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Peer Reviewed Scientific Journals | 2020

A MILP-based modular energy management system for urban multi-energy systems: Performance and sensitivity analysis

Moser AGC, Muschick D, Gölles M, Nageler PJ, Schranzhofer H, Mach T et al. A MILP-based modular energy management system for urban multi-energy systems: Performance and sensitivity analysis. Applied Energy. 2020;2020(261). 114342.

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The continuous increase of (volatile) renewable energy production and the coupling of different energy sectors such as heating, cooling and electricity have significantly increased the complexity of urban energy systems. Such multi-energy systems (MES) can be operated more efficiently with the aid of optimization-based energy management systems (EMS). However, most existing EMS are tailor-made for one specific system or class of systems, i.e. are not generally applicable. Furthermore, only limited information on the actual savings potential of the usage of an EMS under realistic conditions is available. Therefore, this paper presents a novel modular modeling approach for an EMS for urban MES, which also enables the modeling of complex system configurations. To assess the actual savings potential of the proposed EMS, a comprehensive case study was carried out. In the course of this the influence of different user behavior, changing climatic conditions and forecast errors on the savings potential was analyzed by comparing it with a conventional control strategy. The results showed that using the proposed EMS in conjunction with supplementary system components (thermal energy storage and battery) an annual cost savings potential of between 3 and 6% could be achieved.


Conference contributions | 2020

A modular energy management system for multi-energy systems

Muschick D, Kaisermayer V, Moser A, Gölles M. A modular energy management system for multi-energy systems. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Conference contributions | 2020

Advanced biomass CCHP (BIO-CCHP) based on gasification, SOFC and cooling machines

Lagler J, Martini S. Advanced biomass CCHP (BIO-CCHP) based on gasification, SOFC and cooling machines. 6th Central European Biomass Conferenc, 2020, Graz.

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Conference contributions | 2020

Advanced Test Methods for Pellet Stoves

Reichert G, Schmidl C. Advanced Test Methods for Pellet Stoves. 6th Central European Biomass Conference, 2020, Graz.

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Conference contributions | 2020

BIOCHAR - Reaction kinetics under gasification conditions by experimental tests with TGA

Lagler J, Martini S, Kienzl N, Loder A. BIOCHAR - Reaction kinetics under gasification conditions by experimental tests with TGA. 6th Central European Biomass Conference. 2020. Graz.

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Conference contributions | 2020

Biofuels for transport decarbonisation Country specific assessment for Finland, Sweden, Germany, USA and Brazil

Matschegg D, Biofuels for transport decarbonisation Country specific assessment for Finland, Sweden, Germany, USA and Brazil. 6th Central European Biomass Conference, 22-24 January 2020, Graz.

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Peer Reviewed Scientific Journals | 2020

Biomass pyrolysis TGA assessment with an international round robin

Anca-Couce A, Tsekos C, Retschitzegger S, Zimbardi F, Funke A, Banks S, Kraia T, Marques P, Scharler R, de Jong W, Kienzl N. Biomass pyrolysis TGA assessment with an international round robin.Fuel.2020;276:118002.https://doi.org/10.1016/j.fuel.2020.118002

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The large variations found in literature for the activation energy values of main biomass compounds (cellulose, hemicellulose and lignin) in pyrolysis TGA raise concerns regarding the reliability of both the experimental and the modelling side of the performed works. In this work, an international round robin has been conducted by 7 partners who performed TGA pyrolysis experiments of pure cellulose and beech wood at several heating rates. Deviations of around 20 – 30 kJ/mol were obtained in the activation energies of cellulose, hemicellulose and conversions up to 0.9 with beech wood when considering all experiments. The following method was employed to derive reliable kinetics: to first ensure that pure cellulose pyrolysis experiments from literature can be accurately reproduced, and then to conduct experiments at different heating rates and evaluate them with isoconversional methods to detect experiments that are outliers and to validate the reliability of the derived kinetics and employed reaction models with a fitting routine. The deviations in the activation energy values for the cases that followed this method, after disregarding other cases, were of 10 kJ/mol or lower, except for lignin and very high conversions. This method is therefore proposed in order to improve the consistency of data acquisition and kinetic analysis of TGA for biomass pyrolysis in literature, reducing the reported variability.


Conference contributions | 2020

Challenges and recent results in microalgae research

Meixner K. Challenges and recent results in microalgae research. 6th Central european biomass conference, 2020, Graz.

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Conference contributions | 2020

CleanAir by biomass

Sturmlechner R, Stressler H, Golicza L, Reichert G, Schwabl M, Höftberger E, Kelz J. CleanAir by biomass. 6th Central European Biomass Conference, 2020, Graz.

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Peer-reviewed publications | 2020

Combined influence of inorganics and transport limitations on the pyrolytic behaviour of woody biomass

Almuina-Villar H, Sommersacher P, Retschitzegger S, Anca-Couce A, Dieguez-Alonso A. Combined influence of inorganics and transport limitations on the pyrolytic behaviour of woody biomass. Chemical Engineering Transactions. 2020.80:73-78

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A deeper understanding and quantification on the influence of inorganic species on the pyrolysis process, combined with the presence of heterogeneous secondary reactions, is pursued in this study. Both chemical controlled and transport limited regimes are considered. The former is achieved in a thermogravimetric analyser (TGA) with fine milled biomass in the mg range, while the latter is investigated in a particle level reactor with spherical particles of different sizes. To account for the influence of inorganics, wood particles were washed and doped with KCl aqueous solutions, resulting in K concentrations in the final wood of around 0.5% and 5% on dry basis. Gas species and condensable volatiles were measured online with Fourier transform infrared (FTIR) spectroscopy and a non-dispersive infrared (NDIR) gas analyzer. The removal of inorganic species delayed the pyrolysis reaction to higher temperatures and lowered char yields. The addition of inorganics (K) shifted the devolatilization process to lower temperatures, increased char and water yields, and reduced CO production among others. Higher heating rates and temperatures resulted in lower char, water, and light condensable yields, but significantly higher CH4 and other light hydrocarbons, as well as CO. The increase in these yields can be attributed, at least in part, to the gas phase cracking reactions of the produced volatiles. Larger particle size increased the formation of char, CH4 and other light hydrocarbons, and light condensables for low and high pyrolysis temperatures, while reduced the release of CO2 and H2O. This novel data set allows to quantify the influence of each parameter and can be used as basis for the development of detailed pyrolysis models which can include both the influence of inorganics and transport limitations when coupled into particle models.


Peer Reviewed Scientific Journals | 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 Scientific Journals | 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 Scientific Journals | 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.


Peer Reviewed Scientific Journals | 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.


Conference contributions | 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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Conference contributions | 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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Other publication | 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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Peer Reviewed Scientific Journals | 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 contributions | 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 contributions | 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 Scientific Journals | 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.


Conference contributions | 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 contributions | 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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Conference contributions | 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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Peer Reviewed Scientific Journals | 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.