<p>In this master thesis the wake of a hydrofoil have been investigated using PIV. The main goal of this work have been to investigate how vortex generators can create mixing and smoothing of the velocity deficit in hydrofoil wakes. This study is motivated by the rotor stator interactions in Francis turbines with the idea that smoother wakes from the stator can reduce the forces on the rotor and hence increase the life span of Francis turbines. A literature survey of foil theory and wake flows have been carried out. This survey motivated the use of a normalization of the velocity in the wake. Experimental work was carried out at the water tunnel facility at Saint Anthony Falls Laboratory at the University of Minnesota. Tests were performed on a NACA0015 hydrofoil with four different vortex generator configurations, for a range of different angles of attack and velocities. Lift and drag forces on the hydrofoil was measured using a force balance. Because the drag measurement had poor accuracy, it could not be used to compare the different vortex generator configurations in terms of drag. As a result the drag was investigated using the velocity deficit in the wakes. The quality of this analysis have been discussed with the use of CFD. CFD is also used to gain insight into how pressure and velocity is distributed in the water tunnel. The PIV images from the tests have been processed into vector fields with the commercial PIV software DaVis7. For analyzing the PIV data further, different post-processing schemes in DaVis7 was investigated together with programs developed in Matlab. In order to compare the wakes resulting from the use of different vortex generators with measurable quantities, the use of a standard wake profile has been investigated. The standard wake profile is symmetrical and could hence only describe wake measurements done at an angle of attack close to $0^{circ}$. Furthermore it turned out that most vortex generators resulted in a wake that could not be described with the standard wake profile. The vortex generator configurations that gave the best smoothing of the hydrofoil wake for the investigated operation points turned out to be a $1unit{mm}$ V-shaped vortex generator. This vortex generator also caused less drag than than the other vortex generators tested. However, the use of vortex generators resulted in increased drag compared to the plain hydrofoil for the analyzed operating points. The velocity deficit in the wake is shown to get so well smoothed out for some tested cases that it is considered worth while to continue the investigation on vortex generators capability to increase the lifespan of Francis turbines.</p>

<p>Compression and purification processes are considered for CO2 coming from the three different capture methods. By using the simulation tool Pro/II these processes are further optimized.</p>

<p>This Master thesis analyzes the optimal use of the hydro resources in Albania. Albania is a country totally dependent on hydro power. More than 90% of the electricity today comes from hydro power, mainly from the Drin river system. There are three hydro power plants located in the Drin river system: Fierze (500 MW), Koman (600 MW) and Vau Dejes (250 MW). Only one third of Albania’s hydro power potential is today exploited, and Albania is a net importer of energy. The main objective with this study is to analyze the utilization of the hydro resources in Albania and look at potential improvements in the short term (next years) and the long term (after Albania joins the regional market). Two scenarios were worked out. The first scenario focuses on the present market situation in Albania. Investigations are done through simulations with the EOPS model. The results were analyzed and compared with historical data to discover potential upgrades of the utilization of water in Fierze, Koman and Vau Dejes. In the simulations the production in Drin river system is increased with 1.3 TWh in an average year. Fierze power plant has the highest potential with 25% more production in the simulation than what is shown through historical data. Under the process towards a liberalized market, the optimizing problem regarding the production planning will change. Today the main task is cost minimization given an expected demand. In a free market it will be profit maximizing given a price expectation. A second scenario dealing with the potential market situation in Albania in 2020 was worked out. In addition to the new market situation four new power plants were included in the EOPS model. With new plants in the Drin and a functioning market it is possible to achieve 1 TWh more production during an average year compared with the simulation for the present market situation in Albania. If the implementation of the market, new power plants and transmission lines are accomplished, the supply situation in Albania will improve substantially through more secure power delivery. However a participation in a regional market forces the production company to plan each day like the participants in the Nordic market, both in the long and short the term, to be able to exploit the technical and financial opportunities and develop their country.</p>

<p>Wet gas compression technology is of great value to the oil and gas industry for boosting of unprocessed well stream and to reduce investment costs related to equipment and personnel. The growing interest in wet gas compression leads to a general request for accurate performance calculation procedures and proper measurement techniques for multiphase flow metering in compressors. An impeller rig for examination of single-phase and multiphase performance and aerodynamic stability is under construction at the test facility at NTNU. The construction of the compressor rig is behind time due to late deliveries of the compressor components and instrumentation. The performance calculations are therefore based upon one compressor test conducted with dry gas at part-load. The thermodynamic equation of state for ambient air is verified to be consistent with the ideal gas law in the compressor pressure and temperature range. The calculated polytropic performance is calculated with ideal gas assumptions and compared to values estimated by PRO/II. By analyzing the results the sensitivity of the calculation procedures is identified and the suitability for the ideal polytropic performance calculations is validated for the actual compressor test and operating range. A sensitivity analysis is conducted in order to determine the effect of measurement uncertainties on performance calculations. Due to the low pressures involved for the compressor test, the performance calculation procedures are highly sensitive to uncertainties in the pressure measurements. Uncertainties in the temperature measurements will only slightly influence the polytropic head, but have great influence on the polytropic efficiency. The efficiency and operating range of a compressor are constrained by aerodynamic instabilities. This thesis describes the different flow phenomena associated with compressor instability and presents recommendations for suitable instrumentation and measuring techniques. Various visualization techniques are in addition evaluated to determine the suitability for multiphase compressors. Dynamic pressure transducers installed in the inlet and discharge piping are recommended for detection of pressure pulsation throughout the compressor system. Unsteady internal pressure measurements can be obtained from circumferentially distributed pressure transducers at various locations within the compressor components. Vibration probes installed at each end of the rotor are recommended for the vibration measurements. By analyzing the frequency spectrum for the pressure fluctuation and radial vibrations one can identify the type of instability phenomenon that occur. Laser measurement techniques are recommended for the flow visualization in order to obtain information on the main features of the multiphase flow field.</p>

<p>Gas turbines in offshore power systems contribute to about 23% of Norway’s total emissions of CO2. One method for reducing these emissions could be the addition of wind turbines to the offshore utility grids. Power from shore is another alternative, but has been proven costly due to long cables and expensive HVDC converter stations. In this thesis work, the behaviours of different wind turbine technologies during transient fluctuations in an offshore utility grid have been studied. For this purpose, a dynamic model for an offshore oil platform was developed. Models of squirrel cage and doubly fed induction generator based turbines were developed as well. None of the modelled generators experienced problems with the disturbances caused by the electromechanical transient fluctuations. Based on the behaviour of the DFIG’s grid side converter, it is believed that the result would be the same for a wind turbine with full frequency conversion. Variable speed wind turbines are expected to remain controllable throughout electromechanical transient fluctuations such as for the simulated case. However, the controllers, converters and equipment have to be designed while bearing these fluctuations in mind. The controllability of the variable speed wind turbines could be used to contribute to voltage control by production and consumption of reactive power. A controller scheme with the purpose of stabilising the voltage at the gas turbine generators’ terminal was developed, but had low impacts on the power system behaviour. A stator flux feed forward term for the speed controller was developed. The term stabilised the power output of the doubly fed induction generator. However, the impact on the power system’s frequency response was minimal, and there is probably no material value of such an addition to the control loop.</p>

The panel bed filter (PBF) is a granular filter patented by A. M. Squires in the late sixties. PBFs consist of louvers with stationary, granular beds. Dust is deposited in the top layers and on the bed surface when gas flows through. PBFs are resistant to high temperatures, variations in the gas flow and hot particles. The filter is cleaned by releasing a pressure pulse in the opposite direction of the bulk flow (a puff back pulse). A new louver geometry patented by A. M. Squires is the filter tray louvers. The new design is believed to reduce the pressure drop and the number of louvers, and to make the filter more compact. We have designed and built a laboratory scale PBF with filter tray louvers based on the patent. Experiments with the prototype show that the new louver can be cleaned with a puff back pulse. A PBF system for a hypothetical biomass combustion plant has been designed. The heat from the flue gas will be used for district heating. The proposed PBF system design consists of double-sided modules with 46 filter tray louvers on top of each other. Five modules are mounted together in module columns, sharing the same clean gas duct and puff back pipe. The granular medium chosen is Sintered Bauxite 20/40 (SB). The module columns are placed in an enveloping house. SB and dust fall into bins in the bottom of the enveloping house during puff back cleaning. A vacuum pneumatic conveying system brings the dust and SB to the top of the filter. Dust and SB are separated in a sieve. Dust is deposited, and SB is transported back to the modules. NTNU is currently involved in the BioSOFC project. The objective of this project is to increase efficiency in energy production from biomass by using producer gas from a biomass gasification plant in a Solid Oxide Fuel Cell. Field tests will be performed at a plant in Güssing, Austria. A PBF will be used for gas filtration. The operating temperature will be 500 °C to avoid tar condensation. We have performed heating experiments on the BioSOFC filter system. The results were not satisfactory, as the temperature in the filter ranged from 384 to 625 °C. The filter system was due to be shipped, and new tests could not be performed. This work proposes that modifications to the heating cable circuits are made, and new heating tests are performed before the field testing.

It is clear that society worldwide must immediately begin to mitigate its environmental damage in order to sustain life on Earth. In this regard, researchers all over the global are exploring new energy efficient alternatives to power everything from cars to cell phones. The following brief describes research conducted on Microbial Fuel Cells (MFC) and its ability to utilize bacteria to produce electricity from biological masses for low energy consumer products While structurally the MFC is very similar to a Conventional Fuel Cell, the two systems have inherent differences that change the reactions, inputs and energy output. Currently, we have found MFC to produce only a fraction of the power (~1A/cm2 vs ~1mA/ cm2 ) produced by a conventional CFC, however, its versatility keeps MFCs as a promising fuel source potential. A Multi-disciplinary University Research Initiative has organized to examine and test the potential of MFC. The team is divided into three teams based on industry domains and expertise: microbiology, chemistry and electrochemistry, and engineering and modeling. The followin master thesis research was part of the engineering and modeling team lead by Professor Ronney XX. The goal of our team was to construct a first version of a computational model simulating the MFC system. The computational model is be based on combustion kinetics and a diffusion-reaction system theories, and is manipulated to immatate a biological system that can maximize its energy output. The model has been constructed in Fluent. Starting out with a 1D model, and consequently moved on to a 2D version. The final model is a diffusion-reaction system with 6 different species, a 3-step reaction, including a bacterial anodic oxidation, a cathodic reduction, and a possibility of taking into account a counteracting anodic reaction for oxygen crossover through the membrane. While the model has been proven to correlate well with lab tested experimental results, the team will continue to identify conditions to maximize the MFC’s efficiency and energy output.

There were three main objectives in this thesis. The first objective was to find the utility patent of a building at the Norwegian University of Science &amp; Technology. This was performed using logged data from infrared motion sensor readings over a period of twenty nine days. Main finding suggests an average presence during working hours (8 AM – 3 PM) of 57 %. A utility patent developed and based on the twenty nine days of logged data shows the expected occupancy at any time during a normal working day. The second objective, sensor accuracy, is estimated based on comparison of logged data and manual registrations over two days. This information formed a basis for discussion of how well the infrared motion sensors performed. In this building, the conclusion is that ceiling mounted sensors perform better than wall mounted sensors. The third objective is to develop a computer model of the building and simulate it with two different ventilation systems. One simulation is of a CAV system, while the other is a VAV system that is able to adjust its minimum OA requirements according to the registered utility patent found in the first objective of the thesis. The computer model was developed with DOE2. The VAV system proved to perform far more efficient than the CAV system for a one year simulation. The hot water demand was reduced by 51%, cold water by 57%, and fan energy dropped by 76%.

This study investigates the behaviour of a vertically distributed source of buoyancy on the vertical stratification in a ventilated space, an important factor for determining indoor comfort when using displacement ventilation. A new theory describing the behaviour of this buoyancy source in a ventilated space was presented previous to this work, but experimental results were required in order to validate the theoretical and numerical modelling. The behaviour of this source of buoyancy on the stratification in a ventilated space is studied for a mechanically ventilated at steady-state and for a linearly stratified environment using salt water in a water scale model. The stratifications were measured using a traversing conductivity probe and then compared to theoretical predictions by numerically solving the plume equations for the new theory in Fortran. High quality measurements were produced, showing excellent repeatability for stratification measurements at steady-state with deviations of less than 1 %. Moreover, the linear stratifications had linear best fits up to R2 = 0.999 by using the double-bucket method. The theoretical predictions of the influence of the vertically distributed source correlate quantitatively with the mechanically ventilated experiments, showing good agreement to the strength of the ambient stratification, the position of the first front and the ventilation flow rate. The experimental results for the determination of the height of a horizontal intrusion of fluid into the linearly stratified environment were severely affected by the occurrence of gravity current at the ceiling of the ventilated space and comparisons to the new theory was not successful because of this. A two-layer stratification is observed where the upper layer had a weakly stratified density profile, instead of the multi-layer stratification predicted by previous researchers in their theoretical model. This discrepancy is due to smoothing and vertical turbulent mixing in the water scale model. It is recommended that the characteristic of the membrane that is used in the water scale model is investigated in relation to the gravity currents for future research.

It has been proposed to supply heat and power to Snøhvit Train II (STII) from onsite heat generation based on natural gas and power import from the power grid. Without carbon capture and storage, greenhouse gas (GHG) emissions from the combustion of natural gas in furnaces make a considerable contribution to the global warming potential (GWP) of this energy system. Depending on the interpretation of marginal power consumption, the power import also contributes to and increases this system’s GWP. A recent SINTEF report claimed that European CO2 emissions are reduced with additional renewable power production in Norway, and it has been suggested to invest in wind power in order to completely offset the GWP of the STII energy system. This paper provides investment analyses for the proposed energy system. A scenario approach was used, with six different scenarios covering two dimensions. The first dimension is the origin of the grid power, with three different interpretations of marginal power representing Cases A, B and C. The other dimension is the STII train size, with two different sizes being analyzed, namely 50 % and 70 % of the Snøhvit Train I design capacity. The proposed energy system was also analyzed with respect to security of supply. Improved reliability and transmission capacity, together with a stable, positive power balance, make a good foundation for security of power supply. The power demand of the two train sizes was estimated to 101 MW and 141 MW, with corresponding heat demand of 94 MW and 131 MW. These estimates were based on a combination of HYSYS simulations and data provided by StatoilHydro (SH), and provided input for both the GWP analysis and the investment analysis. The GWP impact of each scenario determined the share of power import from the grid that would have to be replaced by energy harnessed from wind. The applied capacity factor was 39.6 %, and the rated wind power requirement for the six different scenarios ranged from 101 MW for the A.50 scenario to 257 MW for the C.70 scenario. The break even (BE) energy prices were calculated for each of the six scenarios analyzed. If the power consumption is based solely on power import, with zero StatoilHydro (SH) share of grid reinforcements and no SH development of wind power, the BE power price would be 466 NOK/MWh. The inclusion of wind power development as part of the investment will increase the BE power price by up to 33 NOK/MWh. The additional SH share of grid reinforcement will add 86 NOK/MWh for the 50 % STII or 62 NOK/MWh for the 70 % STII. It was shown that the investment in wind power to offset the GWP of the energy system might also be a reasonable way of hedging against increases in the market price of electricity. It was found that the share of STII power demand that is provided by wind power is one of the parameters that have the least influence on the project’s net present value (NPV). A high share of wind power is an inexpensive investment in improving reputation and predictability of energy price.