The energy sector is a motor to speed up the economy development but is also a major pollutant. Rwanda, having about 60% of its total electricity production from imported fossil fuel (diesel generators), has adopted a strategy of energy diversification especially from renewable energy sources. Geothermal energy utilization in Rwanda is at the beginning stage and its development is ongoing, all efforts are made for electrical generation from geothermal energy in order to increase the installed capacity in Rwanda and to achieve the Millennium Development Goals objectives. Apart from electrical generation, geothermal energy can be used directly in thermal applications for various industrial or recreational purposes.   This study focuses on geothermal direct use in Rwanda. It is understandable that space heating is not an option in Rwanda because of the predominantly warm climate conditions, however, there are still many direct heating applications that can successfully be served by the existing geothermal fields. The current status of energy situation in Rwanda and the geothermal potential in the region have been examined. Many hot springs and volcanic areas having a feasible geothermal potential for direct applications are spread over the Northern province of Rwanda. Several possible geothermal energy projects are shortly discussed in the report, targeting mostly various drying processes. The specific focus of investigation has been the Gisenyi hot spring site, where temperature measurements were taken as well as the flow rate was evaluated in order to assess the applicability of a fish drying facility in Rubavu district near lake Kivu. Thermal calculations have been performed to estimate the heating energy required to dry 25 tons of fish per month from 80% down to 10% moisture content. The result shows that the available temperature and flow rate of the Gisenyi spring can easily cover the demand for fish drying even if the fishing industry doubles the production in the future. In addition, the parameters of the required heat exchanger were preliminary evaluated. A simplified economy analysis was attempted as well, resulting in an expected feedback period of 2.25 years.

Within this thesis work a strongly simplified yet complete, component-based numerical model for load analysis of a horizontal wind turbine is built up. The model is written in the open-source, object-orientated and equation-based modelling language Modelica and designed in a modular structure which allows integration in OneWind, a specialised Modelica library for components of wind power plants which is being built by Fraunhofer IWES. The model makes continuous use of three-dimensional mechanical elements of the Modelica Standard Library. It comprises all components of an onshore wind turbine including independent subcomponents such as rotor, drivetrain, generator, controls and tower, as well as different wind models. A main focus is put on energy conversion in the rotor. With the established model an analysis of expectable blade root forces in a 5MW turbine under extreme conditions is performed, which are modelled using two different certification load cases. Based on these results a rough preselection of an appropriate blade bearing is carried out.

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An energy calculation model for Swedish houses   that is fast, flexible and user-friendly has been developed within the   framework of this thesis.  The model   also provides a set of actions which may be investigated in the model based   on savings and payback period. Energy use in a house depends on the technical   conditions, such as building envelope and heating systems, which outdoor   climate the house is exposed to and who lives in the house. Energy use for a   house can be divided into heating, hot water and household electricity. There   are several methods to calculate the energy use of a house. This report   summarizes the methods that may be suitable for a fast and user-friendly   calculation model. Various energy efficiency measures as may be appropriate   for a house are described in terms of cost and savings perspectives. The   analytical model includes a model that calculates the use of household   electricity, based on the residents of the house. The household-electricity   model is based on raw data from a survey of 400 households conducted by the   Swedish Energy Agency. A sensitivity analysis has been made in the energy   calculation model, which gives a sensitivity of about 18 percent. Of the   total sensitivity more than half (10 points) consists of the sensitivity of   the indoor temperature and efficiency of heating systems.

The natural catastrophe at Fukushima Dai-ichi 2011 enlightened the nuclear community. This master thesis reveals the non-negligible risks regarding the short term storage of spent nuclear fuel. The thesis has also investigated the possibility of using natural circulation of air in a passive safety system to cool the spent nuclear fuel pools. The results where conclusive: The temperature difference between the heated air and ambient air is far too low for natural circulation of air to remove any significant amount of heat from the spent nuclear fuel pool in a worst case scenario. Air, as with any gas, has too low density and a specific heat too low to be able to remove the heat generated by spent nuclear fuel shortly after it has been removed from the reactor core. The author does not deny the possibility of slightly prolonging the boiling with other designs. The author does however suggest other possibilities to prolong cooling with the conclusion that large enough spent fuel pools would constitute the simplest solution.

The PWR PACTEL test facility was built in Lappeenranta (Finland) to gain experience in thermal-hydraulics behavior of vertical steam generators used by EPR (European Pressurized Water Reactor) during SBLOCA (Small Break Loss of Coolant Accident) transient, which involves natural circulation phenomenon. The benchmark, which consisted of blind and open part, offered a unique opportunity for code users to improve and test their knowledge and skills in developing the input deck models and performing calculations. For a purpose of this investigation, Royal Institute of Technology (KTH) has developed two TRACE code models. The main point of this thesis is to study TRACE code performance during SBLOCA transient and sensitivity of the developed TRACE models for the time and space convergence, which is very important for transients involving natural circulation phenomenon. Four different nodalizations coarse, inter-medium, fine and fine-sliced (space convergence), are designed for both designed models, which are calculated with different maximum time steps (time convergence). The results assessment was made by comparisons of the main parameters e.g.: Pressure of upper plenum, Inlet/outlet temperature of Core/SGs, Collapsed water level in the core, among others. In addition, discussion about vertical SGs performance during natural circulation phenomenon and conclusions for both, code users and developers, are provided.

The present Master thesis is concerned with forced convection heat transfer in laminar and turbulent flowwith nanofluids. Nanofluids are defined as a colloidal suspension of particles in a base fluid, where theparticles have a characteristic length of less than 100 nm. Experiments were conducted to determine thequalification of nanofluids for laminar and turbulent flow forced convection heat transfer. Theexperiments were conducted in two different devices: Firstly, a stainless steel pipe with an inner diameterof 3.7 mm, heated directly by a DC current in the pipe wall, and secondly, a tubular heat exchanger, whichthe fluid was cooled down in. The tested nanofluids were not only assessed considering Nu/Re, as it hasbeen found to be common in a short literature review, but also by taking into account the pressure drop indifferent ways. A way of considering pressure drop in non-dimensional quantities was introduced that hadnot been seen in literature. In some cases, an opposite assessment for the fluid could be found fromcomparing Nu/Re of base fluid and nanofluid and comparing h/Δp. Difficulties during validation of thetest rig had called for system improvement; an extensive error investigation was conducted on the test rigand the calculation. The error investigation resulted in changes concerning the calculation and the test rig.

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