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Ricercatore t.d. art. 24 c. 3 lett. B presso: Dipartimento di Ingegneria "Enzo Ferrari"

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2020 - A simple test method for measurement of the interface thermal resistance of coated and uncoated metal surfaces [Relazione in Atti di Convegno]
PEDRAZZI, Simone; Vergnano, A.; Allesina, G.; VERONESI, Paolo; Leali, F.; Tartarini, P.; Muscio, A.

Dies for metal casting must often be coated internally to minimize interaction between the surface of the steel die and the melt metal during pouring and solidification. However, the added coating increases the thermal interface resistance during the cooling process and can thus extend the process duration. For example, numerical predictions and experimental results are matched if the interface resistance is even quintupled in the presence of usual interface coating, compared to the uncoated mold. In order to have a reasonable estimate of the interface thermal resistance, an easy to use measurement approach has been tested. This consists of contacting a cold and a hot samples of metals with known thermal properties, one at ambient temperature and the other one much hotter. The temperatures of the two samples, assumed to be uniform in each sample, are measured by thermocouples, and the interface resistance is retrieved from the time evolution pattern of those temperatures during the thermal transient that follows the instant in which the samples have been contacted.

2020 - Combined Effects of Dewatering, Composting and Pelleting to Valorize and Delocalize Livestock Manure, Improving Agricultural Sustainability [Articolo su rivista]
Ronga, Domenico; Mantovi, Paolo; Pacchioli, Maria Teresa; Pulvirenti, Andrea; Bigi, Francesco; Allesina, Giulio; Pedrazzi, Simone; Tava, Aldo; Dal Prà, Aldo

An agronomic strategy to mitigate climate change impact can be the build-up of soil organic carbon. Among agronomic management approaches, the administration of organic fertilizers like livestock manure represents an eective strategy to increase soil organic carbon. However, livestock manure usually contains a high amount of water, reducing its sustainable delocalization and impacting on greenhouse gas emissions and nutrient leaching. Furthermore, the possible presence of weed seeds and harmful microorganisms could reduce the agronomic value of the manure. To overcome these issues, the combined eects of dewatering, composting and pelleting were investigated on livestock manure to produce sustainable organic fertilizers. Our results showed that composting and pelleting can represent a feasible and sustainable solution to reduce the potential risks related to the presence of weed seeds and harmful bacteria, concentrating nutrients and allowing a sustainable valorization and delocalization of the livestock manure. In addition, the processed manures were assessed as fertilizers in the growing medium (GM), displaying an increase in water retention and nutrient availability and a decrease of GM temperature and weed seed emergences. However, further study is needed to validate, both in open field and greenhouse productions, the eects of the proposed fertilizers in real cropping systems.

2020 - Progressi nel condizionamento del gas di sintesi per impianti di gassificazione di piccola taglia [Tesi di dottorato]

The transition towards sustainable energy development involves the efficiency improvement of the processes, the current technologies, and the ever increasing use of renewable energy sources. In this scenario, biomasses have the potential to constitute a low environmental impact energy reservoir that can be used in the combined production of electrical and thermal energy. Among the different methods of energy conversion of lignocellulosic biomass, gasification applied to CHP gensets emerges due to the high electrical efficiency and scalability, which make it applicable also outside purely industrial contexts. The key to large-scale using of small-scale gasification plants lies in the ability to produce simple and effective filtration systems with a low maintenance cost. In order to pursue these objectives it is essential to have a deep knowledge of the phenomena of multiphase fluid dynamics, as well as of the thermal exchanges that take place in gasification plants. To this end, this thesis work is divided into two sections: the first in which the theoretical frame of reference is constructed, aimed at defining the thermo-fluid dynamic variables at stake, and a second operative part in which a series of solutions are proposed, ranging from hot filtration, up to the use of biological means to reduce pollutants. Specifically, the first chapter will introduce the different processes and technologies available for the energy conversion of biomasses, including them in the broader European renewable energy scenario. The gasification process of woody biomasses for the production of electricity will be described, reviewing the main components common to this type of plant. The key theme of this thesis will therefore be anticipated by describing the currently available techniques for the filtration of the syngas, focusing on the methods of conditioning its physical properties. The second chapter will deal with the effects of pollutants, present in the syngas, on the mechanical parts of internal combustion engines thus fueled. The psychrometric approach, supported by computational methods, will allow to know the optimal conditions for a safe operation of these generators. The third chapter will describe the experimental characterization of a filter made with biochar from gasification, carried out on a micro biomass CHP plant. This study will lay the foundations for what will be discussed in the next chapter, namely the design and study, both experimental and numerical, of a heat exchanger for synthesis gas. The fifth and sixth chapters will finally describe the most recent research activities that led to both the experimentation of polymer filter bags for a commercial small-scale gasifier, and the investigation in the field of micro-algae for the realization of a syngas water scrubbing system aimed at eliminating the pollutants present therein. During the discussion, the critical issues and potentialities encountered in the use of the various syngas conditioning systems will be exposed. The definition of key thermo-fluid dynamic parameters will result in the simplification of the initial multiphase system, building a solid starting point for the continuous improvement of these technologies.

2020 - Thermodynamic approach to gas analysis in gasification systems [Articolo su rivista]
Allesina, G.; Pedrazzi, S.

Gas analysis is the primary method for performance evaluation in gasification systems. Ratio between CO and CO2 as well as the methane content, give valuable information about the quality of the ongoing gasification process. Furthermore, the heating value of the gas is the fundamental parameter for the calculation of cold gas efficiency. The most common way to perform gas analysis consists of using gas chromatography, this method provides high precision but lacks some fundamental points that would make it a perfect match for gasification systems: robustness to tar and soot pollution, capability to operate with wet hot gases above tar dew point and fast responsiveness. This work lays the basis of a different approach for gas analysis. The proposed methodology uses a Junker-Boys calorimeter, the basic calorimetric approach is hybridized with the boundary conditions imposed by gasification, enabling users to define and solve a system of linear equations. This system uses the few data that can be collected from the calorimeter and the gasifier then it calculates the gas composition. An experimental campaign is used to validate the proposed approach. Results showed a good fit between the composition calculated with the calorimetric approach and the one evaluated through standard methods.

2020 - Using digestate and biochar as fertilizers to improve processing tomato production sustainability [Articolo su rivista]
Ronga, D.; Caradonia, F.; Parisi, M.; Bezzi, G.; Parisi, B.; Allesina, G.; Pedrazzi, S.; Francia, E.

The principal goal of the organic farming system (OFS) is to develop enterprises that are sustainable and harmonious with the environment. Unfortunately, the OFS yields fewer products per land than the non-organic farming system in many agricultural products. The objective of our study was to assess the effects of digestate and biochar fertilizers on yield and fruit quality of processing tomato produced under the OFS. The experiment was carried out in Po Valley, during the 2017 and 2018 growing seasons. Liquid digestate (LD), LD + biochar (LD + BC) and pelleted digestate (PD) were evaluated and compared to biochar (BC) application and unfertilized control. The results showed that plants fertilized with LD + BC recorded the maximum marketable yield (72 t ha-1), followed by BC (67 t ha-1), PD (64 t ha-1) and LD (59 t ha-1); while the lowest production (47 t ha-1) was recorded in unfertilized plants. Over the two cropping seasons, LD + BC, BC, PD, and LD, increased fruit number per plant (+15%), fruit weight (+24%), Brix t ha-1 (+41%) and reduced Bostwick index (-16%), if compared to the untreated control. Considering the overall agronomic performances, digestate and biochar can be useful options for increasing yield and quality of processing tomato production in the OFS. Hence, these fertilizers can be assessed in future research both on other crops and farming systems.

2019 - Biomass-based systems for atmospheric water generation, a 1.75 m$ idea account of the x-prize award [Relazione in Atti di Convegno]
Mason, J.; Kauffman, B.; Hertz, D.; Doss, L.; Smith, T.; Allesina, G.

This work is based on the modeling and experimental processes that allowed the win of the 1.75 M$ Water abundance X-Prize in 2018. Teams around the globe challenged each other to better demonstrate the capability to harvest 200 liters/day of water from atmosphere using 100% renewable energy resources, in a process where the final cost of water set below 0.02 $ / liter. A team only succeeded. The key idea was the innovative use of combined biomass gasification and atmospheric water generators (AWG). Biomass-based systems not only provided energy to run the AWG machines but they also generated new unique opportunities to harvest moisture from the gasification drying stage as well as from the engine exhausts. The virtuosity of the integrated system helped the Skysource APL Alliance to be on of the two teams only that worldwide made it to the final, while the 24h test performed, secured the victory to them. This paper describes the basic math and report the tests the lead to the X-Prize award.

2019 - Easy to implement ventilated sunspace for energy retrofit of condominium buildings with balconies [Articolo su rivista]
Allesina, Giulio; Ferrari, Chiara; Muscio, Alberto; Pedrazzi, Simone

Energy retrofit of the facade of condominium buildings may be a difficult task because thermal bridges such as those due to balconies, common elements in the architecture of many countries, are often arduous to correct by added insulation due to several constraints. An alternative retrofit approach is therefore analyzed, easy to implement and relatively inexpensive. It consists in changing a balcony into a ventilated sunspace during the cold season, exploiting solar gains to compensate heat loss. More specifically, transparent plastic roll-up sheets are installed along the balcony perimeter, removable in the hot season, to enclose the volume between two superposed balcony slabs. The obtained sunspace is then used as a pre-heating chamber for a single-flow ventilation system that ensures the air changes required indoors. Heat gain to the indoor environment can thus be increased with respect to a simpler sunspace without ventilation, and possibly modulated along the day by proper control of the flow rate. In this work, the proposed approach and a small-scale physical model are presented. The model will serve to validate analyses aimed to forecast and optimize the performance of ventilated sunspaces built around balconies.

2019 - Effects of innovative biofertilizers on yield of processing tomato cultivated in organic cropping systems in northern Italy [Relazione in Atti di Convegno]
Ronga, D.; Caradonia, F.; Setti, L.; Hagassou, D.; Giaretta Azevedo, C. V.; Milc, J.; Pedrazzi, S.; Allesina, G.; Arru, L.; Francia, E.

Nowadays agriculture needs to increase crop sustainability and the organic cropping system has emerged as an interesting alternative approach with respect to the conventional one. On the other hand, the current unfavorable yield gap between organic and conventional systems reduces the organic system’s value. Processing tomato is a globally important horticultural crop and used as crop model. The objective of this study was to investigate different biofertilizers that could improve the yield and quality of processing tomato in organic cropping system. An experiment was conducted in Po Valley, northern Italy, during spring-summer 2017. The cultivar used was ‘Barone Rosso’ blocky fruit genotype, using 2.8 plants m-2, in randomized complete block design with seven biofertilizer treatments (pelleted digestate, granular biofertilizer, biochar, compost tea as foliar spray biostimulant, SiO2 as foliar spray biostimulant, compost tea + SiO2 as foliar spray biostimulant, zero biofertilizer as a control) and three replications. Agronomical and physiological parameters were recorded during the crop cycle. Results showed that tomato grown with biochar recorded the maximum commercial yield (136 t ha-1), followed by pelleted digestate (117 t ha-1) and compost tea + SiO2 as foliar spray biostimulant (113 t ha-1) while the minimum production (71 t ha-1) was recorded in untreated plots. On average, the results revealed that biochar, pelleted digestate and compost tea + SiO2 as foliar spray biostimulant, increased the vegetative vigor of plant (+10%), the number of flowers (+13%) and fruits (+41%), the average weight of fruits (+20%), the total biomass production (+48%), the harvest index (+15%) and the Brix t ha-1 (+49%), with respect to the control. Considering the overall performance, innovative biofertilizers could be promising to improve yield and quality of processing tomato cultivated in organic cropping systems, reducing the yield gap with conventional one.

2019 - Energy and biochar co-production from municipal green waste gasification: A model applied to a landfill in the north of Italy [Articolo su rivista]
Pedrazzi, Simone; Santunione, Giulia; Minarelli, Andrea; Allesina, Giulio

This work discusses the advantages that can be obtained from the integration of landfill gas with biomass gasification. The case study presented consists of a landfill located in the province of Reggio Emilia, in the north of Italy. Landfill gas from municipal-waste fuels four internal combustion engines with overall nominal power of 2 MW, the electricity is sold back to the grid, while the thermal power is used for the heating of an industrial greenhouse compartment for basil production. Within the same facility, green waste is collected from the surrounding municipalities then chipped and sieved. Fine particles are disposed into a composting plant close by, while the sieved fraction is sold to the market for electricity production in large-scale boiler-based power plants. The idea here presented and discussed consists of the implementation of a gasifier to convert the sieved fraction of green waste into a syngas fuel directly on site. Syngas is blended with the landfill gas and then fed to the gas engines. In this work green waste gasification is tested in a commercial small-scale gasifier, proving that sifted green waste is a suitable fuel for this application. A specific consumption of 1.2 kg/kWh and a total electrical efficiency of 16.22% were measured. The sizing of the full-scale gasification facility is based on both the experimental results and data about the local availability of green waste. The economic return of the investment is then discussed. Finally, a further level of integration between gasification and the existing site is proposed: gasification-derived biochar is investigated as soil amendment for the on site company at the landfill that grows basil commercially. Results of 55 days in vivo tests show an increase in the biomass production of the basil of 53% compared to the control test group.

2019 - Hybridization of solar power plants with biogas from anaerobic digestion: A modeled case study [Relazione in Atti di Convegno]
Pedrazzi, S.; Masetti, F.; Allesina, G.; Tartarini, P.

This work shows the numerical simulation of a hybrid renewable power plant composed of a Concentrated Solar Plant (CSP) with molten salt storage sub-system, a Rankine steam cycle power plant and a biomass anaerobic digester. Biogas produced by the digester is used as fuel in the boiler of the steam cycle coupled with methane. "Greenius" software has been used to simulate the CSP system aimed to satisfy an electrical power demand of the city Messaad, Algeria. Results concerning electrical energy produced, biogas and methane consumption was used with CAPEX and OPEX costs of the plant to calculate the Levelized Cost of the Electrical energy produced (LCoE). Several simulation were done varying the size of the solar field and of the thermal storage in order to find the compromise configuration with an high renewable energy production, a low methane consumption and a low LCOE. Simulations show that the CSP configuration with 2.07 of Solar Multiple (SM) and 9 of Full Load Hour (FLH) result in a low LCOE value (97.32 €/MWh), high annual system efficiency (11.51%), low methane share (8.73%) and low dumped heat ratio (10.22%).

2019 - Integration of biological waste conversion and wastewater treatment plants by microalgae cultivation [Articolo su rivista]
Altunoz, Meltem; Allesina, Giulio; Pedrazzi, Simone; Guidetti, Emilio

In this study, growth performance and lipid content of two microalgae species Neochloris oleoabundans and Chlorella vulgaris are monitored by using three different types of sludge waste feedstocks obtained from the water treatment plants located in Bedonia, Borgotaro and Fornovo (Montagna2000 Spa, Province of Parma, Italy). The sludge waste is optimized in order to achieve microalgal growth media and dispose of the sewage sludge produced at the wastewater treatment facilities. Both photoautotrophic and heterotrophic growth conditions are applied to the microalgal cultivations. The growth parameters of microalgae strains such as cell concentration, growth rate, optical density, cell biovolume, photosynthetic pigments and lipid contents are monitored. The amounts of total dried lipid biomass, obtained by the biological conversion of the wet sludge waste, are determined. Lipid production of microalgal cells grown in the medium optimized from sludge waste from the Fornovo site provides the highest amount of microalgal lipid content for N. oleoabundans and C. vulgaris photoautotrophic cultivations, while sludge waste from the Bedonia site provides for N. oleoabundans heterotrophic cultivation.

2019 - Modeling and optimization of industrial internal combustion engines running on Diesel/syngas blends [Articolo su rivista]
Rinaldini, Carlo Alberto; Allesina, Giulio; Pedrazzi, Simone; Mattarelli, Enrico; Tartarini, Paolo

The paper presents a numerical analysis of combustion, carried out on a compression ignition indirect injection engine fueled by both Diesel and syngas, the latter obtained from biomass gasification and introduced in the intake manifold. The computational fluid dynamics model includes an improved chemical kinetics scheme, tailored on the syngas-diesel dual fuel combustion. The model was validated by an experimental campaign, on the same engine. The syngas fuel was produced by a small scale gasifier running on wood chips. Several simulations were performed varying both the share of syngas and the Diesel start of injection angle. The total amount of heat released by combustion can increase up to 50%, along with the indicated work and the cylinder peak pressure. The start of injection angle should be modified in order to preserve the mechanical integrity of the engine, as well as to maximize its brake efficiency. The numerical analysis provides the guidelines for setting the injection strategy, as a function of the syngas share.

2019 - Predictive algorithms for energy performance evaluation of banking institutions [Relazione in Atti di Convegno]
Fondriest, M.; MacChitelli, G.; Stancari, S.; Montanari, D.; Fiorini, C.; Anceschi, G.; Pedrazzi, S.; Allesina, G.

This work investigates the use of predicting algorithms for energy consumption in the tertiary sector. Tertiary sector is fast-growing, in fact it used 23% of Italian electricity in 2000 reaching the 35% in 2016. The focus of this paper is on banker institutions spread across the Italian country. Several algorithms are taken into account and compared in order to find the best solution. The proposed algorithms underwent a training period where the parameter with higher impact on the overall consumption are taken into account. Once the model was trained, the last year of historical data was used to verify the quality of the proposed approach. Final remarks discuss possible algorithm refinement as well as its use for the quick detection and correction of anomalies in the energy use profile curves.

2019 - Smart use of mechanical ventilation for energy retrofit of residential dwellings [Relazione in Atti di Convegno]
Pedrazzi, S.; Ferrari, C.; Allesina, G.; Muscio, A.

Residential buildings of Italy built during the last century usually show very poor energy performance. The only retrofit action widely implemented on their envelope is substitution of windows. These are very seldom coupled with mechanical ventilation, however, so their high air tightness induces serious problems of moisture condensation and mold formation-unless they are left open and their usefulness nullified. In this work, a smart combination is simulated of single flow mechanical ventilation, in itself essential to control indoor air quality and ventilation heat loss, with a relatively inexpensive sunspace built on an existing balcony, aimed to behave as a preheating chamber of the inlet cold air in winter. Moreover, mechanical ventilation is combined with an electric heat pump for hot water production, in which the outlet air flow of warm exhaust air is introduced to improve the coefficient of performance of the heat pump in the cold seasons. Energy savings allowed by such smart yet simple combination of existing technologies are discussed.

2019 - Spent Coffee Grounds in the Production of Lightweight Clay Ceramic Aggregates in View of Urban and Agricultural Sustainable Development [Articolo su rivista]
ANDREOLA, Nora Maria; Borghi, Alessandro; PEDRAZZI, Simone; ALLESINA, GIULIO; TARTARINI, Paolo; LANCELLOTTI, Isabella; BARBIERI, Luisa

This paper presents an innovative application for spent coffee grounds (SCGs) used as filler for the formulation of lightweight clay ceramic aggregates (LWA). LWA can be used for urban and agricultural purposes as a sustainable solution. Spent coffee grounds were tested as a pore forming agent partially acting as a replacement for red clay in material formulation before firing. Substitutions of 10, 15, and 20 wt.% of red clay were tested. The properties of lightweight aggregates with 15 wt.% of SCGs were improved using a specifically tailored fertilizer glass due to its low pH and conductivity within the soil tolerance range. Packaging glassy sand, cattle-bone flour ash, and potassium carbonate were mixed and melted in order to obtain this glass, which when added to the clayey batch functionalized the aggregates by phosphorus and potassium nutrients. The results (in particular, porosity and bulk density) show that the lightweight aggregates obtained have interesting properties for possible uses both in urban (e.g., green roofs as a drainage layer) and agricultural purposes. Moreover, pH and conductivity are in line with the Italian Standard regarding soil amendment (D.lgs. 75/2010). In addition, several leaching tests were performed in a solution containing 2 vol.% citric acid (C6H8O7) to evaluate the release capacity not only of nutrients (P and K)mbut also to check the presence and release of heavy metals, such as lead (Pb), that may come from the glassy precursor. The results obtained showed that nutrients are effciently released in 21 days (P = 87.73% and K = 25.74% of released percentage) and Pb release is under the standard threshold of 30 ppm.

2019 - Use of light scattering for online detection of tar and particulate matter from biomass gasification [Relazione in Atti di Convegno]
Allesina, G.; Pedrazzi, S.; Rogak, S.; Grace, J. R.; Tartarini, P.

Gasification is one of the most promising technology for an efficient use of biomass fuels. A gate-keeper issue that is holding this technology from being widely used is gas conditioning. All gasifiers architecture suffer in some degree due to tar and particulate content in the gas stream. Depending on the final application, different level of pollutant may preclude a specific use. The cleaning level is more and more relevant moving from IC engines to gas turbine or fuel cells. For this reason this work want to explore an on-line method for tar and particulate detecting using a light scattering system. The proposed solution is based on a dual stage gas dilution combined with the use of a commercial air monitoring device.

2019 - Valorization of Vineyard By-Products to Obtain Composted Digestate and Biochar Suitable for Nursery Grapevine (Vitis vinifera L.) Production [Articolo su rivista]
Ronga, Domenico; Francia, Enrico; Allesina, Giulio; Pedrazzi, Simone; Zaccardelli, Massimo; Pane, Catello; Tava, Aldo; Bignami, Cristina

Although compost and biochar received high attention as growing media, little information is available on the potential of vineyard by-products for the production and use of composted solid digestate (CSD) and biochar (BC). In the present study, two experiments are reported on CSD and BC mixed with commercial peat (CP) for grapevine planting material production. Four doses (0, 10%, 20%, 40% vol.) of CSD and BC were assessed in the first and second experiment, respectively. CSD mixed at a dose of 10% recorded the highest values of shoot dry weight (SDW) and a fraction of total dry biomass allocated to shoot (FTS), both cropping bench-graft and bare-rooted vine. On the other hand, CSD mixed at a dose of 40% displayed the highest values of SDW and FTS, cropping two-year-old vine. BC used at a dose of 10% improved SDW, root dry weight, total dry weight, FTS, shoot diameter, and height on bare-rooted vine. The present study shows that CSD and BC, coming from the valorization of vineyard by-products, can be used in the production of innovative growing media suitable for nursery grapevine production. Further studies are needed to assess the combined applications of CSD and BC in the same growing media.

2018 - A calibration methodology for building dynamic models based on data collected through survey and billings [Articolo su rivista]
Allesina, G.; Mussatti, E.; Ferrari, F.; Muscio, A.

A correct dynamic building modeling requires a proper definition of all the parameters that can affect the model outputs. While a preliminary survey will lead to a precise design of the building envelope, other parameters, such as the temperature set-point and the air leakage, are difficult to accurately evaluate, thus introducing errors in the model. Furthermore electrical and thermal consumption invoices are based on monthly records while simulations tools use hours or even more detailed time steps. For all these reasons, the present work is aimed at the definition of a calibration process based on survey, billings and dynamic modeling that takes into account the operator-dependent parameters. The innovative idea behind this calibration process consists of the comparison of the real and simulated energy signatures. 176 + 40 simulations were run in order to find the set of parameters that most accurately overlap the simulated and real energy signatures leading to the calibration of the model. The case study is a retail superstore of 3544 m2floor area built in central northern Italy. Results demonstrate the validity of the approach proposed showing a calibrated signature with about 1% discrepancies from the real case one. The approach can be extended to different simulation software since the main advantage of the energy signature is to simplify consumption outputs interpretation even in case of complex buildings. A further innovative consequence of the methodology proposed is its capability to promptly identify inefficiencies in the building subsystems, i.e. the HVAC control, thus leading to a fast correction of the root cause without the implementation of complex and expensive monitoring devices.

2018 - Are Nano-Composite Coatings the Key for Photovoltaic Panel Self-Maintenance: An Experimental Evaluation [Articolo su rivista]
Pedrazzi, Simone; Allesina, Giulio; Muscio, Alberto

This article shows the influence of an anti-fouling nano-coating on the electrical energy produced by a string of photovoltaic modules. The coating effect was evaluated comparing the energy produced by two strings of the same PV power plant: one of them was cleaned and the other was cleaned and treated with the coating before the monitoring campaign. The PV plant is located in Modena, north of Italy. A first monitoring campaign of nine days after the treatment shows that the treatment increases the energy production on the PV arrays by about 1.82%. Results indicate that the increase is higher during sunny days with respect to cloudy days. A second monitoring campaign of the same length, but five months later, shows that the energy gain decreases from 1.82% to 0.69% due to the aging of the coating, which is guaranteed for one year by the manufacturer. A technical-economical analysis demonstrates that at the moment the yearly economic gain is 0.43 € per square meter of panel and the cost of the treatment is about 1 € per square meter. However, large scale diffusion can reduce the production cost and thus increase the affordability of the coating.

2018 - Carbonization of residual biomass from river maintenance using waste heat from gasification power plants [Relazione in Atti di Convegno]
Puglia, Marco; Pedrazzi, Simone; Allesina, Giulio; Morselli, Nicolò; Tartarini, Paolo

This work follows the study presented in Stockholm at the 2017th EUBCE titled: “The Energetic Recover of Biomass from River Maintenance: the REBAF Project”. This previous work focused on the multidisciplinary approach to river maintenance in order to create more resilient systems together with the production of renewable energy. One of the outputs of the preliminary work presented was the distinction of the biomass from river maintenance into two major groups: suitable for gasification and not suitable for gasification. It was necessary to determine suitable and sustainable solutions for the energy recovery of both these groups. The final idea is discussed in this work, it consists in having an integrated system as depicted in Figure 2. The gasifier-engine system is fed with the higher quality biomass; it provides electrical power and hot exhaust gases that are used for the pyrolysis of the low-quality feedstock. The purpose of the pyrolysis reactor is to produce biochar to be used together with clay and other aggregates to produce highly porous, carbon negative, building materials. In this work a prototype reactor was assembled and tested using herbaceous biomass. Several configurations, in terms of exhaust gas temperature and biomass residence time were tested. Results showed the capability of coupling gasification and pyrolysis into integrated systems to increase the overall sustainability of the processes. On the other hand, char quality is strongly affected by the way this interaction is performed due to the quick cool down of the exhaust gases when the connection lines are not properly insulated.

2018 - Chemically enhanced char for syngas filtering purposes [Relazione in Atti di Convegno]
Pedrazzi, S.; Allesina, G.; Sebastianelli, L.; Puglia, M.; Morselli, N.; Tartarini, P.

This paper investigates the performance of gasification char as syngas filter medium. Char obtained from a small-scale downdraft gasifier was analyzed and chemically enhanced through an acid treatment using a sulfuric acid solution in a thermostatic bath at 40 °C. The treated char presents a higher BET value of 465.9557 m2/g in comparison with the untreated sample which has a BET value of 394.4430 m2/g. However, the treated sample has a low metallic cations content (K, Fe and Sr) and consequentially a low ash content compared to the untreated sampled. Char samples are used as cartridge filter media in order to assess their tar adsorption potential using a modified “Tar Sampling Protocol” method. Experimental results show a noticeable tar content reduction in the syngas using char as filter, in fact the treated char reduces the tar number from 1456 mg/Nm3 to 267.2 mg/Nm3 and the untreated char reduces the tar number from 1456 mg/Nm3 to 179.6 mg/Nm3. The difference in the tar adsorption is probably given by the char ash content that it is less in the treated sample.

2018 - Energy production and carbon sequestration in wet areas of Emilia Romagna region, the role of Arundo Donax [Articolo su rivista]
Allesina, Giulio; Pedrazzi, Simone; Ginaldi, Fabrizio; Cappelli, Giovanni A.; Puglia, Marco; Morselli, Nicolò; Tartarini, Paolo

This work investigated the utilization of giant reed as energy crop applied marginal areas of the municipality cluster "Unione Terre d'Argine" (UTA), Northern Italy. On one hand, the researchers modeled the giant reed productivity in terms of ton/year for each town of the cluster. They focused on those areas neighboring the local rivers and channels kept unused for farming activities: i.e. riverbanks or detention basin shores. On the other hand, experimental tests were performed to determine the behavior of giant reed as fuel in pilotscale gasification power plants. Results showed the high potential of small or pilot-scale gasifiers to increase the sustainability of river maintenance operations. From its gasification it is possible to produce electrical power together with biochar. Biochar is a powerful soil amendment that can be used straight in the riverbanks. The tandem process between giant reed growth and its gasification leads to 150 kg of CO2 sequestered for every ton of giant reed processed. Furthermore, the energy production from waste biomasses will help to perform better and more regular maintenance operation to the local rivers and channels, thus reducing the negative effects of possible floods.

2018 - Exploratory modeling and experimental investigation of a vibrating-stripe wind energy converter [Articolo su rivista]
Allesina, Giulio; Cingi, Pietro; Gessani, Gabriele; Angeli, Diego

The future of portable devices is ultimately a challenge on energy conversion and storage, fought on two fronts: battery life and distributed availability of power sources. Nano-scale energy conversion devices are highly attractive for the market, but the non-PV systems still lack in efficiency and portability. Few years ago the Windbelt® system was presented with a new ingenious rotor-free approach for nanoscale wind energy harvesting through aeroelastic fluttering. Aim of this work is to provide a mathematical model with experimental validation to the scientific framework related to the Windbelt technology. An experimental device with variable length was built and tested under different belt tension conditions. The basis of the windbelt technology consists in the movement of a magnet linked to the belt that oscillates between two coils. In the tested device the movement of the magnet was recorded with a high speed camera and the images processed in order to evaluate instantaneously its rotation and vertical deviation from the resting position. Results of the experimental campaign were compared with the output of an aero-elastic model of the belt. The model is based on the assumption of a belt composed of two interconnected sections: the free belt section, whose aeroelastic behaviour is represented by a nonlinear lift coefficient, and the magnet section, where the motion is governed by the inertial and elastic forces. The results of the testing campaign and the model outputs showed a remarkable agreement for what concerns the frequency response of the system.

2018 - Gasification and wine industry: Report on the use vine pruning as fuel in small -scale gasifiers [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; Puglia, Marco; Morselli, Nicolò; Allegretti, Francesco; Tartarini, Paolo

Ten different types of vine prunings were tested in a small-scale commercial gasifier produced by the All Power Labs. The specific consumption of the wood biomass power plant was measured for each type of biomass showing results from 0.92 to 1.32 kg/kWh. Syngas analyses and HHV calculation showed results higher than the reference calculated value from the gasification of typical wood biomass. On the other hand, the feeding operations resulted more complicated, here vine prunings are more likely to create bridging problems.

Vezzali, Vittorio; Andreola, Nora Maria; Barbieri, Luisa; Lancellotti, Isabella; Pozzi, Paolo; Allesina, Giulio; Pedrazzi, Simone; Tartarini, Paolo

This paper exposes the research activities regarding REBAF (Energetic Recover of River Biomasses) project, focused on the maintenance operations self-sustainability of the Secchia river (Italy). Poplar was found as the most abundant and representative wood plant of Secchia riverbanks, with a good behavior during gasification process: from 1 hectare of maintenance every three year, it was possible to produce 23 MWh of electrical power and 31 MWh of thermal power. The biochar obtained was characterized and mixed with local red clay to create both lightweight aggregates (LWAs) for green roofs applications and bricks. Ashes coming from the gasifier cyclone were characterized and used to create bricks. The aims are the saving of raw materials and the obtaining of weight-lightened products with high porosity. Biochar and ashes were found to be suitable for this purpose given their organic carbonaceous nature, according to X-ray diffractometry, Loss on Ignition (LOI) and TG-DTA results. Application on LWAs by substituting 15%wt of the clay with biochar leads to a weight-lightening of the material. To optimize LWAs pH, spent coffee grounds (SCG) were added with proportion of 85% clay-15% biochar/SCG. A greater decrease in weight and pH values in the neutrality range were observed. Adding 20%wt biochar or ashes on bricks led to a significant reduction of materials bulk density (from 2 to 1.5 g/cm3) and the achievement of 40-45% porosity. With higher additions (until 40%wt) bulk density gets lower (1.2 g/cm3–1.3 g/cm3), but the material results weaker with a worst mechanical strength.

2018 - Gasification of cotton crop residues for combined power and biochar production in Mozambique [Articolo su rivista]
Allesina, Giulio; Pedrazzi, Simone; Allegretti, Francesco; Morselli, Nicolò; Puglia, Marco; Santunione, Giulia; Tartarini, Paolo

Cotton agricultural industry is an important sector for some developing countries, whose energy consumption is dramatically rising. Here, biomass is the most important source of energy, but they are used in an inefficient way, causing atmospheric pollution and wasting resources. Combined energy generation and biochar production using cotton residues briquettes as fuel in a PP20 gasifier plant is investigated. The machine has demonstrated similar performances to its “conventional” use: 14% global efficiency and 1.16 kg/kWhelspecific consumption of cotton briquettes are observed. It is calculated that one-hectare field can generate more than 4 MWh and about 130 kg of biochar per year. Biochar represents a valuable by-product; if used as amendment for cotton growth it can improve the soil conditions, both decreasing the need of fertilizers up to 50%. A circular economic model based on cotton waste gasification is proposed. Clean and affordable energy can be produced, in order to promote a sustainable development of rural areas.

2018 - Use of gasification char for hot gas filtration in micro-scale power plants [Relazione in Atti di Convegno]
Morselli, Nicolò; Allesina, Giulio; Pedrazzi, Simone; Puglia, Marco; Mason, James; Lemberger, Adrienne; Tartarini, Paolo

Char is a carbonaceous gasification by-product often used as soil amendment due to its high porosity and recalcitrant structure. Porosity is a fundamental feature when char is used to adsorb liquids and aerosol. This paper investigates gasification char as filtering medium for producer gas in small-scale gasifiers. Two metallic candle filters filled with about 1 kg of gasification char each were fabricated and tested under different temperature conditions (60, 70 to 80 °C). Char behavior as tar and particulate filter is qualitative and quantitative assessed evaluating tar deposits afterwards the engine governor as well as using the “Tar Sampling Procedure” methodology. Encouraging performance of char candle filters was achieved with a producer gas temperature of 60 °C and with gas-air mixture temperature of 70 °C at the engine manifold. Furthermore pressure drop across the filters was monitored and its influence on the engine maximum power output was evaluated.

2017 - Application of OLTT in gasification power systems [Articolo su rivista]
Quinlan, Brendan; Kaufmann, Bear; Allesina, Giulio; Pedrazzi, Simone; Whipple, Samuel

A series of results obtained from a quasi-real-time analysis of tar concentration in small scale gasification systems is presented in this work. The instrument used to measure tar concentration is an online tar testing apparatus that was designed and built by the authors. Using the online tar testing apparatus enables phenomena to be observed that previously could not using standard methods. The influence of tar concentration due to four scenarios is presented using the online tar testing apparatus: dynamic behavior at different testing locations, impact as electrical output applied to the engine increases or decreases, impact of refueling events, and impact of different gasifier reactor architectures. Dynamic behavior of tar concentration was captured over all scenarios. Consistent results were obtained and results proved to be nonlinear and sometimes unpredictable.

2017 - Combined Effects of LED Lights and chicken manure on Neochloris oleoabundans Growth [Articolo su rivista]
Altunoz Hatipoglu, Meltem; Pirrotta, Onofrio; Forti, Luca; Allesina, Giulio; Pedrazzi, Simone; Obali, Olcay; Tartarini, Paolo; Arru, Laura

In this study a photobioreactor prototype is presented for the culture growth of microalgae model organism Neochloris oleoabundans by using chicken manure waste as feedstock along with the optimum combination of led light wavelengths and light intensity. Particularly interesting results are observed on the strains fed by chicken manure medium under the proper combination of red and blue LED light illumination, the microalgal growth resulted comparable with the strains fed by the costly commercial microalgal growth medium (BG 11 medium). Cell concentration, optical density, growth rate, cell size, total lipid and photosynthetic pigment content have been monitored during a time-course experiment. The data suggest that there are difficulties due to white light diffusion into the dark chicken medium, which leads to a generally lower intensity scattered along all wavelengths; blue or combined red and blue lights resulted in a higher irradiation density, affecting microalgae cell growth.

2017 - Dynamic behavior investigation of a micro biomass CHP system for residential use [Articolo su rivista]
Malaguti, Vania; Lodi, Chiara; Sassatelli, Matteo; Pedrazzi, Simone; Allesina, Giulio; Tartarini, Paolo

Aim of this work is to define a dynamic model developed in the Trnsys software environment where a biomass boiler and two micro-CHP gasifiers are considered as heat source for a detached house. The selected case study is a detached house of about 240 m2near Bologna, Northern Italy, where the HVAC system is currently equipped with a diesel oil boiler with 40 kW of thermal power. The building is connected to a farm and the total electrical consumption is about 13850 kWh/year. The thermal energy demand was calculated and validated in Trnsys using measured diesel oil consumption data. Two different retrofitting solutions for the heating system have been investigated: biomass boiler and micro-CHP gasifiers. Results show the capability to use biomass boiler and micro-scale gasifiers as heat source for the building with a wood consumption of 23 and 86 ton/year respectively. The gasifier electricity production is greater than the electrical demand and an extra energy of 64800 kWh/year is injected into the grid. The cost-benefits economical assessment of these retrofitting solutions is reported considering subsidies for renewable energy production.

2017 - Experimental investigation on a Common Rail Diesel engine partially fuelled by syngas [Articolo su rivista]
Rinaldini, Carlo Alberto; Allesina, Giulio; Pedrazzi, Simone; Mattarelli, Enrico; Savioli, Tommaso; Morselli, Nicolo'; Puglia, Marco; Tartarini, Paolo

The high efficiency, reliability and flexibility of modern passenger car Diesel engines makes these power units quite attractive for steady power plants totally or partially running on fuels derived from biomass, in particular on syngas. The engine cost, which is obviously higher than that of current industrial engines, may not be a big obstacle, provided that the re-engineering work is limited and that performance and efficiency are enhanced. The goal of this work is to explore the potential of a current automotive turbocharged Diesel engine running on both Diesel fuel and syngas, by means of a comprehensive experimental investigation focused on the combustion process. The engine is operated at the most typical speed employed in steady power plants (3000 rpm), considering three different loads (50–100–300 Nm/16–31–94 kW). For each operating condition, the syngas rate is progressively increased until it provides a maximum heating power of 85 kW, while contemporarily reducing the amount of injected Diesel oil. Maximum care is applied to guarantee a constant quality of the syngas flow throughout the tests, as well as to maintain the same engine control parameters, in particular the boost pressure. It is found that in-cylinder pressure traces do not change very much, even when drastically reducing the amount of Diesel fuel: this is a very encouraging result, because it demonstrates that there is no need to radically modify the standard stock engine design. Another promising outcome is the slight but consistent enhancement of the engine brake efficiency: the use of syngas not only reduces the consumption of Diesel oil, but it also improves the combustion quality. The authors acknowledge that this study is only a starting basis: further investigation is required to cover all the aspects related to the industrial application of this syngas-Diesel combustion concept, in particular the impact on pollutant emission and on engine durability.

2017 - Gasification biochar amendment effects on O. basilicum growth [Poster]
Santunione, Giulia; Pedrazzi, Simone; Allegretti, Francesco; Sebastianelli, Lorenzo; Allesina, Giulio

In this work, the application of biochar from gasification as soil amendant, is studied. The effect on Ocimum basilicum growth with three different substrates was investigated: standard soil as the control sample, soil with 30% wt. of compost added, soil with 30% wt. of biochar added, which biochar was obtained as by-product of a fixed bed gasification process. Five samples for each of the substrates were used in order to increase the statistical validity of the results. 55 days of Ocimum basilicum growth showed that the biochar contributed to an acceleration of the growth and increased the fresh and dry weights with about 50%. In addition, plant height and essential oil content was higher with biochar-based substrates. This application can lead to more efficient and sustainable agricultural processes, giving new impulse to bio-energy production and recycling of by-products in a circular economy context.

2017 - Infrared thermography as a Non-destructive Testing solution for thermal spray metal coatings [Articolo su rivista]
Santangelo, Paolo Emilio; Allesina, Giulio; Bolelli, Giovanni; Lusvarghi, Luca; Matikainen, Ville; Vuoristo, Petri

In this work, an infrared (IR) thermographic procedure was evaluated as a non-destructive testing tool to detect damage in thermal spray metallic coatings. As model systems, polished HVOF- and HVAF-sprayed Fe-based layers deposited onto steel plates were employed. Damage by external-object impingement was simulated through a cyclic impact-test apparatus, which induced circumferential and radial cracks across all model systems, and interface cracks of different sizes in distinct samples. Damaged and undamaged plates were bulk-heated to above 100 °C using an IR lamp; their free-convection cooling was then recorded by an IR thermocamera. The intentionally induced defects were hardly detectable in IR thermograms, due to IR reflection and artificial ‘‘hot’’ spots induced by residuals of transfer material from the impacting counterbody. As a micrometer-thin layer of black paint was applied, surface emissivity got homogenized and any artifacts were effectively suppressed, so that failed coating areas clearly showed up as ‘‘cold spots.’’ This effect was more apparent when large interface cracks occurred. Finite-element modeling proved the physical significance of the IR-thermography approach, showing that failed coating areas are cooled by surrounding air faster than they are heated by conduction from the hot substrate, which is due to the insulating effect of cracks.

2017 - Multi-phase fluid dynamic of syngas flow across a throttle body in a gasifier-engine system [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; Puglia, Marco; Morselli, Nicolò; Mason, Jim; Tartarini, Paolo

Electronically controlled throttle valves are often used in syngas fueled engines in order to maintain the engine speed constant under variable load and gas composition conditions. The producer gas carries two macrocategories of pollutants: tars (naphthalene, benzene, toluene etc. in vapor phase) and particulate matter; a high concentration of these species leads, almost certainly, to governor stuck or failure. These malfunctions force to engine shutdown. Since it is not always possible to move towards to a better syngas filtration, especially on small scale systems, it is fundamental to investigate the way of fouling of this device. This preliminary study lead to the conclusion that a combined CFD and psychrometric approach is required for a better comprehension of the fouling phenomena.

2017 - Preliminary Analyses on an Algae-Based Water Scrubber for Syngas Cleaning [Articolo su rivista]
Allesina, G; Pedrazzi, S; Altunoz, M; Morselli, N; Puglia, M; Allegretti, F; Leonardi, C; Giorgini, L; Arru, L; Tartarini, P

Common issues of the gasification systems relate to filtering apparatus. Dry filtering processes are simple and reliable. However, the filtering material defines the maximum and minimum temperature at which the filter can operate properly. In addition, dry filtration is not effective on light tar compounds (i.e. benzene and toluene) or ammonia compounds. On the other hand, despite being very efficient, wet filters drop the gas temperature below the line of condensation of tar, ammonia and steam. The resulting condensate is normally disposed at a high cost on account of the high amount of hydrocarbons it contains. This work investigates the effects of a specific micro-algae growth on the waste-water from a syngas water scrubber. The results demonstrated the capability of the algal growth in the tar-contaminated water in which a certain amount of contaminants have been dissolved. Quantitative analyses of the compounds outlined the effect of algal growth on the reduction of several chemical species derived from the syngas filtration.

2017 - Spent coffee grounds as heat source for coffee roasting plants: Experimental validation and case study [Articolo su rivista]
Allesina, Giulio; Pedrazzi, Simone; Allegretti, Francesco; Tartarini, Paolo

The aim of this work is to validate a new sustainable economic circle where coffee roasting companies recycle spent coffee grounds as a source of thermal energy to produce roasted coffee. The green coffee beans need a significant quantity of heat in the roasting process and this energy could be obtained from the spent coffee grounds discarded by espresso bars. According to the concept of circular economy, a coffee company collects the coffee disposed by the bars where it was brewed, and uses it in a heat generator for the roasting process. This paper presents the feasibility of SCG-wood sawdust pelletization and combustion in a 29 kWthair furnace. Results of the tests report a thermal efficiency of 41.2% instead of 37.7% obtained with only wood pellet. In addition, the case study of a small Italian roasting company is discussed. The company produces about 5 tons of roasted coffee per day and it uses 400 Nm3/day of natural gas as heat source. The company totally satisfies its energy demand through wood-coffee pellet combustion instead of natural gas. According to the business plan, the pay-back period of the investment is four years after which company CO2emissions significantly decrease.

2017 - The energetic recover of biomass from river maintenance: The rebaf project [Relazione in Atti di Convegno]
Pedrazzi, Simone; Allesina, Giulio; Morselli, Nicolò; Puglia, Marco; Barbieri, Luisa; Lancellotti, Isabella; Ceotto, Enrico; Cappelli, Giovanni Alessandro; Ginaldi, Fabrizio; Giorgini, Loris; Malcevschi, Alessio; Pederzini, Chiara; Tartarini, Paolo

This paper exposes the first year of activities regarding an Italian regional project called REBAF (RecuperoEnergeticoBiomasse Alvei Fluviali = Energetic Recover of River Biomasses). The project concerns the modeling, realization and experimental validation of innovative pathways for the exploitation of grass and woodsy biomasses from river maintenance operations. The project is focused on the Secchia river situated in the mid North of Italy. The final goal is to make the river maintenance operations self-sustainability from the economic and environmental point of views. During the first year of the project, the typical biomasses of the Secchia river was recognized and quantified. Poplar was chosen as major representative of the wood biomasses. An evaluation about wood biomass quantity obtainable for every hectare of riverbanks maintenance was made. Several gasification tests of poplar wood chips from river maintenance was done in a small CHP gasifier. The biochar obtained was characterized and it was applied on field to some giant reed plantations in order to evaluate if there will be a productivity increase with biochar as soil amendant. In addition, a model to evaluate the giant reed annual productivity in the Secchia river banks was developed.

2017 - The use of on-line colorimetry for tar content evaluation in gasification systems [Articolo su rivista]
Quinlan, Brendan; Kaufmann, Bear; Allesina, Giulio; Pedrazzi, Simone; Hasty, Julia; Puglia, Marco; Morselli, Nicolò; Tartarini, Paolo

Gasification of biomass has the potential to become a relevant technology for a sustainable future. However, the content of tar in the gas produced through gasification needs to be managed properly in order to increase the reliability of the technology. Accurate measurement of tar gas concentrations enables management and technology improvement. Standardized offline measurement methods require a long time to produce a numerical result from a test. This work presents a novel colorimetric method to assess the tar concentration contained in syngas. The method uses an apparatus that includes a heated thimble filter (to remove particulate), gas quenching with isopropyl alcohol (IPA), a vapor knockout and cooling system including a final stage fritted glass bubbler/impinger, IPA removal via a peristaltic pump controlled by a capacitive level sensor, IPA flow metering, colorimeter for IPA/tar solution light absorbance measurement, and gas pumping/metering circuit. The method is robust and fast because it is based on a continuous light absorbance measurement. The system was compared against the tar protocol standard showing good correlation between average absorbance and tar concentration. Results demonstrate the capability of the proposed method to give continuous real-time measurement of the tar concentration in the gas.

2017 - Vine prunings biomass as fuel in wood stoves for thermal power production [Articolo su rivista]
Puglia, Marco; Pedrazzi, Simone; Allesina, Giulio; Morselli, Nicolò; Tartarini, Paolo

Wine industries by-products consist in various biomasses. The major in abundance are the vine prunings, derived from the annual vine plant maintenance. Literature suggests a variable production of 1-5 ton/year for every hectare of vine plantation. Vine prunings have a higher heating value of about 18 MJ/kg and an ash amount of about 4%. This paper analyzes the behavior as solid fuel in domestic stove of 4 variety of vine prunings from Emilia Romagna, a region in the north of Italy. First, physical and chemical characterization of the biomass samples were performed, then ash sintering and melting temperatures were evaluated. Combustion tests on a commercial multi-fuel biomass stove were performed. During the tests, mean combustion temperatures, biomass consumption, thermal power and combustion efficiency were calculated and compared with data regarding tests with A1 plus wood pellets. In addition, qualitative results about biomass sintering and stove flame stability was discussed. Results show a thermal efficiency comparable to the one obtained with wood pellet and the sintering of ashes was neglectable. Concluding, pre-treated vine prunings confirmed good properties as fuel in wood stove.

2016 - Effects of upgrading systems on energy conversion efficiency of a gasifier - fuel cell - gas turbine power plant [Articolo su rivista]
Pedrazzi, Simone; Allesina, Giulio; Tartarini, Paolo

This work focuses on a DG-SOFC-MGT (downdraft gasifier - solid oxide fuel cell - micro gas turbine) power plant for electrical energy production and investigates two possible performance-upgrading systems: polyphenylene oxide (PPO) membrane and zeolite filters. The first is used to produce oxygen-enriched air used in the reactor, while the latter separates the CO2 content from the syngas. In order to prevent power plant shutdowns during the gasifier reactor scheduled maintenance, the system is equipped with a gas storage tank. The generation unit consists of a SOFC-MGT system characterized by higher electrical efficiency when compared to conventional power production technology (IC engines, ORC and EFGT). Poplar wood chips with 10% of total moisture are used as feedstock. Four different combinations with and without PPO and zeolite filtrations are simulated and discussed. One-year energy and power simulation were used as basis for comparison between all the cases analyzed. The modeling of the gasification reactions gives results consistent with literature about oxygen-enriched processes. Results showed that the highest electrical efficiency obtained is 32.81%. This value is reached by the power plant equipped only with PPO membrane filtration. Contrary to the PPO filtering, zeolite filtration does not increase the SOFC-MGT unit performance while it affects the energy balance with high auxiliary electrical consumption. This solution can be considered valuable only for future work coupling a CO2 sequestration system to the power plant.

2016 - Modified diesel engine fueled by syngas: Modeling and experimental validation [Relazione in Atti di Convegno]
Pedrazzi, Simone; Allesina, Giulio; Morselli, Nicolò; Puglia, Marco; Rinaldini, Carlo Alberto; Savioli, Tommaso; Mattarelli, Enrico; Giorgini, Loris; Tartarini, Paolo

Diesel engines are robust and reliable machine for stationary electrical energy production. In fact, these engines are designed to run continuously for thousands of hours and with low maintenance. However, several issues affect the application of syngas as fuel in this kind of engines. The full conversion from diesel to gas fuel need the presence of the spark plug instead of the diesel injection. Therefore, the high compression ratio in this kind of engines increase the possibility of the knocking phenomenon inside the combustion chamber. The knocking damages the engine mechanical structure and reduce the engine reliability. Several works set the limit of the compression ratio to 17 in order to overcome this issue. In addition, the velocity of the syngas combustion flame is higher compared to the diesel one as result to the presence of hydrogen in the syngas. This difference forces to reduce the spark ignition time from 0 to 15 ° in advance respect the Bottom Top Dead Center (BTDC) in order to limit the peak pressure inside the cylinders to the design value of the engine. Aim of this work is to compare results of a 0D mathematical model of a converted diesel engine with the results obtained in an experimental campaign. For the tests a Fiat Power Train (FPT) 4.5 liters commercial diesel engine converted to syngas is used. The model calculates the maximum power output of the engine at different rpm starting from syngas composition, airsyngas mixture temperature and diesel nominal power. The model takes into account the friction losses, air to fuel ratio and intake manifold pressure. Experimental tests were run on a gasification facility consisting in a fixed bed wood chip downdraft gasifier that generates syngas to fuel the FPT engine. The engine is connected to a MeccAlte generator for electrical power production. An Arduino based controller sets the position of the air valve in order to stabilize the lambda value of the exhaust of the engine to 1.05. A variable electrical load was applied and it was increased as long as the engine was able to drag the generator at 1500 rpm. During the tests, the following parameters were monitored: syngas volumetric flow rate and composition, syngas pollutants concentration (tar, particulate and water), air-gas mixture temperature and intake manifold pressure. An HT electrical circuit analyzer recorded the power output of the generator. Several tests were run at 1500 rpm varying the air-syngas mixture temperature and the intake manifold pressure and experimental results was compared to 0D model predictions. A good agreement of the model to experimental data was achieved. Syngas conversion reduces the maximum electrical power output of the engine generator from 49.7 kW to about 22 kW as result of the lower air-syngas mixture calorific value and density compared to diesel-air mixture. However, the engine mechanical efficiency is comparable using syngas or diesel fuel (about 30%) and pollutant emissions are strongly lower with syngas fuel.

2016 - Preliminary analyses on an algae-based water scrubber for syngas cleaning [Abstract in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; ALTUNOZ HATIPOGLU, Meltem; Morselli, Nicolo'; Puglia, Marco; Leonardi, Chiara; Giorgini, L; Arru, Laura; Tartarini, Paolo

Aim of this work is to try to put together the two worlds of syngas filtering and syngas upgrading trough the use of a water-algae water photo-bio-scrubber. The system studied consists of a 10 kWel downdraft gasifier provided with a water scrubber where the syngas is bubbled in a solution of water, nutrients, algae and artificial light (. The heat provided by the syngas keeps the scrubber to the proper temperature where tars are condensed and algae can grow at proper rate. At the same time the CO2 content in the gas can be, in part, converted into biomass by the algae. From the scrubber it is disposed a multi-phase liquid composed of water, biomass, tars and char. The first analysis carried out in this work consisted in a two phases process of the gas. First, in the gasification system, part of the gas was derived into a simple water scrubber where all the flows where measured and the temperature was kept constant at 30 °C. Then the water obtained in such a way was used as basis for algae grown in lab conditions. Results shown the capability of such a system to be used in existing gasification facilities.

2016 - Preliminary Analysis on an Algae-Based Water Scrubber For Syngas [Abstract in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; ALTUNOZ HATIPOGLU, Meltem; Morselli, Nicolo'; Puglia, Marco; Allegretti, Francesco; Leonardi, Chiara; Giorgini, Loris; Arru, Laura; Tartarini, Paolo

In this study, two major advantages of microalga Neochloris oleoabundans have been taken into account: purification of the syngas contaminant water (SCW) and providing biomass yield from microalgae growth by using syngas contaminant together with BG11 microalgal growth medium [1] as a feedstock. 10 kW imbert type downdraft gasifier fueled with wood chips have been used to obtain syngas contaminant [2]. A certain amount of the wood-gas is derived after the biofiltering process and is sent to the Water Algae Photo-Bio-Scrubber System (WAPBS): a series of Drechsel bottles are filled with syngas cleansing water (SCW). Tar and particulate are trapped in the water inside the WAPBS, while part of the syngas contaminant is available for the micro algae to be converted into biomass. At the end of the process char and tar content of the syngas contaminant used by microalgae have been observed and microalgal growth of N. oleoabundans have been monitored during the process of WAPBS.

2016 - Uses of a water-algae-photo-bio-scrubber for syngas upgrading and purification [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; Arru, Laura; Altunöz Hatipoğlu, Meltem; Puglia, Marco; Tartarini, Paolo

Aim of this work is to try to put together the two worlds of syngas filtering and syngas upgrading troughthe use of a water-algae water photo-bio-scrubber. The system studied consists of a 10 kWel downdraft gasifier provided with a water scrubber where the syngas is bubbled in a solution of water, nutrients, algae and artificial light (. The heat provided by the syngas keeps the scrubber to the proper temperature where tars are condensed and algae can grow at proper rate. At the same time the CO2content in the gas can be, in part, converted into biomass by the algae. From the scrubber it is disposed a multi-phase liquid composed of water, biomass, tars and char. The first analysis carried out in this work consisted in a two phases process of the gas. First, in the gasification system, part of the gas was derived into a simple water scrubber where al the flows where measured and the temperature was kept constant at 30 °C. Then the water obtained in such a way was used as basis for algae grown in lab conditions. Results shown the capability of such a system to be used in existing gasification facilities.

2016 - Uses of a Water-Algae-Syngas-Photo-Scrubber for gas upgrading and purification in small-scale gasifiers [Abstract in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; Arru, Laura; ALTUNOZ HATIPOGLU, Meltem; Tartarini, Paolo

Aim of this work is to try to put together the two worlds of syngas filtering and syngas upgrading trough the use of a water-algae water photo- bio-scrubber. The system studied consists of a 10 kWel downdraft gasifier provided with a water scrubber where the syngas is bubbled in a solution of water, nutrients, algae and artificial light (. The heat provided by the syngas keeps the scrubber to the proper temperature where tars are condensed and algae can grow at proper rate. At the same time the CO2 content in the gas can be, in part, converted into biomass by the algae. From the scrubber it is disposed a multi-phase liquid composed of water, biomass, tars and char. The first analysis carried out in this work consisted in a two phases process of the gas. First, in the gasification system, part of the gas was derived into a simple water scrubber where all the flows where measured and the temperature was kept constant at 30 °C. Then the water obtained in such a way was used as basis for algae grown in lab conditions. Results shown the capability of such a system to be used in existing gasification facilities.

2015 - Approaching sustainable development through energy management, the case of Fongo Tongo, Cameroon [Articolo su rivista]
Allesina, Giulio; Pedrazzi, Simone; Sgarbi, Federico; Pompeo, Elisa; Roberti, Camilla; Cristiano, Vincenzo; Tartarini, Paolo

This work is aimed at defining a possible solution for sustainable energy development in the Menoua Department, West Cameroon. The purpose of the cooperation between ALA Milano Onlus and the Biomass Energy Efficiency Laboratory of the University of Modena and Reggio Emilia was to analyze the case study in order to propose a solution for energy production capable of meeting the needs of the Cameroonian society while also heading towards a sustainable development. Primary researches suggested that the most viable solution was to integrate the corn food processing with the gasification of the cobs. The thermo-conversion process was modeled with a black-box approach; the results of the model were further compared with the energy required for corn processing, therefore demonstrating the sustainability and virtuosity of the chosen solution. A commercial 20 kW$$_el$$el gasifier was selected for supplying electrical power to three central buildings: the city hall, the Chaufferie and the school. This solution is a security measure assuring continue power supply to these vital buildings. Furthermore, it will bind the relation between the rural and the city areas through the energy exchange process.

2015 - Digestate as bio-fuel in domestic furnaces [Articolo su rivista]
Pedrazzi, Simone; Allesina, Giulio; Belló, Tobia; Rinaldini, Carlo Alberto; Tartarini, Paolo

This study investigates the use of the biogas power plants byproduct (digestate) as biofuel in an ordinary domestic air furnace. The digestate, disposed by a 1 MW biogas plant located in Italy, was dried out and pelletized in order to be used as fuel in a wood pellet furnace with 29 kW(th) of nominal power, commonly installed in industrial HVAC systems. The first test was carried out starting from a heavily dried pellet called "digestate 0" characterized chemically and physically in order to obtain its composition, while its ashes were tested using an optical thermal dilatometer for the softening point evaluation. This first test outlined that the "digestate 0" pellets were not suitable for combustion applications even when mixed with an equal part of pure wood pellets. The research then focused on the raw digestate drying process through a set of physical and chemical tests. It was found that a temperature of 150 degrees C maximizes the higher heating value of the new "digestate 1" at 16.6 MJ/kg. However, to further avoid the ash sintering, "ultimate digestate" pellets were prepared mixing 50% of "digestate 1" and 50% of wood. The digestate obtained in such a way was experimentally tested through several runs of the air furnace. In these tests, the overall efficiency as well as the furnace emissions was measured.

2015 - Experimental-analytical evaluation of sustainable syngasbiodiesel CHP systems based on oleaginous crop rotation [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; Rinaldini, Carlo Alberto; Savioli, Tommaso; Morselli, Nicolo'; Mattarelli, Enrico; Tartarini, Paolo

This work is aimed at investigating how the solutions adopted for the SRF (short rotational forestry) can be applied to oleaginous cultures for bioenergy production with a dual fuel diesel engine. The method is based on four sub-systems: a seed press for oil production, a downdraft gasifier, a biodiesel conversion plant and a dual fuel biodiesel IC engine for CHP (combined heat and power) production. The plant is analytically modeled except for the IC engine that was tested via experimental analysis. Results showed that, in the hypothesis of 8000 hours/year of power plant run, a surface of 27 hectares can supply enough syngas and biodiesel to run a CHP unit with nominal electrical power of 13.61 kW. Moreover, the experimental analysis outlined how the engine running with dual fuel is not almost affected by significant losses in its performance. Besides, the use of syngas yields strong benefits in terms of soot emissions (measured by an opacimeter), as well as in terms of brake fuel conversion efficiency.

2015 - Increased maize power production through an integrated biogas-gasification-SOFC power system [Relazione in Atti di Convegno]
Pedrazzi, Simone; Allesina, Giulio; Puglia, Marco; Guidetti, Luca; Tartarini, Paolo

This work is aimed at demonstrating by modeling and simulation how a synergy of state-of-the-art technologies can boost of about 50% the maximum power output that can be obtained from maize silage biogas power plants. The starting point is the subdivision of the maize plant into grains and stover (that is composed of cobs, stalks and leaves). Grains are rich of starch, soluble sugars, fat and protein suitable for the anaerobic digestion, instead the stover is rich of hemicellulose and lignin which are characterized by a slow and incomplete degradability. This consideration brings to the core of the paper: grains are used as fuel in an anaerobic digester, while stover is converted into syngas in a fixed bed downdraft gasifier reactor. The biological degradation of grains is based on equilibrium kinetic models obtained from literature review, the stover gasification is modeled with an equilibrium model implemented in Python™ language. Biogas and syngas streams are used together as fuel in a Solid Oxide Fuel Cell (SOFC) conversion unit modeled through a MatlabTM script. Simulations were done considering a conventional maize silage biogas power plant with 100 kW electrical nominal power. Results outlined that the SOFC has a higher conversion rate than the conventional IC engine, in fact the replacement of the generator with a SOFC increases the power output of the plant to about 118 kW. Finally, the combined effects of coupling digestion of grains with the gasification of the stover and the use of a SOFC boost the peaks power output to 150 kW.

2015 - Modeling of coupling gasification and anaerobic digestion processes for maize bioenergy conversion [Articolo su rivista]
Allesina, Giulio; Pedrazzi, Simone; Guidetti, Luca; Tartarini, Paolo

This work estimates the advantages of using maize as fuel in a power plant composed of an anaerobic digester, a gasifier and an Internal Combustion (IC) engine. The digester is fed with maize grains, while, the remaining part of the plant, the stover, is gasified. Then biogas and syngas streams are both used as fuel into the engine. The performance of this plant was evaluated coupling gasification and anaerobic digestion mathematical models. Results of the proposed solution are compared with the performance of a 100 kW biogas power plant fed with the whole crop silaged. Results show that the overall energy yield of the improved solution is 39% higher than the conventional one fed with maize silage. This method will lead to the design of small and cheap digesters as a result of the increased conversion rate. In fact, the solution proposed fully converts the high cellulose-fiber parts of the maize plant that were tough to degrade in anaerobic digesters.

2015 - Which thermochemical conversion process for agricultural waste? Physical and chemical analyses to guide the choice [Articolo su rivista]
Pedrazzi, Simone; Allesina, Giulio; Puglia, Marco; Morselli, Nicolò; Tartarini, Paolo

This study investigates how physical and chemical analyses may lead the choice of the more suitable thermochemical energy conversion process for agricultural wastes. Four different case study are presented: corn cobs, digestate pellets from anaerobic digestion, wood biomass from river maintenance and seed cake from vegetable oil production. For all the cases analyzed the physical as well as the chemical characterization of the feedstocks are presented and discussed. Outputs of these analyses are: chemical composition, moisture content, ash content, ash softening point and particle size. These outputs, together with logistic considerations about availability and preconditioning of the biomasses allow to properly define the optimal process for each biomass. Three thermochemical processes are taken into account: pyrolysis, gasification and direct combustion.

2014 - An experimental analysis of a stand-alone standing wave thermoacoustic refrigerator [Articolo su rivista]
Allesina, G.

In the last years, the thermoacoustic phenomena had risen the scientific community interest due to its implications in thermodynamics, heat transfer and acoustic matters, that make possible the conversion between sound and heat. This work aimed at exploring the Russell–Weibull refrigerator, analyzing the behavior of the different parts to achieve a good level of thermal separation, together with the capability of working standalone. Special attention was paid to all those parts that need to be designed properly with explanation of the physics that ruled them, such as the sound generator, the woofer box, the stack and the tube insulation. During the second part of the work, the results obtained are discussed, consistently showing that, if some expedients are adopted, this simple refrigerator can achieve a temperature difference of 24 °C. The design choices concerning materials and geometries had great influence on the device behavior.

2014 - Biodiesel and electrical power production through vegetable oil extraction and byproducts gasification: Modeling of the system [Articolo su rivista]
Allesina, Giulio; Pedrazzi, Simone; Tebianian, Sina; Tartarini, Paolo

Aim of this work is to introduce an alternative to the standard biodiesel production chain, presenting an innovative in situ system. It is based on the chemical conversion of vegetable oil from oleaginous crops in synergy with the gasification of the protein cake disposed by the seed press. The syngas from the gasifier is here used to produce electrical power while part of it is converted into methanol. The methanol is finally used to transform the vegetable oil into biodiesel. Through a coupled use of ASPEN PLUS (TM) and MATLAB (TM) codes, a rapeseed, soy and sunflower rotation, with a duration of three year, was simulated considering 15 ha of soil. This surface resulted sufficient to feed a 7 kW(el) power plant. Simulation outputs proven the system to be self-sustainable. In addition, economical NPV of the investment is presented. Finally the environmental, economical and social advantages related to this approach are discussed.

2014 - Energy and economical comparison of possible cultures for a total-integrated on-field biodiesel production [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; S., Tebianian; Muscio, Alberto; Tartarini, Paolo

This work is aimed at investigating the energy conversion effectiveness and the economical advantages of a total integrated solution for on-field biodiesel and electrical energy production. The system proposed here is based on the synergy of four sub-systems: a seed press for oil production, a downdraft gasifier, a biodiesel conversion plant and a Solid Oxide Fuel Cell (SOFC). Two possible culture rotations, suggested by literature review, were analyzed here from economical and energy balance points of view. Both the rotations were composed of oleaginous crops only, therefore the seeds collected from the different cultures were pressed, then the protein cake produced in the process was gasified in the downdraft reactor. The gasification process was modeled here, and its output suggested that, for a precise number of hectares, the syngas obtained through the cake gasification was enough for producing methanol required for oil-biodiesel conversion and feeding a 10-kW SOFC. The purge line in the methanol reactor was used in the SOFC as well. The system was simulated using ASPEN PLUSTMand MATLABTMcodes. Results of the SOFC and gasifier models underlined the capability of the fuel cell to work with this particular system, furthermore the whole system analysis suggested that the surface required for sustainability of the processes is a function of the rotation choice. In both cases little surfaces ranging from 11 to 21 hectares were found to be enough for system self-sustainability with a ROI under 7 years in all the operating conditions analyzed.

2014 - Energy-Based Assessment of Optimal Operating Parameters for Coupled Biochar and Syngas Production in Stratified Downdraft Gasifiers [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; LA CAVA, Emma; Orlandi, Michele; Hanuskova, Miriam; Fontanesi, Claudio; Tartarini, Paolo

Biochar represents a valuable solution for carbon sequestration. Infact, it has aroused the interest of the scientific community due to its resistance to the degradation and its potential of soil improving. Stratified downdraft gasifier reactors are characterized by extreme design simplicity and it was proved that are able to operate with non-homogeneous feedstock. On the other hand, stratified reactors dispose a higher amount of char when compared to other downdraft gasifier. This work is aimed at characterizing the char produced through downdraft stratified reactors. Particular conditions which maximize both the quality and the amount of syngas and biochar was investigated. The whole system was evaluated through a composed coefficient Ip (performance index) which takes into account the energy content in the gas stream and the characteristics of the char produced. A lab-scale reactor, able to operate under different conditions, was designed considering the requirements of this work. It was implemented with a sophisticated heating system which allow us to control the reactor surface temperatures independently zone to zone. Results shown the capability of stratified gasifiers to be used for biochar disposal. Results outlined the Ip trend as function of the SV of the gasifier. and tar production was considered to find the more suitable condition.

2014 - Porous filtering media comparison through wet and dry sampling of fixed bed gasification products [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; Montermini, Luca; Giorgini, L.; Bortolani, G.; Tartarini, Paolo

The syngas produced by fixed bed gasifiers contains high quantities of particulate and tars. This issue, together with its high temperature, avoids its direct exploitation without a proper cleaning and cooling process. In fact, when the syngas produced by gasification is used in an Internal Combustion engine (IC), the higher the content of tars and particulate, the higher the risk to damage the engine is. If these compounds are not properly removed, the engine may fail to run. A way to avoid engine fails is to intensify the maintenance schedule, but these stops will reduce the system profitability. From a clean syngas does not only follow higher performance of the generator, but also less pollutants in the atmosphere. When is not possible to work on the gasification reactions, the filter plays the most important role in the engine safeguard process. This work is aimed at developing and comparing different porous filters for biomass gasifiers power plants. A drum filter was developed and tested filling it with different filtering media available on the market. As a starting point, the filter was implemented in a Power Pallet 10 kW gasifier produced by the California-based company «ALL Power Labs». The original filter was replaced with different porous biomasses, such as woodchips and corn cobs. Finally, a synthetic zeolites medium was tested and compared with the biological media previously used. The Tar Sampling Protocol (TSP) and a modified «dry» method using the Silica Gel material were applied to evaluate the tars, particulate and water amount in the syngas after the filtration process. Advantages and disadvantages of every filtering media chosen were reported and discussed.

2014 - Thermal Stabilization of Digesters of Biogas Plants by Means of Optimization of the Surface Radiative Properties of the Gasometer Domes [Relazione in Atti di Convegno]
Bavutti, M.; Guidetti, L.; Allesina, G.; Libbra, A.; Muscio, A.; Pedrazzi, S.

A new incentive scheme for power generation from biogas is favoring in Italy the construction of small plants. These ones, however, have poorer financial viability and biological stability than larger plants. In order to ensure adequate performance and a reasonable payback period it is therefore essential that every aspect of their operations is carefully designed. In this respect, summer overheating of anaerobic digesters due to solar gains must be prevented. A solution relies upon the implementation of a ‘cool’ gasometer dome with properly chosen solar reflectance, whose effectiveness was assessed through the use of a calculation code specifically built and validated by comparison with experimental data.

2013 - Biodiesel production through sinergy of on-field PVO extraction and protein cake gasification [Relazione in Atti di Convegno]
Allesina, Giulio; Muscio, Alberto; S., Tebianian; Pedrazzi, Simone; Tartarini, Paolo

This work is aimed at demonstrating the advantages of on-field oil extraction and protein cake exploitation from biomasses produced by a three-years crop rotation. The rotation that has been taken into account is rapeseed-sunflowerflax, suitable for most Mediterranean climatic zones. The process is divided in differents phases: extraction of pure vegetable oil (PVO) from seeds, gasification of the protein cake remaining from oil extraction and trans-esterification of the PVO using the methanol obtained by conversion of part of the syngas from gasification. In this way, instead of selling the seeds to the market, it is possible to sell the biodiesel and the electrical energy obtained from an IC engine operating with the excess of syngas. The effectiveness evaluation of this approach has been obtained through energetic and economical modeling of the whole system. The system has been simulated using ASPEN PLUSTM and MATLABTM codes. The results show the advantages related to the installation of micro power plants of 10 kWel, involving little surfaces tilled. The minimum surface necessary for system self-sustainability has been estimated as a function of field productivity and fuels characteristics. Moreover, the outputs of the economical analysis show the effectiveness of this innovative approach.

2013 - Modeling and investigation of the channeling phenomenon in downdraft stratified gasifiers. [Articolo su rivista]
Allesina, Giulio; Pedrazzi, Simone; Tartarini, Paolo

Downdraft stratified gasifiers seem to be the reactors which are most influenced by loading conditions. Moreover, the larger the reactor is, the higher the possibility to stumble across a channeling phenomenon. This high sensitivity is due to the limited thickness and superficial placement of the flaming pyrolysis layer coupled with the necessity to keep all the zones parallel for a correct running of this kind of gasifier. This study was aimed at modeling and investigating the channeling phenomenon generated by loading condition variations on a 250-kWe nominal power gasification power plant. The experimental campaign showed great variations in most of the plant outputs. These phenomena were modeled on two modified mathematical models obtained from literature. The results of the models confirmed the capability of this approach to predict the channeling phenomena and its dependency on the loading method.

2013 - Modeling and simulation of a DG-SOFC-MGT hybrid system [Relazione in Atti di Convegno]
Pedrazzi, Simone; Allesina, Giulio; Muscio, Alberto; Tartarini, Paolo

This paper describes the modeling and the simulation of an advanced gasification power plant composed of a Downdraft Gasifier (DG) and a Solid Oxide Fuel Cells - Micro Gas Turbine unit (SOFC-MGT). The gasifier converts the woodsy biomass into syngas that it is cooled and filtered before entering in a compressed storage tanks sub-system. A hybrid SOFC-MGT unit uses the stored syngas to produce electrical energy that it is sent to the electrical grid. The system has been modeled starting from literature. The simulations were made for different types of woodsy biomass over a year long period. Poplar, peach tree and vineyards pruning have been adopted with a variable moisture content ranging from 5% to 30%. The electrical energy produced and the overall electrical efficiency have been calculated setting the biomass consumption to 187 kg/hour for different biomasses and moistures scenarios. Maintenance of the gasifier has taken into account imposing a cycle of 120 hours of operating and 12 hours of maintenance. Starting from that, the storage sub-system has been design to assure the continuous operation of the SOFC-MGT unit all over the annual simulation. Sensitive analysis of the performance of the system varying the biomass type and the biomass moisture have been developed in order to find the best working conditions. Moreover, the annual energy balance of the system has been evaluated with these conditions to point out where the most relevant energy losses take place. Results show that the maximum overall electrical efficiency is around 33.5% for poplar biomass with 10% of moisture. In this scenario the average electrical power production is about 223 kW, the annual electrical energy amount sent to the grid is about 1956 MWh. In this conditions, the 42% of the chemical energy of the biomass is lost in the SOFC-MGT unit.

2013 - Simulation of GEMASOLAR-based solar tower plants for the Chinese energy market: Influence of plant downsizing and location change. [Articolo su rivista]
Amadei, C. A.; Allesina, Giulio; Tartarini, Paolo; Yuting, W.

In many countries that are experiencing a steep increase of energy demand, there is a growing challenge of responding to this demand by investing in renewable technologies for new power plants. Solar energy seems to be one of the best solutions to reduce the fossil fuels consumption for energy production purposes. In terms of high-power solar plants, concentrating towers are characterized by high efficiencies, but the investment costs are high as well. For this reason, a fundamental issue consists in simulating the solar tower behavior in different locations, in order to provide a precise estimation of both annual energy production and return of the investment. Among these types of solar plants, GEMASOLAR has been recently (2011) put in operation in Andalusia, Spain, and the data that have been obtained by this plant allow one to study its potential for application in different locations. The present work is aimed at simulating the GEMASOLAR plant behavior in some Chinese areas suitable for such a technology. All the simulations proposed here have been obtained through a Solar Advisor Model (SAM). Some of the simulations of the original plant have been modified forcing the plant to run without fossil fuel hybridization or changing its nominal power. After model validation, results have shown encouraging perspectives for the exploitation of this technology in China, with annual overall efficiencies of 14% for the 20 MW power plant (GEMASOLAR nominal power). In addition, the down-scaled plants have been optimized through native SAM software algorithm focusing on geometrical parameters. This procedure has been proved to be able of maintaining a high efficiency (14.97%) even for a 10 MW power plant. The focus has been on pilot plants, since they could represent the first step towards a deep exploitation of concentrating solar thermal power in China, with a relatively low capital risk.

2012 - Aige conference: A kinetic model for a stratified downdraft gasifier [Relazione in Atti di Convegno]

A model for a stratified downdraft gasifier has been developed. It has been adapted from two different models from literature with appropriate modifications and improvements. The new “interacting” model is able to predict the syngas composition, input and output flow rates and the gasifier cold efficiency under different working condition and with different biomass input. It works assuming a constant biomass consumption. The results of the model has been compared to experimental data taken from a downdraft gasifier power plant system with nominal power output of 200 kWel. The plant has been set at 160 kWel in order to avoid system instabilities related to high power runs.

2012 - Increase of Net Power Generation Of Biogas Plants By Reduction Of Heat Loss [Relazione in Atti di Convegno]
G., Grinzi; L., Guidetti; Allesina, Giulio; Libbra, Antonio; P., Martini; Muscio, Alberto

in this work, a comprehensive mathematical model of a biogas power generation plant is exploited to investigate the advantages of heat loss reduction. The model allows simulating the whole generation process, from biological breakdown of the biomass mixture to final generation of electricity and heat by combustion of the biogas. Either a thermal sub-model of the digestors or a fluid-dynamic sub-model of ducts and heat exchangers of the auxiliary heating system have been implemented, in order to evaluate heat loss, head loss in the ducts and power absorption of the pumps. An innovative approach to the exploitation of solar gains through the gasometer domes is also evaluated, based on the use of surface coatings with high solar absorptance and low thermal emittance. The theoretical reduction of auxiliary energy need is thus predicted as a function of local meteorological data on a monthly average. The results of the analysis show that proper insulation of the digestors and coating of the gasometer domes can increase the net production of electric energy up to a few percentage points. If waste heat is also exploited externally, the net increase of heat production is much greater, especially in cold climates.

2011 - Experimental assessment and modeling of energy conversion effectiveness in a gasification power plant [Relazione in Atti di Convegno]
Allesina, Giulio; Pedrazzi, Simone; Cattini, Caterina

National and international energy scenarios seem to be rediscovering a new confidence in gasification power plants as a valuable technology for biomass conversion. Their adaptability, in both direct power production and biofuels synthesis, has been manifested into the development of wide varieties of reactor models and sizes. An appropriate modeling of the system, supported by experimental analysis, is necessary to achieve the high level of efficiency of the gasifier and the proper effectiveness of the entire energy plant conversion. This work is aimed at studying a stratified downdraft gasifier coupled to two IC engines with the total nominal power of 250 kWel. The model of the system is based on mass and energy balance; the model outputs are compared here with those coming from the experimental campaign. All the major thermo-chemical parameters are monitored, these include: air and gas flow rate, biomass moisture content, consumption and ultimate analysis, reaction zones temperatures, tars and char production. In this paper, the model outputs have been compared with the data to evaluate the sensitivity of the model. Moreover, the difference between the theoretical data and the experimental data have been exanimate.