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Peer Reviewed Scientific Journals | 2020

Robust design of microgrids using a hybrid minimum investment optimization

Pecenak ZK, Stadler M, Mathiesen P, Fahy K, Kleissl J. Robust design of microgrids using a hybrid minimum investment optimization. Applied Energy. 2020;276:115400.

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Recently, researchers have begun to study hybrid approaches to Microgrid techno-economic planning, where a reduced model optimizes the DER selection and sizing is combined with a full model that optimizes operation and dispatch. Though providing significant computation time savings, these hybrid models are susceptible to infeasibilities, when the size of the DER is insufficient to meet the energy balance in the full model during macrogrid outages. In this work, a novel hybrid optimization framework is introduced, specifically designed for resilience to macrogrid outages. The framework solves the same optimization problem twice, where the second solution using full data is informed by the first solution using representative data to size and select DER. This framework includes a novel constraint on the state of charge for storage devices, which allows the representation of multiple repeated days of grid outage, despite a single 24-h profile being optimized in the representative model. Multiple approaches to the hybrid optimization are compared in terms of their computation time, optimality, and robustness against infeasibilities. Through a case study on three real Microgrid designs, we show that allowing optimizing the DER sizing in both stages of the hybrid design, dubbed minimum investment optimization (MIO), provides the greatest degree of optimality, guarantees robustness, and provides significant time savings over the benchmark optimization.


Peer Reviewed Scientific Journals | 2020

Scale-up methodology for automatic biomass furnaces

Barroso G, Nussbaumer T, Ulrich M, Reiterer T, Feldmeier S. Scale-up methodology for automatic biomass furnaces. Journal of the Energy Institute 2020.93:591-604.

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This work presents a methodology to perform the scale-up of a solid fuel furnace to a higher heat output with maintaining or improving the burn-out quality. As basis to derive the scale-up concept, an example of a 35 kW screw burner for biomass fuels is investigated. Based on the Pi-theorem, the relevant dimensionless parameters are derived and similarity rules for the scale-up are proposed as follows: As initial conditions, the height to diameter ratio of the combustion chamber, the mean Reynolds number in the combustion chamber and the mean square velocity through the combustion chamber shall be kept constant or in the case of the Reynolds number may also increase. Additionally the effective momentum flux ratio between the secondary air injected in the combustion chamber and the gases from the pyrolysis and gasification section also shall be kept constant to maintain the mixing conditions between combustible gases and secondary air. Finally the thermal surface load on the screw also shall be kept constant. The influence of different scale-up approaches on thermal surface load, gas velocity, pressure losses, Reynolds number and height-to-diameter ratio are compared and discussed and a scaling approach to increase the heat output from 35 kW to 150 kW is described. For a theoretical validation of the scale-up, CFD simulations are performed to investigate the predicted pollutant emissions and the pressure loss for the scaled 150 kW furnace.


Conference Papers | 2020

Simultaneous state and fuel property estimation in biomass boilers - theory and practice

Zemann C, Gölles M, Horn M. Simultaneous state and fuel property estimation in biomass boilers - theory and practice. 1st Virtual IFAC World Congress. 2020.

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A key factor for the further distribution of biomass boilers in modern energy systems is the capability of changing the applied feedstock during normal plant operation. This is only possible with the application of advanced control strategies that utilize knowledge about the state variables and varying fuel properties. However, neither the state variables nor the fuel properties are measurable during plant operation and, thus, need to be estimated. This contribution presents a method for the simultaneous real-time estimation of the state variables and the fuel properties in fixed-bed biomass boilers which is a novel approach in the field of biomass boilers. The method bases on an Extended Kalman Filter using a nonlinear dynamic model and measurement data from the combustion process. The estimated variables are the masses of dry fuel and water in the fuel bed as well as the fuel's bulk density, water content, chemical composition and lower heating value. The proposed method is easy to implement and requires moderate computational effort which increases the potential of its application at actual biomass boilers. The proposed method is verified with simulation studies and by test runs performed at a representative small-scale fixed-bed biomass boiler. The estimation results show a good agreement with the actual values, demonstrating that the proposed method is capable of accurately estimating the biomass boiler's state variables and simultaneously its fuel properties. For this reason, the presented method is a key technology to ensure the further distribution of biomass boilers in modern energy systems.


Peer Reviewed Scientific Journals | 2020

Simultaneous state and fuel property estimation in biomass boilers - theory and practice

Zemann C, Gölles M, Horn M. Simultaneous state and fuel property estimation in biomass boilers - theory and practice. IFAC-PapersOnLine. 2020;53(2):12763-12770. https://doi.org/10.1016/j.ifacol.2020.12.1920

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A key factor for the further distribution of biomass boilers in modern energy systems is the capability of changing the applied feedstock during normal plant operation. This is only possible with the application of advanced control strategies that utilize knowledge about the state variables and varying fuel properties. However, neither the state variables nor the fuel properties are measurable during plant operation and, thus, need to be estimated. This contribution presents a method for the simultaneous real-time estimation of the state variables and the fuel properties in fixed-bed biomass boilers which is a novel approach in the field of biomass boilers. The method bases on an Extended Kalman Filter using a nonlinear dynamic model and measurement data from the combustion process. The estimated variables are the masses of dry fuel and water in the fuel bed as well as the fuel’s bulk density, water content, chemical composition and lower heating value. The proposed method is easy to implement and requires moderate computational effort which increases the potential of its application at actual biomass boilers. The proposed method is verified with simulation studies and by test runs performed at a representative small-scale fixed-bed biomass boiler. The estimation results show a good agreement with the actual values, demonstrating that the proposed method is capable of accurately estimating the biomass boiler’s state variables and simultaneously its fuel properties. For this reason, the presented method is a key technology to ensure the further distribution of biomass boilers in modern energy systems.


Conference Papers | 2020

Soft-Sensor for the on-line estimation of the flue gas mass flow in biomass boilers with additional monitoring of the heat exchanger fouling

Niederwieser H, Zemann C, Gölles M, Reichhartinger M. Soft-Sensor for the On-Line Estimation of the Flue Gas Mass Flow in Biomass Boilers with Additional Monitoring of the Heat Exchanger Fouling. In Proceedings of the 28th European Biomass Conference and Exhibition 2020 (eEUBCE 2020). 2020. p. 280 - 284

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The flue gas mass flow is one of the fundamental quantities of the combustion process in biomass boilers. Since it directly relates to the enthalpy flow entering the heat exchanger, its knowledge is highly advantageous for a sophisticated load control of the biomass boiler. It also includes information regarding the primary and secondary air mass flows as well as the mass flows of potentially occurring leakage air and thermally decomposed fuel. However, in practical application it is not possible to obtain a reliable measurement of the flue gas mass flow. For this reason, this work presents a soft-sensor for the on-line estimation of the flue gas mass flow in biomass boilers. The approach is robust against fouling of the relevant boiler components and is based on standard measurements which are typically available in biomass boilers. In addition, the soft-sensor offers the possibility of monitoring the degree of heat exchanger fouling.


Peer Reviewed Scientific Journals | 2020

Surface characterization of ash-layered olivine from fluidized bed biomass gasification

Kuba M, Fürsatz K, Janisch D, Aziaba K, Chlebda D, Łojewska J, Forsberg F, Umeki K, Hofbauer H. Surface characterization of ash-layered olivine from fluidized bed biomass gasification. Biomass Conversion and Biorefinery. 2020

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The present study aims to present a comprehensive characterization of the surface of ash-layered olivine bed particles from dual fluidized bed gasification. It is well known from operation experience at industrial gasification plants that the bed material is activated during operation concerning its positive influence on gasification reactions. This is due to the built up of ash layers on the bed material particles; however, the chemical mechanisms are not well understood yet. Olivine samples from long-term operation in an industrial-scale gasification plant were investigated in comparison to fresh unused olivine. Changes of the surface morphology due to Ca-enrichment showed a significant increase of their surface area. Furthermore, the Ca-enrichment on the ash layer surface was distinctively associated to CaO being present. The presence of CaO on the surface was proven by adsorption tests of carbon monoxide as model compound. The detailed characterization contributes to a deeper understanding of the surface properties of ash layers and forms the basis for further investigations into their influence on gasification reactions.


Books / Bookchapters | 2020

Technische Optionen für die Umrüstung und Nachrüstung von Industrien mit Bioenergie

Rutz D, Janssen R, Reumerman P, Spekreijse J, Matschegg D, Bacovsky D, et al. Technische Optionen für die Umrüstung und Nachrüstung von Industrien mit Bioenergie. WIP Renewable Energies.2020

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Conference contributions | 2020

Techno-economic modelling of bioeconomy value chains

Fuhrmann Marilene

Dißauer C, Fuhrmann M, Strasser C, Enigl M, Matschegg D. Techno-economic modelling of bioeconomy value chains. 6th Central European Biomass Conference. 2020. Graz.

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In the context of Austria´s and the EU´s ambitious goals to combat climate change by reducing the demand for fossil fuels in all sectors, many industries plan to increase the share of renewable energy in their production processes. Furthermore greenhouse gases shall be reduced by 36 % until 2030 (compared to 2005), which means another 14 Mio. tons CO2eq will have to be reduced per year in comparison to data from 2016. In doing so, some industries find it sufficient to use green electricity or green gas from the grid, but for some industries the use of biomass is particularly interesting. In particular, the wood-based economy as an essential part of the Austrian bio-based economy is needed to promote the development of sustainable production and sustainable energy generation. Besides the increasing demand for woody biomass, the supply side will also undergo substantial changes since increasing calamities (such as bark beetle infestation and windthrow) caused by climate change will affect the wood supply to a varying extend. Hence, within the project “BioEcon” the BIOENERGY 2020+ team together with industry partners analyses the effects of these developments on the wood-based economy and the corresponding supply chains in terms of economic and technological perspectives including econometric models to evaluate woody biomass supply and demand.
 


Conference contributions | 2020

The Contribution of advanced renewable transport fuels to transport decarbonisation in 2030 and beyond

Bacovsky D, Laurikko J. The Contribution of advanced renewable transport fuels to transport decarbonisation in 2030 and beyond. 28th European Biomass Conference and Exhibition (oral presentation) 2020.

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In the light of climate change, there is an urgent need to decarbonize our societies. The transport sector is specifically challenging, as transport demand is still growing, and so are the sector´s GHG emissions. Several countries have set ambitious national targets for GHG reduction in the transport sector. These are often backed with policy measures for implementation of both advanced renewable transport fuels and electrification.
In a project set up jointly by two Technology Collaboration Programmes of the International Energy Agency, namely the IEA Bioenergy TCP and the Advanced Motor Fuels TCP, the contribution that advanced renewable transport fuels should make to the decarbonisation of the transport sector is assessed by means of country-specific assessments.


Peer Reviewed Scientific Journals | 2020

The effect of the reaction equilibrium on the kinetics of gas-solid reactions — A non-parametric modeling study.

Birkelbach F, Deutsch M, Werner A. The effect of the reaction equilibrium on the kinetics of gas-solid reactions — A non-parametric modeling study. Renewable Energy 2020.152:300-307.

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The viability of thermochemical energy storage for a given application is often determined by the reaction kinetics under process conditions. For high exergetic efficiency the process needs to operate in close proximity to the reaction equilibrium. Thus, accurate kinetic models that include the effect of the reaction equilibrium are required.

In the present work, different parametrization methods for the equilibrium term in the General Kinetic Equation are evaluated by modeling the kinetics of two reaction systems relevant for thermochemical energy storage (CaC2O4 and CuO) from experimental data. A non-parametric modeling method based on tensor decompositions is used that allows for a purely data driven assessment of different parametrization methods.

Our analysis shows that including a suitable equilibrium term is crucial. Omitting the equilibrium term when modeling formation reactions can lead to seemingly negative activation energies. Our tests also show that for formation reactions, the reaction rate decreases much faster towards the equilibrium than theory predicts. We present an empirical modeling approach that can predict the reaction rate of gas-solid reactions, regardless of the shortcomings of theory. In this way, non-parametric modeling offers a powerful tool for applied research and may contribute to the advancement of the thermochemical energy storage technology.


Conference contributions | 2020

The modification of biogenic carbon-rich solids opens new possibilities

Martini S, Kienzl N, Ortner M, Loipersböck J. The modification of biogenic carbon-rich solids opens new possibilities. Biochar Workshop @ 6th Central European Biomass Conference (oral presentation). 2020.

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Peer Reviewed Scientific Journals | 2020

Thermochemical equilibrium study of ash transformation during combustion and gasification of sewage sludge mixtures with agricultural residues with focus on the phosphorus speciation

Hannl TK, Sefidari H, Kub M, Skoglund N, Öhmann M. Thermochemical equilibrium study of ash transformation during combustion and gasification of sewage sludge mixtures with agricultural residues with focus on the phosphorus speciation. Biomass Conversion and Biorefinery.2020

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The necessity of recycling anthropogenically used phosphorus to prevent aquatic eutrophication and decrease the economic dependency on mined phosphate ores encouraged recent research to identify potential alternative resource pools. One of these resource pools is the ash derived from the thermochemical conversion of sewage sludge. This ash is rich in phosphorus, although most of it is chemically associated in a way where it is not plant available. The aim of this work was to identify the P recovery potential of ashes from sewage sludge co-conversion processes with two types of agricultural residues, namely wheat straw (rich in K and Si) and sunflower husks (rich in K), employing thermodynamic equilibrium calculations. The results indicate that both the melting behavior and the formation of plant available phosphates can be enhanced by using these fuel blends in comparison with pure sewage sludge. This enhanced bioavailability of phosphates was mostly due to the predicted formation of K-bearing phosphates in the mixtures instead of Ca/Fe/Al phosphates in the pure sewage sludge ash. According to the calculations, gasification conditions could increase the degree of slag formation and enhance the volatilization of K in comparison with combustion conditions. Furthermore, the possibility of precipitating phosphates from ash melts could be shown. It is emphasized that the results of this theoretical study represent an idealized system since in practice, non-equilibrium influences such as kinetic limitations and formation of amorphous structures may be significant. However, applicability of thermodynamic calculations in the prediction of molten and solid phases may still guide experimental research to investigate the actual phosphate formation in the future.


Peer Reviewed Scientific Journals | 2020

Transient CFD simulation of wood log combustion in stoves

Scharler R, Gruber T, Ehrenhöfer A, Kelz J, Mehrabian Bardar R, Bauer T, Hochenauer C, Anca-Couce A. Transient CFD simulation of wood log combustion in stoves. Renewable Energy 2020.145:651-662

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Wood log stoves are a common residential heating technology that produce comparably high pollutant emissions. Within this work, a detailed CFD model for transient wood log combustion in stoves was developed, as a basis for its optimization. A single particle conversion model previously developed by the authors for the combustion of thermally thick biomass particles, i.e. wood logs, was linked with CFD models for flow and turbulence, heat transfer and gas combustion. The sub-models were selected based on a sensitivity analysis and combined into an overall stove model, which was then validated by simulations of experiments with a typical wood log stove, including emission measurements. The comparison with experimental results shows a good accuracy regarding flue gas temperature as well as CO2 and O2 flue gas concentrations. Moreover, the characteristic behavior of CO emissions could be described, with higher emissions during the ignition and burnout phases. A reasonable accuracy is obtained for CO emissions except for the ignition phase, which can be attributed to model simplifications and the stochastic nature of stove operation. Concluding, the CFD model allows a transient simulation of a stove batch for the first time and hence, is a valuable tool for process optimization.


Conference contributions | 2020

Valorisation of industrial by-products from the pulp&paper and rendering industry

Ortner M, Valorisation of industrial by-products from the pulp&paper and rendering industry. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference contributions | 2020

Virtual biomass combustion plant

Schulze K, Virtual biomass combustion plant. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference Papers | 2019

Performance evaluation of an electrostatic precipitator in a small-scale biomass boiler by using different biomass feedstocks

Kelz J, Zemann C, Muschick D, Hofmeister G, Gölles M. & Retschitzegger S. Performance evaluation of an electrostatic precipitator in a small-scale biomass boiler by using different biomass feedstocks. Proceedings 27th European Biomass Conference and Exhibition, 27-31 May 2019, Lisbon, Portugal.1932-1938.

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In order to evaluate the performance of an electrostatic precipitator (ESP), comprehensive test runs investigating both particulate matter (PM) and gaseous emissions were performed by using softwood pellets as well as alternative biomass feedstocks such as short rotation coppice (poplar) and biomass residues (maize). An ESP was directly integrated in a commercially available small-scale biomass boiler. Based on wet chemical analyses of the fuels, so-called fuel indexes were calculated to deliver primary information on the expected combustion behaviour. The overall aim was to determine appropriate operating conditions, to optimise combustion parameters in order to minimise PM and gaseous emissions as well as to inhibit ash related problems. This was done by an efficient combination of primary (air staging in combination with an innovative control system) and secondary measures (integration of an ESP) and showed an enormous potential for both, a stable plant operation and reduced PM emissions. Thus the findings provide the basis for developing a fuel flexible, low emission and highly efficient biomass boiler in the sector of small-scale combustion systems.


Conference contributions | 2019

A CFD-method for the analysis and optimization of the fixed bed conversion in biomass grate furnaces

Singer M, Gruber T, Mehrabian R, Scharler R. A CFD-method for the analysis and optimization of the fixed bed conversion in biomass grate furnaces. 27th European Biomass Conference & Exhibition (Poster). 2019.

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To optimize the combustion of biomass grate furnaces a sensitivity analysis is carried out by means of CFD simulation. The methodical procedure consists of a 3D packed bed biomass combustion model, which describes the most essential characteristics of the thermal conversion of biomass particles, such as the detailed consideration of drying, pyrolysis and char oxidation in parallel processes. Within the sensitivity analysis the following parameters have been investigated: distribution of false air, residence time of fuel on the grate and distribution of recirculated flue gas and primary air below the grate. To evaluate the influence of the varied parameters on the combustion process the focus lied on the position of the thermal conversion of the biomass and the CO at the outlet of the simulation domain. The results of the sensitivity analysis show a shift of the thermal conversion towards the grate end for increased false air as well as for reduced momentum of primary air/recirculated flue gas mixture. An increase of the fuel residence time leads to a shift of the thermal conversion towards the fuel inlet. Consequently a large region of the primary combustion zone is not used due to earlier release of CO inside the fuel bed.


Conference Papers | 2019

A Generalization of Ackermann’s Formula for the Design of Continuous and Discontinuous Observers

Niederwieser H, Koch S, Reichhartinger M. A Generalization of Ackermann’s Formula for the Design of Continuous and Discontinuous Observers. 58th IEEE Conference on Decision and Control. 2019.

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This paper proposes a novel design algorithm for nonlinear state observers for linear time-invariant systems. The approach is based on a well-known family of homogeneous differentiators and can be regarded as a generalization of Ackermann's formula. The method includes the classical Luenberger observer as well as continuous or discontinuous nonlinear observers, which enable finite time convergence. For strongly observable systems with bounded unknown perturbation at the input the approach also involves the design of a robust higher order sliding mode observer. An inequality condition for robustness in terms of the observer gains is presented. The properties of the proposed observer are also utilized in the reconstruction of the unknown perturbation and robust state-feedback control


Peer Reviewed Scientific Journals | 2019

A generally applicable, simple and adaptive forecasting method for the short-term heat load of consumers

Nigitz T, Gölles M. A generally applicable, simple and adaptive forecasting method for the short-term heat load of consumers. Applied Energy 2019;241:73-81.

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Energy management systems aiming for an efficient operation of hybrid energy systems with a high share of different renewable energy sources strongly benefit from short-term forecasts for the heat-load. The forecasting methods available in literature are typically tailor-made, complex and non-adaptive. This work condenses these methods to a generally applicable, simple and adaptive forecasting method for the short-term heat load. From a comprehensive literature review as well as the analysis of measurement data from seven different consumers, varying in size and type, the ambient temperature, the time of the day and the day of the week are deduced to be the most dominating factors influencing the heat load. According to these findings, the forecasting method bases on a linear regression model correlating the heat load with the ambient temperature for each hour of the day, additionally differentiating between working days and weekend days. These models are used to predict the future heat load by using forecasts for the ambient temperature from weather service providers. The model parameters are continuously updated by using historical data for the ambient temperature and the heat load, i.e. the forecasting method is adaptive. Additionally, the current prediction error is used to correct the prediction for the near future. Due to their simplicity, all necessary steps of the forecasting method, the update of the model parameters, the prediction based on linear regression models and the correction, can be implemented and computed with little effort. The final evaluation with measurement data from all seven consumers investigated leads to a Mean Absolute Range Normalized Error (MARNE) of 2.9% on average, and proves the general applicability of the forecasting method. In summary, the forecasting method developed is generally applicable, simple and adaptive, making it suitable for the use in energy management systems aiming for an efficient operation of hybrid energy systems.


Scientific Journals | 2019

A practical field trial to assess the potential of Sida hermaphrodita as a versatile, perennial bioenergy crop for Central Europe.

von Gehren P, Gansberger M, Pichler W, Weigl M, Feldmeier S, Wopienka E, Bochmann G. A practical field trial to assess the potential of Sida hermaphrodita as a versatile, perennial bioenergy crop for Central Europe. Biomass and Bioenergy 2019;122:99-108.

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Due to high biomass accumulation ability and multiple ecological benefits, the versatile, perennial bioenergy crop Sida hermaphrodita has sparked the interest of researchers in Central Europe. We assessed the crop's agronomy and bioenergy potential when grown under Austrian climate and soil conditions. A field trial was established in Austria, where the factors planting density and utilization strategy (thermal or biogas) were monitored for three growing seasons. Harvesting lignified biomass for thermal utilization at the end of the growing period resulted in higher dry matter yields than green biomass for biogas utilization which was harvested with a two-cut strategy. Due to lower costs but similar yield, a planting density of 1.77 plants m-2 is preferable over 2.66 plants m-2. The pelletizing process of the biomass was analyzed iteratively in 20 runs to optimize the energy efficiency and process stability while simultaneously increasing pellet durability. A simple drying step, disintegration with a pan grinder mill and pelletizing using a flat die pellet press resulted in stable, high quality pellets. Fuel characteristics of the biomass were favorable and all requirements to be categorized as solid biofuel were met, while combustion tests showed a good applicability of the produced pellets. When green biomass was used for biogas production, a significant drop in methane yield could be noted from the second growing season onward, indicating that older plants are less suitable for biogas production. Our results hint towards the potential of lignified S. hermaphrodita biomass to be used as a solid fuel for energy production.


Books / Bookchapters | 2019

Adaptive Methods for Energy Forecasting of Production and Demand of Solar-Assisted Heating Systems

Unterberger V, Nigitz T, Luzzu M, Muschick D, Gölles M. Adaptive Methods for Energy Forecasting of Production and Demand of Solar-Assisted Heating Systems. In: Valenzuela O, Rojas F, Pomares H, Rojas I. (eds) Theory and Applications of Time Series Analysis. ITISE 2018. Contributions to Statistics. Springer, Cham. 2019.

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Solar-assisted heating systems use the energy of the sun to supply consumers with renewable heat and can be found all over the world where heating of buildings is necessary. For these systems, both heat production and heat demand are directly related to the weather conditions. In order to optimally plan production, storage, and consumption, forecasts for both the future heat production of the thermal solar collectors as well as the future heat demand of the connected consumers are essential. For this reason, this contribution presents adaptive forecast methods for the solar heat production and the heat demand of consumers using weather forecasts. The developed methods are easy to implement and therefore practically applicable. The final verification of the methods shows good agreement between the predicted values and measurement data from a representative solar-assisted heating system.


Scientific Journals | 2019

Ammonia as Promising Fuel for Solid Oxide Fuel Cells: Experimental Analysis and Performance Evaluation

Stöckl B, Preininger M, Subotic V, Schröttner H, Sommersacher P, Seidl M, Megel S, Hochenauer C. Ammonia as Promising Fuel for Solid Oxide Fuel Cells: Experimental Analysis and Performance Evaluation. ECS Transactions; The Electrochemical Society 2019.91:1601-1610

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n the course of this study the direct utilization of ammonia in different types of solid oxide fuel cells (SOFCs), such as anode- and electrolyte-supported SOFC, is investigated. Experiments in low fuel utilization, exhibited excellent performance of ammonia in SOFCs, although the power outputs of equivalent hydrogen/nitrogen fuels were not attained due to the incomplete endothermic ammonia decomposition. Next, the single cells were operated under high fuel utilization conditions and methane was added to the humidified ammonia stream, where they showed excellent ammonia- and methane conversions. The stability of the cells used was proven over a period of at least 48 hours with a variety of fuel mixtures. Post mortem scanning electron microscopy analysis of the anode micro-structures indicated nitriding effects of nickel, as microscopic pores and enlargements of the metallic parts occurred. Finally, a long-term test over 1,000 hours was carried out using a ten-layer stack consisting of electrolyte-supported cells.


Peer Reviewed Scientific Journals | 2019

Applicability of Fuel Indexes for Small-Scale Biomass Combustion echnologies, Part 2: TSP and NOx Emissions

Feldmeier S, Wopienka E, Schwarz M, Schön C, Pfeifer C. Applicability of Fuel Indexes for Small-Scale Biomass Combustion echnologies, Part 2: TSP and NOx Emissions. Energy & Fuels. 2019.33:11724-11730.

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Several studies pointed out that emission release is related to the concentration of particular elements in the fuel. Fuel indexes were developed to predict emissions of biomass combustion based on the elemental composition of the fuel. This study focuses on emissions of different biomass combustion technologies for domestic heating. Based on combustion tests with a wide range of fuel qualities we validated fuel indexes from the literature. We calculated the values for predicting total suspended particulate (TSP) matter and nitrogen oxide (NOx) emission of 39 biomass-derived fuels. Combustion tests conducted in 10 different small-scale appliances provided experimental data. The combustion technologies had a nominal load between 6 and 140 kWth. We measured TSP and NOx emissions during the stable phases of the experiments. The evaluation considered 529 combustion test intervals. All tested indexes for predicting the TSP corresponded well to the measured values. The correlation analysis confirmed that these indexes are associated with each other and are basically dominated by the concentration of potassium. The results regarding NOx emissions confirm previous findings from the literature by showing the typical nonlinear relation between nitrogen content of the fuel and NOx in the flue gas. Overall the comparison of the fuel indexes with the practical data indicated also an influence of the combustion technologies.


Peer Reviewed Scientific Journals | 2019

Applicability of the SOFC technology for coupling with biomass-gasifier systems: Short- and long-term experimental study on SOFC performance and degradation behaviour

Subotić V, Baldinelli A, Barelli L, Scharler R, Pongratz G, Hochenauer C, Anca-Couce A. Applicability of the SOFC technology for coupling with biomass-gasifier systems: Short- and long-term experimental study on SOFC performance and degradation behaviour. Applied Energy. 2019.256:113904

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Coupling biomass gasification with high temperature Solid Oxide Fuel Cells (SOFCs) is a promising solution to increase the share of renewables and reduce emissions. The quality of the producer gas used can, however, significantly impact the SOFC durability and reliability. The great challenge is to ensure undisturbed operation of such system and to find a trade-off between optimal SOFC operating temperature and system thermal integration, which may limit the overall efficiency. Thus, this study focuses on experimental investigation of commercial SOFC single cells of industrial size fueled with different representative producer gas compositions of industrial relevance at two relevant operating temperatures. The extensive experimental and numerical analyses performed showed that feeding SOFC with a producer gas from a downdraft gasifier, with hot gas cleaning, at an operating temperature of 750 °C represents the most favorable setting, considering system integration and the highest fuel utilization. Additionally, a 120 h long-term test was carried out, showing that a long-term operation is possible under stated operating conditions. Local degradation took place, which can be detected at an early stage using appropriate online-monitoring tools.


Conference contributions | 2019

Aqueous phase reforming of Fischer-Tropsch water fraction

Zoppi G, Pipitone G, Gruber H, Weber G, Reichhold A, Pirone R, Bensaid S. Aqueous phase reforming of Fischer-Tropsch water fraction. ICPS 2019.

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