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As renewable, intermittent energy sources are expected to increasingly replace fossil based energy, energy storage technologies are crucially important in achieving the goal of fossil free energy, a cornerstone of sustainable development. Liquid air energy storage (LAES) is a novel technology that liquefies air when excess electricity is available. The liquid air is stored and, when electricity is needed, expanded in a turbine to generate electricity. The purpose of the project is to present the round trip efficiency of LAES, discuss how it can be improved and how it depends on relevant parameters and to evaluate LAES compared to other energy storage technologies. A literary review of existing energy storage methods and LAES research is presented. The efficiency is calculated using a model of a combined Linde (liquefaction) and Rankine (discharge) cycle built in Excel. We found that the efficiency of LAES is 21,6% without heat and cold recycle and above 50% with more than 60% recycle. Access to waste heat and cold can further increase the efficiency. A heat pump affects the efficiency very little, but is useful to protect the turbines from low working temperatures that can damage them. The biggest advantage of LAES is its high energy density, comparable to batteries and chemical energy storage. It is much higher than pumped hydro and compressed air energy storage (CAES). No toxic materials are used and it has reasonably cheap and long lasting components. It uses air, which is free as an energy carrier. The biggest disadvantage of LAES is its low round trip efficiency, probably under 50%, which is much lower than that of batteries and pumped hydro. It is similar to CAES and other chemical storage. LAES is only practical on a relatively large scale. Also, concentration of oxygen and cold working temperatures pose some safety risks. / Eftersom förnyelsebara, intermittenta energikällor i allt större utsträckning förväntas ersätta fossil energi är energilagring av avgörande betydelse för att nå målet om fossilfri energi, en hörnsten i hållbar utveckling. Energilagring i flytande luft (LAES) är en ny teknologi som tillverkar flytande luft när det finns ett elöverskott. Den flytande luften lagras sedan och när elektricitet behövs expanderas den i en turbin för att generera elektricitet. Syftet med detta projekt är att presentera den totala verkningsgraden för LAES, diskutera hur den kan förbättras och hur den beror på relevanta parametrar och utvärdera LAES jämfört med andra energilagringstekniker. En litteraturstudie om existerande energilagringsmetoder och LAES presenteras. Verkningsgraden beräknas med en modell konstruerad i Excel över en kombinerad Linde (överföring till vätskeform) och Rankine (expansion). Vi fann att verkningsgraden hos LAES är 21,6% utan återvinning av värme och kyla och över 50% med mer än 60% återvinning. En värmepump har endast marginell inverkan på verkningsgraden men är nödvändig för att skydda turbinerna från låga temperaturer som kan skada dem. Den största fördelen med LAES är dess höga energidensitet, jämförbar med batterier och kemisk energilagring och mycket högre än pumpvattenkraft och tryckluftslagring. LAES använder inga giftiga material och relativt billiga och robusta komponenter. Det använder gratis luft som energibärare. Den största nackdelen med LAES är dess låga verkningsgrad, troligen under 50% vilket är mycket lägre än för batterier och pumpvattenkraft och jämförbart med tryckluftslagring och kemisk energilagring. LAES är endast rimligt i relativt stor skala. Dessutom medför koncentration av syre och låga temperaturer vissa säkerhetsrisker.

A compact air separator demonstrator based on centrifugally enhanced distillation has been studied. The full size device is meant to be used on board of a Two Stage To Orbit vehicle launcher. The air separation system must be able to extract oxygen in highly concentrated liquid form (LEA, Liquid Enriched Air) from atmospheric air. The LEA is stored before being used in a subsequent rocket propulsion phase by the second stage of the launcher. Two reference vehicles are defined, one with a subsonic first stage and one with a supersonic first stage. In both cases, oxygen collection is performed during a cruise phase (M 0.7 and M 2.5 respectively). The aim of the project is to demonstrate the feasibility of the air separation system, investigate the separation cycle design, and assess that the separator design selected is suitable for the reference vehicles. The project is described from original base ideas to design, construction, extended testing and analysis of experimental results. Preliminary computations for a realistic layout have been performed and the motivations for the choices made during the process are explained. Test rig design, separator design and technical discussion are provided for a subscale pilot unit. Mass transport parameters and flooding limits have been estimated and experimentally measured. Performance has been assessed and shown to be sufficient for the reference Two Stage To Orbit vehicles. The technology developed is found suitable without further optimization, although some volume and mass reduction would be desirable for the supersonic first stage concept. There are many ways of optimisation that can be further investigated. The aim of this program, however, is not to fully optimize the device, but to demonstrate that a device based on a simple, robust, low-risk design is already suitable for the launch vehicles. On top of that analysis, directions for improvements are suggested and their potentials estimated. A complete assessment of those improvements requires further maturation of the technological concept through further testing and practical implementations. Directions for future work, general conclusions and a vehicle development roadmap have also been provided.

In this thesis the structure and hydration of small organic and amphipilic compounds adsorbed at the air-liquid interface, have been studied using the nonlinear optical technique Vibrational Sum Frequency Spectroscopy (VSFS). The second order nature of the sum frequency process makes this technique particularly surface sensitive and very suitable for interfacial studies, as molecules at the surface can be distinguished even in the presence of a vast excess of the same molecules in the bulk. Particular emphasis was given to the surface water structure and how it is affected by the presence of small model compounds such as acetic acid and formic acid, and also non-ionic surfactants with sugar based and ethylene oxide based polar headgroups. Understanding the structure of water at these interfaces is of considerable fundamental importance, and here VSFS provided unique information. Upon addition of tiny amounts of these surface active compounds, the ordered surface structure of water was found to be significantly perturbed, as revealed by the changes observed in the characteristic spectroscopic signature of the dangling OH bond of water molecules, which vibrate free in air and are present in the top monolayer. Dramatic differences between the different compounds were also observed in the bonded OH region, providing a valuable insight into the hydration of polar groups at interfaces. Additionally, by employing different polarization combinations of the laser beams involved in the sum frequency process, information about the different water species present at the surface and their average orientation were extracted. In particular an unusual state of water was found with a preferred orientation in a non-donor configuration in close proximity to the hydrophobic region formed by the hydrocarbon tails of the surfactant molecules. The conformation and orientation of the different adsorbates were also characterized, targeting their specific vibrational frequencies. Noteworthy is the orientation of the fluorocarbon chain of ammonium perfluorononanoate (APFN), which in contrast to the hydrocarbon chains of the other surfactant molecules studied, remained constant over a wide range of surface densities. This behaviour was also observed for the anionic headgroup of sodium dodecyl sulphate (SDS). Other interesting findings were the formation of a cyclic dimer bilayer at the surface of concentrated aqueous solutions of acetic acid and the water structuring effect induced by poly(ethylene-oxide) headgroups, in spite of being themselves disordered at the air-liquid interface.

<p>In this thesis the structure and hydration of small organic and amphipilic compounds adsorbed at the air-liquid interface, have been studied using the nonlinear optical technique Vibrational Sum Frequency Spectroscopy (VSFS). The second order nature of the sum frequency process makes this technique particularly surface sensitive and very suitable for interfacial studies, as molecules at the surface can be distinguished even in the presence of a vast excess of the same molecules in the bulk. Particular emphasis was given to the surface water structure and how it is affected by the presence of small model compounds such as acetic acid and formic acid, and also non-ionic surfactants with sugar based and ethylene oxide based polar headgroups. Understanding the structure of water at these interfaces is of considerable fundamental importance, and here VSFS provided unique information. Upon addition of tiny amounts of these surface active compounds, the ordered surface structure of water was found to be significantly perturbed, as revealed by the changes observed in the characteristic spectroscopic signature of the dangling OH bond of water molecules, which vibrate free in air and are present in the top monolayer. Dramatic differences between the different compounds were also observed in the bonded OH region, providing a valuable insight into the hydration of polar groups at interfaces. Additionally, by employing different polarization combinations of the laser beams involved in the sum frequency process, information about the different water species present at the surface and their average orientation were extracted. In particular an unusual state of water was found with a preferred orientation in a non-donor configuration in close proximity to the hydrophobic region formed by the hydrocarbon tails of the surfactant molecules.</p><p>The conformation and orientation of the different adsorbates were also characterized, targeting their specific vibrational frequencies. Noteworthy is the orientation of the fluorocarbon chain of ammonium perfluorononanoate (APFN), which in contrast to the hydrocarbon chains of the other surfactant molecules studied, remained constant over a wide range of surface densities. This behaviour was also observed for the anionic headgroup of sodium dodecyl sulphate (SDS). Other interesting findings were the formation of a cyclic dimer bilayer at the surface of concentrated aqueous solutions of acetic acid and the water structuring effect induced by poly(ethylene-oxide) headgroups, in spite of being themselves disordered at the air-liquid interface.</p>

No description available.

No description available.

A compact air separator demonstrator based on centrifugally enhanced distillation has been studied. The full size device is meant to be used on board of a Two Stage To Orbit vehicle launcher. The air separation system must be able to extract oxygen in highly concentrated liquid form (LEA, Liquid Enriched Air) from atmospheric air. The LEA is stored before being used in a subsequent rocket propulsion phase by the second stage of the launcher. Two reference vehicles are defined, one with a subsonic first stage and one with a supersonic first stage. In both cases, oxygen collection is performed during a cruise phase (M 0.7 and M 2.5 respectively). The aim of the project is to demonstrate the feasibility of the air separation system, investigate the separation cycle design, and assess that the separator design selected is suitable for the reference vehicles.<p><p>The project is described from original base ideas to design, construction, extended testing and analysis of experimental results. Preliminary computations for a realistic layout have been performed and the motivations for the choices made during the process are explained. Test rig design, separator design and technical discussion are provided for a subscale pilot unit. Mass transport parameters and flooding limits have been estimated and experimentally measured. Performance has been assessed and shown to be sufficient for the reference Two Stage To Orbit vehicles. The technology developed is found suitable without further optimization, although some volume and mass reduction would be desirable for the supersonic first stage concept. There are many ways of optimisation that can be further investigated. The aim of this program, however, is not to fully optimize the device, but to demonstrate that a device based on a simple, robust, low-risk design is already suitable for the launch vehicles. On top of that analysis, directions for improvements are suggested and their potentials estimated. A complete assessment of those improvements requires further maturation of the technological concept through further testing and practical implementations.<p><p>Directions for future work, general conclusions and a vehicle development roadmap have also been provided.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished