Publikationen

Peer reviewed papers | 2020

Consequential Life Cycle Assessment of energy generation from waste wood and forest residues: The effect of resource-efficient additives

Corona B, Shen L, Sommersacher P, Junginger M. Consequential Life Cycle Assessment of energy generation from waste wood and forest residues: The effect of resource-efficient additives. Journal of Cleaner Production 2020. 259:120948.

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Combustion of waste wood can cause slagging, fouling and corrosion which lead to boiler failure, affecting the energy efficiency and the lifetime of the power plant. Additivation with mineral and sulfur containing additives during waste wood combustion could potentially reduce these problems. This study aims at understanding the environmental impacts of using additives to improve the operational performance of waste wood combustion. The environmental profiles of four energy plants (producing heat and/or power), located in different European countries (Poland, Austria, Sweden and Germany), were investigated through a consequential life cycle assessment (LCA). The four energy plants are all fueled by waste wood and/or residues. This analysis explored the influences of applying different additives strategies in the four power plants, different wood fuel mixes and resulting direct emissions, to the total life cycle environmental impacts of heat and power generated. The impacts on climate change, acidification, particulate matter, freshwater eutrophication, human toxicity and cumulative energy demand were calculated, considering 1 GJ of exergy as functional unit. Primary data for the operation without additives were collected from the power plant operators, and emission data for the additives scenarios were collected from onsite measurements. A sensitivity analysis was conducted on the expected increase of energy efficiency. The analysis indicated that the use of gypsum waste, halloysite and coal fly ash decreases the environmental impacts of heat and electricity produced (average of 12% decrease in all impacts studied, and a maximum decrease of 121%). The decrease of impacts is mainly a consequence of the increase of energy generation that avoids the use of more polluting marginal technologies. However, impacts on acidification may increase (up to 120% increase) under the absence of appropriate flue gas cleaning systems. Halloysite was the additive presenting the highest benefits.

Peer reviewed papers | 2020

Control of biomass grate boilers using internal model control

Schörghuber C, Gölles M, Reichhartinger M, Horn M. Control of Biomass Grate Boilers using Internal Model Control. Control engineering practice. 2020.

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A new model-based control strategy for biomass grate boilers is presented in this paper. Internal model control is used to control four outputs of the plant and to achieve a control structure with fewer control parameters needing to be experimentally tuned. A nonlinear state–space model describing the essential behaviour of the biomass grate boiler is used for controller design. The inverse system dynamics representing the main part of internal model control are designed with the help of this model. In doing so the properties of differentially flat systems are used. Due to a time delayed input, the inverse system is determined only for three input output channels. The stabilization of the inverse system dynamics, however, is a challenging task. A stabilization method with the help of the time delayed input is suggested and a stability analysis is given. The new control strategy has only three parameters to be tuned, representing a major reduction of complexity in comparison to existing model-based approaches. Finally, experimental results of the implemented control strategy on representative biomass grate boiler with a nominal capacity of 180 kW are presented and compared to an existing model-based control strategy based on input output linearization. The experimental evaluation proves that it is possible to operate the biomass boiler in all load ranges with high efficiency and low pollutant emissions.

Peer reviewed papers | 2020

Correction to: Investigation of solid oxide fuel cell operation with synthetic biomass gasification product gases as a basis for enhancing its performance

Pongratz G, Subotić V, Schroettner H, Stoeckl B, Hochenauer C, Anca-Couce A, Scharler R. Correction to: Investigation of solid oxide fuel cell operation with synthetic biomass gasification product gases as a basis for enhancing its performance. Biomass Conversion and Biorefinery. 2020

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The authors want to acknowledge, that during the production of the final version of the publication the image for Figure 9 has been replaced with the image for Figure 12, however without changing the content of the paper. This issue is resolved in the current version of the publication.

Conference presentations and posters | 2020

Customizing biomass as reducing agent in blast furnace steelmaking – Reduction potential and fluidization

Deutsch R, Strasser C, Martini S, Kienzl N. Customizing biomass as reducing agent in blast furnace steelmaking – Reduction potential and fluidization. 28th European Biomass Conference and Exhibition (oral presentation) 2020.

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The reduction of greenhouse gas emissions is an important issue for iron and steel industry. One possibility is to use biomass-based reducing agents, also called bioreducers, to replace at least partly the fossil reducer agents. In a first step woody biomass was treated in a lab-scale muffle furnace and afterwards ground with a ball mill. The powder characteristics were investigated in respect to the flow behavior. For a certain treatment temperature the particle size distribution and as well the flow behavior shows similarities to lignite. The next stage was to identify relations between powder characteristics and its fluidization behavior. A fluidization device was assembled and used to determine the minimum fluidization gas velocity for various bioreducer powders.

Conference presentations and posters | 2020

Das neue Holzwärmeszenario "Holz ersetzt Heizöl"

Schmidl C, Reichert G. Das neue Holzwärmeszenario "Holz ersetzt Heizöl". World Sustainable Energy Days 2020, Wels, Austria (oral presentation). 2020.

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Peer reviewed papers | 2020

Decentralized heating grid operation: A comparison of centralized and agent-based optimization

Lichtenegger K, Leitner A, Märzinger T, Mair C, Moser A, Wöss D, Schmidl C, Pröll T. Decentralized heating grid operation: A comparison of centralized and agent-based optimization. Sustainable Energy, Grids and Networks. 2020;2020(21).

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Moving towards a sustainable heat supply calls for decentralized and smart heating grid solutions. One promising concept is the decentralized feed-in by consumers equipped with their own small production units (prosumers). Prosumers can provide an added value regarding security of supply, emission reduction and economic welfare, but in order to achieve this, in addition to advanced hydraulic control strategies also superordinate control strategies and appropriate market models become crucial.

In this article we study methods to find a global optimum for the local energy community or at least an acceptable approximation to it. In contrast to standard centralized control approaches, based either on expert rules or mixed integer linear optimization, we adopt an agent-based, decentralized approach that allows for incorporation of nonlinear phenomena. While studied here in small-scale systems, this approach is particularly attractive for larger systems, since with an increasing number of interacting units, the optimization problem becomes more complex and the computational effort for centralized approaches increases dramatically.

The agent-based optimization approach is compared to centralized optimization of the same prosumer-based setting as well as to a purely central setup. The comparison is based on the quality of the optimization solution, the computational effort and the scalability. For the comparison of these three approaches, three different scenarios have been set up and analysed for four seasons. In this analysis, no approach has emerged as clearly superior to the others; thus each of them is justified in certain situations.

Peer reviewed papers | 2020

Detailed experimental investigation of the spatially distributed gas release and bed temperatures in fixed-bed biomass combustion with low oxygen concentration

Archan G, Anca-Couce A, Gregorc J, Buchmayr M, Hochenauer C, Gruber J, Scharler R. Detailed experimental investigation of the spatially distributed gas release and bed temperatures in fixed-bed biomass combustion with low oxygen concentration. Biomass and Bioenergy. 2020;141:105725

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This publication focuses on the experimental investigation of a novel small-scale fuel flexible biomass combustion technology with a fixed-bed employing a low oxygen concentration. It was obtained through a low primary air ratio and the additional supply of recirculated flue gas. The plant was operated with spruce wood chips, which contained three different mass fractions of water, and miscanthus pellets. All relevant components of the released gas above the fixed-bed were measured, as well as the 3D bed temperature distribution. The balances confirmed a high experimental data consistency. Therefore, it was possible to determine the location of the four different conversion zones inside the fixed-bed: drying, pyrolysis, char gasification and char oxidation. The reduction of CO2 to CO in the char reduction zone worked efficiently across the entire grate area. Furthermore, the results showed that the water mass fraction of the fuel did not influence the dry product gas composition, but significantly affected the location for the release of pyrolysis products such as tars. It was found that the low oxygen concentration in the fixed-bed combined with flue gas recirculation was an effective method to reduce bed temperatures and therefore its inorganic emissions while significantly increasing feedstock flexibility. The investigations provided fundamental findings on the conversion and release behavior of the new technology under real operating conditions and are very useful for further experimental work and CFD simulations targeting the reduction of PM and NOX emissions.

Conference presentations and posters | 2020

Detailed investigations of high terpene concetrations in biogas laboratory trials

Knoll L, Sumethberger-Hasinger M, Nussbaumer M, Dalnodar D, Loibner A, Drosg B. Detailed investigations of high terpene concetrations in biogas laboratory trials. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Peer reviewed papers | 2020

Developing an adsorption-based gas cleaning system for a dual fluidized bed gasification process

Loipersböck J, Weber G, Rauch R, Hofbauer H. Developing an adsorption-based gas cleaning system for a dual fluidized bed gasification process.Biomass Conversion and Biorefinery. 2020.

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Biomass has the potential to make a major contribution to a renewable future economy. If biomass is gasified, a wide variety of products (e.g., bulk chemicals, hydrogen, methane, alcohols, diesel) can be produced. In each of these processes, gas cleaning is crucial. Impurities in the gas can cause catalyst poisoning, pipe plugging, unstable or poisoned end products, or harm the environment. Aromatic compounds (e.g., benzene, naphthalene, pyrene), in particular, have a huge impact on stable operation of syngas processes. The removal of these compounds can be accomplished by wet, dry, or hot gas cleaning methods. Wet gas cleaning methods tend to produce huge amounts of wastewater, which needs to be treated separately. Hot gas cleaning methods provide a clean gas but are often cost intensive due to the high operating temperatures and catalysts used in the system. Another approach is dry or semi-dry gas cleaning methods, including absorption and adsorption on solid matter. In this work, special focus was laid on adsorption-based gas cleaning for syngas applications. Adsorption and desorption test runs were carried out under laboratory conditions using a model gas with aromatic impurities. Adsorption isotherms, as well as dynamics, were measured with a multi-compound model gas. Based on these results, a temperature swing adsorption process was designed and tested under laboratory conditions, showing the possibility of replacing conventional wet gas cleaning with a semi-dry gas cleaning approach.

Other papers | 2020

Development and experimental validation of a linear state-space model for absorption heat pumping systems for model-based control strategies

Zlabinger S, Unterberger V, Gölles M, Horn M, Wernhart M, Rieberer R. Development and experimental validation of a linear state-space model for absorption heat pumping systems for model-based control strategies. International Sorption Heat Pump Conference 2020.

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Control strategies of absorption heat pumping systems (AHPS, comprising heat pumps and chillers) often
perform insufficiently well, since they usually do not explicitly consider the systems’ dynamics and crosscoupling effects. One promising approach to improve their performance is to apply model-based control strategies since they would allow for an explicit consideration of these system characteristics. Therefore, mathematically simple models of the system to be controlled are required. This contribution proposes a new approach for such a model for a H2O-LiBr AHPS. The model results from the linearization of a more complex, nonlinear simulation model, leading to a simple, but physically still meaningful linear state-space model structure. The experimental validation shows that the developed model describes the system’s dynamics and cross-coupling effects sufficiently well and indicates that it is suitable to serve as a basis for the development of a model-based control strategy for AHPS.

Conference presentations and posters | 2020

Die Donau - Eine Chance für die Bioenergiebranche?

Dißauer C, Strasser C. Die Donau - Eine Chance für die Bioenergiebranche? 6th Central European Biomass Conference, 2020, Graz.

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Conference presentations and posters | 2020

Dual fluidized bed steam gasification of biomass – the basic technology for a broad product portfolio

Kuba M. Dual fluidized bed steam gasification of biomass – the basic technology for a broad product portfolio. 6th Central European Biomass Conference (oral presentation). 2020.

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Other papers | 2020

Dynamische Simulation von Absorptionskälteanlagen – Dymola-Modell einer H2O/LiBr-Absorptionskälteanlage

Wernhart M, Rieberer R, Zlabinger S, Unterberger V, Gölles M. Dynamische Simulation von Absorptionskälteanlagen: Dymola-Modell einer H2O/LiBr-Absorptionskälteanlage. in Proc. Deutsche Kälte-Klima-Tagung 2020. Deutscher Kälte- und Klimatechnischer Verein e.V. 2020

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Absorptionskälteanlagen können einen wesentlichen Beitrag zur Verringerung von CO2-Emissionen leisten, wenn Wärme aus regenerativen Energieträgern oder Abwärme aus industriellen Prozessen zum Antrieb verwendet wird. Absorptionskälteanlagen weisen bereits jetzt eine hohe Effizienz auf, bei veränderlichen Betriebsbedingungen kann diese je nach vorhandenen Stellgliedern weiter gesteigert werden. Dazu werden im Rahmen des Forschungsprojektes „Heat Pumping Systems Control (HPC)“ zwei Absorptionskälteanlagen – eine mit der Stoffpaarung Ammoniak/Wasser (NH3/H2O) und eine mit der Stoffpaarung Wasser/Lithiumbromid (H2O/LiBr) – untersucht, um für unterschiedliche Anwendungen optimale Betriebsstrategien zu entwickeln. Zur Berücksichtigung der Zustandsänderungen in der Absorptionskälteanlage, werden dynamische Simulationsmodelle in der Modellierungssprache Modelica entwickelt und mit Messdaten validiert.

Im Rahmen dieses Konferenzbeitrags werden Komponentenmodelle für die NH3/H2O-Absorptionskälteanlage und Simulationsrechnungen bei veränderlichen Randbedingungen präsentiert, sowie ein Vergleich mit Messdaten diskutiert.

Peer reviewed papers | 2020

Effects of Pyrolysis Conditions and Feedstocks on the Properties and Gasification Reactivity of Charcoal from Woodchips

Phounglamcheik A, Wang L, Romar H, Kienzl N, Broström M, Ramser K, Skreiberg Ø, Umeki K. Effects of Pyrolysis Conditions and Feedstocks on the Properties and Gasification Reactivity of Charcoal from Woodchips. Energy and Fuels. 2020;34(7):8353-8365.

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Pyrolysis conditions in charcoal production affect yields, properties, and further use of charcoal. Reactivity is a critical property when using charcoal as an alternative to fossil coal and coke, as fuel or reductant, in different industrial processes. This work aimed to obtain a holistic understanding of the effects of pyrolysis conditions on the reactivity of charcoal. Notably, this study focuses on the complex effects that appear when producing charcoal from large biomass particles in comparison with the literature on pulverized biomass. Charcoals were produced from woodchips under a variety of pyrolysis conditions (heating rate, temperature, reaction gas, type of biomass, and bio-oil embedding). Gasification reactivity of produced charcoal was determined through thermogravimetric analysis under isothermal conditions of 850 °C and 20% of CO2. The charcoals were characterized for the elemental composition, specific surface area, pore volume and distribution, and carbon structure. The analysis results were used to elucidate the relationship between the pyrolysis conditions and the reactivity. Heating rate and temperature were the most influential pyrolysis parameters affecting charcoal reactivity, followed by the reaction gas and bio-oil embedding. The effects of these pyrolysis conditions on charcoal reactivity could primarily be explained by the difference in the meso- and macropore volume and the size and structural order of aromatic clusters. The lower reactivity of slow pyrolysis charcoals also coincided with their lower catalytic inorganic content. The reactivity difference between spruce and birch charcoals appears to be mainly caused by the difference in catalytically active inorganic elements. Contrary to pyrolysis of pulverized biomass, a low heating rate produced a higher specific surface area compared with a high heating rate. Furthermore, the porous structure and the reactivity of charcoal produced from woodchips were influenced when the secondary char formation was promoted, which cannot be observed in pyrolysis of pulverized biomass.

Conference presentations and posters | 2020

Energy Communities – Four Austrian Pioneering Initiatives: Microgrid Lab – Wieselburg

Zellinger M, Aigenbauer S, Stadler M. Energy Communities – Four Austrian Pioneering Initiatives: Microgrid Lab – Wieselburg. Mission Innovation Austria Online. 13 May 2020.

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Conference presentations and posters | 2020

Erneuerbare in Österreich - Die Marktdiffusion im Lichte der Klima- und Energieziele

Biermayr P, Leonhartsberger K, Dißauer C; Eberl M, Enigl M, Fechner H, Lukas Fischer L, Fürnsinn B, Moidl S, Schmidl C, Strasser C, Weiss W, Wonisch P, Wopienka E. Erneuerbare in Österreich - Die Marktdiffusion im Lichte der Klima- und Energieziele. EnInnov 2020, 16. Symposium Energieinnovation (oral presentation). 2020.

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Conference presentations and posters | 2020

Evaluation of gas cleaning processes for the coupling of biomass gasification with Solid Oxide Fuel Cells (SOFC)

Martini S, Lagler J, Kienzl N, Tsiotsias T, Rettschitzegger S. Evaluation of gas cleaning processes for the coupling of biomass gasification with Solid Oxide Fuel Cells (SOFC). 6th Central European Biomass Conference (oral presentation). 2020.

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Peer reviewed papers | 2020

Evaluation of heat transfer models at various fluidization velocities for biomass pyrolysis conducted in a bubbling fluidized bed

von Berg L, Soria-Verdugo A, Hochenauer C, Scharler R, Anca-Couce A. Evaluation of heat transfer models at various fluidization velocities for biomass pyrolysis conducted in a bubbling fluidized bed. International Journal of Heat and Mass Transfer. 2020;160:120175

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Four different models for heat transfer to the particles immersed in a fluidized bed were evaluated and implemented into an existing single particle model. Pyrolysis experiments have been conducted using a fluidized bed installed on a balance at different temperatures and fluidization velocities using softwood pellets. Using a heat transfer model applicable for fluidized beds, the single particle model was able to predict the experimental results of mass loss obtained in this study as well as experimental data from literature with a reasonable accuracy. A good agreement between experimental and modeling results was found for different reactor temperatures and configurations as well as different biomass types, particle sizes – in the typical range of pellets - and fluidization velocities when they were higher than . However, significant deviations were found for fluidization velocities close to minimum fluidization. Heat transfer models which consider the influence of fluidization velocity show a better agreement in this case although differences are still present.

Other papers | 2020

Evaluation of the Transient Behaviour of a Fixed-Bed Biomass Gasifier for Demand-Oriented Electricity Production

Hollenstein C, Zemann C, Antolini D, Patuzzi F, Martini S, Baratieri M, Gölles M. Horn M. Evaluation of the Transient Behaviour of a Fixed-Bed Biomass Gasifier for Demand-Oriented Electricity Production. 28th European Biomass Conference & Exhibition. 6-9 July 2020.

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The majority of renewable energy technologies are volatile in nature. External factors such as weather conditions lead to fluctuations in their produced electricity and heat. This results in a demand either not being covered or dissatisfied since too much electricity and heat is produced in the energy system. Although energy storages can counteract these fluctuations, renewable energy technologies that are capable of producing energy on demand are needed as well. As such, technologies based on the thermochemical conversion of biomass are especially relevant as they are considered to be CO2-neutral. Although most existing implementations are based on combustion of biomass, fixed-bed biomass gasification is of growing relevance due to higher overall efficiencies and low pollutant emissions. Currently, fixed-bed biomass gasifiers are usually operated at steady-state operation to produce the maximum amount of energy possible. This contribution investigates, whether they can be used as a technology for demand-oriented electricity and heat production

Other Publications | 2020

EVEmBi – Bestimmung von Methanemissionen aus Biogasanlagen und Reduktionsstrategien

Meixner K. EVEmBi – Bestimmung von Methanemissionen aus Biogasanlagen und Reduktionsstrategien. CEBC 2020

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Conference presentations and posters | 2020

Experimental investigation of biomass based reducing agents for blast furnace ironmaking

Kienzl N, Strasser C, Deutsch R. Experimental investigation of biomass based reducing agents for blast furnace ironmaking. 6th Central European Biomass Conference (oral presentation). 2020.

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Other papers | 2020

Experimentally verified dynamic simulation model of a NH3/H2O-absorption refrigeration system

Wernhart M, Rieberer R, Zlabinger S, Unterberger V, Gölles M. Experimentally verified dynamic simulation model of a NH3/H2O-absorption refrigeration system. in Japan Society of Refrigerating and Air Conditioning Engineers, Hrsg., 14th IIR Gustav-Lorentzen Conference on Natural Fluids, GL 2020 - Proceedings. International Institute of Refrigeration. 2020. S. 103-109. (Refrigeration Science and Technology). https://doi.org/10.18462/iir.gl.2020.1145

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The operation characteristics of thermally driven absorption refrigeration systems (ARS) are strongly dependent on their hydraulic integration. Therefore, varying operating conditions of the hydraulic supply have a great influence on the behaviour of ARS and lead to dynamic operation, which can affect the efficiency and is largely unexplored so far. To enable a simple investigation of ARS integration considering their dynamic behaviour and to develop modern, efficiency-enhancing control strategies, dynamic simulation models of ARS are developed in Modelica Code.

In this paper, a dynamic simulation model of an ARS with the working pair ammonia/water (NH3/H2O) is presented. The parameterization and the physical correlations of selected components of the simulation model are described. Afterwards, the simulation model is verified by comparing simulation results with measurement data of the NH3/H2O-ARS. Finally, the capabilities of the simulation model are demonstrated by performing a simulation-based analysis of the temperature glide of the refrigerant in the evaporator.

Other papers | 2020

Experimentally verified dynamic simulation model of a NH3/H2O-absorption refrigeration system

Wernhart MW, Rieberer R, Zlabinger S, Unterberger V, Gölles M. Experimentally verified dynamic simulation model of a NH3/H2O-absorption refrigeration system.14th IIR-Gustav Lorentzen Conference on Natural Refrigerants: GL 2020. 7 Dec 2020. Oral presentation (online).

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Peer reviewed papers | 2020

Fate of Phosphorus in Fluidized Bed Cocombustion of Chicken Litter with Wheat Straw and Bark Residues

Häggström G, Fürsatz K, Kuba M, Skoglund N, Öhman M. Fate of Phosphorus in Fluidized Bed Cocombustion of Chicken Litter with Wheat Straw and Bark Residues. Energy and Fuels. 2020.34:1822-1829

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This study aims to determine the fate of P during fluidized bed co-combustion of chicken litter (CL) with K-rich fuels [e.g., wheat straw (WS)] and Ca-rich fuels (bark). The effect of fuel blending on phosphate speciation in ash was investigated. This was performed by chemical characterization of ash fractions to determine which phosphate compounds had formed and identify plausible ash transformation reactions for P. The ash fractions were produced in combustion experiments using CL and fuel blends with 30% CL and WS or bark (B) at 790–810 °C in a 5 kW laboratory-scale bubbling fluidized bed. Potassium feldspar was used as the bed material. Bed ash particles, cyclone ash, and particulate matter (PM) were collected and subjected to chemical analysis with scanning electron microscopy–energy-dispersive X-ray spectrometry (SEM–EDS) and X-ray diffraction. P was detected in coarse ash fractions only, that is, bed ash, cyclone ash, and coarse PM fraction (>1 μm); no P could be detected in the fine PM fraction (<1 μm). SEM–EDS analysis showed that P was mainly present in K–Ca–P-rich areas for pure CL as well as in the ashes from the fuel blends of CL with WS or B. In the WS blend, P was found together with Si in these areas. The crystalline compound containing P was hydroxyapatite in all cases as well as whitlockite in the cases of pure CL and WS blend, of which the latter compound has been previously identified as a promising plant nutrient. The ash fractions from CL and bark blend only contained P in hydroxyapatite. Co-combustion of CL together with WS appears to be promising for P recovery, and ashes with this composition could be further studied in plant growth experiments

Conference presentations and posters | 2020

GrateAdvance - Advanced adjustable grate solutions for future fuel flexible biomass combustion technologies

Barroso G, Essl M, Feldmeier S, Mehrabian R, Nussbaumer T, Öhman M, Reiterer T, Schwarz M, Shiehnejad-Hesar A, Wopienka E. GrateAdvance - Advanced adjustable grate solutions for future fuel flexible biomass combustion technologies. 6th Central European Biomass Conference, 2020, Graz.

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Conference presentations and posters | 2020

GrateAdvance – Advanced adjustable grate solutions for future fuel flexible biomass combustion technologies

Barroso G, Essl M, Feldmeier S, Mehrabian R, Nussbaumer T, Öhman M, Reiterer T, Schwarz M, Shiehnejad-Hesar A, Wopienka E. GrateAdvance – Advanced adjustable grate solutions for future fuel flexible biomass combustion technologies. 6th Central European Biomass Conference - IEA-Workshop: TASK 32 (oral presentation). 2020.

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Other Publications | 2020

GreenGas die Alternative zu Erdgas

Strasser C, Luisser M, Drosg B. GreenGas die Alternative zu Erdgas. TGA Planung 2021. December 2020.

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Reports | 2020

Handbook: Technical options for retrofiting industries with bioenergy

Rutz D, Janssen R, Reumerman P, Spekreijse J, Matschegg M, Bacovsky D, et al. Handbook: Technical options for retrofiting industries with bioenergy. March 2020

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Conference presentations and posters | 2020

How to create value chains from different feedstocks

Enigl M, How to create value chains from different feedstocks. 6th Central Eurpean Biomass Conference, 22-254 January 2020, Graz.

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Peer reviewed papers | 2020

Impact of residual fuel ash layers on the catalytic activation of K-feldspar regarding the water–gas shift reaction

Fürsatz K, Kuba M, Janisch D, Aziaba K, Hammerl C, Chlebda D, Łojewska J, Hofbauer H. Impact of residual fuel ash layers on the catalytic activation of K-feldspar regarding the water–gas shift reaction. Biomass Conversion and Biorefinery. 2020

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Interaction of biomass ash and bed materials in thermochemical conversion in fluidized beds leads to changes of the bed particle surface due to ash layer formation. Ash components present on the bed particle surface strongly depend on the ash composition of the fuel. Thus, the residual biomass used has a strong influence on the surface changes on bed particles in fluidized bed conversion processes and, therefore, on the catalytic performance of the bed material layers. Ash layer formation is associated with an increase in the catalytic activity of the bed particles in gasification and plays a key role in the operability of different biomass fuels. The catalytic activation over time was observed for K-feldspar used as the bed material with bark, chicken manure, and a mixture of bark and chicken manure as fuels. The changes on the bed material surfaces were further characterized by SEM/EDS and BET analyses. Raman, XPS, and XRD analyses were used to characterize the crystal phases on the bed material surface. An increase in surface area over time was observed for K-feldspar during the interaction with biomass ash. Additionally, a more inhomogeneous surface composition for fuels containing chicken manure in comparison to pure bark was observed. This was due to the active participation of phosphorus from the fuel ash in the ash transformation reactions leading to their presence on the particle surface. A decreased catalytic activity was observed for the same BET surface area compared to bark combustion, caused by the different fuel ash composition of chicken manure.

Peer reviewed papers | 2020

Increased efficiency of dual fluidized bed plants via a novel control strategy

Nigitz T, Gölles M, Aichernig C, Schneider S, Hofbauer H, Horn M. Increased efficiency of dual fluidized bed plants via a novel control strategy. Biomass & Bioenergy. 2020 Okt;141. 105688. https://doi.org/10.1016/j.biombioe.2020.105688

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Industrial plants using DFB biomass gasification are on the verge of profitability. These plants should be operated more economically in order to support the industrial applications for renewable technologies of this kind. Since some parts of such plants are typically difficult to control, a state-of-the-art control strategy is analyzed here in the context of its potential for increased economic efficiency. The DFB gasification plant “HGA Senden” in Ulm, Germany is considered on an exemplary basis here. A process analysis reveals a high potential in the synchronization of product gas generation and utilization. At the present time a relevant surplus of product gas is burned in an auxiliary boiler for synchronization purposes and regular manual adjustments at the fuel feed are necessary by the plant operators. For this synchronization a novel control strategy is developed that actuates the auxiliary boiler and the fuel feed simultaneously. The novel control strategy was experimentally validated for a period of over one month. Due to this long-term evaluation the fuel consumption was reduced by 5% and the manual adjustments of the fuel feed that were necessary on average every 30min were eliminated. As a result DFB gasification plants can be operated more economically by applying the novel control strategy for synchronization of product gas generation and utilization.

Conference presentations and posters | 2020

Individiual heat management in the living room

Schwabl M. Individiual heat management in the living room. 6th Central European Biomass Conference (oral presentation. 2020.

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Conference presentations and posters | 2020

Individual heat management in the living room

Schwabl M. Individual heat management in the living room. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference presentations and posters | 2020

Influence of ash forming elements from biogenous residues on fluidized bed conversion processes

Fürsatz K, Influence of ash forming elements from biogenous residues on fluidized bed conversion processes. 6th Central Eurpean Biomass Conference, 22-24 January 2020, Graz.

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Peer reviewed papers | 2020

Influence of bed materials on the performance of the Nong Bua dual fluidized bed gasification power plant in Thailand

Siriwongrungson V, Hongrapipat J, Kuba M, Rauch R, Pang S, Thaveesri J, Messner M, Hofbauer H. Influence of bed materials on the performance of the Nong Bua dual fluidized bed gasification power plant in Thailand. Biomass Conversion and Biorefinery. 2020;

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Bed materials and their catalytic activity are two main parameters that affect the performance of the dual fluidized bed (DFB) gasification system in terms of product gas composition and tar levels. Two sources of bed materials were used for the operation of a commercial DFB gasification system in Thailand, using woodchips as a biomass feedstock. One source of the bed materials was the calcined olivine which had been used in the Gussing Plant, Austria, and the other activated bed material was a mixture of fresh Chinese olivine and used Austrian olivine with additives of biomass ash, calcium hydroxide and dolomite. These bed materials were collected and analysed for morphological and chemical composition using a scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray fluorescence spectroscopy (XRF). The product gas was cleaned in a scrubber to remove tars, from which the samples were collected for gravimetric tar analysis. Its composition data was automatically recorded at the operation site before it entered the gas engine. From the SEM, EDS and XRF analyses, calcium-rich layers around the bed materials were observed on the activated bed material. The inner layers of bed materials collected were homogeneous. Biomass ash, which was generally added to the bed materials, had significant calcium and potassium content. These calcium-rich layers of the bed materials, from the calcium hydroxide, biomass ash and dolomite, influenced system performance, which was determined by observing lower tar concentration and higher hydrogen concentration in the product gas.

Conference presentations and posters | 2020

Integrating steam gasification into established infrastructure in the pulp and paper industry

Karl T, Integrating steam gasification into established infrastructure in the pulp and paper industry. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference presentations and posters | 2020

Integration von Biogas in Bioprozesse - Nährstoffrückführung und Energiegewinnung

Drosg B. Integration von Biogas in Bioprozesse - Nährstoffrückführung und Energiegewinnung. 6th Central European Biomass Conference (oral presentation). 2020.

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Peer reviewed papers | 2020

Investigation of solid oxide fuel cell operation with synthetic biomass gasification product gases as a basis for enhancing its performance

Pongratz G, Subotić V, Schroettner H, Stoeckl B, Hochenauer C, Anca-Couce A, Scharler R. Investigation of solid oxide fuel cell operation with synthetic biomass gasification product gases as a basis for enhancing its performance. Biomass Conversion and Biorefinery.2020.

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Solid oxide fuel cells represent a promising technology to increase the electrical efficiency of biomass-based combined-heat-power systems in comparison to state-of-the-art gas engines, additionally providing high temperature heat. To identify favorable fuel gas compositions for an efficient coupling with gasifiers at low degradation risk is of major importance to ensure stability, reliability, and durability of the systems used, thus increasing attractiveness of electricity production from biomass. Therefore, this study presents a comprehensive analysis on the influence of main gas components from biomass gasification on the performance and efficiency of a cell relevant for real application. An industrial-size electrolyte supported single cell with nickel/gadolinium-doped ceria anode was selected showing high potential for gasifier-solid oxide fuel cell systems. Beneficial gas component ratios enhancing the power output and electric efficiency are proposed based on the experimental study performed. Furthermore, the degradation stability of a SOFC fueled with a synthetic product gas representing steam gasification of woody biomass was investigated. After 500 h of operation under load at a steam-to-carbon ratio of 2.25 in the fuel gas, no performance or anode degradation could be detected.

Reports | 2020

Investigation of the formation of coherent ash residues during fluidized bed gasification of wheat straw lignin

Priscak J, Fürsatz K, Kuba M, Skoglund N, Benedikt F, Hofbauer H. Investigation of the formation of coherent ash residues during fluidized bed gasification of wheat straw lignin. Energies. 2020;13(15):3935:

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Thermal conversion of ash-rich fuels in fluidized bed systems is often associated with extensive operation problems caused by the high amount of reactive inorganics. This paper investigates the behavior of wheat straw lignin—a potential renewable fuel for dual fluidized bed gasification. The formation of coherent ash residues and its impact on the operation performance has been investigated and was supported by thermochemical equilibrium calculations in FactSage 7.3. The formation of those ash residues, and their subsequent accumulation on the surface of the fluidized bed, causes temperature and pressure fluctuations, which negatively influence the steady-state operation of the fluidized bed process. This paper presents a detailed characterization of the coherent ash residues, which consists mostly of silica and partially molten alkali silicates. Furthermore, the paper gives insights into the formation of these ash residues, dependent on the fuel pretreatment (pelletizing) of the wheat straw lignin, which increases their stability compared to the utilization of non-pelletized fuel.

Conference presentations and posters | 2020

Lessons Learned from Alternative Fuels Experience

Sonnleitner A, Bacovsky D. Lessons Learned from Alternative Fuels Experience. 6th Central European Biomass Conference, 22-24 January 2020, Graz

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Decarbonising the transport sector is one of the key goals of national and international climate change mitigation policies. Rapid and effective market introduction of alternative fuels and vehicles is needed to reduce greenhouse gas emissions from the existing vehicle fleet as soon as possible and as extensively as possible.

However, experience with various attempts to introduce alternative fuels and vehicles to the market has shown that this is not always successful. Several participants in the Advanced Motor Fuels Technology Collaboration Program (AMF TCP) have therefore proposed an annex on lessons learned from market launch attempts.

The circumstances of the introduction of advanced motor fuels and the factors influencing their commercialization (resource, transport infrastructure, economic situation, etc.) in each country are different, and it is difficult to universally evaluate an advanced motor fuels policy.

For this reason, this annex clarifies the background and objective of the central government and local governments’ introduction policy and specific measures on advanced motor fuels in the past, and summarizes the effectiveness, successes, and lessons learned regarding the promotion of advanced motor fuels in each individual case of introduction and commercialization.

The participating countries Austria, China, Finland, Japan, Sweden and the USA conduct analyses of their own case studies on past market introductions taking into account specific framework conditions for each country:

Austria: low blend biofuels, CNG-driven cars, prevented introduction of E10

China: Ethanol

Finland: E10, E85, drop-in components for diesel, biogas

Japan: FAME, natural gas

Sweden: reduction obligation, high blend biofuels and biogas, E85

USA: low and high level blends of ethanol, methanol and FFVs, natural gas

The sum of the case studies is analysed and key drivers of successes and key barriers of failures are identified. Preliminary results from this work will be discussed in an expert workshop in 2020, and then the final lessons learned and recommendations will be derived. Policy briefs including key messages, best practices, lessons learned and avoided mistakes related to advanced motor fuels covering both fuels and related vehicle technologies will be developed and provided as recommendations for political decision makers.

Other papers | 2020

Long-term validation of a new modular approach for CO-lambda-optimization

Zemann C, Hammer F, Gölles M, Horn M. Long-term validation of a new modular approach for CO-lambda-optimization. 28th European Biomass Conference & Exhibition. 6-9 July 2020.

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Long Term Validation of a New Modular Approach for CO-Lambda-Optimization

The optimization of existing biomass boilers in terms of efficiency and pollutant emissions is essential for their continued economic and ecological viability in future energy systems. These improvements are typically achieved by constructive changes which are expensive and can require prolonged downtimes. A well-known method for optimizing biomass boilers in terms of efficiency and pollutant emissions without constructive changes is the so-called CO-lambda-optimization. While multiple approaches for CO-lambda-optimization have been presented in literature, they are still rarely used in real biomass boilers. This is partly due to the fact that these approaches do not meet the requirements associated with their long-term operation in real biomass boilers. This contribution presents a new and modular approach for the CO-lambda-optimization which is specifically designed to meet these requirements. Particular emphasis in this contribution is laid on the long-term validation of the presented approach for CO-lambda-optimization at a medium-scale fixed-bed biomass boiler.

Conference presentations and posters | 2020

Mapping bioenergy retrofitting in Europe´s industry - BIOFIT first results

Reumerman P, Rutz D, Janssen R, Bacovsky D, Gröngröft A, Saastamoinen H, Mäki E, Karampinis E. Mapping bioenergy retrofitting in Europe´s industry - BIOFIT first results. 28th European Biomass Conference and Exhibition (poster) 2020.

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Conference presentations and posters | 2020

Microgrid Lab 100 % - R&D project for decentralized energy supply with biomass and other Distributed energy Resources

Aigenbauer S. Microgrid Lab 100 % - R&D project for decentralized energy supply with biomass and other Distributed energy Resources. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference presentations and posters | 2020

Microgrid Lab 100% Testbed for the development of control algorithms for microgrids

Aigenbauer S, Microgrid Lab 100% Testbed for the development of control algorithms for microgrids. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Microgrids are local energy grids that (partly) cover their own energy demand. Decentralized renewable energy sources reduce energy costs and CO2 emissions in a microgrid. Various storage systems and strategies like load shift are employed to balance the volatile energy flows. Intelligent controllers improve the energy management of the micro and smart grids. BEST GmbH is the industry leader when it comes to biomass control systems in Austria. Thus, BEST GmbH is already combining this knowledge within the “OptEnGrid” (FFG 858815) and “Grundlagenforschung Smart- und Microgrid“ (K3-F-755/001-2017) research projects, which are based on the leading microgrid optimization tool DER-CAM from Lawrence Berkeley National Laboratory at the University of California. These two BEST GmbH basic research projects form the basis for new innovative microgrid controller concepts which will be implemented and tested in the presented Microgrid Research Lab in Wieselburg (project Microgrid Lab 100%). The Microgrid Research Lab will include the Technology- und Reseach Centre (tfz) Wieselburg-Land and the new firefighting department next to the tfz.

Conference presentations and posters | 2020

Microgrid Lab – R&D project for 100% decentralized energy supply with biomass and other Distributed Energy Resources (DER)

Aigenbauer S, Zellinger M, Stadler M. Microgrid Lab – R&D project for 100% decentralized energy supply with biomass and other Distributed Energy Resources (DER). 6th Central European Biomass Conference (poster). 2020.

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Microgrids, a research topic within the smart grids area, build on close relationships between demand and supply and will create a 170 Mrd. € market potential in 2020[1]. These individual markets are characterized by different technologies in use. For example, biogas will play a key role in microgrids in Asia compared to Photovoltaics, Combined heat and Power (CHP), as well as storage technologies in North America. All these different technologies need to be coordinated and controlled. BIOENERGY2020+ GmbH is the industry leader when it comes to biomass control systems in Austria. Thus, BIOENERGY2020+ GmbH is already combining this knowledge within the OptEnGrid and “Grundlagenforschung Smart- und Microgrid“ (K3-F-755/001-2017) research projects, which are based on the leading microgrid optimization tool DER-CAM from Lawrence Berkeley National Laboratory at the University of California in Berkeley. These two BIOENERGY2020+ GmbH basic research projects constitute the basis for new innovative microgrid controller concepts and these new microgrid controller will be implemented and tested in the suggested Microgrid Research Lab in Wieselburg. The Microgrid Research Lab will include the Technology- und Reseach Centre (tfz) Wieselburg-Land and the new firefighting department next to the tfz.

 

 

Peer reviewed papers | 2020

Model-based control of hydraulic heat distribution systems — Theory and application

Unterberger V, Muschick D, Loidl A, Poms U, Gölles M, Horn M. Model-based control of hydraulic heat distribution systems — Theory and application. Control Engineering Practice. 2020;2020(101).104464. https://doi.org/10.1016/j.conengprac.2020.104464

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With the share of renewable energy sources increasing in heating and hot water applications, the role of hydraulic heat distribution systems is becoming more and more important. This is due to the fact that in order to compensate for the often fluctuating behaviour of the renewables a flexible heat transfer must be ensured by these distribution systems while also taking the optimal operating conditions (mass flow, temperature) of the individual components into consideration. This demanding task can be accomplished by independently controlling the two physical quantities mass flow and temperature. However, since there exists an intrinsic nonlinear coupling between these quantities this challenge cannot be handled sufficiently by decoupled linear PI controllers which are currently state-of-the-art in the heating sector. For this reason this paper presents a model-based control strategy which allows a decoupled control of mass flow and temperature. The strategy is based on a systematic design approach from models described in this contribution, which are validated by commercially available components from which most of them can be parametrized by the data sheet. The control strategy is designed for a typical hydraulic configuration used in heating systems, which will allow the accurate tracking of the desired trajectories for mass flows, temperatures and consequently heat flows. The controllers are validated experimentally and compared to well-tuned state-of-the-art (PI) controllers in order to illustrate their superiority and prove their decoupling of the control of mass flow and temperature in real world applications.

Conference presentations and posters | 2020

Model-based estimation of the flue gas mass flow in biomass furnaces

Niederwieser H. Model-based estimation of the flue gas mass flow in biomass furnaces. 6th Central European Biomass Conference. 22-24 January 2020, Graz.

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Other Publications | 2020

Modern control strategies for biomass combustion systems in residential heating systems

Gölles M, Zemann C. Modern control strategies for biomass combustion systems in residential heating systems. At 6th Central European Biomass Conference IEA-Workshop: TASK 32. Oral Presenation. 23.01.2020.

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Conference presentations and posters | 2020

Modification of ash properties in fixed bed combustion systems

Sommersacher P, Retschitzegger S. Modification of ash properties in fixed bed combustion systems. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Peer reviewed papers | 2020

Multi-stage model for the release of potassium in single particle biomass combustion

Anca-Couce A, Sommersacher P, Hochenauer C, Scharler R. Multi-stage model for the release of potassium in single particle biomass. Fuel. 2020:280:118569.

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The release of potassium during biomass combustion leads to several problems as the emissions of particle matter or formation of deposits. K release is mainly described in literature in a qualitative way and this work aims to develop a simplified model to quantitatively describe it at different stages. The proposed model has 4 reactions and 5 solid species, describing K release in 3 steps; during pyrolysis, KCl evaporation and carbonate dissociation. This release model is coupled into a single particle model and successfully validated with experiments conducted in a single particle reactor with spruce, straw and Miscanthus pellets at different temperatures. The model employs same kinetic parameters for the reactions in all cases, while different product compositions of the reactions are employed for each fuel, which is attributed to differences in composition. The proposed model correctly predicts the online release at different stages during conversion as well as the final release for each case.

Conference presentations and posters | 2020

NOx Modelling and Emission Reduction

Eßl M, NOx Modelling and Emission Reduction. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Other papers | 2020

Numerical simulation of fuel nitrogen conversion and NOx emissions in biomass boilers with advanced air staging technology

Essl M, Schulze K, Scharler R. Numerical simulation of fuel nitrogen conversion and NOx emissions in biomass boilers with advanced air staging technology. 3RD DOCTORAL COLLOQUIUM BIOENERGY. 2020

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The increased biomass utilization leads to the need of an efficient and flexible usage of available sources. Therefore, it is necessary to combust low-cost biogenic residues, which inherently have higher nitrogen contents that lead to increased NOx emissions. In order to tackle this issue a new combustion technology with double air staging and flue gas recirculation is under development. The technology also features an increased fuel bed height and very low oxygen concentrations in the fuel bed to reduce fuel bed temperatures. This work focuses on the CFD simulation of the formation and reduction of NOx emissions of in a small scale boiler (35 kWth). Compared to previously applied models, major modification concerning the heat and mass transfer in the fuel bed as well as the subsequent conversion in the freeboard were made. The fuel bed is modelled via representative fuel particles with a Lagrangian approach and a thermally thick particle model considering intra-particle
gradients. Due to the increased fuel bed height and the relatively low oxygen concentration the formation and cracking of tars has to be considered in the simulation. This heavily influences the formation and reduction of NOx and its precursors. The fuel bound nitrogen is released via the particle model in the form of NO during char burnout and via a lumped tar species during pyrolysis. The cracking of the lumped tar species is modelled via two global gas phase reactions that releases the NOx precursors NH3 and HCN. The cracking reactions are added to a skeletal reaction mechanism with 28 species and 102 reactions that includes the fate of the N species. The simulation results are compared to experimental data from test runs with spruce wood chips and Miscanthus pellets as fuels. The comparison showed good agreement for the test runs with wood chips, where the temperature distribution inside the fuel bed and the released species above the fuel bed were predicted well. The test runs with Miscanthus showed a greater deviation between the measured and simulated values. For both fuels the NOx reduction that was experimentally observed in the secondary combustion zone could not be predicted with reasonable agreement. Therefore, it is necessary to further investigate the cracking of the tars and the subsequent formation of the NOx precursors. The presented work forms the basis for further improvements of the numerical models and subsequently the optimization of the new technology.

Peer reviewed papers | 2020

Off-gassing reduction of stored wood pellets by adding acetylsalicylic acid

Sedlmayer I, Bauer-Emhofer W, Haslinger W, Hofbauer H, Schmidl C, Wopienka E. Off-gassing reduction of stored wood pellets by adding acetylsalicylic acid. Fuel Processing Technology 2020.198:106218.

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During transportation and storage of wood pellets various gases are formed leading to toxic atmosphere. Various influencing factors and measures reducing off-gassing have already been investigated. The present study aims at applying an antioxidant, acetylsalicylic acid (ASA), to reduce off-gassing from wood pellets by lowering wood extractives oxidation. Therefore, acetylsalicylic acid was applied in industrial and laboratory pelletizing processes. Pine and spruce sawdust (ratio 1:1) were pelletized with adding 0-0.8% (m/m) ASA. Glass flasks measurements confirmed off-gassing reduction by adding ASA for all wood pellets investigated.The biggest effect was achieved by adding 0.8% (m/m) ASA in the industrial pelletizing experiments where the emission of volatile organic compounds (VOCtot) was reduced by 82% and a reduction of carbon monoxide (CO) and carbon dioxide (CO2) emissions by 70% and 51%, respectively, could be achieved. Even an addition of 0.05% (m/m) ASA led to off-gassing reduction by >10%. A six week storage experiment to investigate the long-term effectivity of ASA addition revealed, that antioxidant addition was effective in reducing CO-, CO2- and VOCtot-release, especially during the first four weeks of the storage experiment, after which time the relative reduction effect was significantly decreased.

Peer reviewed papers | 2020

Online determination of potassium and sodium release behaviour during single particle biomass combustion by FES and ICP-MS

Paulauskas R, Striūgas N, Sadeckas M, Sommersacher P, Retschitzegger S, Kienzl N. Online determination of potassium and sodium release behaviour during single particle biomass combustion by FES and ICP-MS. Science of the Total Environment. 2020;746:141162.

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This study focuses on the determination of alkali release from wood and straw pellets during combustion. The aim is to expand the knowledge on the K and Na release behaviour and to adopt chemiluminescence-based sensors for online monitoring of alkali detection which can be applied for the prevention of fouling formation in low quality biomass combustion plants. Flame emission spectrometry (FES) was used for optical detection of chemiluminescence spectra of K and Na using optical bandpass filters mounted on an ICCD (Intensified Charge Coupled Device) camera. FES data were verified by additional experiments with a single particle reactor (SPR) coupled with an inductively coupled plasma mass spectrometer (ICP-MS). Using both techniques, the release profiles of K and Na during a single pellet combustion at 1000 °C were determined and obtained K* and Na* emission intensities directly correlated with the results from the ICP-MS. It was determined that the emission intensity of alkali radicals depends on alkali concentrations in the samples and K and Na radical emission intensities increase with increasing alkali amounts in the samples. The ICP-MS data revealed that the release of K and Na mainly takes place during the stage of devolatilization. During devolatilization, almost all potassium and sodium are released from wood samples, while only 65–90% of K and 74–90% of Na are released from straw samples. Based on the results, the flame emission spectroscopy technique is capable to fully detect released alkali metals in the gas phase during combustion and proves a possibility to use flame emission sensors for monitoring the release of alkali species from biomass during combustion processes.

Peer reviewed papers | 2020

Optimal operation of residential heating systems with logwood boiler, buffer storage and solar thermal collector

Zemann C, Deutsch M, Zlabinger S, Hofmeister G, Gölles M, Horn M. Optimal operation of residential heating systems with logwood boiler, buffer storage and solar thermal collector. Biomass and Bioenergy, 2020,140:105622.

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Modern central heating systems with logwood boilers are comprised of the boiler, a buffer storage and solar thermal collectors. Conventional control strategies for these heating systems do not coordinate the utilization of all components. This can lead to a sub-optimal operation of the entire heating system resulting in a loss of efficiency and increased pollutant emissions. This contribution presents a control strategy which considers all components of the heating system including the user and forecasts for the solar yield and heat demand. It determines and carries out an optimal operating strategy that improves the user utility and maximizes the heating system efficiency while also ensuring a clean and efficient combustion. The control strategy continuously learns the user behavior and instructs the user when to refill the logwood boiler and how much fuel to use. The new control strategy was verified through test runs performed at an experimental setup consisting of a commercially available logwood boiler with a nominal capacity of 28 kW , two buffer storages with a capacity of 1.5 m3 each and a heating device with a thermal output of up to 12 kW simulating a solar thermal collector. During these test runs, the CO emissions were reduced 93.6 %by in the main combustion phase, 7.1 % more solar yield was utilized, the buffer losses were reduced by - 16.9 % and the overall efficiency was increased by 3.1 % . Thus, the application of this control strategy resulted in a significantly improved user utility and heating system efficiency.

Conference presentations and posters | 2020

Optimization based planning of energy systems

Zellinger M, Optimization based planning of energy systems. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference presentations and posters | 2020

Optimizing of a hydrogen production plant by optimization of the CO2 removal step

Loipersböck J. Optimizing of a hydrogen production plant by optimization of the CO2 removal step. 6th Central European Biomass Conference (oral presentation) 2020.

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Hydrogen production in 2010 was estimated to 50 Mt/a. 96 % of today’s hydrogen is produced by converting fossil fuels in thermochemical processes. As main conversion technology steam reforming of natural gas and naphtha has been established. Hydrogen is mainly used in refineries, for ammonia production and in several chemical production plants. Hydrogen is also seen as a promising alternative energy carrier for the transport sector. Therefor an increasing demand on hydrogen over the next years can be assumed.  
To substitute fossil produced hydrogen several renewable hydrogen routes have been established. Beside electrolysis of water also steam reforming of biogas, methane pyrolysis and gasification technologies have been developed. This work will focus on hydrogen production based on dual fluidized bed gasification of biomass.  
Dual fluidized bed gasification gives the possibility to establish a renewable hydrogen production route and substitute fossil fuels. A hydrogen production plant consisting of a dual fluidized bed gasifier, a water gas shift stage, a CO2 removal, a pressure swing adsorption and a steam reformer were erected and operated over 1000 h. The gathered data was validated and a model for up-scaling was developed. A benchmark size of 10 MW fuel input power was used as base for economic estimations. As described in previous work an overall efficiency of 55 % can be achieved, which is comparable to alternative technologies. Compared to other renewable routes, hydrogen production based on dual fluidized bed gasification gives the possibility of a fuel flexible system for continuous hydrogen production.  
Hydrogen production derived by DFB gasification of wood is a reliable process, which needs to be optimized due to economic reasons. Special attention has to be paid on the CO2 removal, to obtain an economic efficient process.  
In this study a parameter variation of the CO2 removal, which consists of absorption and desorption column, was done. Mono-ethanol-amine (MEA) was used as a solvent. One focus of the experimental investigations was the desorption at low temperatures to gain the possibility of using temperature levels which are common in district heat grids. For the experiments real synthesis gas with impurities was used. Over the gas cleaning steps of the hydrogen production plant, impurities were removed and hydrogen content was increased. To increase the efficiency of the CO2 removal and further the hydrogen production, a parameter study was done. A good correlation between separation efficiency and desorption temperature could be observed.  
Economics were calculated comparing natural gas steam reforming, electrolysis and hydrogen production based dual fluidized bed gasification. First results show a high potential for establishing the BioH2 plant as a commercial production plant. An economic plant operation with wood chips can be achieved at plant sizes of 20-30 MW fuel input power. A switch to lower quality biomass can reduce the economic feasible plant size even further.  
Keywords: hydrogen, up-scaling, economics, CO2 removal

Peer reviewed papers | 2020

Performance Comparison between Two Established Microgrid Planning MILP Methodologies Tested On 13 Microgrid Projects

Stadler M, Pecenak Z, Mathiesen P, Fahy K, Kleissl J. Performance Comparison between Two Established Microgrid Planning MILP Methodologies Tested On 13 Microgrid Projects. Energies.2020;13:446

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Mixed Integer Linear Programming (MILP) optimization algorithms provide accurate and clear solutions for Microgrid and Distributed Energy Resources projects. Full-scale optimization approaches optimize all time-steps of data sets (e.g., 8760 time-step and higher resolutions), incurring extreme and unpredictable run-times, often prohibiting such approaches for effective Microgrid designs. To reduce run-times down-sampling approaches exist. Given that the literature evaluates the full-scale and down-sampling approaches only for limited numbers of case studies, there is a lack of a more comprehensive study involving multiple Microgrids. This paper closes this gap by comparing results and run-times of a full-scale 8760 h time-series MILP to a peak preserving day-type MILP for 13 real Microgrid projects. The day-type approach reduces the computational time between 85% and almost 100% (from 2 h computational time to less than 1 min). At the same time the day-type approach keeps the objective function (OF) differences below 1.5% for 77% of the Microgrids. The other cases show OF differences between 6% and 13%, which can be reduced to 1.5% or less by applying a two-stage hybrid approach that designs the Microgrid based on down-sampled data and then performs a full-scale dispatch algorithm. This two stage approach results in 20–99% run-time savings.

Conference presentations and posters | 2020

PHB from cyanobacteria - Why phototrophic biotechnology is interesting for Europe.

Fritz I, Drosg B, Meixner K, Daffert C, Troschl C, Silvestrini L. PHB from cyanobacteria - Why phototrophic biotechnology is interesting for Europe. Eurobiotech 2020. 24-26 September 2020.

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Other papers | 2020

Power Systems in the context of district heating and cooling networks as an integrated energy system approach -Regulations and Business Cases within the IEA DHC Annex TS3

Kneiske T, Kallert A, Cronbach D, Yu Y, Schmidt D, Johannsen R, Sorknæs P, Muschick D, Ianakiev A, Svensson I, Schmidt R, Terreros O, Widl E. Power Systems in the context of district heating and cooling networks as an integrated energy system approach - Regulations and Business Cases within the IEA DHC Annex TS3. 48. CIGRE conference 2020. July 2020.

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Integrated energy systems 1 couples power systems, district heating and cooling (DHC), and gas grids, thereby enabling the storage and distribution of energy across different infrastructure types. Supply and demand follow different patterns in these different domains, which can lead to synergies in generation, storage and consumption, if planned and managed as one energy system. An integrated approach has the potential to increase reliability, flexibility and supply safety and efficiency. Moreover, network coupling increases local utilization of renewables, avoiding problems in the distribution networks, as well as transmission losses. In addition, hybrid energy networks are a promising opportunity to manage and mitigate temporal imbalances of supply and demand in energy systems with a high share of volatile renewables, mainly PV and wind energy. The IEA DHC Annex TS3 provides a holistic approach for designing and assessing hybridization schemes, focusing on the district heating and cooling (DHC) networks and considering both technical (system configuration, operational strategy) and strategic aspects (business models, regulatory frame). These aspects will be discussed within the framework of the IEA DHC Annex TS3 in order to promote the benefits of DHC networks in an integrated energy system. Furthermore we can establish a common direction for the development and implementation of hybrid energy concepts. The IEA DHC Annex TS3 will connect existing national and international projects and thus benefit from interdisciplinary experience and exchange. The primary result of the IEA DHC Annex TS3 will be a guidebook including:  Analyses of available technologies and synergies / application areas  An overview of international case studies including simulation scenarios 1 Different alternative notations can be found in literature, e.g. multi-energy networks, hybrid energy networks, sector coupling, multi-domain networks, cross energy systems. However, since no standard definition is available, those notations are used synonymously.

Peer reviewed papers | 2020

Prediction of slag related problems during fixed bed combustion of biomass by application of a multivariate statistical approach on fuel properties and burner technology

Rebbling A, Näzelius IL, Schwabl M, Feldmeier S, Schön C, Dahl J, Haslinger W, Boström D, Öhman M, Boman C. Prediction of slag related problems during fixed bed combustion of biomass by application of a multivariate statistical approach on fuel properties and burner technology. Biomass and Bioenergy 2020.137:105557.

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Slag is related to the melting properties of ash and is affected by both the chemical composition of the fuel ash and the combustion parameters. Chemical analysis of slag from fixed bed combustion of phosphorus-poor biomass show that the main constituents are Si, Ca, K, O (and some Mg, Al, and Na), which indicates that the slag consists of different silicates. Earlier research also points out viscosity and fraction of the ash that melts, as crucial parameters for slag formation. To the authors’ knowledge, very few of the papers published to this day discuss slagging problems of different pelletized fuels combusted in multiple combustion appliances. Furthermore, no comprehensive classification of both burner technology and fuel ash parameters has been presented in the literature so far. The objective of the present paper was therefore to give a first description of a qualitative model where ash content, concentrations of main ash forming elements in the fuel and type of combustion appliance are related to slagging behaviour and potential operational problems of a biomass fuel in different small- and medium scale fixed bed appliances.

Based on the results from the combustion of a wide range of pelletized biomass fuels in nine different burners, a model is presented for amount of slag formed and expected severity of operational problems. The model was validated by data collected from extensive combustion experiments and it can be concluded that the model predicts qualitative results.

Conference presentations and posters | 2020

Primary- and Secondary Measures for Manually Fired Stoves - An Overview

Reichert G. Primary- and Secondary Measures for Manually Fired Stoves - An Overview. 6th Central European Biomass Conference, 2020, Graz.

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Conference presentations and posters | 2020

Primary- and Secondary Measures for Manually Fired Stoves – An Overview

Reichert G. Primary- and Secondary Measures for Manually Fired Stoves – An Overview. 6th Central European Biomass Conference - KeepWarm/CleanAir workshop (oral presentation). 2020.

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Conference presentations and posters | 2020

Product flexibility from biomass steam gasification applying gas upgrading and synthesis processes

Binder M, Product flexibility from biomass steam gasification applying gas upgrading and synthesis processes. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Peer reviewed papers | 2020

Progressive Hedging for Stochastic Energy Management Systems: The Mixed-Integer Linear Case

Kaisermayer V, Muschick D, Gölles M, Horn M. Progressive Hedging for Stochastic Energy Management Systems: The Mixed-Integer Linear Case. Energy Systems. 2020 Aug 29. https://doi.org/10.1007/s12667-020-00401-z

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Energy systems have increased in complexity in the past years due to the everincreasing integration of intermittent renewable energy sources such as solar thermal or wind power. Modern energy systems comprise different energy domains such as electrical power, heating and cooling which renders their control even more challenging. Employing supervisory controllers, so-called energy management systems (EMSs), can help to handle this complexity and to ensure the energy-efficient and cost-efficient operation of the energy system. One promising approach are optimization-based EMS, which can for example be modelled as stochastic mixed-integer linear programmes (SMILP). Depending on the problem size and control horizon, obtaining solutions for these in real-time is a difficult task. The progressive hedging (PH) algorithm is a practical way for splitting a large problem into smaller subproblems and solving them iteratively, thus possibly reducing the solving time considerably. The idea of the PH algorithm is to aggregate the solutions of subproblems, where artificial costs have been added. These added costs enforce that the aggregated solutions become non-anticipative and
are updated in every iteration of the algorithm. The algorithm is relatively simple to implement in practice, re-using almost all of a possibly existing deterministic implementations and can be easily parallelized.
Although it has no convergence guarantees in the mixed-integer linear case, it can nevertheless be used as a good heuristic for SMILPs. Recent theoretical results shown that for applying augmented Lagrangian functions in the context of mixed-integer programmes, any norm proofs to be a valid penalty function. This is not true for squared norms, like the squared L 2 -norm that is used in the classical progressive hedging algorithm. Building on these theoretical results, the use of the L 1 and L-infinity-norm in the PH algorithm is investigated in this paper. In order to incorporate these into the algorithm an adapted multiplier update step is proposed. Additionally a heuristic extension of the aggregation step and an adaptive penalty parameter update scheme from the literature is investigated. The advantages of the proposed modifications are demonstrated by means of illustrative examples, with the application to SMILP-based EMS in mind.

Conference presentations and posters | 2020

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

Sommersacher P. REFAWOOD - Reduction of ash-related problems in large-scale biomass combustion systems via resource efficient low-cost fuel additives. 6th Central European Biomass Conference CEBC 2020 (Oral Presentation). 2020.

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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, mainly needed to remove ash depositions, 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. On the one hand, the purpose of the additives is to reduce the Cl concentration in deposits on heat exchangers, which is the main cause for corrosion. On the other hand, the additives shall increase the ash melting temperature of deposits and hereby reduce deposit formation. In a first step the combustion behaviour of 3 different waste wood mixtures without and with the addition of various low-cost additives such as recycled gypsum, coal fly ash and iron sulphide with two different addition ratios were investigated in a laboratory reactor. Using the laboratory reactor allowed the determination of suitable additives and ratios of additivation for further investigations in the industrial plant. This approach represents a cost-effective and time-saving method for determining suitable additives and ratios of additivation. Based on the investigations carried out, the addition of 2% gypsum and 3% coal fly ash was recommended, since an improved ash melting behaviour can be expected with addition of gypsum and coal fly ash. These additives with the recommended mixing rates were then tested in a large scale CHP plant (a 40 MWth grate furnace with additional injection of wood dust above the grate). Extensive test runs 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).

Conference presentations and posters | 2020

Reliability of TGA data for characterization of alternative biomass feedstocks

Retschitzegger S, Kienzl N, Anca-Couce A, Tsekos C, Banks S, Kraia T, Zimbardi F, Funke A, Marques P. Reliability of TGA data for characterization of alternative biomass feedstocks. 6th Central European Biomass Conference, 2020, Graz.

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Peer reviewed papers | 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 papers | 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.

Other 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 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. 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.

Other 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 papers | 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 presentations and posters | 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.
 

Reports | 2020

Test Report - Lean Gas Test Simulated lean gas in the laboratory

Stressler H, Aigenbauer S. Test Report - Lean Gas Test: Simulated lean gas in the laboratory. Projektbericht. February 2020.

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Reports | 2020

Test Report - Lean Gas Test: Operation of a Stirling engine with biogas

Stressler H, Aigenbauer S. Test Report - Lean Gas Test: Operation of a Stirling engine with biogas. Projektbericht. February 2020.

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Reports | 2020

Test Report - Lean Gas Test: Operation of a Stirling engine with landfill gas

Stressler H, Aigenbauer S. Test Report - Lean Gas Test: Operation of a Stirling engine with landfill gas. Projektbericht. February 2020

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Reports | 2020

Test Report - Lean Gas Test: Operation of a Stirling engine with sewage gas

Stressler H, Aigenbauer S. Test Report - Lean Gas Test: Operation of a Stirling engine with sewage gas. Projektbericht. February 2020

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Conference presentations and posters | 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 papers | 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.

Peer reviewed papers | 2020

The impact of project financing in optimizing microgrid design

Pecenak ZK, Mathiesen P, Fahy K, Cannon C, Ayandele E, Kirk TJ, Stadler M. The impact of project financing in optimizing microgrid design. Journal of Renewable and Sustainable Energy. November 2020. 12:026187.

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A disconnect between real world financing and technical modeling remains one of the largest barriers to widespread adoption of microgrid technologies. Simultaneously, the optimal design of a microgrid is influenced by financial as well as technical considerations. This paper articulates the interplay between financial and technical assumptions for the optimal design of microgrids and introduces a design approach in which two financing structures drive an efficient design process. This approach is demonstrated on a descriptive test case, using well accepted financial indicators to convey project success. The major outcome of this paper is to provide a framework which can be adopted by the industry to relieve one of the largest hurdles to widespread adoption, while introducing multiple debt financing models to the literature on microgrid design and optimization. An equally important outcome from the test case, we provide several points of intuition on the impact of varying financing terms on the optimal solution.

Conference presentations and posters | 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 papers | 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 papers | 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 presentations and posters | 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 presentations and posters | 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 presentations and posters | 2021

A platform for energy management in communities

Derflinger N, Zellinger M. A platform for energy management in communities. ComForEn 2021 11. Symposium Communications for Energy Systems. 23 November 2021.

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Peer reviewed papers | 2021

A review on bed material particle layer formation and its positive influence on the performance of thermo-chemical biomass conversion in fluidized beds

Kuba M, Skoglund N, Öhman M, Hofbauer H. A review on bed material particle layer formation and its positive influence on the performance of thermo-chemical biomass conversion in fluidized beds.Fuel.2021.291:120214. https://doi.org/10.1016/j.fuel.2021.120214

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Bed material particle layer formation plays a significant role in thermo-chemical conversion of biomass. The interaction between biomass ash and bed material in fluidized bed conversion processes has been described for a variety of different applications and spans from fundamental research of formation mechanisms to effects of this layer formation on long-term operation in industrial-scale. This review describes the current state of the research regarding the mechanisms underlying layer formation and the positive influence of bed material particle layer formation on the operation of thermo-chemical conversion processes. Thus, the main focus lies on its effect on the catalytic activity towards gasification reactions and the impact on oxygen transport in chemical looping combustion. The review focuses on the most commonly investigated bed materials, such as quartz, feldspar or olivine. While the most relevant results for both the underlying mechanisms and the subsequently observed effects on the operation are presented and discussed, knowledge gaps where further research is necessary are identified and described.

Peer reviewed papers | 2021

Advanced Optimal Planning for Microgrid Technologies including Hydrogen and Mobility at a real Microgrid Testbed

Mansoor M, Stadler M, Auer H, Zellinger M. Advanced Optimal Planning for Microgrid Technologies including Hydrogen and Mobility at a real Microgrid Testbed. International Journal of Hydrogen Energy.2021.

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This paper investigates the optimal planning of microgrids including the hydrogen energy system through mixed-integer linear programming model. A real case study is analyzed by extending the only microgrid lab facility in Austria. The case study considers the hydrogen production via electrolysis, seasonal storage and fueling station for meeting the hydrogen fuel demand of fuel cell vehicles, busses and trucks. The optimization is performed relative to two different reference cases which satisfy the mobility demand by diesel fuel and utility electricity based hydrogen fuel production respectively. The key results indicate that the low emission hydrogen mobility framework is achieved by high share of renewable energy sources and seasonal hydrogen storage in the microgrid. The investment optimization scenarios provide at least 66% and at most 99% carbon emission savings at increased costs of 30% and 100% respectively relative to the costs of the diesel reference case (current situation).

Conference presentations and posters | 2021

Advances in biomass gasification for the production of Bioheat, bioelectricity and biofuels

Anca-Couce A, Archan G, Von Berg L, Pongratz G, Martini S, Buchmayr M, Rakos C, Hochenauer C, Scharler R. Advances in biomass gasification for the production of Bioheat, bioelectricity and biofuels. 29th European Biomass Conference and Exhibition, EUBCE 2021, 26-29 April 2021. 2021.

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Current barriers to increase the use of bioenergy for different applications are first discussed. Then, recent advances are presented on gasification-based technologies to overcome these barriers that have been reached at TU Graz together with several partners. Gasification-based fuel bed concepts integrated in biomass combustion can significantly reduce emissions for bioheat production. Advances are presented for modern biomass boilers, significantly reducing nitrogen oxides and particle matter emissions as well as increasing the feedstock flexibility; and micro-gasifiers for traditional biomass utilization, significantly reducing the emissions of unburnt products. Gasification-based processes have as well the possibility to score high electrical efficiencies and to synthetize several products as second-generation biofuels. Advances are presented on measures for reducing the presence of contaminants as tars, including the catalytic use of char for tar cracking; and in applications of the producer gas, including gas cleaning and direct coupling with a solid oxide fuel cell to maximize electricity production. © 2021, ETA-Florence Renewable Energies.

Other Publications | 2021

Algae4Fish - Video

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Peer reviewed papers | 2021

An adaptive short-term forecasting method for the energy yield of flat-plate solar collector systems

Unterberger V, Lichtenegger K, Kaisermayer V, Gölles M, Horn M. An adaptive short-term forecasting method for the energy yield of flat-plate solar collector systems. Applied Energy. 2021 Apr 16;2021(293). https://doi.org/10.1016/j.apenergy.2021.116891

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The number of large-scale solar thermal installations has increased rapidly in Europe in recent years, with 70 % of these systems operating with flat-plate solar collectors. Since these systems cannot be easily switched on and off but directly depend on the solar radiation, they have to be combined with other technologies or integrated in large energy systems. In order to most efficiently integrate and operate solar systems, it is of great importance to consider their expected energy yield to better schedule heat production, storage and distribution. To do so the availability of accurate forecasting methods for the future solar energy yield are essential. Currently available forecasting methods do not meet three important practical requirements: simple implementation, automatic adaption to seasonal changes and wide applicability. For these reasons, a simple and adaptive forecasting method is presented in this paper, which allows to accurately forecast the solar heat production of flat-plate collector systems considering weather forecasts. The method is based on a modified collector efficiency model where the parameters are continuously redetermined to specifically consider the influence of the time of the day. In order to show the wide applicability the method is extensively tested with measurement data of various flat-plate collector systems covering different applications (below 200 Celsius), sizes and orientations. The results show that the method can forecast the solar yield very accurately with a Mean Absolute Range Normalized Error (MARNE) of about 5 % using real weather forecasts as inputs and outperforms common forecasting methods by being nearly twice as accurate.

Peer reviewed papers | 2021

Analysing price cointegration of sawmill by-products in the forest-based sector in Austria

Fuhrmann M, Dißauer C, Strasser C, Schmid E. Analysing price cointegration of sawmill by-products in the forest-based sector in Austria. Forest Policy and Economics. 2021.131:102560.

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Empirical analyses of interlinkages and price dependencies in the forest-based sector support the forecast of market developments and the design of efficient utilization pathways. This article aims at analysing price cointegration between roundwood (sawlogs, pulpwood), sawmill by-products (sawdust, wood chips) and wood products (pellets, particle board) in the forest-based sector in Austria. Monthly price data for the period 2005–2019 were used for the following statistical tests: (1) The Augmented-Dickey-Fuller and Zivot-Andrews unit root tests were conducted to investigate stationarity of the data; (2) The Johansen Cointegration test was pairwise applied to price time series; (3) The Granger Causality test was used for cointegrated time series to examine which one is price leading. Furthermore, sawmill by-product prices were modelled as Vector Error Correction Models (VECM) to analyse their common behaviour. The dataset was divided to a training (2005–2017) and test (2018–2019) subset to assess the prediction accuracy of the models. The training data were used to estimate a VAR model as basis for forecasts, which were compared to the test data. Results show that sawdust prices are cointegrated and thus modelled with pellet and particle board prices. In contrast, wood chips are used for several applications and thus prices are cointegrated and modelled with prices of sawlogs, pulpwood, pellets and particle board. The comparison with the test data showed that forecasts were able to predict data from 2018 to 2019 well. However, a decrease in prices, starting in 2019 and intensified by the Covid-19 pandemic, could not be fully captured by these forecasts.

Peer reviewed papers | 2021

Analysis of H2S-related short-term degradation and regeneration of anode- and electrolyte supported solid oxide fuel cells fueled with biomass steam gasifier product gas

Pongratz G, Subotić V, Schroettner H, Hochenauer C, Skrzypkiewicz M, Kupecki J, Anca-Couce A, Scharler R. Analysis of H2S-related short-term degradation and regeneration of anode- and electrolyte supported solid oxide fuel cells fueled with biomass steam gasifier product gas. Energy.2021.218:119556.

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Using solid oxide fuel cells in biomass gasification based combined heat and power production is a promising option to increase electrical efficiency of the system. For an economically viable design of gas cleaning units, fuel cell modules and further development of suitable degradation detection methods, information about the behavior of commercially available cell designs during short-term poisoning with H2S can be crucial. This work presents short-term degradation and regeneration analyses of industrial-relevant cell designs with different anode structure and sulfur tolerance fueled with synthetic product gas from wood steam gasification containing 1 to 10 ppmv of H2S at 750°C and 800°C. Full performance regeneration of both cell types was achieved in all operating points. The high H2O content and avoided fuel depletion may have contributed to a lower performance degradation and better regeneration of the cells. A strong influence of the catalytically active anode volume on poisoning and regeneration behavior was quantified, thereby outlining the importance of considering the anode structure besides the sulfur tolerance of the anode material. Hence, cells with less sulfur tolerant anode material but larger anode volume might outperform cells less sensitive to sulfur in the case of an early detection of a gas cleaning malfunction.

Peer reviewed papers | 2021

Ash Transformation during Single-Pellet Combustion of Agricultural Biomass with a Focus on Potassium and Phosphorus

Hedayati A, Lindgren R, Skoglund N, Boman C, Kienzl N, Öhman M. Ash Transformation during Single-Pellet Combustion of Agricultural Biomass with a Focus on Potassium and Phosphorus. Energy and Fuels. January 2021. 35(2):1449–1464.

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In this study, ash transformation and release of critical ash-forming elements during single-pellet combustion of different types of agricultural opportunity fuels were investigated. The work focused on potassium (K) and phosphorus (P). Single pellets of poplar, wheat straw, grass, and wheat grain residues were combusted in a macro-thermogravimetric analysis reactor at three different furnace temperatures (600, 800, and 950 °C). In order to study the transformation of inorganic matters at different stages of the thermal conversion process, the residues were collected before and after full devolatilization, as well as after complete char conversion. The residual char/ash was characterized by scanning electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, inductively coupled plasma, and ion chromatography, and the interpretation of results was supported by thermodynamic equilibrium calculations. During combustion of poplar, representing a Ca–K-rich woody energy crop, the main fraction of K remained in the residual ash primarily in the form of K2Ca(CO3)2 at lower temperatures and in a K–Ca-rich carbonate melt at higher temperatures. Almost all P retained in the ash and was mainly present in the form of hydroxyapatite. For the Si–K-rich agricultural biomass fuels with a minor (wheat straw) or moderate (grass) P content, the main fraction of K remained in the residual ash mostly in K–Ca-rich silicates. In general, almost all P was retained in the residual ash both in K–Ca–P–Si-rich amorphous structures, possibly in phosphosilicate-rich melts, and in crystalline forms as hydroxyapatite, CaKPO4, and calcium phosphate silicate. For the wheat grain, representing a K–P-rich fuel, the main fraction of K and P remained in the residual ash in the form of K–Mg-rich phosphates. The results showed that in general for all studied fuels, the main release of P occurred during the devolatilization stage, while the main release of K occurred during char combustion. Furthermore, less than 20% of P and 35% of K was released at the highest furnace temperature for all fuels.

Peer reviewed papers | 2021

Ash transformation during single-pellet gasification of agricultural biomass with focus on potassium and phosphorus

Hedayati A, Sefidari H, Boman C, Skoglund N, Kienzl N, Öhman M. Ash transformation during single-pellet gasification of agricultural biomass with focus on potassium and phosphorus. Fuel Processing Technology. 15 June 2021.217:106805

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Agricultural biomasses and residues can play an important role in the global bioenergy system but their potential is limited by the risk of several ash-related problems such as deposit formation, slagging, and particle emissions during their thermal conversion. Therefore, a thorough understanding of the ash transformation reactions is required for this type of fuels. The present work investigates ash transformation reactions and the release of critical ash-forming elements with a special focus on K and P during the single-pellet gasification of different types of agricultural biomass fuels, namely, poplar, grass, and wheat grain residues. Each fuel was gasified as a single pellet at three different temperatures (600, 800, and 950 °C) in a Macro-TGA reactor. The residues from different stages of fuel conversion were collected to study the gradual ash transformation. Characterization of the residual char and ash was performed employing SEM-EDS, XRD, and ICP with the support of thermodynamic equilibrium calculations (TECs). The results showed that the K and P present in the fuels were primarily found in the residual char and ash in all cases for all studied fuels. While the main part of the K release occurred during the char conversion stage, the main part of the P release occurred during the devolatilization stage. The highest releases – less than 18% of P and 35% of K – were observed at the highest studied temperature for all fuels. These elements were present in the residual ashes as K2Ca(CO3)2 and Ca5(PO4)3OH for poplar; K-Ca-rich silicates and phosphosilicates in mainly amorphous ash for grass; and an amorphous phase rich in K-Mg-phosphates for wheat grain residues.

Other Publications | 2021

Betrieb verbundener Nahwärmenetze mit getrennten Eigentümern

Zemann C, Muschick D, Kaisermayer V, Gölles M. Betrieb verbundener Nahwärmenetze mit getrennten Eigentümern. QM Heizwerke Fachtagung, Bad Vöslau, 14. Oktober, 2021. (oral presentation)

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Warum ist es sinnvoll, Wärmenetze zu verbinden?

  • Erläuterung am Beispiel des Projekts Thermaflex
  • Drei Wärmenetze bei Leibnitz in der Steiermark.
  • Sind gewachsen und haben die Grenzen ihrer Nachbar-Wärmenetze erreicht.
  • Die Wärmenetze werden durch zwei getrennte Eigentümer betrieben.
Peer reviewed papers | 2021

Bioenergy technologies, uses, market and future trends with Austria as a case study

Anca-Couce A, Hochenauer C, Scharler R. Bioenergy technologies, uses, market and future trends with Austria as a case study. Renewable and Sustainable Energy Reviews.2021;135:110237.

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The current bioenergy uses and conversion technologies as well as future trends for the production of heat, power, fuels and chemicals from biomass are reviewed. The focus is placed in Austria, which is selected due to its high bioenergy utilization, providing 18.4% of the gross energy final consumption in 2017, and its strong industrial and scientific position in the field. The most common bioenergy application in Austria is bioheat with 170 PJ in 2017 mainly obtained from woody biomass combustion, followed by biofuels with 21 PJ and bioelectricity with 17 PJ. Bioheat has a stable market, where Austrian manufacturers of boilers and stoves have a strong position exporting most of their production. Future developments in bioheat production should go in the line of further reducing emissions, increasing feedstock flexibility and coupling with other renewables. For bioelectricity and biofuels, the current framework does not promote the growth of the current main technologies, i.e. combined heat and power (CHP) based on biomass combustion or biogas and first generation biofuels. However, an increase in all bioenergy uses is required to achieve the Austrian plan to be climate neutral in 2040. The current initiatives and future possibilities to achieve this increase are presented and discussed, e.g. mandatory substitution of old oil boilers, production of biomethane and early commercialization of CHP with a high efficiency or demonstration of advanced biofuels production based on gasification.

Peer reviewed papers | 2021

Categorization of small-scale biomass combustion appliances by characteristic numbers

Feldmeier S, Schwarz M, Wopienka E, Pfeifer C. Categorization of small-scale biomass combustion appliances by characteristic numbers. Renewable Energy. 2021.163:2128-2136.

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The market offers a broad range of different combustion appliances dedicated to residential heating with biomass. The effect of fuel properties on the formation of slag and emissions varies and the technology influences the impact to a certain extent. The applicability of biomass fuels is not only determined by operational settings but also by the design of boiler components as grate area and combustion chamber. Aspects as the fuel load on the grate, residence time, geometry of grate and combustion chamber design, as well as feeding and de-ashing influence the extent of slag formation and emission release. The determination of characteristic numbers by means of constructional measures allows a systematic comparison and - in a further step - an assessment/categorization of combustion technologies. After conducting a boiler survey relevant parameters regarding grate, combustion chamber, feeding, and ash removal were gathered. Characteristic numbers were specified in order to compare technological aspects. The results of this study allow the investigation of the influence of the combustion technology on the performance. They will assist the systematic and targeted design of small-scale boilers and the optimization of combustion appliances in future, especially when it comes to fuel-flexibility.

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