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Liquid hydrocarbons are considered as an option to store renewable energy while decoupling the supply and demand of renewable resources. They can also be used as transportation fuel or as feedstock for the chemical industry and are characterized by a high energy density. A process concept using renewable energy from fluctuating wind power and CO 2 to produce liquid hydrocarbons was modeled by a flowsheet simulation in Aspen Plus®. The capacity of the plant was set to 1 GW LHV of hydrogen input, using water electrolysis, reverse water–gas shift reaction (RWGS) and Fischer–Tropsch (FT) synthesis. A feed of 30 t / h of H 2 generated 56.3 t / h ( 12 , 856 bbl / d ) of liquid hydrocarbons. A Power-to-Liquid efficiency of 44.6% was calculated for the base case scenario. Net production cost ranged from 12.41 $ / GGE to 21.35 $ / GGE for a system powered by a wind power plant with a full load fraction of about 47%, depending on the assumed electricity feedstock price and electrolyzer capital cost. For systems with full load fractions between 70% and 90%, the production cost was in the range of 5.48 $ / GGE to 8.03 $ / GGE .

Future aviation, shipping and heavy load transportation will continue to depend on energy carriers with a high energy density. The Power-to-Liquid technology is an approach to produce synthetic hydrocarbons, which fulfill this requirement. The proposed concept is based on H 2 from electrolysis, which reacts with CO 2 via the reverse water-gas shift reaction to syngas. Syngas is then synthesized to liquid hydrocarbons by Fischer-Tropsch synthesis. A downstream product separation and upgrading section allows the production of defined fractions for specific applications. A flowsheet process model is build and heat integration is conducted. The input capacity is set to 100 MW LHV of H 2 . A total amount of 1260 bbl / d liquid hydrocarbons (67.1 MW LHV ) is generated. The carbon conversion and the Power-to-Liquid efficiency, which is defined as the fraction of the electrical energy chemically bound into liquid hydrocarbons, are identified as the parameters to evaluate the overall process performance. The Power-to-Liquid efficiency is found to be 43.3%. The carbon conversion rate of 73.7% indicates the exploiting of the introduced CO 2 .

Thermal energy storage (TES) is capable to reduce the demand of conventional energy sources for two reasons: First, they prevent the mismatch between the energy supply and the power demand when generating electricity from renewable energy sources. Second, utilization of waste heat in industrial processes by thermal energy storage reduces the final energy consumption. This review focuses mainly on material aspects of alkali nitrate salts. They include thermal properties, thermal decomposition processes as well as a new method to develop optimized salt systems.

Distributed hydrogen generation from liquid fuels has attracted increasing attention in the past years. Petroleum-derived fuels with already existing infrastructure benefit from high volumetric and gravimetric energy densities, making them an interesting option for cost competitive decentralized hydrogen production.In the present study, direct steam reforming of diesel and diesel blends (7 vol.% biodiesel) is investigated at various operating conditions using a proprietary precious metal catalyst. The experimental results show a detrimental effect of low catalyst inlet temperatures and high feed mass flow rates on catalyst activity. Moreover, tests with a desulfurized diesel–biodiesel blend indicate improved long-term performance of the precious metal catalyst. By using deeply desulfurized diesel (1.6 ppmw sulfur), applying a high catalyst inlet temperature (>800 °C), a high steam-to-carbon ratio (S/C = 5) and a low feed mass flow per open area of catalyst (11 g/h cm2), a stable product gas composition close to chemical equilibrium was achieved over 100 h on stream. Catalyst deactivation was not observed.

Thermochemical reactions can be employed in heat storage devices. The choice of suitable reactive material pairs involves a thorough kinetic characterisation by, e.g., extensive thermogravimetric measurements. Before testing a material on a reactor level, simulations with models based on the Theory of Porous Media can be used to establish its suitability. The extent to which the accuracy of the kinetic model influences the results of such simulations is unknown yet fundamental to the validity of simulations based on chemical models of differing complexity. In this article we therefore compared simulation results on the reactor level based on an advanced kinetic characterisation of a calcium oxide/hydroxide system to those obtained by a simplified kinetic model. Since energy storage is often used for short term load buffering, the internal reactor behaviour is analysed under cyclic partial loading and unloading in addition to full monotonic charge/discharge operation. It was found that the predictions by both models were very similar qualitatively and quantitatively in terms of thermal power characteristics, conversion profiles, temperature output, reaction duration and pumping powers. Major differences were, however, observed for the reaction rate profiles themselves. We conclude that for systems not limited by kinetics the simplified model seems sufficient to estimate the reactor behaviour. The degree of material usage within the reactor was further shown to strongly vary under cyclic loading conditions and should be considered when designing systems for certain operating regimes.

In order to investigate thermochemical energy storage in larger scale, a test bench as well as a reactor containing around 20kg of reaction material has been built and brought into operation. This investigation is based on the reversible decomposition reaction of calcium hydroxide, due to its wide availability, high reaction enthalpy and promising temperature range for CSP plants. Additionally, a developed simulation tool was used to analyze the experimental results. The comparison of the discharging processes showed a good agreement but also revealed thermal losses due to the experimental setup and the operation mode of the thermochemical storage. Therefore, first operation strategies of thermal energy storages based on chemical reactions can be derived.

Thermochemical energy storage can play an important role in the establishment of a reliable renewable energy supply and can increase the efficiency of industrial processes. The application of directly permeated reactive beds leads to strongly coupled mass and heat transport processes that also determine reaction kinetics. To advance this technology beyond the laboratory stage requires a thorough theoretical understanding of the multiphysics phenomena and their quantification on a scale relevant to engineering analyses. Here, the theoretical derivation of a macroscopic model for multicomponent compressible gas flow through a porous solid is presented along with its finite element implementation where solid–gas reactions occur and both phases have individual temperature fields. The model is embedded in the Theory of Porous Media and the derivation is based on the evaluation of the Clausius–Duhem inequality. Special emphasis is placed on the interphase coupling via mass, momentum and energy interaction terms and their effects are partially illustrated using numerical examples. Novel features of the implementation of the described model are verified via comparisons to analytical solutions. The specification, validation and application of the full model to a calcium hydroxide/calcium oxide based thermochemical storage system are the subject of part 2 of this study.

Compared to other energy storage concepts, thermochemical energy storage stands out with high storage densities and the possibility of heat transformation. However, up to now only few chemical reactions have been characterized sufficiently for this application. In this paper, calcium chloride is analyzed as a possible storage material. CaCl2 is known for its high deliquescence. Its exothermal hydration reaction can be used for storage applications from 80 °C to 200 °C. This paper reports on the hydration and dehydration behavior at different partial vapor pressures. Reversibility, intermediate reaction steps and their stability are studied. The presented results are in good agreement with literature data. The hydration reaction provides good reversibility and cycling stability for 20 cycles. Therefore, CaCl2 can be considered as a reference material for thermochemical storage application in the temperature range studied.

Heat storage technologies are used to improve energy efficiency of power plants and recovery of process heat. Storing thermal energy by reversible thermo-chemical reactions offers a promising option for high storage capacities especially at high temperatures. Due to its low material cost, the use of the reversible reaction Ca(OH) 2 ⇌ CaO + H 2 O has been proposed. This paper reports on the physical properties such as heat capacity, thermodynamic equilibrium, reaction enthalpy and kinetics. To achieve high reaction temperatures, high H 2 O partial pressures are required. Therefore the cycling stability is confirmed for H 2 O partial pressures up to 95.6 kPa and the dehydration and hydration kinetics are studied. Quantitative data are collected and expressions are derived which are in good agreement with the presented measurements. At 1 bar H 2 O partial pressure the expected equilibrium temperature is 505 °C and the reaction enthalpy is 104.4 kJ/mol.

Das Interesse an innovativen, verlustfreien, thermischen Energiespeichern mit hoher Speicherkapazitat ist in den letzten Jahren zunehmend gestiegen. Als vielversprechende Technologie wird hier vor allem die thermochemische Energiespeicherung angesehen. Dieser Artikel beschreibt den Stand der Wissenschaft im Bereich der Materialforschung, Prozessfuhrung, Verfahrensentwicklung und zeigt die technischen Herausforderungen und Potenziale der thermochemischen Energiespeicherung auf. Beispielhaft werden zwei Systemkonzepte, eins fur den Niedertemperaturbereich und eins fur den Hochtemperaturbereich, diskutiert. Anhand dieser werden die Einsatzmoglichkeiten der thermochemischen Energiespeicherung aufgezeigt. A loss-free, thermal energy storage technology attracts a rising interest over the past years. The thermochemical energy storage is seen as a promising technology for a loss-free thermal energy store with high storage density. This paper presents the state of the art in the field of material research, process design and process development as well as the technological challenges of the thermochemical energy storage. Exemplarily two system concepts, one for low temperature applications and one for high temperature applications, are shown to demonstrate the technical capabilities of the thermochemical energy storage.

Sewage sludge can be disposed of by fermentation, incineration or gasification. Conversion of the resulting biogas, combustion heat or gasification gas into electricity is often employed. Since sewage sludge cannot be fermented completely and due to the significant heat requirements for drying it in the incineration plant or before the gasifier, the electrical output in all cases is very low. Consequently, this work seeks to investigate a combination of fermentation and gasification in which dried fermentation waste is converted in a gasifier. With the aim of combining these two biomass conversion processes with power generation in an efficient manner, a hybrid system consisting of a SOFC and a gas turbine is investigated. This combination of a biogas plant and a gasifier has the advantage that waste heat can be used as a heat source in drying the fermentation waste. Another advantage is the combined conversion of biogas and gasification gas in the SOFC. As steam from gasification gas is used for internal reforming of methane out of biogas at the anode of the SOFC, the complexity of the plant is reduced and the efficiency is increased. A configuration including a pressurized gasification process was identified as most efficient in terms of electrical output.

The partial catalytic dehydrogenation has been carried out with defined model components and model mixtures representing hydrocarbon groups and chemical composition of desulfurized Jet A-1 over 1.0 wt% Pt/Sn catalyst on γ-Al2O3 carrier. The hydrogen yield, cracking products and carbon deposit on the catalyst surface are studied in order to define suitable reaction conditions for a pressurized auxiliary power unit concept with gas conditioning for fuel cell systems. The results show that alkanes lead to high cracking rate and carbon deposit which can be suppressed with increased pressure up to 8 bar. The hydrocarbon group cycloalkanes represented by methylcyclohexane shows sufficient conversion of 32 wt% towards hydrogen evolution in model mixtures under pressurized conditions. The average hydrogen yield of the model mixture of 72 nl H 2 /kgfeed was achieved under defined reaction conditions of 425 °C catalyst bed temperature, 8 bar system pressure and 4 s of contact time on the catalyst.

Recently, liquid biofuels have attracted increasing attention as renewable feedstock for hydrogen production in the transport sector. Since the lack of hydrogen infrastructure and distribution poses an obstacle for the introduction of fuel cell vehicles to the market, it is reasonable to consider using liquid biofuels for on-board or on-site hydrogen generation. Biodiesel offers the advantage of being an environmentally friendly resource while also having high gravimetric and volumetric energy density.The present study constitutes an experimental investigation of biodiesel steam reforming, the main emphasis of which is placed on finding optimum operating conditions in order to avoid catalyst deactivation. Temperature was varied from 600 °C to 800 °C, pressure from 1 bar to 5 bar and the molar steam-to-carbon ratio from 3 to 5. Based on the experimental results, coke formation and sintering are identified as the main deactivation mechanisms. Initiation of catalyst deactivation primarily depends on catalyst inlet temperature and feed mass flow per open area of catalyst. By using a metallic based precious metal catalyst, applying low feed flow rates (31 g/h∙cm2) and a sufficiently high catalyst inlet temperature (>750 °C) coking can be minimized, thus avoiding catalyst deactivation. A stable product gas composition close to chemical equilibrium has been achieved over 100 h with a biodiesel conversion rate of 99%.

Fractionation of kerosene by rectification leads to fuel fractions characterized by different proportions of iso-paraffins, n -paraffins, cyclic, dicyclic, aromatics and diaromatics. Fractions of progressively higher boiling point range are characterized by progressively higher average carbon chain length, as well as increasing content of sulfur containing molecules. Three fractions, corresponding to 5, 14 and 32 wt.% of the original kerosene and having boiling point ranges 140–150 °C; 150–160 °C; 160–170 °CM, respectively, containing predominantly C 8 –C 9 , C 9 –C 10 and C 10 , respectively, and 4, 12 and 24 ppm sulfur, respectively, were fed to a partial dehydrogenation reactor using a Pt–Sn/BaO–γ–Al 2 O 3 catalyst. A hydrogen productivity increase up to a factor 3 for the low-boiling point fraction compared to the original kerosene is observed. The catalyst durability is significantly increased due to lower sulfur and coke deposition on the catalyst for the low boiling point fraction. The fractionation of kerosene Jet A-1 fuel by rectification is a promising approach for the enhancement of durable hydrogen generation via partial dehydrogenation.

A new concept is proposed for combined fermentation (two-stage high-load fermenter) and gasification (two-stage fluidised bed gasifier with CO2 separation) of sewage sludge and wood, and the subsequent utilisation of the biogenic gases in a hybrid power plant, consisting of a solid oxide fuel cell and a gas turbine. The development and optimisation of the important processes of the new concept (fermentation, gasification, utilisation) are reported in detail. For the gas production, process parameters were experimentally and numerically investigated to achieve high conversion rates of biomass. For the product gas utilisation, important combustion properties (laminar flame speed, ignition delay time) were analysed numerically to evaluate machinery operation (reliability, emissions). Furthermore, the coupling of the processes was numerically analysed and optimised by means of integration of heat and mass flows. The high, simulated electrical efficiency of 42% including the conversion of raw biomass is promising for future power generation by biomass.

CO 2 reforming of methane in a solar driven volumetric receiver–reactor has been investigated. This reactor was successfully tested on the Solar Tower Test Facility of the Weizmann Institute, Israel. The power absorbed by the reactor was between 200 and 300 kW. Typical operating temperatures ranged from 700°C to 860°C, with an absolute pressure of 3.5 bars, reaching methane conversions over 80%. Two solar-specific, catalytically-active absorber systems have been developed. These being based on ceramic foam structures, made from α-Al 2 O 3 and SiC ceramics, respectively. γ-Al 2 O 3 was used as support material and Rh was applied as active metal. The absorber systems were characterised by pre- and post-test analysis. Both inserts showed coke deposition after solar testing, this resulting from problems with the methanator part of the test loop. Some sections in the irradiated front side of the first absorber system, being located close to the gas inlet, were subjected to catalyst poisoning by Na deposits. The second absorber insert has not yet been fully characterised after solar testing. Despite local degradation effects, both absorber systems performed well during solar operation.

Heat storage technologies are used to improve energy efficiency of power plants and recovery of process heat. Storing thermal energy by reversible thermo-chemical reactions offers a promising option for high storage capacities especially at high temperatures. Due to its low material cost the use of the gas–solid reaction Ca(OH) 2 ⇌ CaO + H 2 O has been suggested. In Part A of this work the thermal behavior of a reactor with direct heat transfer was experimentally investigated. In this part a two-dimensional model is applied for the specified system. The experimental and simulated results during the exothermic hydration are discussed in order to confirm the validity of the model. The model is validated regarding heat transfer, integral reaction rate and maximum temperatures. In addition, an adaptation of the kinetic equation is proposed in order to take into account rate-limiting effects due to agglomeration in the powder bed.

Heat storage technologies are used to improve energy efficiency of power plants and recovery of process heat. Storing thermal energy by reversible thermo-chemical reactions offers a promising option for high storage capacities especially at high temperatures. Due to its low material cost the use of the reversible reaction Ca(OH)2 ⇌ CaO + H2O has been suggested. This paper reports on the thermal behavior of a reactor with direct heat transfer between the gaseous reactant and the solid material. Cycling stability is confirmed and the impact of the most significant parameters such as the maximum possible enthalpy difference of the heat transfer fluid between inlet and outlet, the heat transfer, the particle reaction rate and the mass transport is derived. In the test system the particle reaction rate could be identified as the main limiting parameter.

Thermal energy storage technologies can facilitate the transition to an energy system based largely on renewable sources and enable efficiency gains for industrial processes in general. Due to their specific advantages, various concepts of thermo-chemical storage systems are being developed. They share characteristic features of mass and heat transport that are strongly coupled through a variety of physical and chemical phenomena. To facilitate the understanding of the coupled multi-physics processes inside such systems, a versatile conceptual model for directly permeated reactive beds was developed in part 1 of this work. It was based on thermodynamic principles and the Theory of Porous Media. The model was then implemented into OpenGeoSys, a scientific finite element simulation software. In this article, the model is specified to the well-studied calcium hydroxide reaction system to illustrate its practical applicability. Sensitivity analyses reveal the influence of particle diameter, porosity, permeability, mass flux, and reaction rate. Two distinct “reaction waves” are identified to migrate through the reactor. The power required to pump the gas stream was decomposed into parts related to the classical mechanical pressure drop and to the chemical reaction. The results can be used for the optimization of thermochemical heat storage systems.

Wasserstofferzeugung aus flussigen Brennstoffen fur die Versorgung von Brennstoffzellensystemen hat das Potenzial, sowohl in der stationaren dezentralen Energieversorgung als auch im mobilen Bereich Anwendung zu finden. Im Flugzeug kann fur die Bordstromversorgung mittels Brennstoffzelle on-board aus Kerosin erzeugter Wasserstoff eingesetzt werden. Damit wird ein wesentlicher Beitrag zur Reduzierung der Emissionen als auch der Larmbeeintrachtigung durch Flugzeuge am Boden geleistet. Neben den bereits intensiv untersuchten Reformierungsverfahren zur Wasserstofferzeugung wird am DLR ein neuartiges Verfahrenskonzept aus Fraktionierung und nachfolgender partieller katalytischer Dehydrierung (PDh) verfolgt. Die Abtrennung einer signifikant schwefelreduzierten Kerosinfraktion mittels Rektifikation konnte bereits erfolgreich experimentell nachgewiesen werden. Mit der partiellen katalytischen Dehydrierung kann bei einer gegenuber der Reformierung deutlich reduzierten Umwandlungstemperatur unterhalb 500°C reiner Wasserstoff erzeugt werden. Dadurch konnen aufwendige Aufbereitungsschritte zur Reinigung des Produktgases fur den Einsatz in der Brennstoffzelle entfallen. Die Herausforderung bei der Dehydrierung des Flugtreibstoffs Jet A1 liegt in dessen komplexer chemischer Zusammensetzung. Durch GCMS und GCFID konnen vier Hauptstoffgruppen, Paraffine, Iso-Paraffine, Naphthene und Aromaten in Jet A1 identifiziert werden. Die Wasserstoffausbeute aus Kerosin ist in hohem Mase von der Art und dem Anteil dieser Stoffgruppen abhangig. Wahrend Naphthene sich gut zu Wasserstoff und Aromaten umsetzen lassen, werden Aromaten bei der PDh nicht umgesetzt und Paraffine und Iso-Paraffine fuhren zu teilweise gasformigen Nebenprodukten wie Methan und Verkokungen am Katalysator. Da in dem vorgeschalteten Fraktionierungsschritt durch thermische Trennung auch die Zusammensetzung der Stoffgruppen des Kerosins verandert wird, ist es von besonderem Interesse, das Verhalten der Stoffgruppen in der PDh durch experimentelle Untersuchungen beurteilen zu konnen. Beim DLR wurde daher ein PDh-Laborteststand zur Untersuchung der erzielbaren Wasserstoffausbeuten und zur Identifizierung geeigneter Betriebsparameter aufgebaut. Qualifiziert werden neben reinem Kerosin und einzelnen Kohlenwasserstoffgruppen auch unterschiedliche, schwefelreduzierte Fraktionen fur die katalytische partielle Dehydrierung. Basierend auf den experimentellen Ergebnissen erfolgt anschliesend eine energetische Bewertung des Verfahrenskonzepts fur die Bordstromversorgung anhand eines Prozessmodells in Aspen Plus. Fur diesen Zweck wurden zwei warmeintegrierte Prozesskonzepte entwickelt. Zum einen wird die PDh mit vorgeschalteter Fraktionierung abgebildet und zum anderen ein vereinfachtes System bei dem bereits schwefelarmes Kerosin fur die PDh bereitgestellt wird aufgrund dessen ein hoherer Wirkungsgrad erzielt werden kann. Im Rahmen des Vortrags werden ausgewahlte experimentelle Ergebnisse zur partiellen katalytischen Dehydrierung sowie die energetische Bewertung der beiden Prozesskonzepte mittels Pinch- Methode vorgestellt.

Chemical hydrogen storage in complex hydrides offers the potential of high gravimetric storage densities compared to intermetallic hydrides, and is therefore a promising technology for mobile applications. The main challenge for mobile application is still the required high refuelling rate of the hydrogen storage tanks. Since hydrogen is bonded by an exothermal chemical reaction in complex hydrides, appropriate storage tanks require high heat transfer rates for the cooling of the tank. Hydride tanks that are state of the art rely on an indirect cooling and are additionally equipped with e.g. finns, foams, etc. to improve the heat transfer rate. For the present study, an improved laboratory tank, which allows for indirect as well as direct cooling by excess H2 gas (flow-through mode), has been designed and built. This laboratory tank is filled with 87 g of NaAlH4 (doped with 2 mol% CeCl3) and equipped with 8 thermocouples as well as two pressure sensors. Experimental results presented in this paper show a significant influence of the cooling by gaseous excess H2 on the flow-directional temperature profiles at the part of the reaction bed close to the inlet. Considering the overall conversion, this influence is rather small due to the low heat capacity flux (ρ cp)H2. Furthermore, it is shown that changes in material properties, attributed to the effects of heat and mass transport as well as intrinsic reaction kinetics, can be measured and assessed by the temperature and pressure sensors. After about 10 complete charging and discharging cycles, the initial permeability K of the bed has decreased by 50% to 1.6·10−12 m2. In the same time, the initial thermal conductivity has increased by a factor of 1.3 to values reported in literature (0.67 Wm−1 K−1) and remains constant during further cycles. Additionally, it is observed that the reaction rate of the second absorption step improves, even after a total of 36 cycles.

Trotz groser technischer Fortschritte existieren noch immer zahlreiche Hindernisse fur eine breite Markteinfuhrung der Wasserstoff- und Brennstoffzellentechnologie. Neben der Senkung der Herstellungskosten ist insbesondere der Aufbau einer Verteilungsinfrastruktur fur Wasserstoff zu nennen. Entscheidend fur die Beurteilung des Sekundarenergietragers Wasserstoff ist nicht zuletzt, ob es gelingt Wasserstoff nachhaltig zu erzeugen. Unter der Annahme eines verstarkten Markteintritts von Brennstoffzellen-Fahrzeugen ab 2020, stellt die Reformierung biogener Flussigbrennstoffe der 1. Generation (insbesondere Pflanzenol) eine alternative Option zur Wasserstofferzeugung dar. Die vorgestellten Potenzialabschatzungen zeigen, dass bei entsprechenden politischen Rahmenbedingungen 2020 etwa 6 – 8% des heutigen Kraftstoffbedarfs durch Wasserstoff abgedeckt werden konnte, der uber den Weg der Reformierung flussiger Biokraftstoffe der 1. Generation gewonnen wird.

High temperature thermal storage technologies that can be easily integrated into future concentrated solar power plants are a key factor for increasing the market potential of solar power production. Storing thermal energy by reversible gas–solid reactions has the potential of achieving high storage densities while being adjustable to various plant configurations. In this paper the Ca(OH)2/CaO reaction system is investigated theoretically. It can achieve storage densities above 300 kWh/m3 while operating in a temperature range between 400 and 600°C. Reactor concepts with indirect and direct heat transfer are being evaluated. The low thermal conductivity of the fixed bed of solid reactants turned out to considerably limit the performance of a storage tank with indirect heat input through the reactor walls. A one-dimensional model for the storage reactor is established and solved with the Finite Element Method. The reactor concept with direct heat transfer by flowing the gaseous reactant plus additional inert gas through the solid reactants did not show any limitation due to heat transfer. If reaction kinetics are fast enough, the reactor performance in case of the Ca(OH)2/CaO reaction system is limited by the thermal capacity of the gaseous stream to take-up heat of reaction. However, to limit pressure drop and the according losses for compression of the gas stream, the size of the storage system is restricted in a fixed bed configuration.

One possibility to store hydrogen in fuel-cell driven automobiles is the storage in solid state hydrides. Sodium alanate (NaAlH4) is a well-known hydride desorbing up to 5 wt.% H2 with reasonable rates at temperatures above 120 °C. Therefore a high temperature PEM fuel cell (HT-PEM FC) system with exhaust temperatures of about 180 °C can be used to provide the required enthalpy of reaction. In this study, the absorption and desorption behaviour of a lab-scale tank containing 304 g cerium-doped NaAlH4 is studied using (exhaust) air as heat transfer medium. For absorption reactions an optimal temperature for maximal reaction rates is identified. Additionally, the importance of an adapted heat management is shown for the present tank. For desorption experiments different operation procedures are used and the constraints in temperature and air-flow given by the HT-PEM are considered. For all 25 experiments a good cycling stability has been measured with a stabilised material capacity of more than 3.7 wt.% H2.

In the 21st century biofuels will play an important role as alternative fuels in the transportation sector. In this paper different reforming options (steam reforming (SR) and autothermal reforming (ATR)) for the on-board conversion of bioethanol and biodiesel into a hydrogen-rich gas suitable for high temperature PEM (HTPEM) fuel cells are investigated using the simulation tool Aspen Plus. Special emphasis is placed on thermal heat integration. Methyl-oleate (C 19 H 36 O 2 ) is chosen as reference substance for biodiesel. Bioethanol is represented by ethanol (C 2 H 5 OH). For the steam reforming concept with heat integration a maximum fuel processing efficiency of 75.6% (76.3%) is obtained for biodiesel (bioethanol) at S/C = 3. For the autothermal reforming concept with heat integration a maximum fuel processing efficiency of 74.1% (75.1%) is obtained for biodiesel (bioethanol) at S/C = 2 and λ = 0.36 (0.35). Taking into account the better dynamic behaviour and lower system complexity of the reforming concept based on ATR, autothermal reforming in combination with a water gas shift reactor is considered as the preferred option for on-board reforming of biodiesel and bioethanol. Based on the simulation results optimum operating conditions for a novel 5 kW biofuel processor are derived.

Thermische Energiespeicher sind entscheidende Komponenten fur eine verstarkte Nutzung industrieller Abwarme und erneuerbarer Energien. Hier bieten thermochemische Systeme mittels reversibel ablaufender Gas-Feststoffreaktionen Moglichkeiten zur Warmespeicherung auch in einem sehr hohen Temperaturbereich. Dabei eignet sich insbesondere das Reaktionssystem Ca(OH)2 ↔ CaO + H2O aufgrund seiner hohen Energiedichte und geringen Materialkosten. Fur Zerfall und Bildung zeigen thermogravimetrische Messungen bei verschiedenen Partialdrucken und Temperaturen bis 500 °C eine hohe Zyklenbestandigkeit und schnelle Reaktionskinetik. Um Aufschluss uber die limitierenden Grosen beim Warmeund Stofftransport in einem thermochemischen Speicherreaktor zu erhalten, wurde ein 2D-Modell aufgestellt und mittels Finite-Elemente-Methode gelost. Simulationsrechnungen unterschiedlicher Reaktorkonzepte zeigen, dass mit direkter Warmeubertragung eine gute Warmeeinbzw. -auskopplung erreicht werden kann. Beschrankende Grosen sind insbesondere der Warmetransport und der Druckverlust, zu deren weiteren Untersuchung ein Laborteststand konzipiert und aufgebaut wurde. Dabei wird ein beheizter Rohrreaktor, in dem sich die pulverformigen Reaktanden befinden, von einem Stickstoff/Dampfgemisch als Warmetrager durchstromt. Die Reaktion wird fur verschiedene Massenstrome, Temperaturen und Dampfpartialdrucke untersucht, wobei der Reaktionsumsatz, die Temperaturverteilung im Reaktor und der Druckverlust gemessen werden.

Vergleich hinsichtlich Kohlenstoffumsatz, energetischer Effizienz und Wasserstoffbedarf für verschiedene Biomass-to-Liquid-Prozesse jeweils mit und ohne Einsatz von zusätzlichem Wasserstoff aus erneuerbaren Energien.

Der Flugverkehr ist auf Energietrager mit einer hohen Energiedichte angewiesen, diese bieten vor allem flussige Kraftstoffe. Dafur ist die Konzeptionierung und Bewertung von nachhaltigen Herstellungsverfahren synthetischer Kraftstoffe notwendig. Als innovativer Ansatz wird ein „Power-to-Liquid“ Prozess analysiert, bei dem Synthesegas uber die reverse Wasser-Gas-Shift-Reaktion aus Elektrolysewasserstoff und CO2 generiert wird. Das Synthesegas wird im folgenden Fischer-Tropsch-Prozessschritt zu flussigen Kohlenwasserstoffen synthetisiert, die anschliesend zur Herstellung definierter Fraktionen aufbereitet werden. Die Prozessschritte werden zu einem Gesamtprozess verknupft und mittels Prozesssimulation in Aspen Plus abgebildet. Dabei wird zuerst eine Technologiestudie durchgefuhrt und basierend hierauf eine Technologieauswahl getroffen. Mit den Ergebnissen wird anhand der entwickelten Methodik der Gesamtprozess nach den technischen Kenngrosen Kohlenstoffumsatz und energetische Effizienz bewertet. Fur den Prozess ist eine energetische Effizienz von 65% und ein Kohlenstoffumsatz von 75% ermittelt worden. Die Warme- und Stoffintegration der einzelnen Prozesskomponenten bildet die Grundlage fur die energetische Optimierung. Der Einfluss verschiedener Betriebsbedingungen und Verschaltungsvarianten auf den Gesamtprozess wird mit Sensitivitatsanalysen untersucht.

toren, was zu einer deutlichen Erhohung der Cobalt-Dispersion fuhrt und somit die Aktivitat positiv beeinflusst. In einem weiteren Ansatz sollen bifunktionale, nanostrukturierte Kern-Schale-Katalysatoren hergestellt werden, um das breite Produktspektrum auf die interessanten flussigen Kraftstoffe einzugrenzen. Der aktuelle Stand der Arbeiten und die Moglichkeiten zur Kombination der Ansatze werden im Beitrag diskutiert.

Untersuchung des Reaktionssystems CaCl2 \ H2O zur thermo-chemischen Warmespeicherung Bei zahlreichen industriellen Prozessen wird niederkalorische Abwarme z.B. in Form von Abdampf ungenutzt an die Umgebung abgegeben. Fur eine Steigerung der Energieeffizienz und Verminderung von Emissionen stellt die Verwendung dieser anfallender Prozessabwarme auf niedrigem Temperaturniveau ein groses Einsparpotential dar. Neben bereits bestehenden Techniken, wie Warmepumpen oder sensiblen bzw. latenten Warmespeichern, werden derzeitig thermo-chemische Speicher fur diese Anwendungsfalle untersucht. Thermo-chemische Speicher mittels reversibler Gas-Feststoff-Reaktionen zeichnen sich dabei durch hohe Speicherdichten bei gleichzeitiger Moglichkeit einer Warmetransformation und einer Minimierung von Verlusten aus. Fur die Nutzung von Abdampf als verfahrenstechnisch vorteilhaftes Reaktionsmedium bieten sich Salzhydrate als Reaktionssysteme an. Dabei stellte sich bei ersten labor-technischen Untersuchungen das Stoffpaar CaCl2 / H2O bezuglich Reversibilitat, Zyklenbestandigkeit und Speicherdichte als ein vielversprechendes Reaktionssystem heraus. In einem zweiten Schritt wurde, nach Aufbau einer Versuchsanlage im Labormasstab, die prinzipielle technische Machbarkeit dieses Reaktionssystems unter Beweis gestellt. Der Fokus der Untersuchungen lag dabei wahrend den Be- bzw. Entladungszyklen auf dem Warme- und Stofftransport innerhalb des Festbettes sowie den daraus resultierenden Energie- und Umsatzbilanzen des Reaktors. Hierbei zeigte sich das prinzipiell eine vollstandige Hydratation bzw. Dehydratation der CaCl2-Schuttung erreicht werden kann und durch geeignete Wahl der Betriebsbedingungen eine Warmetransformation zu hoheren Entladetemperaturen mogliche ist. Im Rahmen des Vortrages wird auf den Aufbau des Versuchsstandes eingegangen sowie einzelne Ergebnisse der durchgefuhrten Versuchsreihe und deren Interpretationen prasentiert.

Zielsetzung des laufenden DLR-Forschungsvorhabens ist es, die Einsatzmoglichkeiten von Kohlegas als Brennstoff in Hochtemperaturbrennstoffzellen zu untersuchen. Ein wesentlicher Aspekt ist dabei die Prozessgasaufbereitung durch einen Wasser-Gas-Shift-Reaktor und CO 2 -Abtrennung. In dieser Arbeit werden Simulationen verschiedener Kohlekraftwerkskonzeptionen mit integrierter Vergasung mit der Prozesssimulationssoftware Aspen PlusTM durchgefuhrt. Das fur Detailuntersuchungen zugrunde gelegte Basiskonzept unterscheidet sich gegenuber dem kommerziell genutzten GuD-Prozess mit integrierter Vergasung (IGCC) durch die Integration einer Brennstoffzelle und der Anpassung des Kraftwerks¬prozesses. Als Varianten werden verschiedene Moglichkeiten der Kraftwerkskonfiguration und der Prozessgasaufbereitung betrachtet. Die unterschiedlichen Prozessvarianten werden miteinander verglichen und hinsichtlich Wirkungsgrad und verbleibender spezifischer CO 2 -Emmisionen bewertet. Dabei ergeben sich betrachtliche energetische Vorteile fur die Prozessgasaufbereitung durch einen Wasser-Gas-Shift-Reaktor, sowohl mit als auch ohne CO 2 -Abtrennung.

One promising possibility to store thermal energy is by means of reversible gas solid reactions. In this context, the endothermal dehydration of calcium hydroxide (Ca(OH)2) to calcium oxide (CaO) is a well known, cycle stable reaction able to store heat at temperatures above 410 °C and pressures above 0.1 bar. Additionally, the storage material itself is a widely available low cost raw material which allows for low cost thermal energy storage capacities. Therefore, a multifunctional test bench for thermochemical storage reactors has been developed and set into operation. Simultaneously an indirect operated reactor for ∼20 kg Ca(OH)2 was designed, manufactured and integrated into the test bench. Within this work the charge and discharge characteristics of the reactor concerning possible limitations due to heat and mass transfer were studied experimentally. Thereby, the possibility to store and release the heat of reaction at an adjustable temperature level was demonstrated in a technical relevant scale. The storage material remained stable and showed no degradation effects after ten cycles.