The use of biomass as a source of energy has been further enhanced in recent years and special attention has been paid to biomass gasification. Due to the increasing interest in biomass gasification, ...several models have been proposed in order to explain and understand this complex process, and the design, simulation, optimisation and process analysis of gasifiers have been carried out. This paper presents and analyses several gasification models based on thermodynamic equilibrium, kinetics and artificial neural networks. The thermodynamic models are found to be a useful tool for preliminary comparison and for process studies on the influence of the most important fuel and process parameters. They have the advantage of being independent of gasifier design, but they cannot give highly accurate results for all cases. The kinetic-based models are computationally more intensive but give accurate and detailed results. However, they contain parameters that limit their applicability to different plants.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•An integration of high-temperature heat pump and trigeneration system is proposed.•The numerical model of the heat pump cycle recommends ammonia as working fluid.•The exergy efficiency of the system ...is higher than those of conventional systems.•The economic viability is proved by means of a levelized cost of electricity method.•The proposed system provides around 40% cost savings when optimized in a case study.
Polygeneration energy systems are proven to be a reliable, competitive and efficient solution for energy production. The recovery of otherwise wasted energy is the primary reason for the high efficiency of polygeneration systems. In this paper, the integration of a high-temperature heat pump within a trigeneration system is investigated. The heat pump uses the low-temperature heat from the condenser of the absorption chiller as heat source to produce hot water. A numerical model of the heat pump cycle is developed to evaluate the technical viability of current heat pump technology for this application and assess the performance of different working fluids. An exergy analysis is performed to show the advantages of the novel trigeneration system with respect to traditional systems for energy production. Moreover, a levelized cost of electricity method is applied to the proposed energy system to show its generic economic feasibility. Finally, actual energy demand data from an Italian pharmaceutical factory are considered to evaluate the economic savings obtainable with the integrated system, implemented in a case study. A two-level algorithm is proposed for the economic optimization of the investment. The synthesis/design problem is addressed by a genetic algorithm and the optimal operation problem is solved by a linear programming method. Results show that the integration of a high-temperature heat pump within a trigeneration system provides flexibility to cover variable energy demands and achieve valuable economic and energy performances, with global cost savings of around 40% with respect to separate production and around 10% with respect to traditional cogeneration and trigeneration systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•We developed a biomass gasification trigeneration plant model.•The model provides five configurations for heat, cold and electricity production.•The outputs for different types of biomass and ...operating conditions can be evaluated.•It is proved to be a useful tool for assessing the performance of trigeneration plants.
The present paper develops a simple but rigorous trigeneration plant model for designing, optimizing and simulating small–medium scale plants including a realistic biomass gasification model. The model provides five different configurations for the simultaneous production of heating, cooling and electricity. It includes modeled components as a gasifier, an internal combustion engine and different kinds of absorption chiller (single- and double-effect) modeled using the characteristic equation approach method. The model enables the outputs of the plant to be evaluated and calculated for different types of biomass, operating conditions and configurations. It has been applied in the case study of the ST-2 polygeneration plant to be built in Cerdanyola del Vallès (Barcelona, Spain). The results demonstrate that it is a useful tool for assessing the performance of trigeneration plants using several types of biomass and enables meaningful comparisons to be made between configurations for real applications.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This paper presents an overview of the absorption cycles proposed in the literature for producing combined power and cooling. The dual output nature of these cycles makes it difficult to evaluate ...their performance so the various criteria used in the literature are presented and discussed. A combined system that simultaneously produces power and cooling can adapt to the whole range of energy demand – from only power to only cooling – with intermediate operation modes producing different ratios of power and cooling. This type of cycle uses highly concentrated ammonia vapour in the expander which can be expanded to a very low temperature without condensation and uses an absorption–condensation process instead of the conventional condensation process. The main advantage of these configurations is that they enable low-grade heat such as solar energy or waste heat to be used. The most suitable combined power and cooling systems for applications characterised by small-to-medium power and cooling capacities seem to be those that are directly derived from high-performance absorption chiller cycles.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Treatment of wastewater in different industrial sectors is a growing great challenge for industry, local communities and governments. The objective of this paper is to review the current state of the ...art and commercially available solar evaporators for the treatment of agro-industry effluents in order to highlight the main technical barriers and solutions to improve its current implementation. The technology improvements are classified into the following groups: passive systems, active systems, modification of the waste characteristics and optimisation of the operation strategy. Passive systems increase the productivity from 10% to 104% improving the heat and mass transfer enhancing the energy efficiency. Active systems like Photovoltaics (PV) improve the productivity with extra heat addition like solar collectors or with energy addition like heat pumps. Active systems performance increase when combined with passive systems like pin fins and fibres that improve the heat transfer rates. A little note of similar commercial and research systems is presented.
•Solar evaporation for the treatment of liquid waste was reviewed.•Simulation, experimental test, commercially available systems, research projects demonstrators and patents are presented.•Evaporation enhancing techniques are divided into passive systems, active systems, pre-treatment and operation strategy.•Evaporation enhancing techniques from solar stills suitable for Advanced Solar Evaporators for liquid waste treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Combining heating and power systems represent an option to improve the efficiency of energy usage and to reduce thermal pollution toward environment. Microturbines generate electrical power and ...usable residual heat which can be partially used to activate a thermally driven chiller. The purpose of this paper is to analyze theoretically the thermodynamic performance of a trigeneration system formed by a microturbine and a double-effect water/LiBr absorption chiller.
The heat data supplied to the generator of the double effect air conditioning system was acquired from experimental data of a 28 kW
E microturbine, obtained at CREVER facilities. A thermodynamic simulator was developed at Centro de Investigación en Energía in the Universidad Nacional Autónoma de México by using a MATLAB programming language. Mass and energy balances of the main components of the cooling system were obtained with water–lithium bromide solution as working fluid. The trigeneration system was evaluated at different operating conditions: ambient temperatures, generation temperatures and microturbine fuel mass flow rate. The results demonstrated that this system represents an attractive technological alternative to use the energy from the microturbine exhaust gases for electric power generation, cooling and heating produced simultaneously.
► The thermodynamic performance of a trigeneration system is analyzed theoretically. ► A microturbine and a double-effect H
2O-LiBr absorption chiller integrate the system. ► The heat data supplied to generator was obtained from experimental data. ► The trigeneration system was evaluated at different operating conditions. ► Results show that this system is an attractive option to use exhaust energy for electricity, cooling and heating generation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A detailed parametric analysis is carried out on both simple and GAX based combined power and cooling cycle. The effect of various parameters such as heat source temperature, refrigeration ...temperature, sink temperature, split ratio (refrigerant flow ratio between power and cooling systems), split factor (solution flow ratio between absorber and GAX heat exchanger) on the performance of the cycle is studied. The results of the analysis show that using the GAX heat exchanger about 20% of internal heat is recovered within the cycle. The optimum split factor is 0.8–0.9 and the split ratio is 0.5:0.5. The maximum combined thermal efficiency of 35–45% and coefficient of performance of about 0.35 is attained at the optimum conditions.
► A GAX based combined power and cooling cycle has been simulated. ► 20% of the internal heat is recovered by the GAX heat exchangers. ► The optimum split factor and split ratio are 0.8–0.9 and 0.5:0.5 respectively. ► A maximum combined thermal efficiency of 35–45% has been obtained at the optimum conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Currently, the pyrolysis process is an important technology for the final treatment of plastic waste worldwide. For this reason, knowing in detail the chemical process and the thermodynamics that ...accompany cracking reactions is of utmost importance. The present study aims to determine the thermodynamic parameters of the degradation process of conventional thermoplastics (polystyrene (PS), polyethylene terephthalate (PET), high-density polyethylene (HDPE), polypropylene (PP) and polyvinyl chloride (PVC)) from the study of their chemical kinetics by thermogravimetric analysis (TG). Non-isothermal thermogravimetry was performed at three heating rates from room temperature to 550 °C with an inert nitrogen atmosphere with a flow of 20 mL min
. Once the TG data is obtained, an analysis is carried out with the isoconversional models of Friedman (FR), Kissinger-Akahira-Sunose (KAS), and Flynn-Wall-Ozawa (FWO) in order to determine the one that best fits the experimental data, and with this, the calculation of the activation energy and the pre-exponential factor is performed. The validation of the model was carried out using the correlation factor, determining that the KAS model is the one that best adjusts for the post-consumer thermoplastic degradation process at the three heating rates. With the use of the kinetic parameters, the variation of the Gibbs free energy is determined in each of the cases, where it is necessary that for structures containing aromatic groups a lower energy is presented, which implies a relative ease of degradation compared to the linear structures.
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•Cold recovery from cryogenic fuels regasification addressed in satellite terminals.•New configuration for boosting the efficiency of sub-zero refrigeration machines.•The system competitiveness ...improves for tropical climates and large plant sizes.•The system would reduce the electricity consumption and emissions up to 9–22%.•A reduction of 5–15% in the cost of refrigeration production would be achieved.
The regasification of liquefied natural gas releases low-temperature thermal energy, which is usually wasted. Most initiatives to recover this cold mainly focus on large-scale harbour terminals rather than on small-scale applications in satellite facilities. This paper proposes a new system configuration that can be used to exploit liquefied natural gas cold as a by-product of regasification in satellite plants supplying sub-zero refrigeration in agro-food industries. Cold is applied indirectly to lower the condensation temperature of the vapour-compression chillers which handle the thermal load of cold rooms. The system seeks to boost efficiency, an effect that would be more marked in warm climates. Performance is best when the peak refrigeration load matches the maximum cold thermal energy available from the regasification site. When this is the case, the annual electricity saving is 9–22% more than when a conventional refrigeration system is used with wet cooling towers and with no liquefied natural gas cold recovery. The economic potential of the system is assessed with a Monte Carlo analysis. The cost of producing refrigeration throughout the system’s lifetime can be reduced by 5–15% with respect to the conventional reference system in warm/temperate locations and for large/medium plant sizes. However, the system is no so competitive in economic terms for cold locations and small-size plants.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, SAZU, SBCE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ
The environmental pressure to reduce the use of fossil fuels such as gasoline generates the need to search for new fuels that have similar characteristics to conventional fuels. In this sense, the ...objective of the present study is the use of commercial gasoline in mixtures with pyrolytic oil from plastic waste and the addition of γ-Fe2O3 nanoparticles (NPs) in a spark ignition engine to analyze both the power generated in a real engine and the emissions resulting from the combustion process. The pyrolytic oil used was obtained from thermal pyrolysis at low temperatures (450 °C) of a mixture composed of 75% polystyrene (PS) and 25% polypropylene (PP), which was mixed with 87 octane commercial gasoline in 2% and 5% by volume and 40 mg of γ-Fe2O3 NPs. A standard sample was proposed, which was only gasoline, one mixture of gasoline with bio-oil, and a gasoline, bio-oil, and NPs mixture. The bio-oil produced from the pyrolysis of PS and PP enhances the octane number of the fuel and improves the engine’s power performance at low revolutions. In contrast, the addition of iron NPs significantly improves gaseous emissions with a reduction in emissions of CO (carbon monoxide), NOx (nitrogen oxide), and HCs (hydrocarbons) due to its advantages, which include its catalytic effect, presence of active oxygen, and its large surface area.
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