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Conference contributions | 2019

Influence of fuel ash and bed material on the water-gas-shift equilibrium in DFB steam gasification

Fürsatz K, Fuchs J, Bartik A, Kuba M, Hofbauer H. Influence of fuel ash and bed material on the water-gas-shift equilibrium in DFB steam gasification. ICPS 2019.

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The bed material chosen for dual fluidized bed steam gasification has an important effect on the performance of gasification. Depending on their characteristics and properties, bed materials can have either a higher or lower catalytic activity, which influences the product gas composition as well as the tar content in the product gas. More catalytically active bed materials, like limestone and olivine, improve the quality of the product gas by e.g. promoting the water-gas-shift reaction and tar reforming reaction. The layers formed on the bed material are another aspect influencing the product gas composition. These layers are formed by the interaction of bed material and fuel ash. The deviation from the water-gas-shift equilibrium was chosen to quantify the effect of several bed materials and ash layers on the catalytic activity. The bed materials tested were K-feldspar, limestone, and activated olivine, while the used fuels were softwood, chicken manure, a bark – chicken manure mixture, and a bark –straw – chicken manure mixture. The performed experiments showed that an increased catalytic activity can be achieved by either using a catalytically active bed materials or ash-rich fuels.

 


Peer Reviewed Scientific Journals | 2019

Input data reduction for microgrid sizing and energy cost modeling: Representative days and demand charges

Fahy K, Stadler M, Pecenak ZK, Kleissl J. Input data reduction for microgrid sizing and energy cost modeling: Representative days and demand charges. Journal of Renewable and Sustainable Energy. 2019.11:065301

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Computational time in optimization models scales with the number of time steps. To save time, solver time resolution can be reduced and input data can be down-sampled into representative periods such as one or a few representative days per month. However, such data reduction can come at the expense of solution accuracy. In this work, the impact of reduction of input data is systematically isolated considering an optimization which solves an energy system using representative days. A new data reduction method aggregates annual hourly demand data into representative days which preserve demand peaks in the original profiles. The proposed data reduction approach is tested on a real energy system and real annual hourly demand data where the system is optimized to minimize total annual costs. Compared to the full-resolution optimization of the energy system, the total annual energy cost error is found to be equal or less than 0.22% when peaks in customer demand are preserved. Errors are significantly larger for reduction methods that do not preserve peak demand. Solar photovoltaic data reduction effects are also analyzed. This paper demonstrates a need for data reduction methods which consider demand peaks explicitly.

 


Scientific Journals | 2019

Interrelation of Volatile Organic Compounds and Sensory Properties of Alternative and Torrefied Wood Pellets

Poellinger-Zierler B, Sedlmayer I, Reinisch C, Hofbauer H, Schmidl C, Kolb LP, Wopienka E, Leitner E, Siegmund B. Interrelation of Volatile Organic Compounds and Sensory Properties of Alternative and Torrefied Wood Pellets. energy & fuels 2019.33:5270-5281.

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The increasing demand for wood pellets on the market, which is caused by their excellent combustion properties, inspires the production as well as the utilization of alternative biomass pellets as fuel. However, the emission of volatile organic compounds gives pellet materials a distinct odor or off-odor, which is directly perceived by the end user. Thus, there is an urgent need for knowledge about the emitted volatile organic compounds and their potential formation pathways as well as their contributions to odor properties of the pellets. In this study, pellets made of biomass energy crops (i.e., straw or miscanthus), byproducts from the food industry (i.e., rapeseed, grapevine, or DDGS (dried distillers grains with solubles from beer production)), or eucalyptus, as well as torrefied pinewood and torrefied sprucewood were investigated with respect to the emitted volatile compounds and their possible impact on the pellet odor. Headspace solid-phase microextraction in combination with gas chromatography–mass spectrometry was used to enrich, separate, and identify the compounds. Techniques used in sensory science were applied to obtain information about the odor properties of the samples. A total of 59 volatile compounds (acids, aldehydes and ketones, alcohols, terpenes, heterocyclic compounds, and phenolic compounds) were identified with different compound ratios in the investigated materials. The use of multivariate statistical data analysis provided deep insight into product–compound interrelation. For pellets produced from bioenergy crops, as well as from byproducts from the food industry, the sensory properties of the pellets reflected the odor properties of the raw material. With respect to the volatiles from torrefied pellets, those volatiles that are formed during the torrefaction procedure dominate the odor of the torrefied pellets covering the genuine odor of the utilized wood. The results of this work serve as a substantiated basis for future production of pellets from alternative raw materials.


Technical Reports | 2019

Langzeitvalidierung eines neuen Ansatzes zur CO-Lambda-Optimierung

Zemann C, Gölles M. Langzeitvalidierung eines neuen Ansatzes zur CO-Lambda-Optimierung. 2019.

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Scientific Journals | 2019

Layer formation mechanism of K-feldspar in bubbling fluidized bed combustion of phosphorus-lean and phosphorus-rich residual biomass.

Wagner K, Häggström G, Skoglund N, Priscak J, Kuba M, Öhman M, Hofbauer H. Layer formation mechanism of K-feldspar in bubbling fluidized bed combustion of phosphorus-lean and phosphorus-rich residual biomass. Applied Energy 2019.248:545-554.

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The use of phosphorus-rich fuels in fluidized bed combustion is one probable way to support both heat and power production and phosphorus recovery. Ash is accumulated in the bed during combustion and interacts with the bed material to form layers and/or agglomerates, possibly removing phosphorus from the bed ash fraction. To further deepen the knowledge about the difference in the mechanisms behind the ash chemistry of phosphorus-lean and phosphorus-rich fuels, experiments in a 5 kW bench-scale-fluidized bed test-rig with K-feldspar as the bed material were conducted with bark, wheat straw, chicken manure, and chicken manure admixtures to bark and straw. Bed material samples were collected and studied for layer formation and agglomeration phenomena by scanning electron microscopy combined with energy dispersive X-ray spectrometry. The admixture of phosphorus-rich chicken manure to bark changed the layer formation mechanism, shifting the chemistry to the formation of phosphates rather than silicates. The admixture of chicken manure to straw reduced the ash melting and agglomeration risk, making it possible to increase the time until defluidization of the fluidized bed occurred. The results also highlight that an increased ash content does not necessarily lead to more ash melting related problems if the ash melting temperature is high enough.


Peer Reviewed Scientific Journals | 2019

Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood Part 1: K-Feldspar

Faust R, Hannl T K, Berdugo Vilches T, Kuba M, Öhmann M, Seemann M C, Knutsson P Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood Part 1: K-Feldspar.Energy&Fuels 2019.33:8:7321-7332

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The choice of bed material for biomass gasification plays a crucial role for the overall efficiency of the process. Olivine is the material conventionally used for biomass gasification due to the observed activity of olivine toward cracking of unwanted tars. Despite its catalytic activity, olivine contains high levels of chromium, which complicates the deposition of used bed material. Feldspar has shown the same activity as olivine when used as a bed material in biomass gasification. As opposed to olivine, feldspar does not contain environmentally hazardous compounds, which makes it a preferred alternative for further applications. The interaction of bed material and ash heavily influences the properties of the bed material. In the present study interactions between feldspar and main ash compounds of woody biomass in an indirect gasification system were investigated. Bed material samples were collected at different time intervals and analyzed with SEM-EDS and XRD. The obtained analysis results were then compared to thermodynamic models. The performed study was divided in two parts: in part 1 (the present paper), K-rich feldspar was investigated, whereas Na-rich feldspar is presented in part 2 of the study (DOI: 10.1021/acs.energyfuels.9b01291). From the material analysis performed, it can be seen that, as a result of the bed materials’ interactions with the formed ash compounds, the latter were first deposited on the surface of the K-feldspar particles and later resulted in the formation of Ca- and Mg-rich layers. The Ca enriched in the layers further reacted with the feldspar, which led to its diffusion into the particles and the formation of CaSiO3 and KAlSiO4. Contrary to Ca, Mg did not react with the feldspar and remained on the surface of the particles, where it was found as Mg- or Ca-Mg-silicates. As a result of the described interactions, layer separation was noted after 51 h with an outer Mg-rich layer and an inner Ca-rich layer. Due to the development of the Ca- and Mg-rich layers and the bed material–ash interactions, crack formation was observed on the particles’ surfaces.


Scientific Journals | 2019

Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood. 1. K-Feldspar

Faust R, Hannl TK, Berdugo Vilches T Kuba M, Öhman M, Seemann M, Knutsson P. Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood. 1. K-Feldspar. Energy and Fuels 2019.33:7321-7332.

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The choice of bed material for biomass gasification plays a crucial role for the overall efficiency of the process. Olivine is the material conventionally used for biomass gasification due to the observed activity of olivine toward cracking of unwanted tars. Despite its catalytic activity, olivine contains high levels of chromium, which complicates the deposition of used bed material. Feldspar has shown the same activity as olivine when used as a bed material in biomass gasification. As opposed to olivine, feldspar does not contain environmentally hazardous compounds, which makes it a preferred alternative for further applications. The interaction of bed material and ash heavily influences the properties of the bed material. In the present study interactions between feldspar and main ash compounds of woody biomass in an indirect gasification system were investigated. Bed material samples were collected at different time intervals and analyzed with SEM-EDS and XRD. The obtained analysis results were then compared to thermodynamic models. The performed study was divided in two parts: in part 1 (the present paper), K-rich feldspar was investigated, whereas Na-rich feldspar is presented in part 2 of the study (DOI: 10.1021/acs.energyfuels.9b01291). From the material analysis performed, it can be seen that, as a result of the bed materials’ interactions with the formed ash compounds, the latter were first deposited on the surface of the K-feldspar particles and later resulted in the formation of Ca- and Mg-rich layers. The Ca enriched in the layers further reacted with the feldspar, which led to its diffusion into the particles and the formation of CaSiO3 and KAlSiO4. Contrary to Ca, Mg did not react with the feldspar and remained on the surface of the particles, where it was found as Mg- or Ca-Mg-silicates. As a result of the described interactions, layer separation was noted after 51 h with an outer Mg-rich layer and an inner Ca-rich layer. Due to the development of the Ca- and Mg-rich layers and the bed material–ash interactions, crack formation was observed on the particles’ surfaces.


Scientific Journals | 2019

Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood. 2. Na-Feldspar

Hannl TK, Faust R, Kuba M, Knutsson P, Berdugo Vilches T, Seemann MC, Öhman M. Layer Formation on Feldspar Bed Particles during Indirect Gasification of Wood Part 2: Na-Feldspar. Energy and Fuels 2019.33:7333-7346.

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Selecting a suitable bed material for the thermochemical conversion of a specific feedstock in a fluidized bed system requires identification of the characteristics of potential bed materials. An essential part of these characteristics is the interaction of the bed material with feedstock ash in a fluidized bed, which leads to layer formation and morphology changes. For this purpose, the interaction of feldspar bed material with the main ash-forming elements in wood ash (Ca, K, Mg, Si) in an indirect gasification system was analyzed using SEM-EDS, XRD, and thermodynamic modeling. In part 1 of this work (DOI: 10.1021/acs.energyfuels.9b01291), the layer formation on K-feldspar dominated by Ca reaction and ash deposition was investigated. The aim of this second part of the work was to determine the time-dependent layer formation on Na-feldspar and compare the results with the findings for K-feldspar. Interaction of Na-feldspar with ash-derived elements resulted in different layers on Na-feldspar: K reaction layers, where K replaced Na and Si shares decreased; Ca reaction layers, where Ca enriched and reacted with the Na-feldspar; and ash deposition layers, where wood ash elements accumulated on the surface. Ca reaction layers were formed first and became continuous on the surface before K reaction layers and ash deposition layers were detected. Cracks and crack layer formation in the Na-feldspar particles were found after several days of operation. The layer compositions and growth rates indicate that the diffusion of Ca and K plays an essential role in the formation of Ca reaction and K reaction layers. The reaction with Ca and the crack formation coincide with the interaction previously found for quartz and K-feldspar. In contrast to K-feldspar, Na-feldspar showed high potential for reaction with K. The findings indicate that the reaction of Na-feldspar with ash-derived K makes Na-feldspar a less stable bed material than K-feldspar during the thermochemical conversion of K-rich feedstocks in a fluidized bed system.


Scientific Journals | 2019

Layer formation on K-feldspar in fluidized bed combustion and gasification of bark and chicken manure

Wagner K, Häggström G, Mauerhofer AM, Kuba M, Skoglund N, Öhman M, Hofbauer H. Layer formation on K-feldspar in fluidized bed combustion and gasification of bark and chicken manure. Biomass and Bioenergy 2019.127:105251.

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Understanding layer formation on bed materials used in fluidized beds is a key step for advances in the application of alternative fuels. Layers can be responsible for agglomeration-caused shut-downs but they can also improve the gas composition in fluidized bed gasification. Layers were observed on K-feldspar (KAlSi3O8) impurities originating from the combined heat and power plant Senden which applies the dual fluidized bed (DFB) steam gasification technology. Pure K-feldspar was therefore considered as alternative bed material in DFB steam gasification. Focusing on the interactions between fuel ash and bed material, K-feldspar was tested in combustion and DFB steam gasification atmospheres using different fuels, namely Ca-rich bark, Ca- and P-rich chicken manure, and an admixture of chicken manure to bark. The bed particle layers formed on the bed material surface were characterized using combined scanning electron microscopy and energy-dispersive X-ray spectroscopy; area mappings and line scans were carried out for all samples. The obtained data show no essential influence of operational mode on the layer-formation process. During the combustion and DFB steam gasification of Ca-rich bark, a layer rich in Ca formed while K was diffusing out of the layer. The use of Ca- and P-rich chicken manure inhibited the diffusion of K, and a layer rich in Ca and P formed. The addition of P to bark via chicken manure also changed the underlying layer-formation processes to reflect the same processes as observed for pure chicken manure.


Technical Reports | 2019

Machbarkeitsuntersuchung Methan aus Biomasse

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Im Rahmen dieser zusammenfassenden Machbarkeitsstudie werden Untersuchungen zum Biomassepotential in Österreich im Jahr 2050 sowie der Synthese von BioSNG auf Basis der Biomassewirbelschichtvergasung durchgeführt. Dabei werden verschiedene Vergasungsverfahren, welche durch den Reaktortyp charakterisiert sind, dargestellt. Bedingt durch das homogene Temperaturprofil, welches in einem Wirbelschichtvergaser gegeben ist und die dadurch gegebene einfache Regelbarkeit des Prozesses, stellt sich die Wirbelschicht als vorteilhaft im Vergleich zu Flugstromvergasern dar, welche durch das hohe Temperaturniveau einen höheren technischen Aufwand mit sich bringen und daher für Anlagen mit großen Brennstoffwärmeleistungen zu bevorzugen sind. In weiterer Folge wird auf den DFB Prozess und dessen Weiterentwicklung, den G-Volution Vergaser eingegangen, welcher den Vorteil eines größeren einzusetzenden Brennstoffspektrums aufweist.


Conference contributions | 2019

Manufacturers' data vs. literature data - a comparison of LCI and LCA results for wood-burning residential heating systems

Rixrath D, Wartha C, Enigl E, Strasser C, Piringer G, Pali E. Manufacturers' data vs. literature data - a comparison of LCI and LCA results for wood-burning residential heating systems. SETAC 19 Conference (Poster). May 2019.

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Scientific Journals | 2019

Mathematical model of Fischer-Tropsch synthesis using variable alpha-parameter to predict product distribution.

Filip L, Zámostný P, Rauch R. Mathematical model of Fischer-Tropsch synthesis using variable alpha-parameter to predict product distribution. Fuel 2019;243:603-609.

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A mathematical model was developed based on data obtained on Fischer-Tropsch (FT) laboratory scale unit operated in steady state, belonging to BIOENERGY 2020+ GmbH, Austria to demonstrate alpha-parameter dependence on carbon number. The lab-scale unit processed the synthesis gas, obtained by the gasification of biomass (woodchips), to produce liquid fuels for transportation applications. The FT reaction took place in a slurry reactor filled with dispersed cobalt-based catalyst. The products were then separated by partial condensation depending on their boiling points. The final output of the FT laboratory scale unit comprised three product streams – wax, diesel and naphtha. The reaction and separation of products were simulated in Aspen Plus software. The mathematical model used kinetic description based on power-law rate equations. The modeled product selectivity was controlled using an alpha-parameter of the Anderson-Schulz-Flory distribution. Because of the significant deviation of products spectrum from typical Anderson-Schulz-Flory distribution, a modified description of reaction selectivity was developed. The description introduces variable alpha-parameter, dependent on number of carbon atoms in the reacting molecule. The mathematical model developed using MATLAB software considered the production of aliphatic paraffins having a number of carbon atoms from C1 to C60. The mathematical model of simulated lab-scale unit comprised an ideally mixed reactor RCSTR and three FLASH2 separators for the separation of desired products. The results from mathematical model were validated by a comparison with experimental results from FT lab-scale unit. The modified polynomial dependency of alpha-parameter on carbon number showed significantly better description of composition and amounts of FT products, especially for wax stream where the description using constant alpha led to enormous deviations. Such better prediction of composition and amounts of acquired products is important for evaluating efficiency of further upgrading the FT products to liquid fuel.


Conference contributions | 2019

Microbial Production of Enzymes from Blood and Pulp Processing Waste Streams

Weiss R, Prall K, Neunteufel E, Ortner M, Guebitz G, Nyanhongo G. Microbial Production of Enzymes from Blood and Pulp Processing Waste Streams. 8th Congress of European Microbiologists (FEMS). July 2019.

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Peer Reviewed Scientific Journals | 2019

New experimental evaluation strategies regarding slag prediction of solid biofuels in pellet boilers

Schön C, Feldmeier S, Hartmann H, Schwabl M, Dahl J, Rathbauer J, Vega-Nieva D, Boman C, Öhman M, Burvall J. New experimental evaluation strategies regarding slag prediction of solid biofuels in pellet boilers. Energy & Fuels. 2019.33:11985-11995

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Pellet boilers and pellet stoves are widely used for heat production. But in most cases, only specific wood pellets with a low ash content are approved due to the increased risk of slagging and limited deashing capacity. The ash fusion test (AFT), according to prCEN/TS 15370-1, is currently the only standard method for the prediction of slagging. This method is not feasible for all biomass fuel types, since sometimes the characteristic temperatures cannot be determined or the characteristic shapes do not occur for temperature determination. Furthermore, the method is costly and requires complex instrumental infrastructure. Hence, a demand for more expressive or more rapid methods to characterize slag formation potential of fuels is often claimed. Based on a literature study, four such laboratory test methods were chosen, partly adapted, and then experimentally investigated. These methods included thermal treatment of the fuel itself or the ashes of the fuel and were the rapid slag test, CIEMAT, the slag analyzer, and the newly developed pellet ash and slag sieving assessment (PASSA) method. Method performance was practically assessed using 14 different biomass fuel pellets, which were mainly from different assortments of wood, but also herbaceous or other nonwoody fuels. The results from the tests with these four alternative methods were evaluated by comparing to both results from standard AFT and results from full-scale combustion tests performed over a maximum of 24 h. Seven different pellet boilers were assessed, of which one boiler was used to apply all 14 test fuels. According to the granulometric ash analysis (i.e., the ratio of >1 mm-fraction toward total ash formed), the sensitivity of the new test methods to depict slagging phenomena at a suitable level of differentiation was assessed. Satisfactory conformity of the boiler ash assessment (reference) was found for both, the slag analyzer and the PASSA method. The latter may, in particular, be seen as a promising and relatively simple low-input procedure, which can provide more real-life oriented test results for fixed-bed combustion. The standardized AFT could, however, not sufficiently predict the degree of slag actually formed in the reference boiler, particularly when only wood fuels are regarded.


Peer Reviewed Scientific Journals | 2019

NPK 2.0: Introducing tensor decompositions to the kinetic analysis of gas–solid reactions

Birkelbach F, Deutsch M, Flegkas S, Winter F, Werner A. NPK 2.0: Introducing tensor decompositions to the kinetic analysis of gas–solid reactions. Int J Chem Kinet. 2019;1–11.

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A method for deriving kinetic models of gas–solid reactions for reactor and process design is presented. It is based on the nonparametric kinetics (NPK) method and resolves many of its shortcomings by applying tensor rank‐1 approximation methods. With this method, it is possible to derive kinetic models based on the general kinetic equation from any combination of experiments without additional a priori assumptions. The most notable improvements over the original method are that it is computationally much simpler and that it is not limited to two variables. Two algorithms for computing the rank‐1 approximation as well as a tailored initialization method are presented, and their performance is assessed. Formulae for the variance estimation of the solution values are derived to improve the accuracy of the model identification and to provide a tool for diagnosing the quality of the kinetic model. The methods effectiveness and performance are assessed by applying it to a simulated data set. A Matlab implementation is available as Supporting Information.


Conference contributions | 2019

Numerical simulation and experimental analysis of a novel small scale biomass grate firing system

Eßl M, Mehrabian R, Shiehnejad-Hesar A, Kelz J, Feldmeier S, Reiterer T, Anca-Couce A, Robert Scharler R. Numerical simulation and experimental analysis of a novel small scale biomass grate firing system. 27th European Biomass Conference & Exhibition (Poster). May 2019.

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The presented grate firing system is a patented small scale screw burner, which is designed for high fuel flexibility. This work focuses on the numerical modelling of the boiler via CFD simulations. The in-house developed CFD models use an Euler – Lagrange approach to predict the thermal degradation of the fuel particles and the subsequent gas-phase reactions. The CFD models are validated with experimental data from a representative measurement campaign where the boiler is operated with softwood pellets and the composition of the flue gas is measured in the primary and secondary combustion zone as well as the boiler outlet. The simulation results agree well with the data acquired in the measurement campaigns.
Keywords: CFD, simulation, combustion, small scale application, wood pellet

 


Conference contributions | 2019

Nutrient recovery by digestate processing

Drosg B, Fuchs W. Nutrient recovery by digestate processing. Second COASTAL Biogas conference (Roskilde, Denmark). Nov 2019.

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Other Presentations | 2019

Optimization Based Design and Control of Distributed Energy Resources and Microgrids

Stalder M, Optimization Based Design and Control of Distributed Energy Resources and Microgrids. LetsCluster, Lighthouse Summit in the heart of Europe: Smart Energy Generation - Management - Optimization, Smart Home / Building, Interface to the Smart Grid, Microgrids, Electric Grid of the Future, Sector Linking, Graz, Österreich, 25 - 27 März 2019

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Peer Reviewed Scientific Journals | 2019

Overview obstacle maps for obstacle‐aware navigation of autonomous drones

Pestana J, Maurer M, Muschick D, Hofer M, Fraundorfer F. Overview obstacle maps for obstacle-aware navigation of autonomous drones. Journal of Field Robotics 2019.

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Achieving the autonomous deployment of aerial robots in unknown outdoor environments using only onboard computation is a challenging task. In this study, we have developed a solution to demonstrate the feasibility of autonomously deploying drones in unknown outdoor environments, with the main capability of providing an obstacle map of the area of interest in a short period of time. We focus on use cases where no obstacle maps are available beforehand, for instance, in search and rescue scenarios, and on increasing the autonomy of drones in such situations. Our vision‐based mapping approach consists of two separate steps. First, the drone performs an overview flight at a safe altitude acquiring overlapping nadir images, while creating a high‐quality sparse map of the environment by using a state‐of‐the‐art photogrammetry method. Second, this map is georeferenced, densified by fitting a mesh model and converted into an Octomap obstacle map, which can be continuously updated while performing a task of interest near the ground or in the vicinity of objects. The generation of the overview obstacle map is performed in almost real time on the onboard computer of the drone, a map of size urn:x-wiley:15564959:media:rob21863:rob21863-math-0001 is created in urn:x-wiley:15564959:media:rob21863:rob21863-math-0002, therefore, with enough time remaining for the drone to execute other tasks inside the area of interest during the same flight. We evaluate quantitatively the accuracy of the acquired map and the characteristics of the planned trajectories. We further demonstrate experimentally the safe navigation of the drone in an area mapped with our proposed approach.


Peer Reviewed Scientific Journals | 2019

Photoautotrophic production of poly-hydroxybutyrate – First detailed cost estimations

Panuschka S, Drosg B, Ellersdorfer M, Meixner K, Fritz I. Photoautotrophic production of poly-hydroxybutyrate – First detailed cost estimations. Algal Research 2019.41:101558.

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Political, economic and ecological reasons have recently been leading to efforts to replace fossil hydrocarbons and their products in a sustainable way. In order to replace fossil-based polymers, photoautotrophically produced polyhydroxybutryrates (PHBs), which are intracellular carbon storage products of nutrient-deprived microorganisms, seem to be a promising, biobased and biodegradable alternative. Although laboratory and pilot scale experiments have already been performed, no economic evaluation has been carried out so far. Consequently, valid claims on PHB production costs and the influence of different parameters, such as intracellular PHB-content, choice of cultivation system or location, cannot be made. In this study potential demonstration plants, equipped with different photoautotrophic cultivation systems and located at two sites, were designed to identify key parameters for a successful economic realization and implementation. Material and energy balances were determined to reveal specific PHB production costs for four different scenarios. Raw material and operating supply costs, expenditures for plant construction and operation as well as product amounts were determined using literature data for specified results from laboratory and pilot scale experiments. The lowest calculated PHB production price (24 € kg−1) accomplished in a thin-layer-system plant located in Southern Europe with 60% PHB-content of the produced biomass is significantly higher than the current market price of heterotrophically produced PHB. The most important cost factors in all scenarios are cultivation and harvesting costs accounting for 62 to 72% of the total specific production costs, followed by maintenance costs with a cost share of 11 to 14%. Therefore, the choice of a suitable cultivation system is the key driving factor for an economic PHB-production due to the currently high investment costs for photosynthetic biomass production systems. Specific production costs for a Southern compared to a Central European location amount to almost half of the costs.


Peer Reviewed Scientific Journals | 2019

Planning and implementation of bankable microgrids

Stadler M, Nasle A. Planning and implementation of bankable microgrids. The Electricity Journal 2019. 32:24-29.

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Currently, many Microgrid projects remain financially uncertain and not bankable for institutional investors due to major challenges in existing planning and design methods that require multiple, complex steps and software tools.

Existing techniques treat every Microgrid project as a unique system, resulting in expensive, non-standardized approaches and implementations which cannot be compared. That is, it is not possible to correlate the results from different planning methods performed by different project developers and/or engineering companies.

This very expensive individual process cannot guarantee financial revenue streams, cannot be reliably audited, impedes pooling of multiple Microgrid projects into a financial asset class, nor does it allow for wide-spread and attractive Microgrid and Distributed Energy Resource projects deployment.

Thus, a reliable, integrated, and streamlined process is needed that guides the Microgrid developer and engineer through conceptual design, engineering, detailed electrical design, implementation, and operation in a standardized and data driven approach, creating reliable results and financial indicators that can be audited and repeated by investors and financers.

This article describes the steps and methods involved in creating bankable Microgrids by relying on an integrated Microgrid planning software approach that unifies proven technologies and tested planning methods, researched and developed by the United States National Laboratory System as well as the US Department of Energy, to reduce design times.


Conference contributions | 2019

Practical example: manufacturers’ data vs data from ecoinvent database – a comparison of LCI and LCA

Rixrath D, Wartha C, Enigl M, Strasser C, Piringer G. Practical example: manufacturers’ data vs data from ecoinvent database – a comparison of LCI and LCA. 15. Minisymposium Verfahrenstechnik MU Leoben (Poster). 2019.

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The aim of this work is to analyze biogenic residues and to test
them for their suitability as feedstocks for hydrothermal
liquefaction (HTL). Green waste, sewage sludge, micelles,
leftovers and organic waste were analyzed and tested. All
experiments were carried out in an autoclave at 350 °C with a
holding time of 15 minutes under an inert argon atmosphere. After
the experiments the yields of the gas, aqueous, biocrude and solid
phase were determined together with lipid contents, heating values
and elemental composition of the raw materials and biocrude
samples. Biocrude yields are of specific interest for a future
commercial use of the HTL-process. In this study we achieved
biocrude yields between 9.43% (green waste) and 34.28%
(leftovers).


Other Presentations | 2019

Primäre und sekundäre Verbesserungen an einem Biomassekessel für Agrarbrennstoffe

Zemann C, Kelz J, Muschick D, Retschitzegger S, Gölles M. Primäre und sekundäre Verbesserungen an einem Biomassekessel für Agrarbrennstoffe. 10. Fachgespräch: Partikelabscheider in häuslichen Feuerungen. 20. März 2019 (2019). [online]. (Tagungsreader, 15). Leipzig: DBFZ. 168 S.

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ie Biomasseverbrennung spielt eine zentrale Rolle bei der Bereitstellung von Wärme aus erneuerbaren Energieträgern. Konventionelle Biomasse-Brennstoffe werden jedoch aufgrund einer steigenden Anzahl stofflicher Verwertungsmöglichkeiten, wie z.B. der Umwandlung in Chemikalien, teurer und schwieriger zugänglich. Agrarbrennstoffe, die bisher nur selten oder gar nicht in Biomasse-Kleinfeuerungen eingesetzt wurden, stellen eine vielversprechende Alternative zu konventionellen Brennstoffen dar. Diese Agrarbrennstoffe, wie zum Beispiel Kurzumtrieb, Maisspindeln oder Stroh sind kostengünstig und in ausreichender Menge vorhanden. Der Einsatz von Agrarbrennstoffen in konventionellen Biomasse-Kleinfeuerungen ist jedoch aufgrund stark variierender Brennstoffeigenschaften mit erhöhten Anforderungen an das Verbrennungssystem verbunden. Erhöhte N, S, Cl, Alkalimetall- und Aschegehalte sowie niedrigere Aschenschmelzpunkte können zu aschebedingten Problemen (Ascheschmelze, Ascheablagerung und Korrosion) sowie erhöhten Konzentrationen von gasförmigen (CO, NOx, HCl und SOx) und partikelförmigen Emissionen bei der Verbrennung führen.

Ziel der in diesem Beitrag präsentierten Arbeiten war die Erhöhung die Brennstoffflexibilität einer handelsüblichen Biomasse-Kleinfeuerung um damit eine Verbrennung von Agrarbrennstoffen mit niedrigen Schadstoffemissionen und einem hohen Wirkungsgrad zu ermöglichen. Hierzu wurde eine modellbasierte Regelung entwickelt, welche insbesondere eine gezielte Einstellung des Luftverhältnisses in der Primärverbrennungszone ermöglicht und damit das Risiko der Ascheschmelze reduziert und Schadstoffmissionen verringert. Soft-Sensoren bestimmen relevante Brennstoffeigenschaften während des Betriebs, welche von der modellbasierten Regelung zur automatischen Anpassung an geänderte Brennstoffeigenschaften genutzt werden. Die modellbasierte Regelung wurde um eine CO-lambda-Optimierung ergänzt, welche auf Basis von Messwerten des Restsauerstoffgehalts und der CO-Emissionen den Wirkungsgrad der Verbrennung maximiert und gleichzeitig die Schadstoffemissionen verringert. Zur weiteren Verringerung von partikelförmigen Schadstoffemissionen wurde ein am Markt verfügbarer Elektrofilter adaptiert und nach dem Wärmeübertrager der Biomasse-Kleinfeuerung angebracht.

Dieses Verbrennungssystem wurde durch umfassende Testläufe mit begleitenden Emissionsmessungen sowie Brennstoff-, Staub- und Ascheanalysen bewertet. Der Einsatz der modellbasierten Regelung führte zu einem stabileren Betrieb bei allen Leistungen und für alle Brennstoffe. Der Elektrofilter zeigte sehr zufriedenstellende Abscheidegrade für alle untersuchten Brennstoffe und Anlagenleistungen. Dadurch konnte die Brennstoffflexibilität der handelsüblichen Biomasse-Kleinfeuerung erhöht und die Verbrennung von Agrarbrennstoffen ermöglicht werden.

 


Scientific Journals | 2019

Real-life emission factor assessment for biomass heating appliances at a field measurement campaign in Styria, Austria

Sturmlechner R, Schmidl C, Carlon E, Reichert G, Stressler H, Klauser F, Kelz J, Schwabl M, Kirchsteiger B, Kasper-Giebl A, Höftberger E, Haslinger W. Real-life emission factor assessment for biomass heating appliances at a field measurement campaign in Styria, Austria. WIT Transactions on Ecology and the Environment 2019.236:221-231

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Biomass combustion is a major contributor to ambient air pollution. Thus, knowing the real-life emissions of biomass heating systems is crucial. Within the project Clean Air by biomass a field measurement campaign was conducted. 15 biomass heating appliances were tested in households at the end user according to their usual operation. Emission factors for gaseous and particulate emissions, as well as for the genotoxic and carcinogenic substance benzo(a)pyrene, were evaluated and compared to current proposed European and Austrian emission factors used for emission inventories. Moreover, the shares of particles and benzo(a)pyrene in hot and cooled flue gas were determined. Results showed a high variability of emissions in the field. Highest values and ranges occurred for room heaters (TSPtotal: 226 mg/MJ). Biomass boilers showed clearly lower emission factors (TSPtotal: 184 mg/MJ) in the field than room heaters and also than the proposed European and Austrian emission factors, in many cases. Emission factors for tiled stoves showed a similar trend (TSPtotal: 67 mg/MJ). The share of condensable particles in the flue gas was remarkable. Especially benzo(a)pyrene was found mostly in the condensable fraction of the particles.


Conference contributions | 2019

Reduction of ash-realted problems in large-scale biomass combustion systems via resource efficient low-cost fuel additives

Sommersacher P, Kienzl N, Retschitzegger S. Reduction of ash-realted problems in large-scale biomass combustion systems via resource efficient low-cost fuel additives. 27th European Biomass Conference & Exhibition (Poster). 2019.

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The incineration of waste wood is very often associated with ash-related problems (deposits, slagging and corrosion). This leads to short maintenance intervals, which result in significant power generation losses and high downtime costs. To avoid these problems, additives can be used, with particularly cost-effective additives being of great interest. Based on pre-evaluations, the addition of 2% gypsum and 3% coal fly ash was recommended, since an improved ash melting behaviour and reduced risk for high-temperature corrosion can be expected with addition of gypsum and coal fly ash. These additives with the recommended mixing rates were then investigated in a large-scale plant. Extensive investigations were carried out without additive (as a reference), and with the additives focusing on dust formation (aerosols and total dust), deposit formation and the corrosion behaviour of superheaters. These investigations were accompanied by fuel and ash analyses (grate, cyclone and filter). The addition of additives increased the amount of total dust in the flue gas up to 195% and 262% for gypsum and coal fly ash respectively. The chemical analysis of the total dust showed an enrichment of refectory species like Al for coal fly ash and Ca and Mg for gypsum which can positively influence the slagging behaviour. Aerosol measurements showed that the addition of coal fly ash minimised the amount of fine particulate matter, as less alkali metals (K and Na) were released into the gas phase. Gypsum addition increases the SO2 concentrations in the gas phase due to the decomposition of gypsum, as in the combustion chamber about 900°C are present. Due to the preferred sulphation reactions (binding of S to alkali metals) less Cl is bound to alkali metals and therefore the Cl concentrations in the aerosols were lower compared to the reference case. This effect was also found in the deposits sampled at the position of the superheater. Based on the chemical composition of deposits the molar 2S/Cl ratios were determined, which can be used to predict the risk for high temperature corrosion. The analysis data showed that an improvement concerning the high temperature corrosion risk is possible by adding coal fly ash, whereas a significant improvement in case of gypsum additions seems very likely. The measurements carried out so far showed the influence (built-up rate, chemical composition etc.) of the additive application on ash fractions, deposits and dusts. By taking a closer look at the change in chemical compositions of dusts and deposits, additives with an appropriate additivation ratio can be suggested. In case of coal fly ash 3% and in case of gypsum 1% additive related to dry fuel seems to be adequate additive ratios to positively influence the risk of high temperature corrosion and reduce the slagging behaviour.