Vaihtoehtoiset liikennepolttoaineet

Tiivistelmä. Tässä työssä selvitetään mitä vähäpäästöisiä vaihtoehtoja nykyisten polttomoottoriajoneuvojen polttoaineeksi löytyy tällä hetkellä ja mahdollisesti lähitulevaisuudessa. Suomen autokanta on Euroopan vanhinta ja sen uusiutuminen on hyvin hidasta. Liikennesektorille asetettujen tiukkojen päästövähennystavoitteiden takia autokannan uusiutuminen ei vähennä päästöjä riittävän nopeasti, joten päästöjä pitää vähentää muilla keinoilla, kuten kehittämällä vähäpäästöisiä polttoaineita. Bensiinin ilmastovaikutusta voidaan alentaa sekoittamalla siihen biopohjaista etanolia. Nykymoottorit sietävät etanolia enimmillään 10 % V/V, mutta muutossarjan avulla etanolipitoisuus voidaan nostaa noin 85 % V/V. Ilmaston kannalta paras vaihtoehto olisi biokaasu, joka valmistetaan esimerkiksi biojätteistä. Biokaasun käyttö ei ratkaisevasti pienennä bensiiniauton paikallispäästöjä, mutta sen kokonaisvaikutukset ilmastoon ovat huomattavasti pienemmät kuin bensiinillä, ja tutkimusten mukaan se on parhaimmillaan hiilinegatiivinen. Dieselin korvaavien bioversioiden valmistamiseen on eri menetelmiä, joiden hinta ja saatavan polttoaineen laatu vaihtelevat suuresti. Biodiesel valmistetaan kasvirasvoista esteröimällä alkoholin kanssa. Sen kokonaispäästöihin vaikuttaa suuresti se, mistä kasveista se valmistetaan, ja onko käytetty alkoholi valmistettu fossiilisten polttoaineiden avulla, vai onko se esimerkiksi bioetanolia. Uusiutuva diesel valmistetaan parhaimmillaan jätebiomassasta ja sen ominaisuudet ovat paremmat kuin perinteisellä dieselillä. Dieselin korvaajaksi löytyy ominaisuuksiltaan hyviä ja täysin biopohjaisia vaihtoehtoja, mutta niiden hinta on vielä korkea. Biopolttoaineita on jo nyt saatavilla sekä diesel- että bensiiniautoihin ja ajoneuvon käyttäjä voi halutessaan vaikuttaa polttoainevalinnalla omaan hiilijalanjälkeensä. Täydellinen siirtyminen biopolttoaineisiin vaatii kuitenkin vielä paljon tutkimusta ja biopolttoaineiden hinnan halpenemista. Tulevaisuudessa Suomen liikenteestä on mahdollista saada hyvin vähäpäästöistä, mikäli uusiutuvien polttoaineiden tutkimus ja käyttöönotto etenevät hyvin ja autokanta uusiutuu ja sähköistyy riittävää vauhtia.Alternative fuels for road vehicles. Abstract. In this bachelor’s thesis I aim to find out what alternative fuels there are at the markets today and in the near future. An average car in Finland is older than in other European countries and therefore the emissions are higher. New cars do produce less greenhouse gases, nitrogen oxides and particle emissions than older cars but there are no signs that the percentage of new cars in Finland is increasing. Low emission fuels of a new kind are needed to fulfil the EU’s emission laws. The easiest way of lowering the emissions of a spark ignition engine is to use fuel that is made by mixing petrol with bioethanol. Today’s petrol engines can run with fuels containing 10% V/V ethanol. Higher ethanol concentration is possible with conversion kit. The highest concentration is about 85% V/V ethanol. The best possible fuel for a spark ignited engine from a climate point of view is biogas because it can be produced from many kinds of biomass, including biowaste. Using biogas as fuel for a car does not lower emissions locally, but global climate effect is much lower than when using petrol. Some studies show that biogas is at the best-case scenario even coal negative fuel. Biodiesel and renewable diesel can be produced from different organic sources with couple of different processes. The quality, cost and climate impact of the final product varies significantly depending on the source and process. Especially renewable diesel has superior properties when compared with fossil diesel and it can be produced from biomass, but cost is high. There are already alternative fuels for petrol and diesel engines and car owners can use those to lower their carbon footprint. There is still lot to do before biofuels are the mainfuel in the traffic in Finland. If the cost of biofuels gets lowers and the car fleet gets slightly younger, the traffic emissions in Finland might be close to zero in the future

d0 Ferromagnetic Interface Between Non-magnetic Perovskites

We use computational and experimental methods to study d0 ferromagnetism at a charge- imbalanced interface between two perovskites. In SrTiO3/KTaO3 superlattice calculations, the charge imbalance introduces holes in the SrTiO3 layer, inducing a d0 ferromagnetic half-metallic 2D electron gas at the interface oxygen 2p orbitals. The charge imbalance overrides doping by vacancies at realistic concentrations. Varying the constituent materials shows ferromagnetism to be a gen- eral property of hole-type d0 perovskite interfaces. Atomically sharp epitaxial d0 SrTiO3/KTaO3, SrTiO3 /KNbO3 and SrTiO3 /NaNbO3 interfaces are found to exhibit ferromagnetic hysteresis at room temperature. We suggest the behavior is due to high density of states and exchange coupling at the oxygen t1g band in comparison with the more studied d band t2g symmetry electron gas.Comment: 5 pages, 5 figure

Evidence for Strain-Induced Ferroelectric Order in Epitaxial Thin-Film KTaO3

In perovskite-structure epitaxial films, it has been theoretically predicted that the polarization and the coherence of polar order can increase with increasing crystallographic strain. Experimental evidence of strain-induced long-range ferroelectric order has not been obtained thus far, posing the fundamental question of whether or not strain can induce the long-range polar order. Here we demonstrate the existence of strain-induced ferroelectric order in quantum paraelectric KTaO3 by combining experimental investigations of epitaxial KTaO3 films and density-functional-theory calculations. The long-range ferroelectric order does exist under a large enough epitaxial strain. We suggest that a region of short-range polar order might appear between paraelectric and ferroelectric states in the strain-temperature phase diagrams.Peer reviewe

Radial Velocity Studies of Close Binary Stars. IX

Radial-velocity measurements and sine-curve fits to the orbital velocity variations are presented for the eighth set of ten close binary systems: AB And, V402 Aur, V445 Cep, V2082 Cyg, BX Dra, V918 Her, V502 Oph, V1363 Ori, KP Peg, V335 Peg. Half of the systems (V445 Cep, V2082 Cyg, V918 Her, V1363 Ori, V335 Peg) were discovered photometrically by the Hipparcos mission and all systems are double-lined (SB2) contact binaries. The broadening function method permitted improvement of the orbital elements for AB And and V502 Oph. The other systems have been observed for radial velocity variations for the first time; in this group are five bright (V<7.5) binaries: V445 Cep, V2082 Cyg, V918 Her, KP Peg and V335 Peg. Several of the studied systems are prime candidates for combined light and radial-velocity synthesis solutions.Comment: 17+ pages, 2 tables, 4 figure

The rate of nitrite reduction in leaves as indicated by O2 and CO2 exchange during photosynthesis

Light response (at 300 ppm CO2 and 10–50 ppm O2 in N2) and CO2 response curves [at absorbed photon fluence rate (PAD) of 550 μmol m−2 s−1] of O2 evolution and CO2 uptake were measured in tobacco (Nicotiana tabacum L.) leaves grown on either NO3− or NH4+ as N source and in potato (Solanum tuberosum L.), sorghum (Sorghum bicolor L. Moench), and amaranth (Amaranthus cruentus L.) leaves grown on NH4NO3. Photosynthetic O2 evolution in excess of CO2 uptake was measured with a stabilized zirconia O2 electrode and an infrared CO2 analyser, respectively, and the difference assumed to represent the rate of electron flow to acceptors alternative to CO2, mainly NO2−, SO42−, and oxaloacetate. In NO3−-grown tobacco, as well as in sorghum, amaranth, and young potato, the photosynthetic O2–CO2 flux difference rapidly increased to about 1 μmol m−2 s−1 at very low PADs and the process was saturated at 50 μmol quanta m−2 s−1. At higher PADs the O2–CO2 flux difference continued to increase proportionally with the photosynthetic rate to a maximum of about 2 μmol m−2 s−1. In NH4+-grown tobacco, as well as in potato during tuber filling, the low-PAD component of surplus O2 evolution was virtually absent. The low-PAD phase was ascribed to photoreduction of NO2− which successfully competes with CO2 reduction and saturates at a rate of about 1 μmol O2 m−2 s−1 (9% of the maximum O2 evolution rate). The high-PAD component of about 1 μmol O2 m−2 s−1, superimposed on NO2− reduction, may represent oxaloacetate reduction. The roles of NO2−, oxaloacetate, and O2 reduction in the regulation of ATP/NADPH balance are discussed

Searches for violation of fundamental time reversal and space reflection symmetries in solid state experiments

The electric dipole moment (EDM) of a particle violates both time reversal (T) and space reflection (P) symmetries. There have been recent suggestions for searches of the electron EDM using solid state experiments [1,2]. These experiments could improve the sensitivity compared to present atomic and molecular experiments by several orders of magnitude. In the present paper we calculate the expected effect. We also suggest that this kind of experiment is sensitive to T,P-violation in nuclear forces and calculate effects caused by the nuclear Schiff moment. The compounds under consideration contain magnetic Gd$^{3+}$ ions and oxygen O$^{2-}$ ions. We demonstrate that the main mechanism for the T,P-odd effects is related to the penetration of the Oxygen 2p-electrons to the Gd core. All the effects are related to the deformation of the crystal lattice.Comment: 13 pages, 6 figure

Theory of Interplay of Nuclear Magnetism and Superconductivity in AuIn2

The recently reported coexistence of a magnetic order, with the critical temperature T_M=35 \mu*K, and superconductivity, with the critical temperature T_S=207 m*K, in AuIn_2 is studied theoretically. It is shown that superconducting (S) electrons and localized nuclear magnetic moments (LM's) interact dominantly via the contact hyperfine (EX) interaction, giving rise to a spiral (or domain-like) magnetic order in superconducting phase. The electromagnetic interaction between LM's and S electrons is small compared to the EX one giving minor contribution to the formation of the oscillatory magnetic order. In clean samples (l>\xi_0) of AuIn$_2$ the oscillatory magnetic order should produce a line of nodes in the quasiparticle spectrum of S electrons giving rise to the power law behavior. The critical field H_c(T=0) in the coexistence phase is reduced by factor two with respect to its bare value.Comment: 4 pages with 2 PS figures, RevTeX, submitted to Physical Review B - Rapid Communication