<p>The environmental impact of a final product can be regarded as the sum of the impacts of all processes needed to obtain it. The impacts of these processes in all individual layers of production can be quantified using contribution analysis methods. SPA is an advanced method used to identify the chain of production processes linking the most highly emitting process with the final product. This analysis was performed in Matlab, using a specialized algorithm developed by Peters and Hertwich in 1996. In this thesis we test an interdisciplinary approach combining LCA and operational research methods for doing a SPA. A mixed integer program was developed and implemented in Gams. The performance of this generalized algorithm was benchmarked against the specialized algorithm for three test cases performed on three databases of increasing complexity. The results suggest the advantage of this algorithm in performing analysis on sparse data systems compared with the classic method involving Matlab. However, Matlab’s specialized algorithm performs better for dense data systems. Many of the requirements and limitations imposed by the software involved in different steps have proved manageable. This study proves that mathematical programming can be a very useful tool for contribution analysis in general and SPA in particular.</p>

<p>This master thesis has been written at the Department of Electric Power Engineering at the Norwegian University of Science and Technology. The work has been carried out at the Royal Institute of Technology in Stockholm, where the author spent the last year of his studies as an exchange student. In the thesis, six different designs of the electrical grid of a 540 MW offshore wind farm, placed 100km off the Norwegian coast, have been studied and compared. At this distance, AC cable transmission might be difficult because of the reactive power production in the cables. Taking this into consideration, two options for the transmission system to shore have been studied. In addition to the AC cable transmission, voltage source converter based HVDC transmission, in the form of HVDC Light, has been studied, giving a total of 12 models. The main scope of the thesis was to study the load flow situation and power system performance of the different offshore wind farm layouts. Two load flow cases were run for each model; the first studying the model when the active power transmission to shore was maximized, the second studying the model under a contingency situation. The reliability of the six designs was compared by calculating the expected number of cable failures during the life time of the wind farm for each design, and what consequence the disconnection of any cable would have on the power losses. In order to study the effect of the offshore grid design and transmission system design on the offshore power system stability, dynamic simulations have also been executed, and the voltage response and rotor speed response following a fault have been studied. All simulations have been executed in version 31 of the program PSS/E. The wind farm was modeled full scale, consisting of 108 wind turbines rated at 5MW. The wind turbines were modeled as doubly fed induction generators, using the generic wind model that comes with the program. The load flow simulations showed that an AC cable connection to shore gave lower total system losses than a DC connection for all designs. The lowest losses were found at the n-sided ring design in the AC/AC system, and the highest losses were found for the star design in the AC/DC system. These losses were 2.33% and 8.19% of the total installed capacity, respectively. In the dynamic simulations, a three phase short circuit fault, lasting 150ms, was applied at three different places in the system. The simulations showed that except from at the wind turbines that were islanded as a result of a fault, all dynamic responses were stable. The HVDC Light transmission to shore gave the highest voltage drops and the lowest voltage peaks offshore. Also, the maximum speed deviation was found to be larger when using HVDC Light transmission compared to using AC cables, with two exceptions; the radial and star designs when a fault was applied to the transmission system. A comparison of the six different grid designs showed that the results were varying. Based on the results in this thesis it has not been concluded that one of the offshore designs have better dynamic qualities than the other. The simulation results indicated that this is case specific, and more dependent on where in the offshore grid the fault occurs rather than the design of the offshore grid.</p>

<p>The European Union has set a binding target saying 20 per cent of their energy consumption shall come from renewable energy sources within 2020. Around 4 per cent of the total amount is planned to come from offshore installations (40 GW). There total amount of planned offshore wind capacity is as of today 37 GW, mainly installations in the North Sea. The technologies that will be used for transporting the power to the shore are either HVAC technology using XLPE cables, transistor or thyristor based HVDC systems or HVAC Gas Insulated Line (GIL) technology. However, as the different technical solutions all have advantages and disadvantages compared to the other, the size of the power plants, distances from the shore and closeness to other wind parks will decide what technology will be used for the different cases.</p>

<p>EU har beslutat sig för att gradvis plocka bort de vanliga glödlamporna från marknaden. Istället ska vi använda energismartare ljuskällor som lågenergi-, halogen- eller LED-lampor.</p><p>Vilken ljuskälla som ersätter den traditionella glödlampan är ännu oklar. Den värdiga ersättaren ska gärna vara fri från kvicksilver, energismart och inte alltför dyr.</p>

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<p>Denna handlar om vilka ord och begrepp elever använder när de beskriver naturvetenskapliga fenomen eller händelser. Genom att visa eleverna olika experiment som de fått förklara så har jag undersökt hur eller om de använder naturvetenskapliga ord.</p><p>Mitt resultat pekar på att elever vill förklara, men orden räcker inte till. De använder sig ofta av vardagsförklaringar som är baserade på tidigare upplevelser. Att förstå hur elever kan förklara och uttrycka sina kunskaper ger mig som pedagog möjlighet att bemöta eleverna på rätt sätt. Ordet är viktigt och elever måste få visa sina kunskaper med ”sina” ord och uttryck och då är det viktigt att jag som lärare förstår vad de säger och vad de menar med sina förklaringar. Och om vi i skolan inte hinner med så får vi använda undervisningsmetoder som ger eleverna möjlighet att kommunicera med varandra.</p>

<p>Sammanfattning Företaget Zetterströms Rostfria AB i Molkom producerar värmeväxlare till olika ändamål. I produktionen använder Zetterströms en sömsvets som kräver kylvatten. Mängden kylvatten som går åt under ett år är cirka 2016m3. Svetsen går på olika effekter beroende på vad för typ av plåt som svetsas, om den är tjock eller tunn. Vid svetsning av en tjock plåt körs svetsen på högre effekt än om det svetsas en tunnare plåt. Studien omfattar två olika effektlägen som svetsen kördes på under mätningarna. Zetterströms vill nu ta till vara på den energi som kylvattnet tar upp i svetsen samt att minska färskvatten förbrukningen. Syftet med denna studie är att göra en kartläggning över hur kylvattenförbrukningen går att minska samt hur spillvärmen från svetsens kylvatten kan tas till vara på ett bra sätt. Målet med studien är att finna energieffektiva lösningar som tar tillvara på svetsens spillvärme samt minskar färskvattenförbrukningen. Metoden har bestått i att analysera Zetterströms uppvärmningssystem för att veta hur systemet är uppbyggt och vilken temperatur värmesystemet har på framledningstemperatur. Därefter gjordes temperatur- och flödesmätningar på svetsens kylvatten. Vid mätningarna på svetsen visade det sig att kylvattnet tog upp en effekt av 40,1 resp. 15,6 kW på de två effektlägen som studien behandlar. När nu effekterna som överförs till vattnet är kända framtogs två olika systemförslag. Ett förslag där flödet sänks till det rekommenderade samt att en luftvärmare installeras i lokalen där svetsen står. Det andra förslaget är ett slutet system med en kylmaskin som kyler kylvattnet så att vattnet återigen lämpar sig till kylvatten då framledningstemperaturen ska ligga mellan 14-15ºC. Värmen som kylmaskinen avger kommer att ligga runt 60ºC som via värmeväxlare kommer att avges i luftvärmare i lokalen som ett komplement till dagens uppvärmningssystem. Kylvattenförbrukningen kommer att med detta förslag att minskas radikalt från dagens situation. Besparningen som kommer att ske för de två olika förslagen blir 12400 resp. 41600kr/år.</p> / <p>Abstract The company Zetterströms Rostfria AB in Molkom producing heat exchangers for different purposes. In the production Zetterströms are using a seam welding machine that demands cooling water. The quantity of cooling water the company consumes is 2016m3/year. The seam welding machine works on different effects depending on the thickness of the sheet metal. Thicker sheet metal demands higher power than a thinner sheet metal. This study handles values from two different effects that the welding machine is working with. Zetterströms wants to reduce the quantity of cooling water and reuse the energy the cooling water receives in the welding machine. The purpose of this study is to survey how to reduce the quantity of cooling water used and how to integrate the energy in the cooling water to the buildings heating system. The objective of the study is to find a solution that takes care of the energy in the cooling water and reduce the quantity of cooling water. The method endures to analyze Zetterströms heating system to find the heating systems operating temperatures. Several measurements on the cooling water temperatures and water flows were made. The results from the measurements showed that the welding machine transferred two different effects to the cooling water. The welding machine transferred 40,1 respective 15,6kW to the cooling water. This study handles these two effects. When this two effects are known, two suggestions where hammered out. One suggestion reduces the cooling water flow to recommended level and a fan coil is installed to warm the industrial premises. The second suggestion is a close system with a heat pump. The heat pump cools the water so it can be reused as cooling water again. The recommended temperature of the cooling water is 14-15ºC. The energy from the cooling water is pumped to 60ºC with the help from a heat pump. The warm water from the heat pump emits in fan coils like the first suggestion. The fresh water consuming will be reduced to minimal level with the second suggestion. The saving for the first suggestion will be 12400kr/year and for the second suggestion 41600kr/year.</p>