An increasing need to find alternatives to fossil fuels, and a growing awareness of the global warming effect has resulted in substantial research and development on biofuels. Biofuels are being considered a potential substitution of petroleum based fuels in the transport sector.With this increasing interest in biofuels comes the need to establish the environmental effect of the fuels. Results from several life cycle assessments reviewed in this report show that there are some benefits of biofuels in global warming impact compared to conventional fuels. How great this benefit is varies between the studies. Differences in critical issues such as allocation, carbon sequestration, and fertilizer use have significant impact on the results of the life cycle assessments. There is a lack of studies dedicated to investigating other environmental areas. The studies that have, show little consistency in their results, but indicate an increase of damage in categories such as acidification and eutrophication. No consistent results were shown on impact categories such as human toxicity potential or photochemical smog.Second generation fuels are claimed to be more sustainable than first generation fuels. There are many different types of second generation fuels being developed. Research and Development have resulted in technologies such as hydrolysis, pyrolysis, gasification and hydrothermal upgrading . Technology challenges and high costs still exist with these technological solutions, the second generation bio-fuels being 2-3 times more expensive than conventional fuels.Most of the second generation fuels are in their pilot phase, but several successful pilot projects exist for both hydrolysis and gasification. Gasification to produce bio-fuels is especially promising. The company Choren, who uses this technique, is planning to produce and sell their products in 2007. One of the main products of the company is Fischer-Tropsch (FT) diesel.A life cycle assessment on a second generation biofuel was performed. This was done by doing a Hybrid analysis on a Fischer- Tropsch diesel following the gasification route. The Hybrid analysis consists of a foreground and background system. The foreground system comprises important processes in the fuels lifetime. This includes biomass production, transport, production and use of the fuel. The background system contains economic data taken from the Norwegian background. The aim of the LCA is to compare the environmental effects of a second generation biofuel with first generation biofuels, and the impact category chosen in the impact assessment is global warming potential.The results of the work show that the global warming impact throughout the life cycle of the biofuel is 39 eq g/km. This proves to show a considerable reduction in the category, compared to both conventional diesel and average values of first generation biofuels. This implies that Fischer –Tropsch diesel is a more sustainable transport solution, yet more work is suggested to be taken on investigating the overall environmental impact of both second generation and first generation biofuels. .

Capture and storage from fossil fuel fired power plants is drawing increasing interest as a potential method for the control of greenhouse gas emissions. An optimization and technical parameter study for a CO2 capture process of the flue gas of a commercial gas power plant, based on absorption/desorption process with MEA solutions, using HYSYS with the Amine Property Package fluid package, has been performed. The optimization has aimed to reduce the energy requirement for solvent regeneration, by investigating the effects of circulation rate, cross-flow heat exchanger minimum approach, desorber operating pressure and the absorber diameter. In addition, an economic evaluation including investment cost has been performed for the first three parameters.Major energy savings can be realized by optimizing the desorber pressure and the solvent circulation rate. The circulation rate will have a clearly defined optimal point, while for the desorber pressure the temperature will be a limiting factor. A too high temperature may lead to amine degradation and corrosion problems. The cross-flow heat exchanger minimum temperature approach will not affect the energy consumption significantly. An optimum absorber column diameter was not found, but the column should be designed with a diameter large enough to prevent flooding through the column. A too large diameter will not favour the energy consumption very much, and other factors will be more decisive when the column diameter is chosen.

Arbeidet som presenteres i denne rapporten er utført i samarbeid med Energiselskapet Buskerud (EB). Oppgavens formål har vært å utarbeide en generell metode for å minimere kostnader knyttet til reaktiv effektflyt i regionalnettet og deretter benytte denne metoden for å optimalisere reaktiv effektflyt i regionalnettet eid av EB. Regulering av reaktiv produksjon i kraftstasjoner og installasjon av kondensatorbatterier er vurdert som mulige tiltak for å endre den reaktive effektflyten. Disse tiltakene medfører kostnader i form av aktive tap i generatorer eller på grunn av kostnader til installasjon av kondensatorbatterier. Reaktiv effektflyt bidrar til kostnader i form av nettap og reaktivt uttak fra sentralnettet tarifferes av Statnett. I optimaliseringen tas det sikte på å minimere summen av disse fire kostnadselementene. Faste kostnader ved installasjon av kondensatorbatterier fører til at optimalisering av reaktiv effektflyt er et diskret optimaliseringsproblem. Optimaliseringen er derfor utført ved bruk av genetisk algoritme, en optimaliseringsmetode som ble antatt å fungere godt for diskrete problemer. Ved optimalisering med genetiske algoritmer er det ikke mulig å fastslå med sikkerhet at optimal løsning blir funnet, og det er derfor knyttet noe usikkerhet til resultatene. Et optimaliseringsprogram ble programmert i Matlab, og programmet Matpower 3.2 ble implementert i optimaliseringsprogrammet for å utføre lastflytberegninger. Resultatene fra optimaliseringen var konsistente og ga en klar kostnadsreduksjon i forhold til dagens drift. Dette tyder på at optimalisering med genetisk algoritme fungerer godt for denne problemstillingen. Beregningstiden for de største optimaliseringene var rundt 5 minutter. Optimalisering av reaktiv effektflyt ble gjennomført for to deler av regionalnettet i Nedre Buskerud. I begge nettene er det i dagens drift noe reaktiv produksjon i kraftstasjoner, men det er også et betydelig reaktivt uttak fra sentralnettet. Begge analysene viste at reaktiv produksjon i nettet bør økes i forhold til dagens nivå, først og fremst på grunn av store besparelser ved redusert reaktivt uttak fra sentralnettet. Også reduserte nettap bidro til kostnadsreduksjonene. Kostnadene kan reduseres betraktelig ved å øke reaktiv produksjon i kraftstasjonene i nettet, men størst kostnadsreduksjon oppnås ved installasjon av nye kondensatorbatterier. Optimaliseringen ble utført for ulike priser på sentralnettsuttak, og resultatene viste at prisen på reaktivt uttak fra sentralnettet må reduseres til under 10 kr/kVAr for at slikt uttak skal være lønnsomt. I dag er prisen på 25 kr/kVAr. Dette viser at konklusjonen om at reaktiv produksjon bør økes for å unngå reaktivt uttak fra sentralnettet er robust for endringer i sentralnettsprisen. I nettet mot Kongsberg ga et kondensatorbatteri på 8 MVAr i Glabak en maksimering av kostnadsreduksjonen. Denne investeringen har en internrente på 10 %. I nettet mot Modum ga kondensatorbatterier på 6,5 MVAr i Hokksund T2 og 9 MVAr i Hovde maksimal kostnadsreduksjon. Den samlede investeringen har en internrente på 12 %. I en eventuell videreføring av arbeidet i denne rapporten kan det være aktuelt å teste optimaliseringsprogrammet for større problemer. Optimalisering med genetisk algoritme kan også brukes i andre nettrelaterte problemstillinger. En mer detaljert behandling av reaktiv produksjon i generatorer vil kunne gi forbedret datagrunnlag for optimaliseringen, og dette bør derfor vurderes i det videre arbeidet.

Denne oppgaven tar for seg hvilke målinger som er nødvendig for å bestemme SFP-faktoren for et typisk nyere kontorbygg med mekanisk ventilasjon. Den tar for seg hvordan disse målingene kan utføres, hva slags måleutstyr som kan benyttes, og hvordan nøyaktigheten til målingene kan bestemmes.Oppgaven tar så for seg gjennomføring av målinger for å bestemme SFP-faktoren for to bygninger. Disse to bygningene er Høyskolen i Oslo (HiO) og PricewaterhouseCoopers-, eller PWC-bygget i Bjørvika i Oslo. Det gis en innføring i de to bygningenes ventilasjonsanlegg og oppbyggingen av disse samt en gjennomgang av styresystemene for ventilasjonsanleggene. Det måles på ett aggregat i hver bygning. For HiO velges aggregat 36.13 som betjener et auditorium med VAV-styring. For PWC-bygget velges aggregat 36.09 som betjener hovedsakelig cellekontorer og styres som CAV. Alle målinger blir utført ved hjelp av differansetrykkmåling over viftene. Aggregatet ved HiO klarer akkurat å komme seg ned på kravet i teknisk forskrift om 2,0 kW/m3/s ved bruk av gjennomsnittlig SFP over driftstiden, men ved personbelastning i lokalet er SFP-verdien 2,66 kW/m3/s. Aggregatet ved PWC-bygget ligger på 2,0 kW/m3/s ved full innregulert drift og klarer dermed fint forskriftskravet. Målingene viser likevel at det ville være mye energi å spare på VAV-styring av anlegget fremfor CAV.Forbedring av ventilasjonsdesign er også en del av oppgaven, og det beregnes hvordan strengere krav til maksimal lufthastighet og alternativ utforming av fordelingskammer kan redusere strømningsmotstanden i et anlegg. Dette viste seg å kunne redusere SFP-faktoren for aggregat 36.09 ved PWC-bygget til 1,52 kW/m3/s ved å ikke tillate hastigheter over 3 m/s samt å benytte en alternativ utforming av fordelingskammeret.Det presenteres forslag til forbedringer i rutiner og programvare for ventilasjonsdesign som kan redusere SFP-fakoren i fremtidige kontorbygninger, og det diskuteres hvorvidt de løsninger som fremkommer i denne oppgaven vil være økonomisk lønnsomme.Til slutt kommer anbefalinger for videre arbeid med problemstillingen.

Føremålet med denne oppgåva har vore å setje seg inn i modellering av turbulent forbrenning og nytte teori i praksis ved simulering med dataprogrammet SPIDER. Rett modellering er viktig sidan både turbulens og forbrenning har innverknad på danninga av NOx.Saman utgjer dei eit komplisert fagfelt. Det har lenge voreforska på desse emna, og i dag eksisterer det fleire modellar.Turbulensen påverkar forbrenninga sidan den står for mykjeav blandinga.Det vert presentert fleire grunnlikningar som er nytta i modelleringa. Teorien presentert omhandlar hovudsakleg k-e-modellen og Magnussen sin EDC-modell for turbulent forbrenning.Likningane som inngår i modellane er diskretisert ogimplementert i programmet SPIDER, som vert presentert i oppgåva. CFD-koda nyttar kurvelineære, ikkje-ortogonale koordinatar og kan rekne på komplekse geometriar. Dei viktigaste NOx-mekanismane er presentert, og nokre metodar for å redusere utslepp er nemnde i rapporten.Det er gjort simuleringar av to turbulente diffusjonsflammer, og resultata er samanlikna med måledata. Den eine er omtala som ``H3-flamma'', og har ei brenselblanding med 50-50% hydrogen og nitrogen. Den andre har ei blanding med CH4, H2 og N2 i brenslet. Fleire variantar av k-e-modellen er samanlikna. Magnussen sin EDC-modell er nytta som forbrenningsmodell. Det ertesta ulike grid for å få ei tilnærma nettverk-uavhengig løysing. Målingar, og metodar på korleis dette har vorte gjort for metan-flamma, er og snakka om i siste kapitlet.For begge flammane er det gjort simuleringar med detaljert kjemi. Dette er naudsynt for å få informasjon om danninga av NOx. Resultata synte at metan-flamma ga større avvik frå målingar.Det vart freista å betre modellen ved å justere blandingsraten iEDC-modellen. Resultat synte at simulering med detaljert kjemi stiller høgare krav til oppløysing på nettverket.NO-verdiar frå simuleringane er samanlikna med måledata formetan-flamma. Resultata er utførleg drøfta.

This master thesis is investigating environmental performance of different alternatives for Combined Heat and Power (CHP) production from Natural Gas (NG) at Mongstad oil refinery. An important objective is to evaluate CHP plants with Carbon Capture and Storage (CCS), and the performance of these compared to a conventional CHP without such application. Life Cycle Assessment (LCA) is the applied methodology for environmental assessment. The LCA results are used to inspect changes in eco-efficiency at the refinery with introduction of a CHP plant.Three CHP configurations have been assessed: 1.Conventional CHP2.Conventional CHP with Post-Combustion (PC) CCS3.Autothermal Reforming (ATR) plant; CHP with pre-combustion CCSThe three alternatives are denoted Conventional, PC and ATR in the following.Global Warming Potential (GWP) emissions per MWh exergy produced from the three CHP’s are 56, 100 and 337 kg CO2-equvivalents for the PC, ATR and Conventional respectively. It is concluded that up-and downstream emissions do not undermine the environmental benefit of applying CCS regarding GWP impacts.The CCS systems have significantly higher impacts of Human Toxicity (HTP), Acidification (AP) and Eutrophication Potentials (EP). HTP impacts are over 50% higher for CCS systems compared to Conventional. Increased NH3 and NOx emissions make up much of the 100-150% rise in AP and EP impacts. It is considered possible that flue gas handling can mitigate a substantial fraction of the increased AP and EP impacts. The system expansion reveal that building a Conventional CHP at Mongstad will not lead to global CO2 reductions if it substitutes renewable electricity production. The CCS systems unreservedly give net global CO2 reductions, disregarding alternative electricity production technology.The GWP eco-efficiency at Mongstad is defined as total LCA emissions from refinery output products divided by the economic value of the products. Introducing a CHP with CCS would significantly improve the eco-efficiency. Installing a Conventional plant, however, would deteriorate eco-efficiency. Installing a CHP with CCS is hence considered a significant step towards a sustainable development at Mongstad refinery. Given improved flue gas handling of NOx and NH3, additional environmental effects are not considered to have potential of jeopardizing this conclusion.

Several power transformers has, during the last two decades, broken down due to the copper sulphideproblem. Corrosive sulphur reacts with the copper conductor contaminating the surroundinginsulating paper. To this day there are no reliable nondestructive methods to detect copper sulphidecontamination in a power transformer.Dielectric frequency measurement is a nondestructive tool used in the transformer industry. Themeasurements can give important information about the condition of the transformer insulation. Inthis master thesis the usage of dielectric frequency measurement as a tool to detect copper sulphideon insulation paper has been investigated.The task has been divided into two subtasks:•Subtask I: Develop and test different methods to create and classify copper sulphide contamination on paper samples.•Subtask II: Examine the dielectric frequency response of the contaminated samples as a function of copper sulphideSolution and results for Subtask IFor sample creation two methods were used:•Creating samples out of paper strips taken from existing transformers•Growing copper sulphide on paper in the laboratory for three, ffve, eleven and fourteen daysFor copper sulphide classiffcation three methods were used:•Resistance measurement•Area percentage calculation•Classiffcation by the number of days grown.For sample creation the growth of copper sulphide samples seemed to be the better choice as the gapsbetween the samples of strips gave large uncertainties in the dielectric frequency response. The growthvaried in some extent and days of growth some times became insuffcient in classifying degree of coppersulphide. Good connection between the copper and paper may be an important factor, and the sizeof the samples is recommended to be kept small. For all samples, contamination got heaviest at theedge. For the samples grown for fourteen days the paper became too fragile for dielectric frequencytesting.The resistance measurement classiffcation method seemed to be the best choice, as it could copewith large variations in the contamination. The area percentage calculation method worked undervery limiting conditions as the contamination had to be of a certain brightness level and with lowvariations in colour. The classiffcation due to days of growth came too short as the contaminationbetween ffve and seven days were not that signiffcant. Larger time intervals can be a solution.Solutions and Results from Subtask IIDielectric frequency measurements were tested with two separate equipments:•The Insulation Diagnostic Analyser: Frequency range: 1mHz-1kHz•.The Alpha-Analyser: Frequency range: 100Hz-1MHzAll tests where performed in equilibrium with air humidity at the time of testing.The gaps between the strips, used in the samples, gave a substantial effect to the dielectric frequencyresponse. This effect was clearest at the lower frequencies, but some effect can also be seen inthe higher region. At the lower frequencies the results gave no indication of any effect in the dielectricresponse due to copper sulphide. However, the gap effect may have concealed the effect, and testingwithout gaps is recommended.At the higher frequencies the grown copper sulphide samples gave some variations in the dielectricfrequency response. The variations in results also occurred between samples with the same creationconditions. This may still indicate a relation between copper sulphide and dielectric response at higherfrequencies. Even with the large deviations there were, at frequencies above 100kHz, a steeper increasein losses for the contaminated samples. Of the grown samples created only samples of ffve and sevendays growth were tested. This gives a limited research foundation and further investigation is needed.Conclusions and Future WorkIn general there might be a correlation between copper sulphide and dielectric frequency measurement.Growing samples has turned out to work well as the test object provider. By combining days of growthwith resistance measurements the classiffcation of the contamination should be suffcient. However,more research is absolutely needed and some suggestions for further work are as follows:•Dry the samples to minimise the water effect on the dielectric frequency measurement.•Creating a new smaller sample cell for the Insulation Diagnostic Analyser, so the sample size can be reduced and sample without gaps can be run in the lower frequency range.•Increase the time gap between the samples grown to get larger differences in contamination, and reduce the effect of variations.•Reducing the temperature may be a way to increase days of growth. However, in this case more research on the temperature dependencies of copper sulphide growth is needed.

China's economy has grown at remarkable rates in the last three decades, bringing about big improvements in people's quality of life. On the downside, the increased economic activity has contributed to serious environmental problems, many of which are related to the country's energy system. Focusing particularly on Beijing, this study aims at illuminating how income growth and lifestyle changes relate to energy use in the society. An extended input-output analysis is applied to estimate the direct and indirect household energy consumption (HEC) of Beijing households at different levels of development in the year 2005. Using observations of how HEC varies across income groups in 2005 as a basis, projections of HEC towards 2015 are made. According to the results, the total HEC in Beijing amounts to 42% of the total direct energy use occurring in all sectors within Beijing's geographical boundaries. Hence, a significant portion of the energy use in the society can be linked with consumer activities. For urban residents, indirect influences on energy use are found to be more than three times greater than the direct influences. Mainly due to growing incomes, total HEC in urban Beijing will grow substantially in the period 2005-2015, even with overall efficiency improvements corresponding to the central government's targets. The results indicate that the share of transport related energy use to total HEC will increase significantly. Without major efficiency improvements, huge increases in transport related energy use is to be expected towards 2015. Air conditioners will be the most important single electrical appliance contributing to increased residential electricity consumption in the near future.Due to significant uncertainty, the figures should be taken as rough guides to the magnitude of different types of energy use only. Nonetheless, it is the author's opinion that the study produces valuable insights that can add to our understanding of the underlying drivers of energy use in the Beijing society. The estimates are considered sufficiently accurate to serve as a basis for making some recommendations for improving the energy efficiency of the society. Based on the findings of the study, the author calls on central and local governments to: 1) Further incorporate the important role of consumer behaviour and lifestyle into energy conservation policies; 2) Make strong efforts to mitigate transport related environmental problems, focusing attention both on producers and consumers; 3) Give high priority to constructing energy efficient buildings; 4) Further strengthen and expand the performance standard and labelling scheme for electrical appliances; 5) Consider imposing constraints on the promotion of consumerism by the mass media and advertising industry.

Liquid-liquid coalescers are devices used for increasing the droplet size of the dispersed phase in continuous phase flow, such as oil droplets in water flow. The efficiency of separation technologies is strongly dependent on the droplet size, which is desirable to shift into larger droplet diameters. Theory behind coalescence and its modeling is studied in this Maser’s thesis. Aker Process Systems AS, Division of Advanced Separation Technology, provided the assignment proposal.The scope of this work is a literature study on the coalescence phenomenon and the closely related break-up phenomenon and CFD modeling in general. Further a mathematical model for simulating coalescence of oil droplets in continuous water flow is developed by the use of the commercial CFD-code FLUENT. The basis for the model is a swirl-based coalescer called Compact Tubular Coalescer (CTC), developed by Aker Process Systems AS.The validity of the model is evaluated before different aspects of the performance of the coalescer are studied. Several validation criteria were tested and were acceptable, but some weaknesses regarding lack of test cases were detected. The performance testing showed good performance of the CTC, it was able to increase the Sauter Mean Diameter (SMD) of the droplet with up to 250% for the smallest droplets (20 μm) and highest volume fractions (7%). Remarkable differences of the performance were observed as the physical properties were changed. Higher viscosity and droplet surface tension lead to increased coalescence rate and decreased break-up rate.Future work is recommended to concentrate on improving the present model and to investigate more aspects of the model. An effort should also be made to use a Eulerian approach to model the dispersed phase with the use of population balances, in order to be able to simulate flows with larger dispersed phase volume fractions.

This thesis is on the design of an airfoil for a downwind wind turbine rotor with thin flexible wings, for offshore floating conditions. It has been suggested that such a system would to be lighter, simpler and allow for the use of more efficient airfoils. There has been a significant amount of work done at NTNU to develop a “high-lift” airfoil. These are airfoils with very high lift-to-drag ratios. They operate very efficiently at their design angle, but tend to not work well over a range of angles and conditions, and have a sudden and dramatic stall characteristic. In this thesis, it is attempted to pick up the work done with the high-lift profiles at NTNU in the 1980’s, and develop a new profile which has performance in the high-lift range, but with a much smoother stall and more stable characteristics, and to do so for the typical conditions expected for the suggested turbine. A fictitious 5 MW version of the suggested turbine was created and analyzed with the blade element momentum method (BEM). This gave informative results about the conditions the new airfoil must operate in. The high-lift technology and the earlier reports from NTNU were studied. Based on this knowledge and the numerical values from the BEM calculations, a serious of new airfoils were developed. By using the simulation programs Xfoil and Fluent (CFD), it was possible to modify and test a large number of airfoils and find the desired qualities.It was possible to design airfoils that had performance in the high-lift range, while maintaining stable operation and having a soft stall, and also increase the lift coefficient to be able to design for lower angles of attack. The profiles created here appear to be suitable for wind turbines, and provide an impressive increase in performance compared to traditional airfoils.Extra effort was put into making airfoils that were unaffected by roughness, air properties and Reynolds number, as stable performance in varying conditions are necessary for wind turbine blades. This was done by using adverse pressure gradients to control the point of transition.A slow stall was achieved by letting the pressure recovery distribution gradually approach the local ideal Stratford distribution when moving back over the airfoil. This caused the flow separate at the back first, and then the separation would grow gradually forward with increasing angle of attack.The inclusion of a separation ramp also worked very well together with the high-lift design, and allowed for an increased lift coefficient and more stable operation during the region of early stall.The most successful profile created appears to be the AR profile. It combines a diverged Stratford distribution with a separation ramp and a pressure spike at the nose to control transition. It has a wider range, stalls later and softer, and has a much more stable performance with varying conditions compared to the original HOG profile from NTNU. At the design point, the maximum performance is reduced only 5.9 % compared to the HOG. For higher and lower angles of attack, and increased values of roughness and turbulence, the AR has an all round higher performance than the HOG. It appears to be usable for wind turbines, and would increase the maximum airfoil performance by up to 40 % compared to commonly used NACA profiles. More good profiles were made, with varying thickness, stall and performance. Depending on the exact local requirements of an application, this report offers several interesting profiles to choose from. For instance, the D2 profile has round shape and over 16 % thickness, it has an even softer stall than the conventional wind turbine profiles, and would increase the maximum airfoil performance by up to ~34%. This profile would also be usable for upwind turbines.It was found that there is a big potential for manipulating the high-lift technology to give various shapes and performances. The usability of these profiles therefore appears to be wider than previously assumed.