Techno-economic evaluation of building energy refurbishment processes from a life cycle perspective

427 p.

Energy retrofits in social housing. Analysis of its thermal behaviour.

468 p.

Analysis and improvement of the envelope, heating and ventilation of a low energy building with district heating

In this thesis project, a building in Vegagatan 12, Gävle has been analysed in order to see why it does consume more energy than it was expected. This building is a low energy building certified by Miljöbyggnad and it should use less than 55kWh/m2 year and nowadays it is using 62.23 kWh/m2. To get the needed data, some information about the building has been gathered, some measurements have been done in the building and some calculations have been done with those measurements. Finally, some possible solutions have been offered to reduce the energy use of the building. Insulating the floor, the pipes and the walls, reducing the indoor temperature in winter... All of these changes need the help of environmentally friendly attitudes, which is a very important fact in low energy buildings.

Energy Audit for an Old Industrial Building in Gävle

(English)The Swedish industrial sector has overcome the oil crisis and has maintained the energy use constant even though the production has grown. This has been achieved thanks to the development of several energy policies, by the Swedish government, towards the 2020 goals. This thesis carries on this path and performs an energy audit for an old industrial building in Gävle (Sweden) in order to propose different energy efficiency measures to use less energy while maintaining the thermal comfort. The building is in quite a bad shape and some of the areas are unused making them a waste of money. By means of the invoices provided by different companies, the information from the staff and some measures that have been carried out in-situ, the energy balance has been calculated from where conclusions have been drawn. Although it is an industrial building, the study is not going to be focused in the industrial process but in the building’s envelope and support processes, since the unit combines both production and office areas. Therefore, the energy balance is divided in energy supplies (district heating, free heating and sun irradiation) and energy losses (transmission, ventilation hot tap water and infiltrations). The results show that the most important supply is that of the DH whereas the most important losses are the transmission and infiltration. Thus, the measures proposed are focused on the reduction of this relevant parameters. The most important measures are the renovation of the windows, heating systems valves and the ventilation. The glazing of the dwelling is old and some of it is broken accounting for quite a large amount of the losses. The radiator valves are not properly working and there does not exist any temperature control. Therefore the installation of thermostatic valves turns out to be a must. Moreover, some part of the building has no mechanical ventilation but conserves the ducts. These could be utilized if they are connected to the workshop’s ventilation which is capable of generating sufficient flow for the entire building. Finally, although other measures could also be carried out, the ones proposed appear to be the essential ones. A further analysis should be carried out in order to analyze the payback time or investment capability of the company so as to decide between one measure or another. A market study for possible new tenants for the unused parts of the building is also advisable.

Performance of an Ocean Energy Conversion System with DFIG Sensorless Control

The 2009/28/EC Directive requires Member States of the European Union to adopt a National Action Plan for Renewable Energy. In this context, the Basque Energy Board, EVE, is committed to research activities such as the Mutriku Oscillating Water Column plant, OWC. This is an experimental facility whose concept consists of a turbine located in a pneumatic energy collection chamber and a doubly fed induction generator that converts energy extracted by the turbine into a form that can be returned to the network. The turbo-generator control requires a precise knowledge of system parameters and of the rotor angular velocity in particular. Thus, to remove the rotor speed sensor implies a simplification of the hardware that is always convenient in rough working conditions. In this particular case, a Luenberger based observer is considered and the effectiveness of the proposed control is shown by numerical simulations. Comparing these results with those obtained using a traditional speed sensor, it is shown that the proposed solution provides better performance since it increases power extraction in the sense that it allows a more reliable and robust performance of the plant, which is even more relevant in a hostile environment as the ocean.

Modeling Innovative Power Take-Off Based on Double-Acting Hydraulic Cylinders Array for Wave Energy Conversion

One of the key systems of a Wave Energy Converter for extraction of wave energy is the Power Take-Off (PTO) device. This device transforms the mechanical energy of a moving body into electrical energy. This paper describes the model of an innovative PTO based on independently activated double-acting hydraulic cylinders array. The model has been developed using a simulation tool, based on a port-based approach to model hydraulics systems. The components and subsystems used in the model have been parameterized as real components and their values experimentally obtained from an existing prototype. In fact, the model takes into account most of the hydraulic losses of each component. The simulations show the flexibility to apply different restraining torques to the input movement depending on the geometrical configuration and the hydraulic cylinders on duty, easily modified by a control law. The combination of these two actions allows suitable flexibility to adapt the device to different sea states whilst optimizing the energy extraction. The model has been validated using a real test bench showing good correlations between simulation and experimental tests.

Collective dynamics of glass-forming polymers at intermediate length scales: a synergetic combination of neutron scattering, atomistic simulations and theoretical modelling

Qens/wins 2014 - 11th International Conference on Quasielastic Neutron Scattering and 6th International Workshop on Inelastic Neutron Spectrometers / editado por:Frick, B; Koza, MM; Boehm, M; Mutka, H