In spite of their high technical maturity, load sensing systems (LS) have system-inherent energy losses that are largely due to the operation of parallel actuators with different loads at the same pressure level. Hereby, the pressure compensators of the system are crucial. So far, excessive hydraulic energy has been throttled at these compensators and been discharged as heat via the oil. The research project “Reduction of System Inherent Pressure Losses at Pressure Compensators of Hydraulic Load Sensing Systems” aims to investigate a novel solution of reducing such energy losses. The pressure of particular sections can be increased by means of a novel hydraulic circuit. Therefore, a recovery unit is connected in series with a hydraulic accumulator via a special valve in the reflux of the actuators. The artificially increased pressure level of the section reduces the amount of hydraulic power to be throttled at the pressure compensators. As long as a section fulfills the switching condition of the valve, pressure losses at the respectiv pressure compensator can be reduced. Thus, via a suitable recovery unit excessive energy can be regenerated and can be directed to other process steps eventually.

The Swedish pulp and paper industry meets higher demand for energy efficiencyi mprovements with increasing energy prices and changes in the Swedish renewable energy certificate system. One action of energy efficiency improvement is by using secondary heat, that otherwise would have been treated as waste heat, for use in a system with lower temperature demands. The aim of this Master´s thesis is to identify possible secondary heat sources in a typical Swedish pulp and paper mill and to investigate what economic benefits the secondary heat will provide when being used for pre heating of wood chips to a kraft digester. The Master´s thesis focuses on three secondary heat sources; dry warm air, warm water and moisture saturated warm air located inside the pulp or paper mill. Two types of kraft digesters are simulated within this study, a typical Scandinavian digester and a modern twin vessel steam phase digester. Due to quality aspects and low temperature level drying is the drying technology with dry warm air rejected. Using warm water in direct contact with wood chips increases the quantity of water to the evaporation plant and thus reduced pulp or paper production and is therefore also rejected. The thesis nevertheless indicates a goodopportunity for further investigation of using moisture saturated warm air for preheating of wood chips. The humid air, from a drying machine or produced from secondary heat warm water, is used in a theoretical modified belt drier. Conservative assumptions regarding heat transfer and investment cost calculations yield a yearly net saving for a typical Swedish pulp mill at over 5 MSEK with a return on investment at 7years.

This dissertation studies hybrid dc-dc power conversion systems based on multiple-input converters (MICs), or more generally, multiport converters. MICs allow for the integration of multiple distributed generation sources and loads. Thanks to the modular design, an MIC yields a scalable system with independent control in all sources. Additional characteristics of MICs include the improved reliability and reduced cost. This dissertation mainly studies three issues of MICs: efficiency improvement, modeling, and control. First, this work develops a cost-effective design of a highly-efficient non-isolated MIC without additional components. Time-multiplexing (TM) MICs, which are driven by a time-multiplexing switching control scheme, contain forward-conducting-bidirectional-blocking (FCBB) switches. TM-MICs are considered to be subject to low efficiency because of high power loss introduced by FCBB switches. In order to reduce the power loss in FCBB switches, this work adopts a modified realization of the FCBB switch and proposes a novel switching control strategy. The design and experimental verifications are motivated through a multiple-input (MI) SEPIC converter. Through the design modifications, the switching transients are improved (comparing to the switching transients in a conventional MI-SEPIC) and the power loss is significantly reduced. Moreover, this design maintains a low parts-count because of the absence of additional components. Experimental results show that for output power ranging from 1 W to 220 W, the modified MIC presents high efficiency (96 % optimally). The design can be readily extended to a general n-input SEPIC. The same modifications can be applied to an MI-Ćuk converter. Second, this dissertation examines the modeling of TM-MICs. In the dynamic equations of a TM-MIC, a state variable from one input leg is possible to be affected by state variables and switching functions associated with other input legs. In this way, inputs are coupled both topologically and in terms of control actions through switching functions. Coupling among the state variable and the time-multiplexing switching functions complicate TM-MICs’ behavior. Consequently, substantial modeling errors may occur when a classical averaging approach is used to model an MIC even with moderately high switching frequencies or small ripples. The errors may increase with incremental number of input legs. In addition to demonstrating the special features on MIC modeling, this dissertation uses the generalized averaging approach to generate a more accurate model, which is also used to derive a small-signal model. The proposed model is an important tool that yields better results when analyzing power budgeting, performing large-signal simulations, and designing controllers for TM-MICs via a more precise representation than classical averaging methods. Analyses are supported by simulations and experimental results. Third, this dissertation studies application of a decentralized controller on an MI-SEPIC. For an MIC, a multiple-input-multiple-output (MIMO) state-space representation can be derived by an averaging method. Based on the averaged MIMO model, an MIMO small-signal model can be generated. Both conventional method and modern multivariable frequency analysis are applied to the small-signal model of an MI-SEPIC to evaluate open-loop and closed-loop characteristics. In addition to verifying the nominal stability and nominal performance, this work evaluates robust stability and robust performance with the structured singular value. The robust performance test shows that a compromised performance may be expected under the decentralized control. Simulations and experimental results verify the theoretical analysis on stability and demonstrate that the decentralized PI controller could be effective to regulate the output of an MIC under uncertainties. Finally, this work studies the control of the MIMO dc-dc converter serving as an active distribution node in an intelligent dc distribution grid. The unified model of a MIMO converter is derived, enabling a systematical analysis and control design that allows this converter to control power flow in all its ports and to act as a power buffer that compensates for mismatches between power generation and consumption. Based on the derived high-order multivariable model, a robust controller is designed with disturbance-attenuation and pole-placement constraints via the linear matrix inequality (LMI) synthesis. The closed-loop robust stability and robust performance are tested through the structured singular value synthesis. Again, the desirable stability and performance are verified by simulations and experimental results. / text

The power sector needs to be decarbonised by 2050 to meet the global target for greenhouse gas emission reduction and prevent climate change. With fossil fuels expected to play a vital role in the future energy portfolio and high efficiency penalties related to mature CO2 capture technologies, this research aimed at evaluating the efficiency improvements and alternate operating modes of the coal-fired power plants (CFPP) retrofitted with post-combustion CO2 capture. To meet this aim, process models of the CFPPs, chilled ammonia process (CAP) and calcium looping (CaL) were developed in Aspen Plus® and benchmarked against data available in the literature. Also, the process model of chemical solvent scrubbing using monoethanolamine (MEA) was adapted from previous studies. Base-load analysis of the 580 MWel CFPP retrofits revealed that if novel CAP retrofit configurations were employed, in which a new auxiliary steam turbine was coupled with the boiler feedwater pump for extracted steam pressure control, the net efficiency penalty was 8.7–8.8% points. This was close to the 9.5% points in the MEA retrofit scenario. Conversely, CaL retrofit resulted in a net efficiency penalty of 6.7–7.9% points, depending on the fuel used in the calciner. Importantly, when the optimised supercritical CO2 cycle was used instead of the steam cycle for heat recovery, this figure was reduced to 5.8% points. Considering part-load operation of the 660 MWel CFPP and uncertainty in the process model inputs, the most probable net efficiency penalties of the CaL and MEA retrofits were 9.5% and 11.5% points, respectively. Importantly, in the CaL retrofit scenarios, the net power output was found to be around 40% higher than that of the CFPP without CO2 capture and double than that for the MEA retrofit scenario. Such performance of the CaL retrofit scenario led to higher profit than that of the 660 MWel CFPP without CO2 capture, especially if its inherent energy storage capability was utilised. Hence, this study revealed that CaL has the potential to significantly reduce the efficiency and economic penalties associated with mature CO2 capture technologies.

The aim of the paper was to proposed new manufacturing technology. In the beginning, the diploma thesis deals with the technological aspects of manufacturing hydraulic valve. Subsequently is described the usage of manufacturing technology. The existing production process is analysed in detail. Better efficiency was achieved by using hard turning instead grinding technology. Economic evaluation is described in the end of thesis, where is efficiency of hard turning technology supported by calculations.

Hydroscand in Örebro is part of the Hydroscand Group, which is the market leader in the Nordic region for customized hydraulic solutions. Hydroscand's main products consist of adapters, couplings, hydraulic hoses, pipes, and hose clamps. Due to the wide range of products offered by Hydroscand, the company's facility in Örebro has experienced recurring production stops linked to material shortages. The Örebro facility comprises three buildings: a production house, a warehouse, and Spendrup, where a large quantity of hoses is stored. This leads to long waiting times in the form of production stops because the transportation time between the buildings is lengthy.Through a systematic approach involving a current state analysis, it was confirmed that production stops related to material shortages should be prevented to streamline production. Following the current state analysis, a root cause analysis was conducted, identifying the root causes of material shortages in production. These root causes included an inadequate material supply strategy that was not tailored to the product flow, a lack of a visual system clarifying empty shelves for material suppliers, improper prioritization of hoses in the hose tower near the production lines, and material suppliers' position in the information flow, which hinderedpreventive actions against material shortages.The proposed solution consisted of four sub-solutions to prevent these root causes, including a shift from a push to a pull material supply strategy. This involved following a material list to ensure the availability of the correct materials in the production house. Implementation of a Kanban system was one of the sub-solutions to simplify the detection of empty shelves. The change in strategy led to a modification in the information flow, resulting in improved communication between production and material suppliers. The final sub-solution was to replace the hoses in the hose tower with the ones that are frequently sold, as the hoses in the highest demand will also be the most needed in production.The proposed solution will result in increased production productivity and the elimination of production stops associated with material shortages, which was the objective of the work. / Hydroscand i Örebro tillhör företagsgruppen Hydroscand Group som är marknadsledande iNorden gällande kundanpassade hydrauliklösningar. Hydroscands huvudsakliga produkter består av adapters, kopplingar, hydraulslangar, rör och slangklämmor. På grund av Hydroscands stora produktvariation så har företagets anläggning i Örebro haft återkommande produktionsstopp som har kopplats till materialbrist i produktionen. Örebros anläggning består av tre byggnader ett produktionshus, ett lagerhus och Spendrup där stora slangkvantitet lagras. Detta medför att materialbristen kan orsaka långa väntetider i form av produktionsstopp, eftersom transporttiden mellan byggnaderna tar lång tid.Genom ett metodiskt arbete där en nulägesanalys genomfördes bekräftades bilden av att produktionsstoppen kopplade till materialbrist bör förebyggas för att effektivisera produktionen. Efter nulägesanalysen genomfördes en rotorsaksanalys som fann rotorsakerna till att materialbrist förekom i produktionen. Dessa rotorsaker var felaktig materialförsörjningsstrategi som inte var anpassad till produktflödet, en avsaknad av ett visuellt system som förtydligar tomma hyllor för materialförsörjare, fel prioritering av slang i slangtornet nära anslutning till produktionslinorna och materialförsörjares position i informationsflödet som försvårade det förebyggande arbetet mot materialbrister.Lösningförslaget bestod av fyra dellösningar som skulle förebygga dessa rotorsaker, lösningen bestod av att förändra materialförsörjnings strategi från push till pull. Detta genom att följa en materiallista för att säkerställa att rätt material finns tillgängligt i produktionshuset. En implementering av ett Kanbansystem var en av dellösningar, detta för att förenkla upptäckten av tomma hyllor. Bytet av strategin ledde till en förändring av informationsflödet, vilket kommer resultera i en förbättrad kommunikation mellan produktion och materialförsörjare. Sista dellösningen var att byta de slang som låg i slangtornet mot de slang som oftast säljs, eftersom slang som har mest efterfrågan kommer även att behövas mest i produktionen.Lösningsförslaget kommer att resultera i ökad produktionsproduktivitet samt en eliminering av produktionsstopp kopplade till materialbrist, vilket var syftet med arbetet.

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In an increasingly competitive market, it is important for companies with distribution centers to have efficient processes limiting non-value adding time as much as possible while still being able to deliver what the customer expects. The purpose of the thesis was to investigate the operating processes at the distribution center at Volvo – Eskilstuna. It services the Scandinavian market with multiple departures per day, supplying directly to end customers and retailers. The goal was to increase the efficiency of the distribution center and increase consolidation of multiple parts ordered by the same customer. Currently, multiple packages get delivered to the same customer who has ordered parts the same day. While investigating this inefficiency, we monitored orders through it registering in the system, assignment to picking lists to be picked by operators, packaging and sorting. There were constraints associated with the layout, IT system and traffic safety laws without compromising on delivery efficiency, quality, implementation costs, and organizational regulations. Observations were carried out on the job floor, interviews were conducted with the management or better: with managers / management team, and an independent analysis was conducted of the historical data collected from the warehouse management system. The main results suggest rearranging the inventory according to consumption frequency classification (Paretto principle). Additional results suggest implementing slotting and postpone packaging to consolidate higher order percentage. Multiple strategies have been put forth which need trials to test the implications. / I en ökad konkurrenskraftig marknad är det viktigt för företag med distributionscenter att få effektivare processer och minimera icke värdeskapande aktiviteter. Detta är nödvändigt för att möta kundernas förväntningar och leverera det som kunderna begär. Syftet med uppsatsen var att undersöka hur processerna fungerade på Volvos distributioncentret i Eskilstuna. Volvo levererar reservdelar till hela den skandinaviska marknaden och har flertal leveranser som lämnar distributioncentret dagligen. Målet var att öka effektiviteten i distributionscentret och möjliggöra konsolideringen när en kund beställt flera varor så att de kommer i samma paket. För närvarande levereras de olika varor i separata paket istället för att komma i en och samma. För att undersöka detta fenomen så samlades data in genom det som registrerades i systemet. Det fanns begränsningar i samband med lagstiftningen, IT-systemet och trafiksäkerhetslagar samt att lösningarna inte skulle kompromissa med leveranseffektivitet, kvalitet, implementeringskostnader och organisatoriska föreskrifter. Observationer genomfördes på arbetsplatsen, intervjuer genomfördes med ledningsgruppen eller relevanta chefer och en oberoende analys genomfördes av de historiska data som samlats in från lagerhanteringssystemet. De viktigaste resultaten föreslår att reservdelar bör förvaras efter Paretto principen som har med konsumtion frekvensen att göra. Ytterligare resultat föreslår att man ändrar på hur varor paketeras samt skjuter upp förpackningar för att konsolidera högre orderprocent.

Logistics is an integral component in making the production process more efficient in companies. An important concept in logistics is lead time, the time it takes for a product to go through the process from inbound and outbound to the customer. A normal logistical process comprises the initial receival of goods, controls upon arrival and further quality controls carried out before the product ends up in the storage. The delivery process is a central process with many sub-processes including varying working methods and routines that can result in permeating inefficiencies in the company if they aren’t done properly. The purpose of the study is to identify causes of inefficiency that might cause extended lead times and reduced productivity in the delivery process. This is achieved by studying the internal workflow and routines of Volkswagen Parts Logistics delivery process.  This study’s based on a case and the data is gathered by semi-structured interviews and observations at Volkswagen Parts Logistics. Thereafter the results are analysed through literature and scientific articles.  The study first identifies one cause of inefficiency through factors such as simplification, synchronization, communication and integration. To identify the root-cause, a root-cause analysis has been used on these factors, which are then compiled into a cause and effect diagram and finally six factors have been explained. From the analysis and discussion of the six factors, four improvement suggestions have been submitted to Volkswagen Parts Logistics. The suggestions included education & training, standardized working methods, understanding the whole process and cooperation between groups. The study presents a scientific gap regarding the efficiency improvement of lead time with Human Lean aspect with a focus on the delivery process. The study contributes to the gap through the six factors and improvement suggestions based on analysis and discussion. / Logistik har blivit allt viktigare för att effektivisera produktionen i företag. Ett viktigt begrepp inom logistik är ledtid, i den här studien innebär ledtid tiden det tar för en reservdel inleverans till utleverans vidare mot kund. En väsentlig del inom logistik är inleveransprocessen för inkommande gods som går igenom godsmottagning, ankomstkontroll och kvalitetskontroll för att sedan hamna på lagerhyllan. Inleveransprocessen är en central process med många delprocesser och varierande arbetssätt samt rutiner som vid brister kan medföra en genomsyrande ineffektivitet i företaget. När avvikelser uppstår kan det medföra en förlängning av ledtiden vilket påverkar resten av processen och framförallt utleveransen till kunden. Studiens syfte är att identifiera orsaker till ineffektivitet som kan leda till förlängda ledtider och minskad produktivitet i inleveransprocessen. Det görs genom att studera arbetssätt och rutiner i inleveransprocessen.  För att utveckla kunskap rörande faktorer som påverkar inleveransprocessen är en fallstudie som grund med genomförda semistrukturerade intervjuer och observationer genomförts på Volkswagen Parts Logistics. Resultat har analyserats med hjälp av litteratur och vetenskapliga artiklar från forskningsområdet. I studien identifieras först orsaken till ineffektivitet genom faktorer som förenkling, synkronisering, kommunikation och integration. För att identifiera rotorsaken till ineffektivitet har en rotorsaksanalys genomförts på dessa faktorer som sedan sammanställts i en orsakverkan-diagram och slutligen har sex stycken faktorer presenterats.  Utifrån analys och diskussion för de sex faktorerna framtogs fyra stycken förbättringsförslag till fallföretaget. Förbättringsförslagen innefattade utbildning & upplärning, standardiserade arbetssätt, förståelse för hela processen och samarbete mellan grupper. I studien framförs ett vetenskapligt gap gällande effektivisering av ledtid med Human Lean aspekt med avgränsning till inleveransprocessen. Studien bidrar till detta gap genom de sex framtagna faktorerna samt formulerade förbättringsförslag baserat på analys och diskussion.