Luminescent solar concentrators (LSC’s) are promising candidates for reducing the cost of solar power generation. Conventional LSC’s are slab waveguides coated or doped with luminescence materials for absorption and guiding of light to the slab edges in order to convert optical energy into electricity via attached photovoltaic (PV) cells. Exploiting the advantages of optical fiber production, a fiber LSC (FLSC) is presented in this thesis, in which the waveguide is a polymeric optical fiber. A hybrid fiber structure is proposed for an efficient two-stage concentration of incident light, first into a small doped core using a cylindrical micro-lens that extends along the fiber, and second to the fiber ends by guiding the fluoresced light from the active dopants. Flexible sheets are assembled with fibers that can be bundled and attached to small-area PV cells. Small dimensions and directional guiding of the fibers allow for approximately one order of magnitude geometrical gain improvement over that of existing flat LSC’s. In addition, the undesired limit of LSC size is eliminated in one direction. Modeling and optimization of an FLSC design is presented using polarization-ray tracing under realistic conditions with solar spectrum radiation and broad-band absorption and emission spectra of fluorescence materials with their inevitable self-absorption effect. Methods and results of fabrication and accurate optical characterization of such FLSC using two off-the-shelf organic dyes and a commercially available polymer, COP, are discussed in detail. Fiber preforms, fabricated under optimized conditions for lowlight transport loss, are thermally iv drawn into sub-millimeter-size fibers. Characterization of several samples with various concentrations of the two dyes shows an optical-to-optical conversion efficiency of 9.1% for a tandem combination of two 2.5-cm-long fibers with the efficiency gradually decreasing to 4.9% with increase in fiber length to 10 cm.

Radiative heat transfer in nanostructures with sub-wavelength dimensions can exceed that predicted by Planck&#039 / s blackbody distribution. This increased effect is due to the tunneling of infrared radiation between nanogaps, and can allow the eventual development of nano-thermo-photo-voltaic (Nano-TPV) cells for energy generation from low temperature heat sources. Although near field radiation effects have been discussed for many years, experimental verification of these effects is very limited so far. In this study, silica coated silicon wafer sample chips have been manufactured by using MEMS fabrication methods for testing the near field radiation effects. A variety of samples with 1&times / 1, 2&times / 2 and 5&times / 5 mm2 area, and with 25 nm, 50 nm, 100 nm and 200 nm (nano-gap) separations have been prepared. 3D structures with vacuum gaps have been obtained by bonding of the silica coated wafers. The samples have been tested in an experimental setup by a collaborative group at &Ouml / zyegin University, Istanbul. An increase in the net radiation heat transfer with decreasing nano-gap size has been reported by the &Ouml / zyegin group who used these samples in a parallel study. The thesis outlines the micro-fabrication techniques used for the sample preparation. Also, the manufacturing problems we have faced during this research program are discussed.

All types of electricity production have a negative impact on the environment, the most sustainable electricity is the one that never has been produced. If the West is to continue living with electricity and at the same time try to reduce the carbon footprints, there must be a change. In order to increase the use of renewable energy, off-grid installations are currently being produced for those houses that are far from civilization. But if you can connect to the grid electricity, what option is best from a sustainability perspective? This project therefore examines the possibilities for energy alternatives and aims to explore which option is most environmentally friendly based on the resources offered by the environment on Bornholm. Based on previous research and data, the conditions for electricity from the grid and an off-grid combination, are examined. The study begins with an in-depth literature study that deals with site data, technical aspects and life-cycle assessments of the energy alternatives that today can be used on Bornholm. Built on the analyses and measurements made on Bornholm's electrical mix and the off-grid system that works best given the conditions that the site has, it is concluded that electricity from the electricity grid is affecting the environment the least. / All elproduktion har en negativ inverkan på miljön. Det mest hållbara är att inte producera någon el. Om världen ska fortsätta leva med elektricitet och samtidigt försöka reducera koldioxidavtrycken måste det ske en förändring. För att öka användningen av förnybar energi tillverkas idag off-grid installationer för de hus som ligger långt från civilisationen. Om det finns möjlighet att ansluta till elnätet, vilket alternativ är då bäst ur ett hållbarhetsperspektiv? I detta projekt undersöks därför möjligheterna till olika energialternativ för trädtoppshus på Bornholm. Målet är att försöka bena ut vilket alternativ som är miljövänligast utifrån de resurser som omgivningen erbjuder. Utifrån tidigare forskning och data undersöks förutsättningarna för el dragen från elnätet, och el från en off-grid kombination. Studien börjar med en djupgående litteraturstudie som behandlar platsdata, tekniska aspekter och livscykelanalyser av de energialternativ som idag kan brukas på Bornholm, samt på olika typer av off-grid alternativ. Utifrån de analyser och mätningar som gjorts på Bornholms elmix, och det off-grid system som fungerar bäst med tanke på de förutsättningar som platsen erbjuder, blir slutsatsen att el från elnätet är det som påverkar miljön minst.