PHOTOCATALYTIC OXIDATION OF AQUEOUS SOLUTIONS OF JET FUEL AND ICING INHIBITORS

The present paper is devoted to the results of experimental research undertaken into photocatalytical oxidation (PCO) of aqueous solutions of de-icing agents and aqueous extract of jet fuel. The report consists of introduction, literature review, description of materials and methods, discussion of results and conclusions. TiO2 was selected as a photocatalyst for the experiments with synthetic solutions of ethylene glycol, 2-ethoxyethanol and aqueous extract of jet fuel. To explain the PCO mechanisms affecting certain behaviour of de-icing agent under distinctive conditions, the following factors were studied: the impact of initial concentration of pollutant, the role of pH, the presence of tert-butanol as OH·-radicals scavenger and mineral admixtures. PCO under solar radiation performed in two ways: catalysed by irradiated TiO2 slurry or by TiO2 attached to buoyant hollow glass micro-spheres. Special attention was paid to the energy-saving PCO with reduced intensity mixing of the slurry. The effect of PCO was assessed by determination of residual chemical oxygen demand of solution (COD) and by measuring of concentration of glycols. The PCO process efficiency was assumed to be dependent on the TiO2 suspension fractional composition. Thus, the following effects of solutions’ media were viewed: presence of organic admixtures, pH influence, mixing mode during the PCO. The effects of mineral admixtures - Ca2+, Fe3+/2+, Mn2+, SO42- - that are often present in natural and wastewater systems or produced during the degradation of organic pollutants and which can affect the rate of PCO of de-icing agents, were also investigated.

Aurinkopaneeleihin liitettävien vaihtosuuntaajien testaussuunnitelman laadinta ja toteutus

Aurinkoenergia on yksi monista uusiutuvan energian muodoista, joiden suosio on viimeisten vuosien aikana kasvanut fossiilisten polttoaineiden kallistumisen sekä ilmaston lämpenemisen vuoksi. Auringon säteilyn energiaa voidaan muuttaa sähköenergiaksi mm. aurinkopaneeleiden avulla. Aurinkopaneeleihin liitetään usein vaihtosuuntaaja, jolla tuotettu teho voidaan muokata sähköverkkoon tai kotitalouden sähköjärjestelmään sopivaksi. Tässä työssä on esitelty aurinkopaneelilla tuotettavan sähköenergian perusperiaatteet sekä tehoa tuottavan järjestelmän reunaehdot. Tutkimuksessa on perehdytty keskeisiin, aurinkopaneeleihin liitettäville vaihtosuuntaajille laadittuihin standardeihin, hyötysuhteen mittaamisen sekä sähkön laadun näkökulmista. Selvityksen avulla järjestelmän hyötysuhteen sekä lähtötehon laadun määrittämiseksi voidaan laatia standardien mukainen mittaussuunnitelma vaihtosuuntaajan nimellistehosta riippumatta. Standardien avulla on laadittu mittaussuunnitelma Global Inversonne, 100 kW - verkkovaihtosuuntaajayksikölle. Suunnitelman mukaisissa mittauksissa on tutkittu yksikön muunnoshyötysuhdetta sekä lähtöjännitteen- ja virran laatua. Lisäksi työssä on analysoitu mittaustulosten mittausepävarmuuksia ja niitä aiheuttavia tekijöitä.

Defects in Persistent Luminescence Materials

Persistent luminescence materials can store energy from solar radiation or artificial lighting and release it over a period of several hours without a continuous excitation source. These materials are widely used to improve human safety in emergency and traffic signalization. They can also be utilized in novel applications including solar cells, medical diagnostics, radiation detectors and structural damage sensors. The development of these materials is currently based on methods based on trial and error. The tailoring of new materials is also hindered by the lack of knowledge on the role of their intrinsic and extrinsic lattice defects in the appropriate mechanisms. The goal of this work was to clarify the persistent luminescence mechanisms by combining ab initio density functional theory (DFT) calculations with selected experimental methods. The DFT approach enables a full control of both the nature of the defects and their locations in the host lattice. The materials studied in the present work, the distrontium magnesium disilicate (Sr₂MgSi₂O₇) and strontium aluminate (SrAl₂O₄) are among the most efficient persistent luminescence hosts when doped with divalent europium Eu²⁺ and co-doped with trivalent rare earth ions R³⁺ (R: Y, La-Nd, Sm, Gd-Lu). The polycrystalline materials were prepared with the solid state method and their structural and phase purity was confirmed by X-ray powder diffraction. Their local crystal structure was studied by high-resolution transmission electron microscopy. The crystal and electronic structure of the nondoped as well as Eu²⁺, R^2+/3+ and other defect containing materials were studied using DFT calculations. The experimental trap depths were obtained using thermoluminescence (TL) spectroscopy. The emission and excitation of Sr₂MgSi₂O₇:Eu²+,Dy³⁺ were also studied. Significant modifications in the local crystal structure due to the Eu²⁺ ion and lattice defects were found by the experimental and DFT methods. The charge compensation effects induced by the R³⁺ co-doping further increased the number of defects and distortions in the host lattice. As for the electronic structure of Sr₂MgSi₂O₇ and SrAl₂O₄, the experimental band gap energy of the host materials was well reproduced by the calculations. The DFT calculated Eu²⁺ and R^2+/3+ 4fn as well as 4f^n-15d¹ ground states in the Sr₂MgSi₂O₇ band structure provide an independent verification for an empirical model which is constructed using rather sparse experimental data for the R³⁺ and especially the R²⁺ ions. The intrinsic and defect induced electron traps were found to act together as energy storage sites contributing to the materials’ efficient persistent luminescence. The calculated trap energy range agreed with the trap structure of Sr₂MgSi₂O₇ obtained using TL measurements. More experimental studies should be carried out for SrAl₂O₄ to compare with the DFT calculations. The calculated and experimental results show that the electron traps created by both the rare earth ions and vacancies are modified due to the defect aggregation and charge compensation effects. The relationships between this modification and the energy storage properties of the solid state materials are discussed.

Aurinkosähkön kannattavuustarkastelu jäähallilla

Tässä kandidaatintyössä selvitetään aurinkosähkön kannattavuutta jäähallissa. Tutkimuksessa huomioidaan paikallisten olosuhteiden kuten auringon säteilynmäärän, lämpötilan ja paneelien asennussuunnan vaikutus tuotetun aurinkosähkön määrään. Tuotannon soveltuvuutta arvioidaan vertaamalla simuloituja aurinkosähkön tuotantolukemia jäähallin sähkönkulutusprofiiliin. Sähkönkulutustiedot perustuvat etäluettavan sähkömittarin tunnittaisiin mittaustuloksiin. Investoinnin kannattavuutta arvioidaan yleisesti käytettyjen tunnuslukujen valossa, jotka lasketaan yksityiskohtaisen tarkastelun avulla. Lisäksi tunnuslukuja analysoidaan herkkyysanalyysiin avulla.

Geographical Studies of Underwater Light Dynamics in the Coastal Archipelago of SW Finland, Baltic Sea

The underwater light field is an important environmental variable as it, among other things, enables aquatic primary production. Although the portion of solar radiation that is referred to as visible light penetrates water, it is restricted to a limited surface water layer because of efficient absorption and scattering processes. Based on the varying content of optical constituents in the water, the efficiency of light attenuation changes in many dimensions and over various spatial and temporal scales. This thesis discusses the underwater light dynamics of a transitional coastal archipelago in south-western Finland, in the Baltic Sea. While the area has long been known to have a highly variable underwater light field, quantified knowledge on the phenomenon has been scarce, patchy, or non-existent. This thesis focuses on the variability in the underwater light field through euphotic depths (1% irradiance remaining), which were derived from in situ measurements of vertical profiles of photosynthetically active radiation (PAR). Spot samples were conducted in the archipelago of south-western Finland, mainly during the ice-free growing seasons of 2010 and 2011. In addition to quantifying both the seasonal and geographical patterns of euphotic depth development, the need and usability of underwater light information are also discussed. Light availability was found to fluctuate in multiple dimensions and scales. The euphotic depth was shown to have combined spatio-temporal dynamics rather than separate changes in spatial and temporal dimensions. Such complexity in the underwater light field creates challenges in data collection, as well as in its utilisation. Although local information is needed, in highly variable conditions spot sampled information may only poorly represent its surroundings. Moreover, either temporally or spatially limited sampling may cause biases in understanding underwater light dynamics. Consequently, the application of light availability data, for example in ecological modelling, should be made with great caution.