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Pyrolysis and combustion kinetic study and complementary study of ash fusibility behavior of sugarcane bagasse, sugarcane straw, and their pellets-case study of agro-industrial residues
(American Chemical Society, 2019-04-01) De Palma, Kelly Roberta; García Hernando, Néstor; Silva, Maria Aparecida; Tomaz, Edson; Soria Verdugo, Antonio
Pyrolysis and combustion kinetics of sugarcane bagasse and straw was analyzed using thermogravimetric measurements and applying the DAEM. The kinetic parameters of pyrolysis and combustion reactions were determined, obtaining pyrolysis activation energies of approximately 175 kJ/mol for bagasse and 200 kJ/mol for straw. The combustion activation energies ranged from 162.3 to 282.7 kJ/mol for bagasse and from 130.7 to 292.0 kJ/mol for the straw. The ash melting temperature of both sugarcane residues was also measured. The fluid temperature values found were 1396 and 1352 degrees C for bagasse and straw, respectively. The analyses were performed for raw material and milled pellets of sugarcane bagasse and straw, obtaining slightly lower values of the kinetic parameters for the milled pellets and negligible differences for the ash melting temperatures.
Validation of a biomass conversion mechanism by Eulerian modelling of a fixed-bed system under low primary air conditions
(Elsevier, 2023-10-01) Alvarez-Bermudez, Cesar; Anca Couce, Andres; Chapela, Sergio; Scharler, Robert; Buchmayr, Markus; Gomez, Miguel Angel; Porteiro, Jacobo
This work presents a three-dimensional Computational Fluid Dynamics study of a small-scale biomass combustion system operating with low primary air ratios. The Eulerian Biomass Thermal Conversion Model (EBiTCoM) was adapted to incorporate a pyrolysis mechanism based on the detailed Ranzi-Anca-Couce (RAC) scheme. Two scenarios were simulated using woodchips with 8% and 30% moisture content, and the results were validated against experimental data, including in-flame and bed measurements. The model accurately predicted bed temperature profiles and the influence of fuel moisture content on the pyrolysis and drying fronts, as well as on the distribution of volatiles and temperatures above the solid fuel bed. For the 8% moisture content case, the average gas temperature above the bed is approximately 700 degrees C, while for the 30% case, it drops to around 400 degrees C. The lower temperatures hinder the tar cracking reaction, resulting in a 25% higher tar content in the producer gas for the 30% moisture content fuel. The lower part of the bed consists of a thick layer of char undergoing reduction reactions, similar to that of an updraft gasifier. The developed model can accurately simulate biomass combustion systems with solid fuel beds consisting of numerous particles, while maintaining low computational requirements.
Extension of the layer particle model for volumetric conversion reactions during char gasification
(Elsevier, 2023-10-01) Steiner, Thomas; Schulze, Kai; Scharler, Robert; Anca Couce, Andres
The so-called 'layer model' or 'interface-based model' is a simplified single particle model, originally developed for shorter computation time during computational fluid dynamics (CFD) simulations. A reactive biomass particle is assumed to consist of successive layers, in which drying, pyrolysis and char conversion occur sequentially. The interfaces between these layers are the reaction fronts. The model has already been validated for drying, pyrolysis and char oxidation. Layer models in the literature have commonly employed surface reactions at the reaction front to describe char conversion. In this work, the suitability of this surface reaction concept is assessed when gasifying biochar. It is shown that a particular layer model, already available, which originally employed surface reactions, was unable to adequately describe the mass loss during gasification of a biochar. In order to overcome this incapability, the model was extended to consider volumetric reactions in the char layer. The influence of intraparticle diffusion was considered through an effectiveness factor. The model is easily adaptable for different gas-solid kinetic rate laws, while still allowing for comparably fast solutions of the model equations. The extended model was validated using theoretical calculations and experimental measurements from literature. It was demonstrated that intraparticle diffusion can significantly slow down the biochar gasification process. A general guideline for when to employ volumetric reactions, rather than surface reactions, and when to consider intraparticle diffusion is provided based on the Thiele modulus as the criterion.
Study of the effects of thermally thin and thermally thick particle approaches on the Eulerian modeling of a biomass combustor operating with wood chips
(Elsevier, 2023-10-15) Gomez, M.A.; Alvarez-Bermudez, C.; Chapela, S.; Anca Couce, Andres; Porteiro, J.; Ministerio de Economía y Competitividad (España)
Two particle treatments, thermally thin and thick, are applied to Eulerian combustion modeling for biomass packed beds and tested through the simulation of an experimental plant. The paper shows the efficiency of the Eulerian approach for large packed beds and tests the behavior of both particle treatments, tested with in-bed and flame temperatures and released volatiles measurements at different locations, which is not common in the literature for a full size boiler. Both approaches are implemented in a model with a comprehensive framework that includes several submodels for the thermal conversion kinetics, bed motion, heat and mass transfer with the gas phase, and gas flow and reaction. Two experiments are performed with wood chips fuels with different moisture contents. The simulations of the two cases result in reasonably good predictions for both particle treatments. The results are similar for higher moisture content and, for the low-moisture test, the bed temperature distribution and reaction fronts are slightly different due to the different predictions of the drying and devolatilization fronts. The volatile measurements show that the T. Thin model results in slightly more accurate predictions than the T. Thick, possibly because the wood chips have a more thermally thin behavior.
Carbon dioxide and acetone mixtures as refrigerants for industry heat pumps to supply temperature in the range 150-220 ºC
(Elsevier, 2023-04-15) Gómez Hernández, Jesús; R., Grimes; Villa Briongos, Javier; Marugán Cruz, Carolina; Santana Santana, Domingo José; Comunidad de Madrid
Industry decarbonization is a key a challenge towards the transition to climate neutrality. Indeed, there is a need to satisfy heat at temperatures higher than 150 °C in relevant industrial sectors by upgrading lower temperature heat flows, such as heat from renewable heat sources, ambient heat or industrial waste heat. High temperature heat pumps (HTHP) can upgrade such heat flows enabling great savings in carbon emissions. New refrigerants are needed to develop HTHPs achieving high performances at high temperatures. This paper proposes the use of a new zeotropic mixture composed of carbon dioxide and acetone as the refrigerant of HTHPs working in the temperature range of 150-220 °C. The new fluid is compared with existing pure refrigerants currently used. The thermodynamic characterization of the CO2/acetone mixtures shows temperature glides below 50 K for CO2 mass fractions up to 10%. The best HTHP performance is shown for the mixture 5% CO2/95% acetone in mass fraction. For instance, such a mixture obtains a COP of 5.63 when the target outlet sink temperature is 200 °C and the temperature difference between the outlet heat sink and the inlet heat source is 70 K, showing an improvement of 46% compared to pure acetone.
Flow and heat transfer analysis of a gas-particle fluidized dense suspension in a tube for CSP applications
(Elsevier, 2023-04-01) Córcoles, J. I.; Díaz-Heras, M.; Fernández Torrijos, María; Almendros Ibáñez, José Antonio; Agencia Estatal de Investigación (España); Ministerio de Ciencia e Innovación (España); Universidad de Castilla-La Mancha; Gobierno Regional de Castilla-La Mancha
This work presents a numerical study of the flow of particles in a gas–particle fluidized dense suspension for CSP applications using the Multi-Phase Particle in Cell (MP-PIC) method, implemented in CPFD-Barracuda software. The study covers two different numerical simulations. The first is a cold and isothermal model in which the fluctuations and control of the mass flow of particles ascending along the vertical tube was studied. In the second, a high-temperature boundary condition was imposed on the external surface of the tube and the energy equation was solved. In this second case, the heat transfer coefficient between the inner surface of the tube and the particles was numerically computed. The numerical results in the cold model are highly consistent with experimental data available in the literature (with values up to 150 kg/h and differences of approximately ±10 kg/h) and underline the significant impact of the pressure at the bottom of the bed and of the aeration flow rate on the mass flow of particles. The results of the non-isothermal case present heat transfer coefficients in the range of 300–400 W∕(m2 K) with transient fluctuations during the fluidization process. These fluctuations may be an influence on the mechanical damage of the tube, which is exposed to high levels of concentrated irradiation.
Thermo-economic optimization of a novel confined thermal energy storage system based on granular material
(Elsevier, 2023-04-01) Cano Pleite, Eduardo; Hernández Jiménez, Fernando; García Gutiérrez, Luis Miguel; Soria Verdugo, Antonio; European Commission; Agencia Estatal de Investigación (España)
Concentrated solar power is a suitable technology for production of green electricity. However, to attain a uniform electricity production, concentrated solar power should be coupled with large Thermal Energy Storage (TES) systems. Among the different technologies of TES systems, storage of sensible heat in granular material is widely used due to its simple operation. These TES systems store energy as an increase of temperature of a large mass of small solid particles, through which a fluid circulates exchanging heat. TES systems are typically operated in a fixed bed regime, maximizing their exergy output, thus limiting the maximum allowable velocity of the fluid flow. In this work, a novel confined bed is proposed to mechanically prevent the motion of the solid particles conforming the TES system even for high fluid velocities, to guarantee that the exhaust temperature of the fluid is maximum during a discharge process. In this novel confined bed, a thermocline evolves from bottom to top of the system, separating the low and high temperature of the bed during the discharge process. An analytical model was applied to describe the evolution of the thermocline and the effect of the different operating parameters on the thermocline thickness. The effect of the thermocline thickness was combined with a thermo-economic analysis of a confined bed TES system proposed for a case of study. The new confined bed here proposed was optimized considering thermodynamics aspects, namely the fluid exergy increment in the bed, and economic factors, specifically the total investment cost of the TES system. The optimization resulted in low values of the fluid velocity, between 0.2 and 0.4 m/s, but still higher than the minimum fluidization velocity of sand particles of 750 mum, justifying the requirement of a confined bed, and low bed aspect ratios, between 0.25 and 0.9, to prevent excessively high fluid pressure drops. However, the bed aspect ratio increases significantly for higher granular material particle sizes, up to a ratio of bed height to diameter of 3 for a particle size of 10 mm and a TES demand time of 6 h.
Influence of eccentricity on the thermomechanical performance of a bayonet tube of a central solar receiver
(Elsevier, 2023-03-25) Pérez Álvarez, Rafael; Marugán Cruz, Carolina; Santana Santana, Domingo José; Acosta Iborra, Antonio; Comunidad de Madrid; Ministerio de Economía y Competitividad (España); Universidad Carlos III de Madrid; Ministerio de Ciencia e Innovación (España); Agencia Estatal de Investigación (España)
This work numerically evaluates the thermal and mechanical behaviors of eccentric bayonet tubes to be used in external central receivers of solar power tower plants. A bayonet tube is composed of two tubes, one inside the other, creating circular and annular sections, through which the molten salt of the receiver sequentially flows. Eccentricity in the annular section is achieved by displacing the axis of the interior tube with regard to the exterior one. For comparative purposes, two examples of conventional tubes (single tubes with circular cross-sections with diameters of 25mm and 50mm) are also investigated in this work to compare their performances with those of bayonet tubes. The results obtained with the eccentric configurations show an enhancement of the heat transfer to the molten salt and a reduction of the tube wall overheating compared with the concentric bayonet tubes and the largest simple tube. For conditions representative of the normal operation of a solar power tower, eccentric bayonet tubes could reduce the pressure drop by 30.8% and increase the convective heat transfer achieved in a concentric configuration of the bayonet tube by 26.1%. Nevertheless, this pressure drop was considerably higher than those obtained in the smallest and largest simple tubes, which were 1.28 bar and 0.13 bar, respectively. To investigate whether the enhancement of the convection heat transfer experienced by bayonet tubes compensates for their higher pressure drop or not, a Performance Evaluation Criterion (PEC) was proposed and used to compare the global performance of bayonet tubes with that of conventional tubes. The bayonet tubes with eccentricity 0.45 obtained the largest PEC, which was up to 13% higher than reference conventional tubes. Enhancement of the tube wall refrigeration produced when increasing the eccentricity is reflected in the maximum tube temperature and thermal stresses, which are found to diminish by approximately 8.8% with the highest eccentricity. In addition, the largest eccentric bayonet tube layout obtains the smallest peak temperatures compared to conventional tubes. The lower inertial moment of the smallest conventional tube indicates that its thermal stress is 2.1% lower than the stress obtained in the most eccentric layout analyzed in this work. Nevertheless, the time to rupture associated with creep damage of the eccentric bayonet tube is 1.04 times higher than that obtained in the smallest simple tube, demonstrating that bayonet tubes could be a potential alternative to the current tubes of external tubular receivers.
Designing a flat beam-down linear Fresnel reflector
(Elsevier, 2022-03-01) Taramona Fernández, Sebastián; González Gómez, Pedro Ángel; Villa Briongos, Javier; Gómez Hernández, Jesús; Comunidad de Madrid; Universidad Carlos III de Madrid
A linear beam-down solar field consists of two reflections that concentrate the solar irradiation on heavy materials located on the ground. Several rows of linear Fresnel reflectors, which have the same width, aim the solar irradiation to a secondary mirror with a hyperbolic shape that redirects the solar concentration towards the ground receiver. This paper overcomes the main limitation of the previously proposed hyperbolic secondary reflector. A new secondary reflector composed by several fixed flat mirrors located at the same height is proposed. A model to calculate the optimal layout of this novel solar field, as well as the efficiency and concentration, is developed and validated against a Monte-Carlo Ray-Tracing software, obtaining relative errors lower than 15%. Two new dimensionless parameters are proposed to facilitate the design of the flat beam-down linear Fresnel reflector. The concentration, optical efficiency and receiver width can be easily obtained, without performing any simulation, as a function of the dimensionless parameters. This novel solar field can achieve concentration ratios of up to 31 and optical efficiencies of up to 60%, obtaining similar concentrations with better optical efficiency than a field using a hyperbolic reflector.
Non-conventional tube shapes for lifetime extend of solar external receivers
(Elsevier, 2022-03) Rodríguez Sánchez, María de los Reyes; Laporte Azcué, Marta; Montoya, Andrés; Hernández Jiménez, Fernando; Comunidad de Madrid; Ministerio de Ciencia e Innovación (España)
In this work, several novel tube shapes of solar tubular receivers that differ from the classical circular shape are analysed aiming to reduce the stresses of the receiver tubes, without penalizing its thermal efficiency. The analysis is performed using analytical thermal and mechanical models of the literature adapted for their use with non-circular tube shapes, verifying the assumptions made with FEM simulations due to the lack of experimental data available. Among the geometries studied, the results show that oval cross-section tubes improve the thermal efficiency of the receiver at the expense of increasing the stresses considerably. Ovoidal tubes show worse thermal and mechanical behaviour when the frontal part becomes peakier. Semicircle tubes reduce the stress by 10.9%, while keeping constant or even slightly improving the thermal performance. The last ones, increase the lifetime of the receiver and reduces the receiver costs if the manufacturing of the new geometries does no overpass 3.5 times the present price of production of the circular tubes. Therefore, the use of asymmetric cross-section tubes with low rear-front surface ratios, and smooth front surfaces can be considered a good alternative for substituting traditional circular cross-section tubes in central receivers.
Experimental determination of the convection heat transfer coefficient in an eccentric annular duct
(Elsevier, 2022-08-01) Serrano García, Daniel; Sánchez Delgado, Sergio; Pérez Álvarez, Rafael; Acosta Iborra, Antonio; Ministerio de Ciencia e Innovación (España); Agencia Estatal de Investigación (España)
The use of bayonet tube heat exchangers and heaters is widespread in many industrial applications and an improvement in the heat transfer coefficient may provide benefits over other technologies. This work presents novel experimental results about the turbulent convection heat transfer coefficient of air in the annular section of a bayonet tube for two different configurations: concentric and eccentric tubes. For both configurations, the convection heat transfer coefficient was obtained at different air flow rates, therefore, at different Reynolds numbers. In the case of the eccentric configuration, the angular position of the inner tube was varied to determine the circumferential distribution of the local convective heat transfer coefficient. An increase of the convection coefficient was observed for both configurations at higher Reynolds numbers. Concerning the angular position with regard the inner tube, the largest local convective heat transfer coefficient was obtained at the angular position where the distance between the inner and outer tubes was maximum, yielding a value 22.3% higher than in the case of a concentric annular section. All these experimental results were used to propose a new correlation for the local convective heat transfer coefficient as a function of the Prandtl and Reynolds numbers, the eccentricity, and the angular position of the inner tube, with a maximum discrepancy between correlation and experimental data below 10%.
Partitioning of a wide bubbling fluidized bed with vertical internals to improve local mixing and bed material circulation
(Elsevier, 2022-08-01) Soria Verdugo, Antonio; Cano Pleite, Eduardo; Panahi, Aidin; Ghoniem, Ahmed F.; European Commission; Ministerio de Educación, Cultura y Deporte (España); Universidad Carlos III de Madrid
Industrial scale fluidized bed reactors are characterized by limited mixing rates, either local or global, especially when using low-pressure drop gas distributors to reduce operational costs. In this work, partitioning of wide beds using vertical internals is proposed as an effective technique to improve local mixing in large reactors, i.e., mixing in specific zones of the bed. The effect of the vertical internals height on local solids mixing within partitions was experimentally evaluated in a pseudo-2D bed by analyzing the velocity and flow structure of the solids and the circulation time within individual partitions. In the presence of internals, global mixing, i.e., mixing between neighboring partitions and across the entire reactor, may be reduced as vertical internals compartmentalize the bed. Thus, the effect of the internals height on global mixing was also quantified while using bed materials with the same properties, but differing in color, in the different partitions, and analyzing the time evolution of the concentration of solids. Furthermore, the effect of internals on bubbles was also evaluated for different internal heights. It was found that internals with a height between the gulf-stream height and the fixed bed height promote the appearance of vortex pair structures in each partition of the wide bed. These structures substantially improve local mixing within each partition, while global mixing between partitions is practically unaffected by the presence of these short internals.
Impact of a mechanical attachment on the preheating temperatures of a central receiver tube
(Elsevier, 2022-10-01) Pérez Álvarez, Rafael; Cano Pleite, Eduardo; Santana Santana, Domingo José; Acosta Iborra, Antonio; European Commission; Ministerio de Ciencia e Innovación (España); Universidad Carlos III de Madrid
The receiver tubes of Solar Power Tower plants are typically attached through clips and sliding rods to the reradiating wall of the receiver in order to reduce the thermal deflection of the tubes. However, as a side effect, these mechanical attachments increase heat dissipation from the tube to the exterior and can reduce the local temperature of the tube during the receiver start-up, an operation performed every morning or after a severe drop of solar irradiation due to passing clouds. In the start-up operation, the empty tubes of molten salt receivers must be preheated with a careful aiming sequence of the heliostat field until their temperature is high enough to avoid the freezing of the incoming flow of the molten salt. This work numerically addresses for the first time the influence of the mechanical attachment on the preheating temperature of a receiver tube. To achieve this goal, a set of three-dimensional thermal fluid simulations of the temperature distribution in the tube and the mechanical attachment, described with different levels of detail, has been performed for the receiver of the Gemasolar Solar Power Tower plant. The results of this work show that the mechanical attachment locally affects the tube temperature, leading to a temperature overestimation above 25.1% when the tube is modeled without a mechanical attachment. In addition, the temperature measured separated from the attachment at the rear face of the tube to control the preheating sequence may not be very representative of the minimum tube temperature, which occurs in the internal face of tube just beneath the mechanical attachment. The results indicate that accumulation of heat not only by the clip but also by the guide and the rod of the mechanical attachment plays a significant role in the dissipation of heat from the tube to the attachment. This reveals the need of considering all the elements of the mechanical attachment if an accurate modeling of the preheat temperatures of the tube is needed. Besides, the use of a simplification in the modeling of the air and radiative heat transfer outside the tube reduces by a factor of 4.9 the computational cost involved in a full simulation of these transfer processes, with a temperature discrepancy between models below 14.3%. Finally, the effect of the size of the attachment clip on the minimum tube temperature is investigated, revealing that the minimum tube temperature of the preheated tube can decrease below the freezing temperature of the molten salt for clip heights larger than 170 mm.
Solar simulator based on induction heating to characterize experimentally tubular solar central receivers
(Elsevier, 2023-02-05) Rodríguez Sánchez, María de los Reyes; Pueyo Balsells, Albert; Montoya Sancha, Andrés; Artero Guerrero, José Alfonso; Comunidad de Madrid; Ministerio de Ciencia e Innovación (España)
Solar receiver tubes in solar power tower plants are subjected to non-homogeneous heat flux and temperature that produce early failure derived from the thermal stress. To reduce these problems, the thermomechanical characterization of the receiver is required. However, there are limitations in the data acquisition during operation due to the extreme working conditions, the different scale lengths, and the disturbance of the normal operation, being not possible to determine experimentally the thermomechanical behaviour of this device or to validate specific models developed. In this work an experimental facility able to reproduce the operation conditions of solar receivers has been designed and tested. To obtain the non-homogenous heat flux an induction heating system has been used. The facility has also been equipping of sensors and cameras that allow to measure the temperature distribution, the displacement and the strain field in a tube stretch. It is obtained a circumferential variation of the temperature of 160 °C, and a tube displacement due to the bending produced by the temperature gradient in combination to the mechanical boundary conditions of 2.251 mm. The data obtained with the cameras have been checked with the displacement and temperature sensors, obtaining maximum differences of 3 %, it means 5 °C and 0.05 mm. Thus, it is possible to derivate the tube displacement to obtain the hoop and axial strain field. These results are the first step for the thermomechanical characterization of tubes with non-homogeneous temperature profiles in the three directions. The proposed solar simulator will allow the validation and development of thermomechanical models able to reproduce the operation conditions of the receiver with the final goal of improving the receiver design and operation.
Effect of particle shape on biomass pyrolysis in a bubbling fluidized bed
(Elsevier, 2023-05-01) Soria Verdugo, Antonio; Cano Pleite, Eduardo; Passalacqua, Alberto; Fox, Rodney O.
The effect of biomass particle shape on the conversion of beech wood during pyrolysis in a bubbling fluidized bed (BFB) was experimentally quantified. A lab-scale BFB installed on a high-precision scale was used to characterize the mass loss of the biomass particles immersed in the bed. The scale could monitor the mass loss of the beech wood particles while moving freely inside the bed, which was operated at 2.5 times the minimum fluidization velocity of the bed material employed. The tests were performed at 500 and 600 °C using beech wood particles of the same mass, but different in shape. All particles used were cylindrical in shape, with the same mass, and differing in their aspect ratio, analyzing particles from typical biomass chips to standard biomass pellets. The experimental results indicate that the velocity of pyrolysis for the different particles is proportional to the characteristic heat transfer length of the particles, with pyrolysis times ranging from 27 to 53 s for a bed temperature of 600 °C and from 43 to 85 s for a bed temperature of 500 °C. The minimum pyrolysis time was obtained for particles with a diameter of 20 mm and a length of 2 mm pyrolyzing in a bed at 600 °C, whereas the maximum pyrolysis time corresponds to particles of 10 mm in diameter and 8 mm in length converting in a bed at 500 °C. Estimations of the conversion time obtained from a Shrinking Unreacted Particle Model (SUPM), assuming a constant density and reducing volume of biomass during conversion, and a Uniform Conversion Model (UCM), considering uniform volume and decreasing density of biomass along the conversion process, were compared to experimental measurements of the conversion time. Qualitative agreement was found between the experimental values and the predictions of the conversion time from the simplified models, obtaining in all cases conversion times proportional to the characteristic length of heat transfer of each particle shape.
Exergy and economic evaluation of a hybrid power plant coupling coal with solar energy
(MDPI, 2019-03-01) Serrano-Sánchez, Cristina; Olmeda-Delgado, Marina; Petrakopoulou, Foteini Konstantina; Ministerio de Ciencia, Innovación y Universidades (España)
Hybrid power plants that couple conventional with renewable energy are promising alternatives to electricity generation with low greenhouse gas emissions. Such plants aim to improve the operational stability of renewable power plants, while at the same time reducing the fuel consumption of conventional fossil fuel power plants. Here, we propose and evaluate the thermodynamic and economic viability of a hybrid plant under different operating conditions, applying exergy and economic analyses. The hybrid plant combines a coal plant with a solar-tower field. The plant is also compared with a conventional coal-fired plant of similar capacity. The results show that the proposed hybrid plant can emit 4.6% less pollutants due to the addition of solar energy. Fuel consumption can also be decreased by the same amount. The exergy efficiency of the hybrid power plant is found to be 35.8%, 1.6 percentage points higher than the efficiency of the conventional coal plant, and the total capital investment needed to build and operate a plant is 8050.32 $ /kW. This cost is higher than the necessary capital investment of 5979.69 $ /kW to build and operate a coal-fired power plant, and it is mainly due to the higher purchased equipment cost. Finally, the levelized cost of electricity of the hybrid plant is found to be 0.19 $/kWh (using both solar and coal resources) and 0.12 $/kWh when the plant is fueled only with coal.
A closer look at the environmental impact of solar and wind energy
(Wiley, 2022-08) Fernández Torres, Jaime; Petrakopoulou, Foteini Konstantina; Ministerio de Ciencia, Innovación y Universidades (España)
Moving towards a sustainable society implies constant improvement in the way energy is supplied and consumed, with wider implementation of solar and wind energy facilities in stand-alone or hybrid configurations. The goal of this work is to evaluate the lifecycle performance (construction and operation-related impact) of large-scale solar and wind energy systems and to compare it with conventional coal and natural gas fossil fuel plants under similar conditions. Environmental analyses of energy conversion systems today usually neglect the construction-related environmental impact of fossil fuel plants, because it is significantly smaller than the impact related to the operation of the plant. However, the construction of large-scale renewable plants implies the use of rare materials, transport-related emissions, and other environmentally impactful activities. The plants evaluated here are configured and compared for similar emissions and similar power output. It is found that the life-cycle environmental impact of the renewable plants could, in some specific cases, exceed that of the fossil fuel plants. Understanding the reasons behind this and the possible limitations of the different technologies can help plan for sustainable energy systems in the future. Finally, solutions to minimize the impact of renewable energy are proposed for more environmentally friendly implementation and future research.
Studying the reduction of water use in integrated solar combined-cycle plants
(MDPI, 2019-04-01) Petrakopoulou, Foteini Konstantina; Olmeda Delgado, Marina; Ministerio de Ciencia, Innovación y Universidades (España)
With vast amounts of water consumed for electricity generation and water scarcity predicted to rise in the near future, the necessity to evaluate water consumption in power plants arises. Cooling systems are the main source of water consumption in thermoelectric power plants, since water is a cooling fluid with relatively low cost and high efficiency. This study evaluates the performance of two types of power plants: a natural gas combined-cycle and an integrated solar combined-cycle. Special focus is made on the cooling system used in the plants and its characteristics, such as water consumption, related costs, and fuel requirements. Wet, dry, and hybrid cooling systems are studied for each of the power plants. While water is used as the cooling fluid to condense the steam in wet cooling, dry cooling uses air circulated by a fan. Hybrid cooling presents an alternative that combines both methods. We find that hybrid cooling has the highest investment costs as it bears the sum of the costs of both wet and dry cooling systems. However, this system produces considerable fuel savings when compared to dry cooling, and a 50% reduction in water consumption when compared to wet cooling. As expected, the wet cooling system has the highest exergetic efficiency, of 1 and 5 percentage points above that of dry cooling in the conventional combined-cycle and integrated solar combined-cycle, respectively, thus representing the lowest investment cost and highest water consumption among the three alternatives. Hybrid and dry cooling systems may be considered viable alternatives under increasing water costs, requiring better enforcement of the measures for sustainable water consumption in the energy sector.
Beam impact tests of a prototype target for the beam dump facility at CERN: Experimental setup and preliminary analysis of the online results
(American Physical Society, 2019-01-01) Cano Pleite, Eduardo
The beam dump facility (BDF) is a project for a new facility at CERN dedicated to high intensity beam dump and fixed target experiments. Currently in its design phase, the first aim of the facility is to search for light dark matter and hidden sector models with the Search for Hidden Particles (SHiP) experiment. At the core of the facility sits a dense target/dump, whose function is to absorb safely the 400 GeV/c Super Proton Synchrotron (SPS) beam and to maximize the production of charm and beauty mesons. An average power of 300 kW will be deposited on the target, which will be subjected to unprecedented conditions in terms of temperature, structural loads and irradiation. In order to provide a representative validation of the target design, a prototype target has been designed, manufactured, and tested under the SPS fixed-target proton beam during 2018, up to an average beam power of 50 kW, corresponding to 350 kJ per pulse. The present contribution details the target prototype design and experimental setup, as well as a first evaluation of the measurements performed during beam irradiation. The analysis of the collected data suggests that a representative reproduction of the operational conditions of the beam dump facility target was achieved during the prototype tests, which will be complemented by a postirradiation examination campaign during 2020. © 2019 authors. Published by the American Physical Society.
Exergoeconomic modeling and evaluation of a combined-cycle plant with MSF and MED desalination
(IWA, 2020-06-01) Khoshgoftar Manesh, M. H.; Kabiri, S.; Yazdi, M.; Petrakopoulou, Foteini Konstantina; Ministerio de Economía y Competitividad (España)
In the coming years, numerous regions are expected to suffer from water scarcity. One of the technologies of great interest in facing this challenge has been the generation of freshwater through water desalination, a process that reduces the amount of salt and minerals to a standard level, making the water suitable for drinking or agricultural/industrial use. The efficiency of each desalination process depends on the concentration of salts in the raw water and the end-use of the produced water. The present study presents the exergetic and exergoeconomic analyses of the coupling of a power plant with desalination units for the simultaneous generation of energy and water in Iran. The plant is integrated, first, with a multi-stage flash (MSF) unit and, then, with a multi-effect desalination (MED) unit. We find that the cost of exergy destruction of the MED and MSF integrated plants is lower when compared to the standalone power plant by about 0.1% and 9.2%, respectively. Lastly, the freshwater production in the plant using MED is significantly higher than that in the plant with MSF (1,000 versus 1,521 kg/s).

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