Search

The deployment of bioenergy has turned into a severe issue associated with energy security and greenhouse gas reduction. The development of technologies in the renewable energy market depends on the profitability of their investment. However, the Net Present Value of new technologies’ investment is affected by technical and economic uncertainties. Hence, the probability assessment of a positive Net Present Value and identifying critical economic and technical parameters can inform investors and decision-makers about any investment risks. This study evaluates the overall uncertainty in the Net Present Value of investment in cogeneration plants composed of a gasifier fed with biomass and a bottoming Internal Combustion Engine fed by the gasification product gas. Monte Carlo simulation assesses the probability of a positive Net Present Value for three sizes of cogeneration plants. Regarding sizes, the chance of generating a positive Net Present Value ranges from 66% to 90%, while the larger plants have a higher chance. The sensitivity analysis findings show that above all, biomass cost and then the sale price of electricity and the quantity of gasification product gas are the most dominant parameters. Using an internally produced biomass waste resource and possible achievement of green energy certificates on energy produced would make the initiative successful.

Bioeconomy, as a key strategic innovation pillar, supports energy transition and involves biomass resource assessment and its application. Biomass has an enormous potential to fulfil the domestic energy demand in Brazil. Hence, this study aims to quantify the theoretical, technical and techno-economic potential of agricultural and forestry residues to generate electricity via thermochemical processes in Brazil for the 2018–2050 timeframe. The analysis was carried out via an integrated approach, according to statistical reports and literature data. Conversion technologies for the estimation of technical potential consist of organic rankine cycle, combustion with conventional rankine cycle and gasification with an internal combustion engine. The results showed that Brazil’s theoretical potential is 7185.39 PJ and 16,708.12 PJ in 2018 and 2050. The technical potential in 2018 is 1795.16 PJ, generating 71,236.47 MWe, while the potential in 2050 is projected as 5771.49.4 PJ providing 229,027.31 MWe. The main restrictions are dispersed distribution of biomass over a large area, supply costs, and low efficiencies for energy conversion. Therefore, the techno-economic potential is around 19,704.01 MWe and 63,348.95 MWe for 2018 and 2050. The north region has the lowest electricity generation potential, while the southeast region takes a prominent position to generate electricity mainly from sugarcane residues. Levelized costs of electricity values varied from 10.532 to 15.507 US$/MWh for 2018 and from 7.320 to 13.002 US$/MWh for 2050, which highly influenced by the biomass price. The results of this study can support policy-making towards future planning on Brazilian bioenergy.

Gasification is one of the most effective and studied methods for producing energy and fuels from biomass as different biomass feedstock can be handled, with the generation of syngas consisting of H2, CO, and CH4, which can be used for several applications. In this study, the gasification of hazelnut shells (biomass) within a circulating bubbling fluidized bed gasifier was analyzed for the first time through a quasi-equilibrium approach developed in the Aspen Plus environment and used to validate and improve an existing bubbling fluidized bed gasifier model. The gasification unit was integrated with a water-gas shift (WGS) reactor to increase the hydrogen content in the outlet stream and with a pressure swing adsorption (PSA) unit for hydrogen separation. The amount of dry H2 obtained out of the gasifier was 31.3 mol%, and this value increased to 47.5 mol% after the WGS reaction. The simulation results were compared and validated against experimental data reported in the literature. The process model was then modified by replacing the PSA unit with a palladium membrane separation module. The final results of the present work allowed comparison of the effects of the two conditioning systems, PSA and palladium membrane, indicating a comparative increase in the hydrogen recovery ratio of 28.9% with the palladium membrane relative to the PSA configuration.

Organic Rankine cycle (ORC) systems are one of the most suitable technologies to produce electricity from low-temperature sources. In this paper, the main components of a non-regenerative, micro-scale ORC unit are modeled using the experimental results. These components are then used as functions in the system-level solver developed in MATLAB© to predict the performances of the system at off-design conditions. The proposed system solver is based on a novel approach, in which no assumptions are made about the system’s state, and only the components’ specifications and the real system boundaries that an operator encounters are adopted as inputs. To this end, the conservation of mass is considered in addition to the conservation of energy in the modeling of the system. Using the assumption-free model, the performances of the ORC system are mapped in the range of the experimental data considering the pump and the expander speeds as variables. The results show that the optimum system net electric performance is achieved at the pump and the expander speeds of 400 rpm and 900 rpm approximately. However, the pump is prone to the risk of cavitation due to low subcooling at the condenser outlet at this condition. Moreover, zero superheating is calculated at the expander suction that is not recommended for its operation. Hence, the developed assumption-free, object-oriented, mass-sensitive model has led to the full understanding of the system limitations and losses in the case of waste heat recovery applications. The proposed approach could be extended also to other ORC systems thus mapping their performances at off-design conditions without making artificial assumptions.

Gasification technology is actually one of the most effective ways to produce power and hydrogen from biomass. Solid oxide fuel cells (SOFCs) have proved to be an excellent energy conversion device. They can transform the chemical energy content in the syngas, produced by a gasifier, directly into electrical energy. A steady-state model of a biomass-SOFC was developed using process simulation software, ASPEN Plus (10, AspenTech, Bedford, MA, USA). The objective of this work was to implement a biomass-SOFC system capable of predicting performance under diverse operating conditions. The system is made of a gasification zone, gas cleaning steps, and SOFC. The SOFC modelling was done without external subroutines, unlike most models in the literature, using only the existing ASPEN Plus blocks, making the model simpler and more reliable. The analysis of the syngas composition out of each cleaning step is in accordance with literature data. Then, a sensitivity analysis was carried out on the main parameters. The results indicate that there must be a trade-off between voltage, electrical efficiency, and power with respect to current density and it is preferable to stay at a low steam-to-biomass ratio. The electrical efficiency achieved under the operating conditions is 57%, a high value, making these systems very attractive.

Italian power generation through anaerobic digestion (AD) has grown significantly between 2009 and 2016, becoming an important renewable energy resource for the country, also thanks to the generous incentives for produced electricity available in the last years. This work focuses on the economic and environmental issues of AD technology and proposes a techno-economic analysis of investment profitability without government support. In particular, the analysis focuses on an AD power plant fed by zootechnical wastewater and agro-industrial residues coupled to a cogeneration (CHP) system and a digestate-composting plant that produces soil fertilizers. We aim to determine the economic profitability of such AD power plants fed by inner-farm biomass wastes, exploiting digestate as fertilizer, using the cogenerated heat and taking into account the externalities (environmental benefits). Environmental analysis was carried out via a life cycle analysis (LCA), and encompassing the production of biogas, heat/electricity and compost in the downstream process. The un-released environmental emissions were converted into economic benefits by means of a stepwise approach. The results indicate that integrating a compost plant with a biogas plant can significantly increase the carbon credits of the process. The results were evaluated by means of a sensitivity analysis, and they report an IRR in the range of 6%–9% according to the Italian legislative support mechanisms, and possibilities to increase revenues with the use of digestate as fertilizer. The results significantly improve when externalities are included.

Wood and agricultural biomass pellets boost the potential as bio-fuels toward power production in tertiary and residential sectors. The production of pellets, however, is a multi-stage process where the supply-processing phases and the overall energy input strongly depend on the characteristics of the input biomass. In this paper, we describe the key features of the market for pellets in Italy, including national production and consumption data, production costs and prices, the available energy conversion systems, and the current regulatory issues. Moreover, we outline the main technical, economic, and end-user barriers that should be addressed in order to foster the growth of Italian pellet production. Additionally, we propose a methodology to evaluate the profitability of the pellet production chain, by assessing the investment and operation costs as a function of the quality of the raw biomass. The approach is applied to a real case study of a small firm producing wooden frames along with dry wood chips as the main by-product, which can be utilized subsequently for pellet production. Moreover, in order to optimize the size of the pellet production plant, further biomass was purchased from the market, including wood pruning and agricultural residues, wood chips from forestry, and uncontaminated residues of wood processing firms. A sensitivity analysis of the main technical and economic parameters (including the cost and quality of raw material, pellet market value, investment and operational costs, and plant lifetime) indicated that the biomass market price considerably affects the profitability of pellet production plants, particularly where the biomass has a high moisture content. Therefore, a 20% increase in the price of biomass with a high moisture content leads to a 60% fall in profitability index, turning it into negative one. This is due in particular to the costs of pre-treatment and drying of biomass, as well as to the lower energy content of wet biomass. As a result, the use of forestry residues with high moisture and high ash content, high costs of collection/transport, and high costs of pre-treatment and drying is not financially competitive.

Between the energy sources biomass waste is considered more and more important and the choice of the most appropriate energy conversion process is essential. The present paper presents a study for biomass waste to two distinguished energy conversion processes and the comparison of their environmental impact. The considered processes are gasification combined with internal combustion engine for power generation and combustion combined with an Organic Rankine Cycle (ORC) system with same electric power and same biomass flow as input to the conversion process. First, energy analysis of both mentioned systems have been investigated by means of Aspen Plus simulation. In the next step, model output is applied to evaluate the environmental profile of these small-scale biomass-based energy production systems. Environmental performance from cradle-to-gate was carried out by life cycle assessment (LCA) methodology. Results reveal that biomass production has a high influence over all impact categories. In both systems, eutrophication (EP), acidification (AP) and global warming potential (GWP) were identified as the main impacts. As a result, ORC system entails higher environmental burdens in all impacts categories.

The development of small-scale efficient and low-cost Organic Rankine Cycle (ORC) units using low temperature waste heat for electricity production is attracting a lot of interest nowadays. This paper presents the thermodynamic simulation of a small scale regenerative ORC testing facility. The facility mainly consists of an electric steam generator to produce steam at 170oC and 7.5 bar as hot source, water at 20oC as cold sink and a scroll compressor converted to be used as expander. Simulation was performed by means of MATLAB, and CoolProp external library was used for the thermo-physical properties of the R245fa, the organic working fluid. The performance of the system in a certain range of working conditions has been calculated, obtaining maximum efficiency of 9.6% and net power of 17 kW. Simulations are used to understand the effect of different characteristics of main components on the performance of the system before running the test bench. Thus, allowing the future experimental campaign that will verify the validity of the model.

Woody biomass has a considerable potential for energy purposes specially after densification processes which convert these materials into solid biofuels with higher energy density. This study focuses on the energy and environmental assessment of pellet production system from vine and olive grove woody biomass. The life cycle assessment (LCA) from grape and olive cultivation up to packed pellet production, ready for delivery to final users was conducted to quantify the eco-profile of agro-pellet production. The results of comparative analysis revealed that pellet production from both biomasses is dominated by cultivation phase. Vine pellet production was more dependent on chemical fertilizers specially potassium sulfate, but olive pellet production was more dependent on copper oxide pesticide. Primary energy use per MJ energy of vine pellet was greater than that of olive pellet (0.6 vs. 0.19). On the other hand, energy return ratio of olive pellet was three times of that of vine pellet (5.22 vs. 1.7). Nevertheless, olive pellet had higher environmental impacts in the forms of human toxicity, freshwater ecotoxicity and marine ecotoxicity. Consequently, sensitivity analysis investigates the impact of variation in input parameters of fertilizers, pesticides, machinery, diesel fuel, transport and pelletizing process on LCA results.

In this study, the performance characteristics of a regenerative flow turbine (RFT) prototype have been investigated by means of a computational fluid dynamics (CFD) study. The prototype has been initially designed to be used in gas pipelines replacing expansion valves but, because of the intrinsic characteristics of this kind of expander, its use can be extended to other applications like the expansion process in small-scale organic Rankine cycle (ORC) plants. In the first part of this work, the numerical results of the CFD analysis have been validated with the experimental data reported in literature for the same turbine prototype. After the validation of the model, a detailed study has been carried out in order to evaluate specific features of the turbine, focusing the attention on the typical operating conditions of small-scale low-temperature ORC systems. Results have shown that the considered RFT prototype operates with higher isentropic efficiencies (about 32% at 6000 rpm) at lower mass flow rates, while the power output is penalized compared to other operating points. The numerical analysis has also pointed out the high impact of the losses in the leakage flow in the gap between the blade tips and the stripper walls. Therefore, the CFD analysis carried out has provided a thoughtful understanding of the performance of the expander at varying operating conditions and useful insights for the future redesign of this kind of machine for the application in small-scale ORCs.

The utilisation of low- and medium-temperature energy allows to reduce the energy shortage and environmental pollution problems because low-grade energy is plentiful in nature and renewable as well. In the past two decades, thanks to its feasibility and reliability, the organic Rankine cycle (ORC) has received great attention. The present work is focused on a small-scale (7.5 kW nominal electric power) combined cooling, heating and power ORC system powered by the combustion of olive pomace obtained as a by-product in the olive oil production process from an olive farm situated in the central part of Italy. The analysis of the employment of this energy system is based on experimental data and Aspen Plus simulation, including biomass and combustion tests, biomass availability and energy production analysis, Combined Cooling Heat and Power (CCHP) system sizing and assessment. Different low environmental impact working fluids and various operative process parameters were investigated. Olive pomace has been demonstrated to be suitable for the energy application and, in this case, to be able to satisfy the energy consumption of the same olive farm with the option of responding to further energy users. Global electrical efficiency varied from 12.7% to 19.4%, depending on the organic fluid used and the working pressure at the steam generator.

Life-cycle assessment (LCA) and data envelopment analysis (DEA) were combined in the environmental sustainability assessment of bioelectricity production by means of vineyard waste biomass gasification. Fifty vineyards were assessed following LCA and DEA methodologies to estimate their technical efficiency. Moreover, target performance values benchmarked for inefficient vineyards, and the potential reductions in their environmental impact linked to the improvement in technical efficiency, were evaluated with the aim of verifying eco-efficiency criteria. The DEA results showed an average reduction of up to 30% per input of material for the vineyards, leading to impact reductions that ranged from 29% to 60% depending on the chosen impact category. Photochemical oxidation and terrestrial ecotoxicity had the highest environmental inefficiencies. Electricity generated from vineyard pruning residue gasification—as an alternative to conventional electricity and in comparison to electricity generation via combustion—was a suitable solution for reducing environmental impact under the studied categories. The innovative value of the present work is further based in the integrated application of LCA and DEA methodologies for the previously unexplored Iranian context. The results show that operational efficiency within vineyards is required to ensure that bioelectricity is significantly advantageous with regards to environmental performance in comparison to national grid electricity. The analysis further emphasises that increasing the operational efficiency of biomass production is a feasible way to achieve significant and wide-ranging environmental sustainability benefits.

It is unclear whether the production of biochar is economically feasible. As a consequence, firms do not often invest in biochar production plants. However, biochar production and application might be desirable from a societal perspective as it might entail net environmental benefits. Hence, the aim of this work has been to assess and monetize the environmental impacts of biochar production systems so that the environmental aspects can be integrated with the economic and social ones later on to quantify the total return for society. Therefore, a life cycle analysis (LCA) has been performed for two potential biochar production systems in Belgium based on two different feedstocks: (i) willow and (ii) pig manure. First, the environmental impacts of the two biochar production systems are assessed from a life cycle perspective, assuming one ton of biochar as the functional unit. Therefore, LCA using SimaPro software has been performed both on the midpoint and endpoint level. Biochar production from willow achieves better results compared to biochar from pig manure for all environmental impact categories considered. In a second step, monetary valuation has been applied to the LCA results in order to weigh environmental benefits against environmental costs using the Ecotax, Ecovalue, and Stepwise approach. Consequently, sensitivity analysis investigates the impact of variation in NPK savings and byproducts of the biochar production process on monetized life cycle assessment results. As a result, it is suggested that biochar production from willow is preferred to biochar production from pig manure from an environmental point of view. In future research, those monetized environmental impacts will be integrated within existing techno-economic models that calculate the financial viability from an investor’s point of view, so that the total return for society can be quantified and the preferred biochar production system from a societal point of view can be identified.

© 2019 The Authors In this paper, two innovative small-scale solar Organic Rankine Cycle (ORC) trigeneration plants are investigated and compared using a simulation analysis. In particular, the first plant (Plant 1) consists of a 146 m 2 Compound Parabolic Collectors (CPC) solar field, a 3 m 3 diathermic oil storage tank, a 3.5 kWe ORC plant and a 17 kWc absorption chiller, while the second plant (Plant 2) consists of a Linear Fresnel Reflectors (LFR) solar field of equal reflecting area, a phase change material storage tank equipped with reversible heat pipes, a 3.2 kWe ORC unit and the same 17 kWc absorption chiller as the former. The dynamic performance of the considered plants has been assessed for two Italian locations representative of the European Mediterranean area, Napoli and Messina, having a similar global radiation but a significantly different ratio of direct normal irradiance to diffuse irradiance. The comparison between the two different solar ORC trigeneration systems has revealed the great influence of the solar radiation on the effectiveness of such systems even for locations at similar latitudes. The energy production has been analysed both on a monthly and daily basis. Results have shown that while the performance of Plant 1 is not so sensitive to location and radiation conditions, Plant 2 is greatly affected by these parameters. Moreover, the higher condensing temperatures necessary in summer to supply the absorption chiller significantly limit the electrical efficiency of the solar CPC ORC. On the contrary, the LFR technology allows the achievement of higher temperatures and conversion efficiencies in summer, thus resulting especially suitable for solar cooling applications. In conclusion, this study has highlighted the importance of adequate technology selection with different radiation conditions in order to better exploit the potential of trigenerative solar ORC systems. ispartof: APPLIED ENERGY vol:242 pages:1176-1188 ispartof: location:ITALY, Palermo status: published

The present paper presents a study of biomass waste to energy conversion using gasification and internal combustion engine for power generation. The biomass waste analyzed is the most produced on Italian soil, chosen for suitable properties in the gasification process. Good quality syngas with up to 16.1% CO⁻4.3% CH4⁻23.1% H2 can be produced. The syngas lower heating value may vary from 1.86 MJ/ Nm3 to 4.5 MJ/Nm3 in the gasification with air and from 5.2 MJ/ Nm3 to 7.5 MJ/Nm3 in the gasification with steam. The cold gas efficiency may vary from 16% to 41% in the gasification with air and from 37% to 60% in the gasification with steam, depending on the different biomass waste utilized in the process and the different operating conditions. Based on the sensitivity studies carried out in the paper and paying attention to the cold gas efficiency and to the LHV, we have selected the best configuration process for the best syngas composition to feed the internal combustion engine. The influence of syngas fuel properties on the engine is studied through the electrical efficiency and the cogeneration efficiency.

Gasification is one of the most effective and studied methods for producing energy and fuels from biomass as different biomass feedstock can be handled, with the generation of syngas consisting of H2, CO, and CH4, which can be used for several applications. In this study, the gasification of hazelnut shells (biomass) within a circulating bubbling fluidized bed gasifier was analyzed for the first time through a quasi-equilibrium approach developed in the Aspen Plus environment and used to validate and improve an existing bubbling fluidized bed gasifier model. The gasification unit was integrated with a water-gas shift (WGS) reactor to increase the hydrogen content in the outlet stream and with a pressure swing adsorption (PSA) unit for hydrogen separation. The amount of dry H2 obtained out of the gasifier was 31.3 mol%, and this value increased to 47.5 mol% after the WGS reaction. The simulation results were compared and validated against experimental data reported in the literature. The process model was then modified by replacing the PSA unit with a palladium membrane separation module. The final results of the present work allowed comparison of the effects of the two conditioning systems, PSA and palladium membrane, indicating a comparative increase in the hydrogen recovery ratio of 28.9% with the palladium membrane relative to the PSA configuration.

Scroll compressors converted into expanders represent a good choice in micro-to-small-scale organic Rankine cycle (ORC) applications. Several studies have tested and modeled scroll expanders in ORC systems in the last decade to assess their performance and reliability in off-design conditions. In this work, SANDEN TRS090F scroll compressor is converted into an expander and tested in a micro-scale ORC system using R134a for power generation from low-grade heat. The experimental data are used to modify the available semi-empirical model in the literature considering a polytropic expansion, a more detailed suction pressure drop model, and a variable loss power correlated to the expander pressure ratio. In addition, the two known expander geometrical parameters, the built-in volume ratio, and the swept volume are considered as fixed inputs to the model instead of being determined as part of the model results. In general, the results of the analysis show that the proposed model can predict the expander's overall performance with good accuracy in different operating conditions. The maximum deviation between the model results and most of the measurements is 5% for the mass flow rate and the shaft power, 15% for the overall isentropic efficiency, and 3 K for the discharge temperature. Then, the impact of the different losses is presented, and finally, the validated model is used to generate the performance maps of the studied expander at different working conditions.

Organic Rankine Cycles (ORCs) are recognized as suitable systems to convert the thermal energy from low-grade heat sources to electricity. However, their performance and reliability are subjected to several deficiencies especially at micro-to-small scales. In this work, the impact of the expander lubricant oil on the performance of the heat exchangers and the scroll expander of a non-regenerative, micro-scale ORC unit is investigated. In particular, the oil circulation rate (OCR) is theoretically assessed for each experimental data set based on the thermal balance between the hot and cold streams of the condenser. Then, the performance of the other components is assessed using the lubricant-R134a mixture properties, assuming the same OCR. Results have shown that the presence of the lubricant oil leads to 5–15% capacity loss of the evaporator and the condenser of the studied ORC system. The calculated mass charge of the evaporator can also be underestimated up to 6.5% approximately if the oil is neglected. In addition, neglecting the lubricant oil may lead to over-estimation of the expander mechanical efficiency and under-estimation of its volumetric efficiency up to about 50% in very low shaft speeds. Hence, despite it is usually neglected in the literature, the results of the present analysis show that the impact of expander oil is relevant in micro-scale ORC systems.

Gasification is currently considered one of the most effective technologies to produce power and hydrogen from biomass and the scope of this work is to determine performances of such an energy system in terms of production of pure hydrogen. The overall plant has been simulated by means of ChemCAD® software. It is composed of a dual fluidized bed biomass gasifier with Catalytic Filter candles (CF), innovatively integrated within the gasification reactor, Water Gas Shift reactor (WGS), equipped with a desulphurization reactor (DeS), and Pressure Swing Adsorber system (PSA), coupled with a micro gas-turbine system (mGT) as an auxiliary power generator aimed to supply inner needs of electricity. Research and pilot scale tests on gasifier, CF, WGS reactor and PSA unit allowed to validate the model. The components have been integrated in a relatively small size and innovative plant (1 MW th as biomass input). This integration entails highly pure H 2 and major efficiency. The model allowed a sensitivity analysis of basic parameters as WGS temperature, residence time and steam to biomass ratio (SB). Important results have been generated reaching a maximum hydrogen yield of 75.2 g H2 /kg bio and a maximum efficiency, HHV based, of 55.1%. Optimal compromise of results was obtained with SB equal to 2, WGS reactor temperature at 300 °C and residence time at 0.8 s. Finally, even the chance to generate hydrogen without consumption of auxiliary fuel (by exploiting off gas and waste heat recovery) has been investigated.

This Special Issue was created through financing by the Italian Ministry for Education, University and Research (MIUR) of the project SAFEMEDSustainability of Agricultural and Forestry systems in the Mediterranean environment in a context of global change (Law 232/2016, Italian University Departments of excellence). This project was financed by the Department of Agrarian and Forest Sciences (DAFNE) at the University of Tuscia (Viterbo, Italy). In particular, within this project, in the context of the Work Package3 objective, there is a need for innovation in the agricultural and forestry sectors for energy sustainability. Renewable energy sources and the rational use of energy represent an important agricultural and forestry resource in a local context against climate change. The first issue that this Special Issue will address is identifying the energy potential from agro-forestry biomass, also dealing with the production of agricultural and forestry biomass in terms of supply and logistics; short rotation forestry (SRF); agricultural and forestry residues and their valorization; the main techniques of cultivation, the mechanization of biomass production, harvesting and pre-treatment; the energy and environmental balance of biomass production; further forms of by-product valorization; evaluation of the potential of land use (GIS—Geographic Information Systems) and planning tools. The second issue focuses on the performance analysis of prototypical systems for energy conversion, including hydrogen, power and/or heat production plants and the pertinent thermodynamic cycles; sustainable renewable energy technologies (RETs); biomass thermochemical energy conversion technologies, such as combustion, gasification, and pyrolysis; biomass biochemical energy conversion technologies, such as fermentation and anaerobic digestion; system analysis and the integration of production and conversion; and integrated bioenergy systems. Economic, environmental and management aspects of the aforementioned technologies will be considered. The third issue focuses on energy sustainability for environmental mitigation such as the impact of large-scale/small-scale bioenergy systems; enhancement of the by-products of thermochemical processes (biochar) for the improvement of the agricultural and forestry sector; evaluation of CO2 storage in the soil and combating desertification; and energy efficiency.

This study evaluates the environmental profile of a real biomass-based hydrogen production small-scale (1 MWth) system composed of catalytic candle indirectly heated steam gasifier coupled with zinc oxide (ZnO) guard bed, water gas shift (WGS) and pressure swing absorber (PSA) reactors. Environmental performance from cradle-to-gate was investigated by life cycle assessment (LCA) methodology. Biomass production shows high influence over all impact categories. In the syngas production process, the main impacts observed are global warming potential (GWP) and acidification potential (AP). Flue gas emission from gasifier burner has the largest proportion of total GWP. The residual off gas use in internal combustion engine (ICE) leads to important environmental savings for all categories. Hydrogen renewability score is computed as 90% due to over 100% decline in non-renewable energy demand. Sensitivity analysis shows that increase in hydrogen production efficiency does not necessarily result in decrease in environmental impacts. In addition, economic allocation of environmental charges increases all impact categories, especially AP and photochemical oxidation (POFP). This research has been supported by the following projects: the Italian national Ricerca di Sistema research project HBF2.0 funded by Italian Ministry for Economic Developments and European project UNIfHY (UNIque gasifier for HYdrogen production) funded by FP7 European Commission Programme. This research has been supported by the following projects: HBF2.0 funded by Italian Ministry of Economic Development within the Italian National System Research, in the Programme called Ricerca di Sistema, and the European project UNIfHY (UNIque gasifier for HYdrogen production) funded by FP7 EuropeanCommissionProgramme. Within these projects we thank especially Andrea Di Carlo of University of L'Aquila, for the plant flowsheet and part of the plant data and Donatella Barisano of ENEA for the data and the picture of the UNIFHY 1000 kWth plant.

In this paper, the potential of a small scale concentrated solar Organic Rankine Cycle unit coupled with an absorption chiller for trigeneration purposes is investigated using a simulation analysis. At the moment, only few research works encompass small-scale solar trigeneration systems and most of them do not refer to real plant. On the contrary, in this work electric, heating and cooling maximum generation of a real and experimental small scale prototype system composed of a 50 m2 CPC solar field, a 3.5 kWe ORC plant and a 17 kWc absorption chiller is investigated by means of TRNSYS. In particular, this work relies on the evaluation of the dynamic performance of the mentioned plant varying some selected system parameters to provide proper modifications of its design configuration and operation. More precisely, working temperature ranges, heating and intermediate fluid flow rates as well as volume of the storage tanks and size of the solar field have been varied within the simulation model. Results have shown that operating temperature ranges of the storage tanks considerably affect the overall performance of the system; by appropriately choosing these ranges the primary energy production can be increased by 6.5% compared to the baseline configuration without any additional investment costs. Moreover, setting suitably some design parameters can significantly contribute to extend the operating hours and the feasibility of a such small scale integrated system for residential applications.

To answer the actual energy, water, economic, social and environmental challenges, renewable, distributed power plants need to be developed. Among renewables, solar tri-generative power plants can be a solution where there is big low temperature heating/cooling demand and small electricity demand, like many residential and industrial utilities. In this case, solar thermal plants can produce thermal energy with low cost and high efficiency. The higher temperature heat not needed by the user can be exploited via Organic Rankine Cycle to produce electrical energy and desalinized water via reverse osmosis. The present paper analyses, via TRNSYS simulation, a system composed of 50 m 2 of CPC solar thermal collectors, 3 m 3 of thermal storage, a synthetic heat transfer fluid, 3 kW e ORC, 8 kW th absorber, 200 l/h direct reverse osmosis desalination device. The system is able to produce power, heating/cooling and fresh water needs for a residential house. Although system's components are well known technologies, the integration to a efficient and economic working system is still a challenge. Global energy and economic analyses have been performed. Low temperature heating/cooling terminals allow to increase not only the use of thermal energy but also the ORCand absorber efficiency. ORC-Absorber configuration and relative fluids and temperatures are central. Government support and/or cost reduction of 30% are necessary to have positive NPV and acceptable PBT and IRR.

This work concerns the issue of the generation of a clean, hydrogen rich syngas by means of biomass gasification for different downstream applications, such as fuel cell feeding. For a direct use of the syngas it is necessary to remove the major pollutants, first of all tar and particulate matter. Furthermore the production of a syngas with high content of hydrogen requires the reforming of methane. Ceramic catalytic filters have been proposed and tested to perform the removal of particulate and the steam reforming of tar and methane. The development of a CFD model is illustrated and discussed in this paper for the simulation of the ceramic catalytic filter behaviour inside the freeboard of a gasifier and the evaluation of its performance in the steam reforming of tar and methane. The kinetics of the chemical reactions inserted in the model were taken from literature. The model was validated by comparing the simulation outputs with experimental results of tests on a bench scale gasifier containing a ceramic catalytic filter. The model was then used to study the main parameters that have an influence on the performance of the catalytic filters. In particular the variables were temperature (750–850 °C) and filtration velocity (70–110 m/h). A stronger temperature dependency on the conversion of some hydrocarbons has been observed; in particular by increasing the temperature of 100 °C the conversion of CH4 and C7H8 rises of approximately 2 times, while the conversion of C6H6 and C10H8 rises of approximately 4 times. The best conditions for the conversion of tar and methane appear to be highest temperature (850 °C) and lowest filtration velocity (70 m/h). In this case the conversion obtained for methane and tar are about 33% for CH4, 41% for C6H6, 75% for C7H8 and 85% for C10H8.

Anaerobic co-digestion technology is increasingly used to simultaneously treat solid and liquid organic waste to balance nutrient content, to reduce the negative effects of toxic compounds in the process, and to increase biogas yield. The aim of this study was to analyze the economic performance of co-digestion plants fed with agro-industrial wastes as a function of installed power, with a method of discounted cash flow. The study focused on Italian framework conditions concerning payment for electricity produced by anaerobic digestion (AD) plants as well as the production costs. The economic analysis was carried out using three different plant sizes: 100 kW, 500 kW, and 1000 kW, which are representative of biogas plants in Italy. The study showed that the improvement of the break-point is closely linked to the increase in corresponding plant size. Given the assumptions of the simulation, the payback for the 100 kW plant was nine years for both the all-inclusive tariff and the basic feed-in tariff (BFT). Regarding the 500 kW and 1000 kW plants, the payback periods were five and four years, respectively.

There have been many scientific advances in the improvement of renewable energy systems. Recently, considerable interest has been given to their optimized management during their service life due to a large increase in the number of new renewable energy source power plants. High reliability levels are as important as high yields in order to maximize the useful green energy produced. Solar energy has been one of the most popular and exploited renewable sources in the market and therefore improvements in its efficiency and reliability have had a considerable impact. All energy systems require an increase in their conversion efficiency to reduce the consumption of primary energy. Moreover, the optimization of the performance of photovoltaic systems has increased their incidence as renewable sources in global power generation and has boosted their profitability. A failure of the components and sub-components of a working energy system cause two main issues; the first direct implication for the plant is the damage of the components and sub-components, and the second indirect implication is the consequent lack of energy production due to the plant being out of order. Furthermore, unforeseen failures of the components increase the uncontrollability of photovoltaic power systems, which worsens electric grid dispatching. The work presented here provides, for the first time, a complete and new assessment of Reliability Centered Maintenance carried out using a failure mode and effect analysis approach to photovoltaic systems. We use a large volume of data derived from a database of real maintenance activities carried out by a multinational company. These data were interpreted by the opinions of experts with specialist experience in the installation, operation, and maintenance of photovoltaic power systems, from small to multi-megawatt size. The present work here has advantages over many previous studies since the information was derived from real experiences of photovoltaic systems which allowed for a more realistic risk analysis and, especially, this information was also used to revise the maintenance plan of photovoltaic installations and to optimize their effectiveness, concentrating on various failure modes which mostly affect production or which can be easily removed/reduced.

Concentrated solar technologies coupled with ORC system is a well-known topic in temperature ranges lower than 200°C. However, the integration to an efficient and economic working system is still a challenge especially at small scale. Efforts exist to achieve higher overall efficiencies but they are solely focused on thermal and electrical production while few of these is encompassing small-scale solar trigeneration systems. In the present article, the potential of a small scale concentrated solar Organic Rankine Cycle plant coupled with an absorber is investigated using a simulation analysis of a small scale 50 m 2 CPC solar field, a 3.5 kWe ORC and a 17.6 kWc absorption chiller to satisfy respectively heating, electricity and cooling needs of a residential user. The simulation analysis of the overall system has been carried out in TRNSYS and an own model of the ORC system has been developed by the authors in Matlab thus improving the previous general model. The final aim of the proposed work is indeed the performance assessment of the small scale integrated system in order to evaluate the potential feasibility of such a system for residential applications.

Fuel Cells fed with locally produced biogenous primary fuels can convert renewable energy into electricity with high efficiencies, in an environment friendly and CO 2 -neutral manner. The paper analyses different biomass conversion processes, gas conditioning technologies, fuel cells typologies and power plant configurations, focusing on the most suitable gasification and anaerobic digestion processes coupled to high temperature fuel cells. The paper shows that the conversion systems have to be analysed from global perspective including feedstock, processes and plant configurations in order to obtain high reliability and efficiency and low emissions. Indeed, the presence, in the raw produced gas, of particulate, organic and inorganic impurities renders the coupling of biomass-derived gases and Fuel Cells problematic, especially in the case of gasification. However, recently developed hot gas cleaning technologies could improve energy efficiency and lower operational costs for high-temperature utilizations of the biomass-derived gas. Finally, further research and demonstration activities are required in order to improve power plant reliability and reduce global capital cost, especially at the more suitable small scale size.

Solar thermoelectric, even for small sizes, is continuing to garner more attention, by virtue of maturation of small size organic Rankine cycle generators, and of small size absorption chiller even if cost and reliability are still not optimal. Indeed, solar thermal power technology improvement would consent to stimulate an ambit already present in Europe and Italy with a well-known tradition and established leadership and efforts focused on a single solar technology would bring to positive effects concerning controllable electric and thermal energy uses. In this context, the present work tries to summarize the possible cycles and fluids that can be applied in a small solar thermal power plant. Despite a plethora of simulated and experimental cycles and fluids, the simplest cycle using near isentropic fluids seems to be the best choice for a small ORC-based CHP system, even if particular attention has to be done to all the sizing parameters (electricity, heating and cooling demand; area and type of solar collector; flow and temperature of the thermal carrier; flow, temperature and pressure of the working fluid; storage volumes; etc.). Indeed, efficiency and reliability of the reported systems are very different, but, it seems that global efficiency of even more than 10% and global cost of even less than 10,000 €/kW can be obtained even at size of few kW if adequate systems are constructed and managed.

The security of supply and climate change issues and the linked recent growth of the local power generation by means of renewable energies technologies are providing real opportunities for the development of small scale biomass gasification systems. The present paper reports the state of art of the small scale gasification power plants. Initial attention has been given to the different biomass feedstock suitable for gasification, focusing on residues with low cost and low environmental impact. Then the two major typologies of gasifiers (fixed and fluidized bed) have been analyzed in terms of raw gas yield, composition and tar and particulate content. The different cold and hot raw gas conditioning systems, highlighting their compatibility with the different gasification system, are described. High efficiency examples of power production by means of internal combustion engine, micro gas turbine, Solid Oxide Fuel Cell or a mix of them, both as realized plants and process simulated ones, have been then reported. The paper provides an overview of the different power plants in terms of efficiency, reliability and cost. © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of ATI NAZIONALE.