaskinsleverantören Sulzer, undersöktes också ur ett energiförbrukningsperspektiv för jämförelse.  Resultatet av simuleringen och effektberäkningen indikerar att den nuvarande styrningen i princip är lika energieffektiv som den simulerade optimala styrningen. I båda fallen kopplas de nya maskinerna in i första hand. Dock visar resultatet på att den simulerade styrningen är effektivare vid flöden där det krävs att de gamla blåsmaskinerna sätts i drift. Sulzers föreslagna styrstrategi är mer energieffektiv än nuvarande styrning, men inte lika effektiv som den optimerade styrstrategin.