• Energy Research

Renewable energy sources exploited for Combined Heat and Power (CHP) generation purposes represent a suitable solution for an efficient energy production in industrial and commercial applications, helping to reduce the consumption of fossil fuels and the related emission of GreenHouse Gases (GHG). The aim of this work is to assess the technical, economic and environmental feasibility of an integrated CHP plant, where an Internal Combustion Engine (ICE) fuelled with syngas deriving from gasification of residual biomass is combined with a PV solar system. The ICE has a rated power of 20 kWel and a thermal capacity of 40 kWth; this last achieved by recovering heat from the cooling circuit and from the exhaust gases; the PV system has a peak power of 20 kWel. A 100-kWh lithium battery is also included in the proposed layout, to manage the electrical energy fluxes to and from the national grid. The overall system is dynamically simulated within the TRNSYS environment, with the scope of assessing the conversion efficiency with respect to an annual dynamic load relevant to the energy consumption of a generical farmhouse where the gasifier feedstock is available. The proposed layout reveals as an efficient solution to totally cover the thermal demand during the whole year, as well as to match the electrical load for most of the period analysed. The implemented solution may lead to a reduction of almost 76 tons of CO2 emitted per year, with a related cost saving of about 393 kEUR in an estimated lifetime of 25 years.

Renewable energy sources exploited for Combined Heat and Power (CHP) generation purposes represent a suitable solution for an efficient energy production in industrial and commercial applications, helping to reduce the consumption of fossil fuels and the related emission of GreenHouse Gases (GHG). The aim of this work is to assess the technical, economic and environmental feasibility of an integrated CHP plant, where an Internal Combustion Engine (ICE) fuelled with syngas deriving from gasification of residual biomass is combined with a PV solar system. The ICE has a rated power of 20 kWel and a thermal capacity of 40 kWth; this last achieved by recovering heat from the cooling circuit and from the exhaust gases; the PV system has a peak power of 20 kWel. A 100-kWh lithium battery is also included in the proposed layout, to manage the electrical energy fluxes to and from the national grid. The overall system is dynamically simulated within the TRNSYS environment, with the scope of assessing the conversion efficiency with respect to an annual dynamic load relevant to the energy consumption of a generical farmhouse where the gasifier feedstock is available. The proposed layout reveals as an efficient solution to totally cover the thermal demand during the whole year, as well as to match the electrical load for most of the period analysed. The implemented solution may lead to a reduction of almost 76 tons of CO2 emitted per year, with a related cost saving of about 393 kEUR in an estimated lifetime of 25 years.

Present paper analyses the flexibility of co-combustion power supply in a Spark Ignition (SI) engine fuelled with Natural Gas (NG) and biogas (BG) for cogenerative purposes. The biogas properties are strongly influenced by the source biomass and by the characteristics of the conversion process, thus the possibility of a double-ramp supply with NG taken from the national distribution network allows to compensate for any decay in engine performance linked to the worst quality of the fuel and, therefore, to ensure more stable operations over time. The effects deriving from the addition of NG are quantified through the development of a dedicated one dimensional (1D) numerical model of the engine in GT-Power environment. The combustion sub-model is properly customized according to the different fuel composition relying on a detailed kinetic model, where the laminar flame rate is evaluated for each specific fuel considered. As a result, co-combustion operation appears to be a feasible solution both on the technical and economic point. The developed model can be properly adapted for the executive design of energy systems powered by NG -biogas mixtures, helping in the optimization of the energy and environmental performance.

Present paper analyses the flexibility of co-combustion power supply in a Spark Ignition (SI) engine fuelled with Natural Gas (NG) and biogas (BG) for cogenerative purposes. The biogas properties are strongly influenced by the source biomass and by the characteristics of the conversion process, thus the possibility of a double-ramp supply with NG taken from the national distribution network allows to compensate for any decay in engine performance linked to the worst quality of the fuel and, therefore, to ensure more stable operations over time. The effects deriving from the addition of NG are quantified through the development of a dedicated one dimensional (1D) numerical model of the engine in GT-Power environment. The combustion sub-model is properly customized according to the different fuel composition relying on a detailed kinetic model, where the laminar flame rate is evaluated for each specific fuel considered. As a result, co-combustion operation appears to be a feasible solution both on the technical and economic point. The developed model can be properly adapted for the executive design of energy systems powered by NG -biogas mixtures, helping in the optimization of the energy and environmental performance.

The development of a one-dimensional (1D) phenomenological model for biomass gasification in downdraft reactors is presented in this study; the model was developed with the aim of highlighting the main advantages and limits related to feedstocks that are different from woodchip, such as hydro-char derived from the hydrothermal carbonization of green waste, or a mix of olive pomace and sawdust. An experimental validation of the model is performed. The numerically evaluated temperature evolution along the reactor gasifier is found to be in agreement with locally measured values for all the considered biomasses. The model captures the pressure drop along the reactor axis, despite an underestimation with respect to the performed measurements. The producer gas composition resulting from the numerical model at the exit section is in quite good agreement with gas-chromatograph analyses (12% maximum error for CO and CO2 species), although the model predicts lower methane and hydrogen content in the syngas than the measurements show. Parametric analyses highlight that lower degrees of porosity enhance the pressure drop along the reactor axis, moving the zones characterized by the occurrence of the combustion and gasification phases towards the bottom. An increase in the biomass moisture content is associated with a delayed evolution of the temperature profile. The high energy expenditure in the evaporation phase occurs at the expense of the produced hydrogen and methane in the subsequent phases.

The development of a one-dimensional (1D) phenomenological model for biomass gasification in downdraft reactors is presented in this study; the model was developed with the aim of highlighting the main advantages and limits related to feedstocks that are different from woodchip, such as hydro-char derived from the hydrothermal carbonization of green waste, or a mix of olive pomace and sawdust. An experimental validation of the model is performed. The numerically evaluated temperature evolution along the reactor gasifier is found to be in agreement with locally measured values for all the considered biomasses. The model captures the pressure drop along the reactor axis, despite an underestimation with respect to the performed measurements. The producer gas composition resulting from the numerical model at the exit section is in quite good agreement with gas-chromatograph analyses (12% maximum error for CO and CO2 species), although the model predicts lower methane and hydrogen content in the syngas than the measurements show. Parametric analyses highlight that lower degrees of porosity enhance the pressure drop along the reactor axis, moving the zones characterized by the occurrence of the combustion and gasification phases towards the bottom. An increase in the biomass moisture content is associated with a delayed evolution of the temperature profile. The high energy expenditure in the evaporation phase occurs at the expense of the produced hydrogen and methane in the subsequent phases.

A Combined Heat and Power (CHP) system fuelled with rice husk is analysed from the thermodynamic, exergetic and economic point of view. The system is based on a gasification process coupled with a rice drying system. The produced syngas is employed to power a Spark Ignition (SI) Internal Combustion Engine (ICE) working as an electric generator, while the jacket cooling water powers a bottoming Organic Rankine Cycle (ORC) to produce electricity for plant self-consumption. A parametric analysis is carried out to investigate thermodynamic performances by varying the gasifier Equivalent Ratio (ER): as the ER increases, the ICE produced power and combustion efficiency decrease, while the thermal efficiency increases. However, the system is always capable to produce power for self-consumption and the desiccant flow for drying. The characterization of the engine is then better assessed by means of a dedicated GT-Power engine model, optimized for syngas fuelling, revealing a power derating of the 30% with respect to the natural-gas feeding operation. Other main findings suggest that the global exergetic efficiency ranges between 10.6% and 8.5%, while the economic profitability, represented by the Simple Pay Back, Net Present Value and Profit Ratio, cannot be considered satisfactory due to the consistent investment cost.

A Combined Heat and Power (CHP) system fuelled with rice husk is analysed from the thermodynamic, exergetic and economic point of view. The system is based on a gasification process coupled with a rice drying system. The produced syngas is employed to power a Spark Ignition (SI) Internal Combustion Engine (ICE) working as an electric generator, while the jacket cooling water powers a bottoming Organic Rankine Cycle (ORC) to produce electricity for plant self-consumption. A parametric analysis is carried out to investigate thermodynamic performances by varying the gasifier Equivalent Ratio (ER): as the ER increases, the ICE produced power and combustion efficiency decrease, while the thermal efficiency increases. However, the system is always capable to produce power for self-consumption and the desiccant flow for drying. The characterization of the engine is then better assessed by means of a dedicated GT-Power engine model, optimized for syngas fuelling, revealing a power derating of the 30% with respect to the natural-gas feeding operation. Other main findings suggest that the global exergetic efficiency ranges between 10.6% and 8.5%, while the economic profitability, represented by the Simple Pay Back, Net Present Value and Profit Ratio, cannot be considered satisfactory due to the consistent investment cost.