This paper treats further development of the TEG injection process described in Bråthen (2007). An introduction to separation technology, conventional glycol regeneration and compact mixing is presented, as these are important parts of the alternative dehydration concept. Advantages, disadvantages and operational problems are pointed out, before the problems with the TEG injection process is described. Using hot stripping gas for regeneration of the TEG is one of the suggested improvements, but large glycol losses, large flow rates of stripping gas and oxidizing of glycol are found to be the consequences, thus making the alternative unfeasible. The only improvements used, are to use inline separators for the first separation stages and compact mixers for mixing of TEG and natural gas. A simulation model is developed using the simulation software HYSYS with the CPA EoS as fluid package. Both the absorption and the regeneration part of the process is modeled, and operational data from the Snøhvit LNG facility is used as reference. From simulations it is found that TEG injection requires about 50% more circulated TEG than conventional absorber dehydration to obtain the same water content in the dehydrated gas. The weight and volume of the absorption part of the process is however found to be considerably smaller than the operational process at the Kristin field in the Norwegian North Sea, thus partly compensating for the increased TEG circulation rate. Use of MEG and DEG instead of TEG for the injection concept is also simulated, but it is concluded that TEG is the best suited because of lower regeneration energy, lower absorbent loss and best dehydration performance for low to intermediate flow rates of stripping gas. MEG is found to be unsuited for dehydration because of very large losses of absorbent.

Abstract This dissertation has been produced during the spring semester of 2008 to serve to the requirements for the degree of “Master of Technology” at the Norwegian University of Science and Technology (NTNU). The thesis has been written at the department of Energy and Process Engineering, with supervision of Professor Helge I. Andersson from the Fluid Dynamics department. The thesis has the title “Computation of Impinging Gas Jets”, and aims to investigate the Impinging Jet Flow (IJF) problem presented in section[2] by means of Computational Fluid Dynamics (CFD). For the work of this thesis the commercially available program package of FLUENT 6.3, and Gambit 2.4 was used for all the simulation and geometry generation tasks. The specific IJF case treated in the thesis work, is the Single Round Nozzle (SRN ) IJF geometry explained in section[2.2] , and displayed in Figure 2.2 . The numerical simulations were carried out by means of 2D and 3D Reynolds Averaged Navier Stokes ( RANS) simulations , and Large Eddy Simulation (LES) with related theory described in the theory section[3]. The work with the simulations of this thesis can roughly be divided into two main components. Firstly there is the part comprising all tasks and operations involved in creating and running the simulations, about which relevant information is provided in section[4]. Secondly, there is the work involving all the tasks related to gathering, interpreting, and analyzing the yielded simulation results. These tasks and their results are mainly treated in sections[5 to 9]. Both numerical and experimental reference IJF cases were used in this thesis work. The reference cases were at first used to guide the beginning of the simulation effort (Figure 6.1). In the later stages of the thesis, the reference results were used to analyze and interpret the results of the thesis simulations. Overall the results from the RANS simulations of this thesis, are found to give good agreement with the reference simulations and experiments, within the limits of what can be expected from the RNG k-ε model which was used. The LES simulations on the other hand, proves to be far more demanding both computation wise, and in relation to issues concerning simulation preparations and setup. In addition the LES simulation is found to be outperformed by the RANS simulations in some regions of the IJF geometry. When analyzed, it is found that this is probably caused by an unfortunate combination of regions with low local mesh quality, and a quite mesh sensitive feature in the Sub Grid Scale model. Nevertheless the LES simulation is found to provide results of good agreement with experimental data in some of the most difficult regions to simulate on the IJF geometry. In this region the LES simulation is also found to outperform the RANS simulations.

In this work, a 23-1 designed experiment has been performed to evaluate the effect of selected operating conditions on PEMFC performance and durability. Relative humidity, clamping pressure and back pressure were studied at two levels for Gore MEAs and GDLs. Two replicated experiments were performed. An ON/OFF test cycle was used to accelerate degradation. Total duration of the tests, after a break in procedure suggested by Gore, was ten days. In addition to sampling of voltage and current response and ohmic resistance, effluents were manually sampled from both electrodes every 24 hours and analyzed. Experiments with low humidification levels showed inferior durability. The combination of high relative humidity (100 %), high clamping pressure (10 barg) and high back pressure (1.5barg) result in the best performance and the lowest degradation rate. Results indicate that relative humidity is important both for performance and durability. Generally, fluoride emission rates (FER) showed an increasing trend with time. Higher rates were observed at the cathode. For the experiment with low relative humidity (25 %), low clamping pressure (5 barg) and high back pressure (1.5 barg) FER was significantly higher compared to the other experiments. For all tests the sulfur emission rates (SER) are initial high. Rates are higher at the anode. For the experiment with high relative humidity, low clamping pressure and no back pressure, the SER was significantly higher than for the other experiments. The sustained high levels of sulfur are probably a result of sulfuric acid residue from production of the MEA and/or GDL. High humidification of gases appears to more effectively wash out the sulfur.

Security in Mobile ad-hoc networks (MANETs) is difficult because of its operating environment and its lack of a central control unit, making classical security measures inapplicable. MIDAS is a project funded by the European Commission which creates a "Middleware platform for developing and deploying advanced mobile services". It is important for MIDAS to find a middle ground where it provides reasonable security, while using little extra processing power and battery and remains easy to use. In this thesis we identify the vulnerabilities and security measures needed to secure MIDAS, while preserving usability. We approach this problem by analysing the MIDAS design and find similarities to other known systems. From the analysis we identify threats and ethical issues, and suggest security mechanisms that solve MIDAS specific problems. The resulting security mechanisms are described in detail and tied together to create four main configurations with increasing levels of security. The configurations can then be used by MIDAS developers to implement security in a consistent way. The results are specific to MIDAS, but issues, requirements and security building blocks can be used by other projects for applicable MANET problems.

Coal is the most common fossil resource for power production worldwide and generates 40% of the worlds total electricity production. Even though coal is considered a pollutive resource, the great amounts and the increasing power demand leads to extensive use even in new developed power plants. To cover the world's future energy demand and at the same time limit our effect on global warming, coal fired power plants with CO2 capture is probably a necessity. An Integrated Gasification Combined Cycle (IGCC) Power Plant is a utilization of coal which gives incentives for CO2 capture. Coal is partially combusted in a reaction with steam and pure oxygen. The oxygen is produced in an air separation process and the steam is generated in the Power Island. Out of the gasifier comes a mixture of mainly H2 and CO. In a shift reactor the CO and additional steam are converted to CO2 and more H2. Carbon dioxide is separated from the hydrogen in a physical absorption process and compressed for storage. Hydrogen diluted with nitrogen from the air separation process is used as fuel in a combined cycle similar to NGCC. A complete IGCC Power Plant is described in this report. The air separation unit is modeled as a Linde two column process. Ambient air is compressed and cooled to dew point before it is separated into oxygen and nitrogen in a cryogenic distillation process. Out of the island oxygen is at a purity level of 95.6% and the nitrogen has a purity of 99.6%. The production cost of oxygen is 0.238 kWh per kilogram of oxygen delivered at 25°C and 1.4bar. The oxygen is then compressed to a gasification pressure of 42bar. In the gasification unit the oxygen together with steam is used to gasify the coal. On molar basis the coal composition is 73.5% C, 22.8% H2, 3.1% O2, 0.3% N2 and 0.3% S. The gasification temperature is at 1571°C and out of the unit comes syngas consisting of 66.9% CO, 31.1% H2, 1.4% H2O, 0.3% N2, 0.2% H2S and 0.1% CO2. The syngas is cooled and fed to a water gas shift reactor. Here the carbon monoxide is reacted with steam forming carbon dioxide and additional hydrogen. The gas composition of the gas out of the shift reactor is on dry basis 58.2% H2, 39.0% CO2, 2.4% CO, 0.2% N2 and 0.1% H2S. Both the gasification process and shift reactor is exothermal and there is no need of external heating. This leads to an exothermal heat loss, but parts of this heat is recovered. The gasifier has a Cold Gas Efficiency (CGE) of 84.0%. With a partial pressure of CO2 at 15.7 bar the carbon dioxide is easily removed by physical absorption. After separation the solvent is regenerated by expansion and CO2 is pressurized to 110bar to be stored. This process is not modeled, but for the scrubbing part an energy consumption of 0.08kWh per kilogram CO2 removed is assumed. For the compression of CO2, it is calculated with an energy consumption of 0.11kWh per kilogram CO2 removed. Removal of H2S and other pollutive unwanted substances is also removed in the CO2 scrubber. Between the CO2 removal and the combustion chamber is the H2 rich fuel gas is diluted with nitrogen from the air separation unit. This is done to increase the mass flow through the turbine. The amount of nitrogen available is decided by the amount of oxygen produced to the gasification process. Almost all the nitrogen produced may be utilized as diluter except from a few percent used in the coal feeding procedure to the gasifier. The diluted fuel gas has a composition of 50.4% H2, 46.1% N2, 2.1% CO and 1.4% CO2. In the Power Island a combined cycle with a gas turbine able to handle large H2 amounts is used. The use of steam in the gasifier and shift reactor are integrated in the heat recovery steam generator (HRSG) in the steam cycle. The heat removed from the syngas cooler is also recovered in the HRSG. The overall efficiency of the IGCC plant modeled is 36.8%. This includes oxygen and nitrogen production and compression, production of high pressure steam used in the Gasification Island, coal feeding costs, CO2 removal and compression and pressure losses through the processes. Other losses are not implemented and will probably reduce the efficiency.

There are two main ways of measuring particle emission from wood combustion. Firstly, particles can be sampled directly in the chimney. Secondly, a dilution tunnel can be used, thus cooling the flue gases parallel to diluting. The purpose of this work is to investigate the differences between both measurements and establish which is the best method to measure particle emission from wood combustion. The approach is to perform particle emission measurements in the chimney and in a dilution tunnel simultaneously during the combustion of wood in a small-scale appliance. Moreover, Flame Ionization Analysis will be carried out to understand the contribution of condensed organic compounds to the total particulate matter emission. The particle emission measured in the dilution tunnel was between 5 and 12 times higher than in the chimney. The more unfavourable combustion conditions, the larger the difference between both measurements was seen. The results also show a factor of about 2,5 between both particle emission measured in the stack and Total Hydrocarbon content in the flue gas and particle emission measured in the dilution tunnel, indicating that about 35 % of the hydrocarbons measured in the stack with the Flame Ionization Detector condense along the dilution tunnel accounting for approximately 85 % of the total particle emission found at this location.

In 2003 the European Commission introduced the Directive 2003/54/EC and Regulation 1228/2003/EC which increased the focus on the liberalization of the European electricity market. The international electricity trade has increased and created new challenges related to cross-border transmission and compensation mechanisms. The focus of the report has been to discuss the development of the electricity market in Europe, and the status of international exchange. The report also discusses the concept of cross-border trade and transit, and investigates a proposed ITC model and whether correct investment incentives are given. Price data from the main power exchanges in Europe indicate that the market is experiencing increasingly integration and efficiency. There has also been a trend towards market based congestion management methods. Regional markets have successfully developed in Spain and Portugal (the Iberian market) and between France, Belgium and The Netherlands (the Trilateral Market Coupling, TLC). Further plans for regional coupling are also underway (see chapter 5. The most common definition of transit is the one adopted by ETSO (Association of European Transmission System Operators), where transit is defined as the minimum between exports and imports. This definition could create opportunities for market participants to manipulate transit income (discussed in chapter 5.3). The Inter-TSO compensation (ITC) model used in this report is based on the With-and-Without transit algorithm. The model only focuses on costs and load flow, and do not include market incentives or evaluation of benefits. The model bases the compensation calculation on the transit term, which can lead to misguided identification of network responsibility. Two scenarios were compared with a base case scenario in order to identify possible investment incentives. The first scenario included a situation where one of the cross-border lines in the network was constrained. Results from this simulation indicate that the transmission system operators involved would experience increased ITC payment, and therefore not receive investment incentives. The TSOs involved would benefit from the bottleneck in form of increased revenue (assuming Cost-Of-Service regulation). In the second scenario an extra cross-border line was implemented, and the situation was compared to the base case. The results from this simulation show that the TSOs involved would receive a positive effect in form of reduced ITC cost. The ITC mechanism would in this case be in line with the European Commission’s Regulation 1228/2003/EC, and give the involved TSOs correct investment incentives. The lack of correlated results in these two cases indicates that the ITC mechanism (in this case modeled by the WWT algorithm) cannot be regarded as relevant from an investment incentive perspective (more information found in chapter 7.3).

In user-centered design the users play an important role in the development process. The users are included in near every step of the process and it is often a problem that they do not have the necessary overview of a technology intended used in the end system. They do not need to know all the technical details, but they do need to know what possibilities the technology makes available. To do this one needs to introduce the users to the technical possibilities, but how does one do this? We had two suggestions as to how this could be done. We proposed introducing the possibilities through abstract concepts not tied to the users' domain. The reason being we did not want to lock the users to concrete ideas given by us, but let them use the abstract concepts to come up with ideas in their own domain. The other suggestion was giving the users hands-on experience with the concepts. Human knowledge is usually derived from experience, and we believe touching and trying out the possibilities of a technology would also be helpful in this kind of setting. To test whether hands-on experience and abstract concepts is valuable in an introduction of new technologies we conducted an experiment involving two workshops. Both workshops got a theoretical presentation of the abstract concepts, while one workshop let the participants explore a demonstrator made by us giving them hands-on experience. These workshops were then analyzed both qualitatively and quantitatively. The quantitative analysis showed that the workshop incorporating hands-on experience generated more unique ideas and also ideas in more categories than the other workshop. However due to low comparability between the groups due to factors such as prior experience with the technologies and current work situation, we do not give these findings much significance. Through the qualitative analysis we see that hands-on experience can be valuable. For one participant in particular, the hands-on experience was very valuable. In addition we found it valuable as a motivational exercise in a user-centered design process. The abstract concepts were analyzed qualitatively, and these were not as valuable as hoped. The users found it hard to map the abstract concepts to their domain. We now see the value of examples closer to the users' domain, but they should be kept as small building blocks for the users to combine to solve larger problems. We end this paper with a suggested approach to introducing new technological possibilities. We still recommend using the abstract concepts, but taking care to exemplify them through many small domain-specific examples. Hands-on experience is recommended if it is feasible to do this within the domain. We also recommend for time to mature and revisiting the participant after they've been back in their domain for a while.

Experimental studies as well as simulations have been performed on the Back-to-Back starting schemes low frequency-, partial frequency-, and soft -start-up. A Back-to-Back configuration of two synchronous machines has been established in the laboratory, upon which parameter estimation and start-up experiments have been performed. Extensive parameter estimation was conducted in order to replicate the laboratory machines in the simulation model as accurately as possible. This was done in order to verify the validity of the simulation model. Studies into the effects of inductance interconnecting the machines were made in the laboratory and in the simulation model. Effects of resistance and inertia were studied in the simulation model. It is concluded that the simulation model appears to be as reliable as is its input parameters. Discrepancies were found in line voltages, due to faulty implementation of field current replication. Full scale simulations using Motorformer parameters were performed in the simulation model, featuring low frequency- and soft -staring. The effects of an interconnecting cable were studied. It is concluded that low frequency starting appears to be most reliable and least violent starting method. However, it might be limited by the availability of a turbine. This is not the case for soft starting, which has a lower starting capability and is more violent to the motor damper- and field windings. Low frequency startig is the recommended starting method of the ones studied. Dynamic short circuit simulations were done on a fixed speed LNG-facility. The fixed speed alternative appears to be more stable when responding to a short circuit. This is because the motors contribute to upholding the voltage during a fault by delivering reactive power to the short circuit, and because the motors do not loose all torque as is the case for LCI drives when the voltage dip exceeds 20$%$. Further work is needed in up-scaling the experiments. A sophisticated simulation model should be established and its validity tested on the up-scaled experiments. Preliminary custom design of machines should be initiated depending on what starting scheme is chosen. Custom machine parameters should then be used in full scale simulation using the more sophisticated model.

As part of the energy recovery part of the ROMA (Resource Optimization and recovery in the Materials industry) project, a laboratory prototype power production system is being built and completed in 2009. The laboratory prototype is based on a new technology for power production from low to medium temperature heat sources (the off gas from electrolysis cells in the aluminum industry) where CO2 is used as a working medium in a trans-critical Rankine cycle. The laboratory rig consists of the power cycle with a prototype expander as the core unit, an air loop to provide the heat, and an ethylene glycol loop to provide condensation of the working fluid in the power cycle. As a preparation to the assembling and instrumentation of the prototype rig, a simulation and an uncertainty analysis were conducted for the prototype rig in the autumn of 2008. This report focuses on the continuation of that work by an experimental investigation of the individual loops and the components of the prototype rig. The emphasis of this investigation has been put on the air loop and the expander unit of the power cycle. This is basically because these are of great importance to the performance of the power production prototype rig. The air loop was thoroughly tested, and from the investigations it was discovered that there was an unfavorable temperature distribution of the air going into the air-to-CO2 heat exchanger. This is the heat exchanger where heat is provided to the power cycle. The source for this temperature maldistribution was identified, and solutions were investigated to improve on the problem without results. The reduced performance of the air loop was incorporated in a new simulation of the power cycle in order to quantify the consequences for the optimization of the power cycle. The simulation was carried out for warm air temperature of 80 °C. The new calculations showed a reduction in maximum net work output of 27 % compared to the original simulation. The optimal conditions for the power cycle were also changed as a consequence of the reduced air loop performance. The investigation of the expander unit revealed that the expander isentropic efficiency was a strong function of the pressure difference across the expander, and a weak function of the expander inlet pressure. It also revealed that overall the isentropic efficiency was much less than the value of 80 % which was used in the original simulation. A new simulation of the power cycle was carried out where the expander isentropic efficiency was incorporated as a function of the pressure difference across the expander. This function was based on the data from the expander testing. The simulation showed a reduction in maximum net work output from 225 W to about 60 W, for warm air temperature of 80 °C. The new expander characteristics also affected the optimization of the power cycle. The simulation results and the results from the prototype investigation will be important in the optimization and control procedures of the assembled prototype power production system.