The aim of this study was to determine the level of environmental impact and primary energy resulting from demands placed on residential ventilation and heating systems; a conventional residential house built to the 2007 Norwegian building code with a standard heating system was compared against three technology scenarios used in a passive house of the equivalent size. Both houses have wooden framework and cladding and are projected by the Norwegian building company Norbohus. An economical evaluation of the heating systems was also done. The alternative heating option for the conventional house, Stord TEK 07, was based on current Norwegian energy consumption patterns; a combination of electricity and firewood is used to meet heating demand. This heating mix was also modeled as an option for the heating requirements of the passive house, named Stord Passive S1. Additionally, a solar collector system (Stord Passive S2) and an air-to-water heat pump (Stord Passive S3) were modeled for the passive house. Finally, a balanced mechanical ventilation system was evaluated for both buildings. The life-cycle assessment method used was the ReCiPe method and the electricity used in the operation phase was based on the Nordic electricity mix.The results of this study indicate that Stord TEK 07 has the largest emission output in relation to output of CO2-eq, presented in the impact category “Climate change”. From a life-cycle perspective, the heating system requirements of a Stord TEK 07 house are 47.5 and 45 percent higher than the renewable energy solutions of passive house scenarios S2 and S3, respectively. Total life-cycle primary energy requirements in the Stord TEK 07 house were almost twice that of the renewable solutions in the passive house. Using the Norwegian standard heating system of Stord TEK 07 in a passive house as was done in Stord Passive S1, also results in a large improvement; output of CO2-eq and use of primary energy was reduced by 34-35 percent. Stord TEK 07 has also the highest emission output in most of the other impact categories and the largest present value costs, when building constructing costs are excluded. The heat pump solution, Stord Passive S3, has the lowest impact in most categories; however, the solar collector system Stord Passive S2, had lower output of CO2-eq. Stord Passive S2 has also lower present value costs then the air-water heat pump Stord Passive S3.A balanced ventilation system with 80 percent heat recovery was studied for both the houses. The benefit of heat recovery is recognizable in all the impact categories considered. The energy consumption and potential harmful emissions resulting from the electrical energy used by fans during the life cycle far exceed the environmental impacts that result from manufacture and transportation of the ventilation unit. The study revealed that the heat-recovery system must have efficiency greater than 15 percent to achieve reduction concerning output of CO2-eq and use of primary energy for Stord TEK 07; this requirement increases to 42 percent in houses built to the passive house standard house, Stord Passive.

The main dynamic loads on a tidal turbine are due to the tidal current variation, turbulence, wave-current interaction and wake from the tower and upstream turbines. The design of the turbine is highly dependent on the dynamic loads acting on the turbine's blades and its structure. Cyclic loading and unloading of any material over a period of time will lead to fatigue and structural damage. In this work dimensioning loads for NTNU's 1 MW reference tidal turbine are calculated due to the vertical no-slip current velocity profile, wave-current interaction, the horizontal and vertical velocity component due to the waves, turbulence and the tidal wave. Based on mathematical models the dimensioning loads for the turbine are calculated with a Matlab code written for this work. The influence of each of the components causing a dynamic load on the tidal turbine blades is evaluated and analyzed with the rainflow counting algorithm, which can be used for fatigue analysis.Results from Matlab calculations are compared to experimental results in order to validate the Matlab code. In the comparison the trends are the same for calculation and experimental results, oscillating curves with the same period. It is noticed that in large waves the Matlab code predicts very well the dynamic loads in terms of mean and peak-to-peak values.For the thrust force and the shaft torque the horizontal component of the velocity due to the waves has the largest influence on the peak-to-peak values and the turbulence induces a high number of cycles. For the pitch moment as well the horizontal component due to the waves has the largest influence on the peak-to-peak values, but also the vertical component has a certain influence. For the pitch moment the consistently main oscillations inducing cyclic loading are due to the vertical no-slip current velocity profile. This is also the case for the yaw moment, but here the vertical wave component has the largest influence on the peak-to-peak values. For calculation with the tidal wave it is noticed that higher velocities gives higher maximum values. The Matlab code is a reliable and fast tool. Despite the simplifications done in the calculations, it calculates the dimensioning loads for a tidal turbine with a good accuracy.

This master's thesis is a continuation of previous theses written at ComputIT AS. It treats heat transfer to LNG pools boiling on water through two heat transfer models, LNGSIM1 and LNGSIM2. LNGSIM1 utilizes heat transfer correlations for pure liquids in combination with physical data of the mixture, while LNGSIM2 uses LNGSIM1 and a simple model for the concentration boundary layer. Both models are implemented in the CFD software Kameleon FireEx (KFX) and thereafter tested and validated against experimental data from the Burro test series. Comparisons with experimental data show that LNGSIM1 often produces correct trends in the downstream gas concentrations. The results are, however, often shifted in time, indicating that the heat transfer in the beginning of the spill is too low. LNGSIM2 is constructed to increase the heat transfer compared to LNGSIM1, hence vaporizing the LNG faster to better fit the experimental data in time. The choice of the constant CSIM2 in LNGSIM2 greatly affects the heat transfer, and it is found to fit experimental data best for 0.70 < CSIM2 < 0.80.An attempt to approximate LNG as pure methane produced erroneous results due to the heat flux remaining constant throughout the spill. Another attempted approximation was the use of a constant heat transfer coefficient. This produced very low heat fluxes towards the end of the spill, making it impossible for the gas concentrations to reach a zero value within the experimental time interval. The use of these simplifications are therefore not advised.A study of rapid phase transitions (RPT) is conducted using a simple criterion for when an RPT can occur. Comparison with a theoretical study gives promising results for describing when, where and why an RPT occur. This can be used to estimate when to release the pressure wave of an RPT.Investigations of the pool boiling correlations for pure liquids conclude that the way of calculating the transition boiling regime results in too high heat fluxes in that regime. To address this, a parameter study using LNGSIM1 and a factor Z is performed in order to reduce the transition boiling heat fluxes. The optimum values of Z are thereafter combined with the optimum values of CSIM2. Combining Z and CSIM2 reveals that most of the investigated values of Z overrides the wanted effect of CSIM2, hence warranting new approaches to reduce the overestimated transition boiling heat fluxes. Nevertheless, LNGSIM1 and LNGSIM2 with 0.70 < CSIM2 < 1.00 appear to be good alternatives to the current heat transfer model in KFX, since the heat transfer coefficient is continuously calculated based on compositions and boiling regimes, whereas the KFX model requires a constant heat transfer coefficient as input.

I september 2009 tok KLP Eiendom i bruk kontorbygget i Professor Brochs gate 2 (PB2) i Teknobyen i Trondheim. Denne bygningen har klimaskjerm og tekniske løsninger som tilsier langt lavere energibruk enn dagens forskriftskrav. Romoppvarmingen i PB2 er kun basert på fjernvarme, med gulvvarme i deler av 1. etasje og radiatorer i resten av bygget. Romkjøling gjøres kun via ventilasjonsanlegget med en kombinert kjølemaskin/varmepumpe tilkoblet kjøle-/varmebatteri i ventilasjonsaggregatene. Et annet mekanisk kjøleanlegg med tørrkjølere på tak dekker IT- og serverrom. Anlegg for snøsmelt dekker ca. 400m2 ved PB2 der fjernvarme også er energikilden.Ventilasjonen i bygget dekkes av 8 ventilasjonsaggregater der alle anleggene er behovstyrt etter tilstedeværelse eller CO2. Ventilasjonsvifter og VAV spjeld styres etter såkalte optimizersystemer med optimal styring av tilluftstrykk. Ventilasjonsluftoppvarming gjøres i sekvens der høyeffektiv roterende varmegjenvinner dekker første oppvarmingen, et kombinert varme- og kjølebatteri tilkoblet luft-vann varmepumpe tar videre oppvarming. Er ikke dette tilstrekkelig finnes et andre varmebatteri tilkoblet fjernvarme som tar resterende luftoppvarming. PB2 har et omfattende EOS og SD-anlegg med totalt 72 målere. Likevel finnes ikke måler på fjernvarmeforbruk til snøsmeltanlegget. Tilgjengelig energibruksdata i EOS database har til dels dårlig kvalitet med hele 23% av 2010 uten registrerte data. Dette er fordelt på både lange og kortvarige perioder. I tillegg viser flere av fjernvarmemålerne direkte feil forbruk i perioder med meget lavt forbruk.Spesifikk levert energi til PB2 var i 2010 på 115,5 kWh/m2år som etter energimerkeordningen gir energikarakter B. Dette forbruket er fordelt på 68,9 kWh/m2år elektrisitet og 46,6 kWh/m2år fjernvarme. Forbruket er høyere enn målsetningen på 94 kWh/m2år. I tillegg skal det her nevnes at bygningen ikke har vært fult utleid i 2010 slik at forbruket kan antas å øke ytterligere. På grunn av den dårlige kvaliteten på tilgjengelige energidata fra undermålerene ble det utført en korrigeringsprosess på disse dataene som bedret kvalitet på data med 20 %, likevel antas disse dataene å ha en feil på mellom 8 og 24% også etter korrigeringen. Ut fra disse dataene fantes spesifikk levert energi til romoppvarming til 27,7 kWh/m2år, ventilasjons oppvarming til 12 kWh/m2år, tappevann til 3,3 kWh/m2år, vifter og pumper til 7,4 kWh/m2år, belysning til 16,4 kWh/m2år, teknisk utstyr til 23,6 kWh/m2år samt kjøling til 9,4 kWh/m2år. Det er hovedsakelig romoppvarmingen som er betydelig høyere enn målsetning.Angående drivende faktorer for energibruk i PB2 er følgende konkludert: Tilstedeværelse driver elektrisitetsforbruk til belysning og teknisk utstyr, samt ventilasjonsvifter og tappevann. Utetemperaturen driver fjernvarmeforbruket til radiatorer, ventilasjonsaggregater samt gulvvarme. I tillegg er varmepumpeanlegg 35.01 påvirket av utetemperaturen med lavest forbruk rundt 12C, og økende ved høyere og lavere temperaturer. Brukeratferd og antall person som jobber i bygget har også stor innvirkning på energibruk til vifter, serverrom, utstyr og tappevann.Betraktninger av innetemperaturer på tre utvalgte kontorer i PB2 viser tilfredsstillende innetemperatur på alle tre kontorer i perioden. Variasjonen mellom hver av kontorene er til dels stor men dette antas å være på grunn av muligheten for individuell regulering av temperaturen på hver cellekontor. Likevel skal det nevnes at kontor 1 har en ugunstig temperaturfordeling i perioden med tanke på energibruk, der temperaturer er lavere i perioder med kjølebehov enn i perioder med varmebehov. Det er identifisert en del forhold ved PB2 som ikke er optimale løsninger. Det kan her nevnes lav utnytting av kondensatorvarme fra kjøleanlegg, unødvendig høyt gulvvarmeforbruk, unødvendig bruk av fjernvarme og varme fra varmepumpe i varmebatterier i ventilasjonsaggregater, samt relativt høyt energiforbruk utenfor driftstid til belysning og teknisk utstyr.Skulle PB2 blitt bygd med tanke på målsetning om nullutslipp vil tiltak som lavtemperatur varmeanlegg med akkumulatortanker tilkoblet solfanger og vann-vann varmepumpe kunne vært en aktuell løsning. I tillegg anbefales bruk av passiv kjøling primært og frikjøling med varmepumpebrønnene som varmesluk sekundært. Ventilasjonsluftoppvarming burde dekkes av høyeffektive roterende varmegjenvinnere primært, samt varmebatteri tilkoblet akkumulatortanker i varmeanlegget sekundært. Tilstedeværelse og dagslyskorrigert styring av høyeffektive lyskilder ville minimert forbruket til belysning.Skal nullutslippsbygg kunne bli en realitet i kalde klima som i Norge vil behovet for videreutvikling av eksisterende og nye løsninger være stort. Det kan her spesielt nevnes utvikling og mer kjennskap til høyeffektive varmegjenvinnere, forenklede lavtemperatur vannbårne systemer inkludert akkumulatortank, luftbåren oppvarming og frikjøling via ventilasjon, samt bruk av kulvert i hybride systemer for passiv forvarming/kjøling av ventilasjonsluft. Robuste og stabile styringssystemer er også helt essensielt her for å oppnå optimalt samspill mellom de ulike systemene i bygget. For å redusere behovet til elektrisitet til belysning og teknisk utstyr til et minimum er både meget energieffektivt utstyr, gode styringsprinsipper og en holdningsendring blant brukerne nødvendig.

This thesis presents two designs of tension-leg-platforms (TLP) support structures for the 10 MW reference wind turbine being developed by the Norwegian Research Centre for Offshore Wind Technology (NOWITECH). The designs result from iterative design processes which account for important design considerations such as performance requirements, natural frequencies and main cost drivers, and differ in their capability of providing stability to the wind turbine. TLP Towed is stable during towing and operation, whereas TLP Transported only provides stability when installed and is dependent on alternative transportation methods. The design processes are validated by investigating the influence from the various requirements and the sensitivity to wind turbine properties. The two resulting designs are compared and discussed in terms of cost competitive advantage. Fully coupled time-domain aero-hydro-servo-elastic models are established in FAST by using hydrodynamic computations from WAMIT, and the models are verified by comparisons to previous time-domain results and frequency-domain calculations. The natural frequencies of the FOWTs are obtained by model linearizations, and a discussion regarding overlap with wind turbine operational frequencies and wave excitation frequencies leads to modifications to the preliminary designs. A number of simulations with different wind and wave conditions are run and the TLP designs are compared based on displacements, upwind and downwind tether tensions, the nacelle's velocity and acceleration and extreme events. Resonant behavior, damping and instabilities are also discussed and suggestions for improvements to the designs are presented. The results presented in this thesis serve as guidance in the process of developing optimized TLP designs for an offshore wind turbine.

Combustion is by far the most commonly used technology for energy conversion. The analysis of entropy generation and exergy loss is normally used to optimize thermal energy technologies such as gas turbines. The loss of exergy in the combustor is the largest of all component losses in gas turbine systems. The exergy efficiency of gas turbine combustors is typically 20-30%. In recent years the focus on reduction of climate gas and pollutant emissions from combustion has been a driving factor for research on combustion efficiency. The emphasis on fuel economy and pollution reduction from combustion motivates a study of the exergy efficiency of a combustion process. A bulk exergy analysis of the combustor does not take into account the complexity of the combustion process. The spatial dimensions of the flame must be accounted for in order gain detailed information about the entropy generation. This motivates a study of the local entropy production in a flame and quantifying the mechanisms that reduce the exergetic efficiency. The entropy production in combustion is also believed to have an effect on the stability of the flame. As most combustors operate with turbulent flow the emphasis of this report is on turbulent combustion.The source of exergy destruction or irreversibility in combustion is generally attributed to four different mechanisms: chemical reaction, internal heat transfer, mass diffusion of species, and viscous dissipation. The irreversibilities from the first three sources have been computed for a turbulent hydrogen H2 jet diffusion flame using prescribed probability density functions and data from experiments. The contribution of each source of exergy destruction is locally quantifed in the flame. Two different modeling assumptions are made, one based on a fast chemistry assumption and the other based on curve fitted relations from experimental data. The second law efficiency of the flame was found to be 98.7% when assuming fast chemistry, and 76.0% when curve fits from experimental data where used.The contribution from viscous dissipation has in previous studies been found to be negligible, and in order to simplify the modeling of the turbulent flow its contribution to the total entropy production has not been studied in this report.

SIMPLE, SIMPLER, SIMPLEC and IDEAL are solution procedures originally developed for incompressible flows and staggered grids. For SIMPLE, SIMPLER and SIMPLEC, extensions for collocated grids and for treatment of flows at all speeds have already been proposed. For IDEAL, only an extension for collocated grids has been found, and an extension for treatment of flows at all speeds is proposed here. Extended versions of SIMPLE and SIMPLER are implemented in Brilliant, a multiphysics CFD-program developed by Petrell AS. These implemented algorithms are compared to the existing solution procedure in Brilliant, an extended version of the SIMPLEC algorithm. As expected, SIMPLE and SIMPLEC gave almost identical solutions for all the three presented test cases. The values given by the SIMPLER algorithm differed slightly from the values given by the two other algorithms. When simulating a shock tube, all three algorithms showed large deviations from the quasi-analytical solution in some regions of the shock tube. The SIMPLER algorithm spent the least CPU time for this simulation example, while SIMPLE and SIMPLEC spent less CPU time than SIMPLER when simulating methane flow in a pipe. Even though the CPU time was not registered for the last simulation example, a pressure relief pipe, it was noticed that the time consumption was much greater for the SIMPLER algorithm than for SIMPLE and SIMPLEC.

A dense gas released into the atmosphere will have a flow development that can be described by a large range of physical scales and quantities. An instantaneous release will slump towards the ground unaffcted by the wind, before it is gradually and increasingly diluted by the turbulence in the surrounding flow. Therefore, when the gas is far from the release point, its movement is determined by that of the wind.The wind's turbulence characteristics varies with the atmospheric stability. An unstably stratified boundary layer will have turbulence production by negative density gradients, regardless of free stream velocity. A stable stratification, however, requires a wind velocity and shear to produce turbulence. The wind profile's velocity and turbulence characteristics can be described by similarity models, which may further be used as initial and boundary conditions in a turbulence model.The ke~model is a second order turbulence closure that has proved succesful in describing several turbulent flow scenarios. The version of the model used in the software package Kameleon FireEx has here been tested for dense gas releases, with a focus on far field development. Wind modeling is an area where the standard k-[epsilon] model is known to have problems, as it gives an unrealistic, inhomogoneous flow field.Three alterations to the k-[epsilon] model were tested in the work on this thesis. The first was a model constant varying with the local turbulence parameters, the second was a modification to the turbulence Schmidt number and, finally, a correctional production was added to the transport equations for k and [epsilon]. Of the three approaches, the last one gave the most encouraging results.There are still problems left regarding the k-[epsilon] model's handling of buoyancy-affected diffusivity. The Schmidt number modification dampens the dense gas' ability to diffuse also in the lateral directions, not only in the vertical, an effect that should be investigated further.

Different concepts for Enhanced Geothermal Systems (EGS) are presented and evaluated according to their potential for medium to large scale power production in Norwegian conditions. Potential locations for geothermal energy in Norway are identified. A fractured EGS with multiple wells situated in a low to medium temperature granitic basement was found to be the concept best suited for medium to large scale power production in Norway. An Organic Rankine Cycle (ORC) is typically used as the heat conversion cycle in low to medium temperatures. The ORC yields a better thermal performance in these temperatures, compared to flash cycles and Stirling engines. It is also a mature technology and commercially available. Thermal efficiency of the ORC was found to decrease drastically when operated at lower than design temperature. A numerical model of a fractured EGS was developed using Matlab. The model was able to capture the long term thermal behavior of a EGS. Based on this model was a sensitivity analysis conducted in order to see how responsive the thermal output is to different parameters. Typical ranges of fractured EGS parameters was found in existing literature regarding EGS. Thermo physical properties, such as thermal conductivity and specific heat, are highly dependent on mineral composition and temperature. They can therefore vary several factors between sites. Typical fracture apertures were found to be between 0.2 mm to 3 mm, and dependent on local geological conditions. The thermal output from the fractured EGS was found to be highly sensitive to changes in parameters like fracture aperture, fracture length and fracture spacing. Geothermal energy is marginal at best, consequently is it vital to extract as much geothermal energy as possible. A typical fractured EGS is therefore designed with a temperature drop of about $10^0C-15^0C$. The result is that the system is highly sensitive to variations in reservoir parameters. It is therefore critical to obtain accurate estimates and models of the fractured reservoir, and to control the fracture development during stimulation and operation. A system consisting of a fractured EGS and ORC was found to be extremely sensitive to variations in geothermal temperature. A temperature decrease of 10% yielded a 25% decrease in net work output.In order to reduce the risk related to the uncertainty of the geothermal temperature over the life time of the EGS is it advisable to combine geothermal energy with an alternative energy source. A hybridization of geothermal energy and a waste combustion plant was found to yield a stable power output regardless of geothermal temperature, and also offered a higher thermal efficiency than a standalone ORC. Geothermal energy could either by used as pre-heat in the waste combustion cycle or a ORC bottoming cycle could be used.

In this paper theory on cylinder and wind turbine wakes have been studied, and experimental work on the wake behind a wind turbine have been carried out in the Fluids engineering laboratory at NTNU.The objective of this paper is to show and explain how the wake from the tower of a wind turbine develops and interacts with the rotor wake. It is desirable to study the wake for different operating conditions of the wind turbine to see how the wake development is affected. A summary of classical wake theory, aerodynamics and wind turbine wakes will be given. Measurements in the wake of a cylinder fitted with pressure taps for drag calculation will be compared to theory and used as a reference. Also, the wake behind the wind turbine tower with the blades taken off will be studied and compared to the tower wake found behind the operating wind turbine.For comparison, reference measurements were done in the wake behind a cylinder and behind the free standing wind turbine tower without blades. The drag coefficient obtained from pressure measurements on the cylinder surface were 1.077 and match the expected value of 1.2 fairly well. However, neither the shape nor the maximum velocity deficit measured in the wake fit the theoretical profile. Drag coefficients calculated from the momentum deficit across the wake were only in the range of 0.65, which is almost half of the expected, and the huge deviation from theory could not be explained. With values between 1.07 and 1.50 the measured drag coefficients in the wake of the tower alone were also not consistent with theory. The shape of the tower wake profile coincides better with theory than the cylinder wake, but the maximum velocity deficit is generally lower than predicted by theory. Difference in drag can be explained with blockage effect and the smaller velocity deficit may be attributed to the free stream flow over the top of the tower interfering with the wake downstream of the tower.Wake surveys behind the wind turbine were done at three operating conditions: Optimum tip speed ratio; low tip speed ratio, with power output half of output at best point operation; and high tip speed ratio, with power output half of output at best point operation. The increased turbulence level behind the rotor the flow seen by the tower is believed to creates a turbulent boundary layer which stays attached to the surface to a point further back on the tower, creating a narrower and weaker wake compared the free standing tower wake. Optimum turbine operation gives a stronger rotation of the wake doe to the higher torque on the blades compared to the two other cases. At high TSR the wake is more uniform, and the tower wake disappears faster than in the wake of the turbine operating at lower TSR. The Strouhal number found in all the wakes match well with theory and does not seem to be affected by the rotor wake except that the tower vortices dies out quicker.