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Detector packages consisting of plastic nuclear track detectors, nuclear emulsions, and theromoluminescence detectors were exposed at different locations inside the space laboratory Spacelab and at the astronauts' body and in different sections of the MIR space station. Total dose, particle fluence rate and linear energy transfer (LET) spectra of heavy ions, number of nuclear disintegrations and fast neutron fluence rates were determined of each exposure. The dose equivalent received by the Payload specialists (PSs) were calculated from the measurements, they range from 190 microSv d-1 to 770 microSv d-1. Finally, a preliminary investigation of results from a particle telescope of two silicon detectors, first used in the last BIORACK mission on STS 76, is reported.

Advanced technologies, optimized operation and infrastructure are not sufficient to achieve the CO2 mitigation goals agreed on for the aviation sector. Carbon neutral alternative liquid fuels are required to fill the gap towards a carbon-neutral growth from 2020 on. The Power-to-Liquid process is one option to produce synthetic jet fuels from renewable energy. The technical and economic performance of production processes based on renewable electricity and CO2 was investigated and evaluated. Hydrogen can be generated by water electrolysis from fluctuating renewable power sources. Together with CO2 the reverse water-gas-shift reaction forms syngas. The Fischer-Tropsch synthesis produces long chained hydrocarbons from syngas. Downstream product separation and upgrading generates gasoline, jet fuel and diesel. Another process concept is based on high temperature co-electrolysis of steam and CO2 producing synthesis gas at high temperature and pressure. The process performance is evaluated via flowsheet simulation models and pinch point analyses comparing the Power-to-Fuel efficiency as well as carbon conversion into liquid fuels. A baseline Power-to-Fuel efficiency of 44 % for the concept based on water electrolysis can be increased to 60 % using the co-electrolysis concept. The baseline carbon conversion of 73 % grows to 98 %. The sensitivity of various operation conditions was analyzed. A cost analysis based on market data and equipment factors was performed for the investment year 2014. Employing stationary power input of 105 €/MWh, production costs of 3.38 €/kg were found for the water electrolysis concept. The production costs of the co-electrolysis concept compare to 2.83 €/kg. The sensitivity of the electrolyzer capital cost and electricity prices were analyzed and their effect on the production costs will be presented. Investment and operating costs to fill the gap towards carbon-neutral air transport growth from 2020 on can be predicted based on 2014 costs and technology status. A comparison to other renewable jet fuels regarding land use, feedstock potential and economic measures will be provided.

AbstractOne of the advantages of solar thermal power plants (STPPs) with molten salt as heat transfer fluid is the direct storage system. This means that the thermal energy collected by the solar field and the electric power generation can be fully decoupled. The plant operator must therefore make the daily decision when to start-up or to shut-down the power block (PB). Normally, the solar field of these STPPs is overdesigned which leads to dumping of solar energy during days with high solar radiation, due to the inability of the hot tank and the PB to consume all the collected thermal energy. The PB must therefore start as soon as possible to prevent excessive dumping of solar energy. Contrarily, on days with low solar radiation, the PB should not start too early to prevent a second start-up on this day, because of a low hot tank level. In order to operate within these counter bounds, a fixed and a dynamic operation strategy are proposed. The so-called solar-driven strategy serves as a reference. Using this strategy, the PB operates whenever the solar field is online. The two proposed operation strategies are compared to the reference strategy by means of a transient STPP simulation model. Using the dynamic operation strategy, the annual unnecessary PB start-ups and the auxiliary heater thermal energy for anti-freeze protection are decreased, whereas the annual net electricity is increased.

Abstract Proper water management plays an essential role in the performance and durability of Polymer Electrolyte Fuel Cells (PEFCs), but it is challenged by the variety of water transport phenomena that take place in these devices. Previous experimental work has shown the existence of fluctuations between low and high current density levels in PEFCs operated with wet hydrogen and dry air feed. The alternation between both performance states is accompanied by strong changes in the high frequency resistance, suggesting a cyclic hydration and dehydration of the membrane. This peculiar scenario is examined here considering liquid water distributions from neutron imaging and predictions from a 3D two-phase non-isothermal model. The results show that the hydration-dehydration cycles are triggered by the periodic condensation and shedding of liquid water at the anode inlet. The input of liquid water humidifies the anode channel and offsets the membrane dry-out induced by the dry air stream, thus leading to the high-performance state. When liquid water is flushed out of the anode channel, the dehydration process takes over, and the cell comes back to the low-performance state. The predicted amplitude of the current oscillations grows with decreasing hydrogen and increasing air flow rates, in agreement with previous experimental data.

The conversion of agricultural waste materials such as bark or straw into 2nd generation biofuels constitutes an auspicious way to meet part of the future fuel demand in a sustainable way. The number of possible production routes is diverse, and the techno-economic analyses of these routes have been conducted in very different ways. The route involving gasification, gas purification, and a subsequent Fischer-Tropsch synthesis enables the production of hydrocarbons that achieve current fuel standards after upgrading in the existing refinery infrastructure. To evaluate a promising biomass-to-liquid process, a methodology is presented that incorporates economic constraints into the process design, allowing identification of a regionally optimal process design. The production costs of the new concepts are estimated by setting up a detailed flowsheet simulation in AspenPlus® based on experimental data from the successful demonstration runs of the EU-Project COMSYN. In addition, an existing techno-economic evaluation methodology incorporated into the in-house software tool TEPET (Techno-Economic Process Evaluation Tool) has been extended to evaluate the processes’ performance in different European regions and to include transportation and refining costs. The approach enables the identification of regional sweet spots shown on a map for Central-Europe, indicating production costs and favorable process design for each region. Furthermore, the results of an automated mapping for the optimal process design depending on the heat and electricity market are presented. The performed analyses show that the techno-economic evaluation tends to expand the technology in regions with low feedstock costs, while the optimal process design is defined by the regional heat and electricity market. In this work, net production costs of less than 1.12 €2019/lbiofuel were determined for regions in Hungary, Poland and Slovakia.