Miguel A Reyes-Belmonte | IMDEA (original) (raw)
Papers by Miguel A Reyes-Belmonte
Introduction: Work disability is a major consequence of rheumatoid arthritis (RA), associated not... more Introduction: Work disability is a major consequence of rheumatoid arthritis (RA), associated not only with traditional disease activity variables, but also more significantly with demographic, functional, occupational, and societal variables. Recent reports suggest that the use of biologic agents offers potential for reduced work disability rates, but the conclusions are based on surrogate disease activity measures derived from studies primarily from Western countries. Methods: The Quantitative Standard Monitoring of Patients with RA (QUEST-RA) multinational database of 8,039 patients in 86 sites in 32 countries, 16 with high gross domestic product (GDP) (>24K US dollars (USD) per capita) and 16 low-GDP countries (<11K USD), was analyzed for work and disability status at onset and over the course of RA and clinical status of patients who continued working or had stopped working in high-GDP versus low-GDP countries according to all RA Core Data Set measures. Associations of work disability status with RA Core Data Set variables and indices were analyzed using descriptive statistics and regression analyses. Results: At the time of first symptoms, 86% of men (range 57%-100% among countries) and 64% (19%-87%) of women <65 years were working. More than one third (37%) of these patients reported subsequent work disability because of RA. Among 1,756 patients whose symptoms had begun during the 2000s, the probabilities of continuing to work were 80% (95% confidence interval (CI) 78%-82%) at 2 years and 68% (95% CI 65%-71%) at 5 years, with similar patterns in high-GDP and low-GDP countries. Patients who continued working versus stopped working had significantly better clinical status for all clinical status measures and patient self-report scores, with similar patterns in high-GDP and low-GDP countries. However, patients who had stopped working in high-GDP countries had better clinical status than patients who continued working in low-GDP countries. The most significant identifier of work disability in all subgroups was Health Assessment Questionnaire (HAQ) functional disability score. Conclusions: Work disability rates remain high among people with RA during this millennium. In low-GDP countries, people remain working with high levels of disability and disease activity. Cultural and economic differences between societies affect work disability as an outcome measure for RA.
Sustainability
In this paper, a bibliometric analysis was performed in order to analyze the state of the art and... more In this paper, a bibliometric analysis was performed in order to analyze the state of the art and publication trends on the topic of ISCC (Integrated Solar Combined Cycles) for the period covering 1990 to July 2020. The Web of Science (WOS) database was consulted, and 1277 publications from 3157 different authors and 1102 different institutions, distributed among 78 countries, were retrieved as the corpus of the study. The VOSViewer software tool was used for the post-processing of the WOS corpus, and for the network data mapping. Multiple bibliometric indicators, such as the number of citations, keyword occurrences, the authors’ affiliations, and the authors, among others, were analysed in this paper in order to find the main research trends on the ISCC topic. The analysis performed in this paper concluded that the main publication source for ISCC research was Energy Conversion and Management, in terms of the total number of publications (158), but Solar Energy had the highest numb...
SOLARPACES 2019: International Conference on Concentrating Solar Power and Chemical Energy Systems
In this work, it is investigated about the application of an Integrated Solar Combined Cycle (ISC... more In this work, it is investigated about the application of an Integrated Solar Combined Cycle (ISCC) that uses particles as heat transfer fluid at the receiver and as the storage medium to provide flexible electricity dispatch without any supplementary gas burning. The paper investigates two cornerstones' of concentrating solar power technologies (CSP); i.e., the application of highly efficient power cycles and the ability to meet grid demand throughout flexible dispatch strategy. Using particles for the solar loop allows meeting both requirements at the same time. On the one hand, very high temperature can be achieved on the solar receiver which enables the use of highly-efficient power cycles according to thermodynamics second statement. On the other hand, particles ease for handling and storage makes them suitable for thermal storage at CSP applications which results into flexible electricity dispatch of the power block. Results shown in this paper prove the feasibility of flexible electricity dispatch of particles-based ISCC following real curve demand.
SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems
Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerge... more Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerged as the preferred commercial solution for solar thermal electricity in central receiver technology. Despite their ability to store large amounts of thermal energy and efficient receiver designs, further efficiency improvements are constrained by tight temperature restrictions when using molten salts (290 C e565 C). In this work, a novel heat transfer fluid based on a dense particle suspension (DPS) is used due to its excellent thermophysical properties that extend the operating temperature of solar receiver and allow its coupling with higher-efficiency power cycles. In this paper, the design of a DPS solar receiver working at 650 C has been optimized for two commercial sizes (50 MW th and 290 MW th) coupled to an optimized subcritical Rankine cycle. The results showed that a five-extraction reheated Rankine cycle operating at 610 C and 180 bar maximizes power plant efficiency when coupled with a DPS central receiver, giving 41% power block efficiency and 23% sun-to-electricity efficiency. For optimization purposes at design point conditions, in-house code programmed into MATLAB platform was used while TRNSYS software was employed for annual plant performance analysis.
In this paper, combined cycle (CC) power block parameters are optimized for its application coupl... more In this paper, combined cycle (CC) power block parameters are optimized for its application coupled to concentrating solar power (CSP) plant. CSP hybrid plant is based on pressurized air receiver technology using natural gas assisted burner while the CC power block consists on high temperature open air Brayton cycle connected to bottoming steam Rankine cycle. Due to plant layout flexibility introduced by CC arrangements, three preferred configurations will be analyzed and optimized based on the intermediate pressure levels of the bottoming cycle. Benefits and drawbacks of each configuration will be discussed along the paper and the optimum solution will be proposed as the reference power block for electricity production at Integrated Solar Combined Cycle (ISCC) power plants. Results demonstrate that using current solar air receiver technology the system efficiency is far (around 47%) from the one expected from modern commercial CC systems (nearly 60%). The lower power cycle efficiency found was mainly based on pressure restrictions
(below 6 bar) imposed by current air receiver designs what also implied lower temperature for the gas turbine.
In this paper, particles-based thermal energy storage (TES) system for concentrated solar power (... more In this paper, particles-based thermal energy storage (TES) system for concentrated solar power (CSP) is presented and applied to different CSP plant-layout scenarios. The key-component of this system is the fluidized-bed heat exchanger (DPS-HX) that is used for coupling particles-based storage system to the solar loop and to the power block. Mathematical model is used for the design and thermal performance analysis of the heat exchanger coupled to subcritical and supercritical Rankine steam cycles for small and commercial plant sizes. Among the benefits of particles-based thermal energy storage it can be pointed out no temperature restrictions with no freezing nor temperature degradation, ease of handling and no toxicity. It has been found that particles heat exchanger operates at high efficiency (from 91% to 99% for most of cases) and that power consumption for fluidization purposes are negligible compared to thermal power transferred to the work transfer fluid. For large power plant size, it is preferred distributing particles among different heat exchangers connected in parallel instead of passing whole particles and work transfer fluid through just one heat exchanger component.
In this work, mathematical model of molten carbonates electrolyzer (MCEC) has been developed for ... more In this work, mathematical model of molten carbonates electrolyzer (MCEC) has been developed for its integration into concentrating solar power (CSP) plant. MCEC modeling has been based on electrochemical and thermodynamics approach using experimental information from a testing device. Despite the high temperature requirements for MCEC operation (above 500 º C), heat generation during the electrolysis process reduces the requirement of external heat addition. Energy optimization approach using ASPEN HYSYS pointed out that MCEC stable operation could be achieved for a wide temperature range of the feeding steam by using smart heat recovery diagram. Temperature conditions that are covering from exothermal to thermoneutral working conditions have been explored depending on the input thermal and electrical requirements. MCEC model described in this work has been encoded into TRNSYS platform for transient performance evaluation. Optimal integration scheme of MCEC coupled to linear-Fresnel solar plant has been proposed and sized for the hydrogen production of a refueling station.
Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerge... more Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerged as the preferred commercial solution for solar thermal electricity in central receiver technology. Despite their ability to store large amounts of thermal energy and efficient receiver designs, further efficiency improvements are constrained by tight temperature restrictions when using molten salts (290 C e565 C). In this work, a novel heat transfer fluid based on a dense particle suspension (DPS) is used due to its excellent thermophysical properties that extend the operating temperature of solar receiver and allow its coupling with higher-efficiency power cycles. In this paper, the design of a DPS solar receiver working at 650 C has been optimized for two commercial sizes (50 MW th and 290 MW th ) coupled to an optimized subcritical Rankine cycle. The results showed that a five-extraction reheated Rankine cycle operating at 610 C and 180 bar maximizes power plant efficiency when coupled with a DPS central receiver, giving 41% power block efficiency and 23% sun-to-electricity efficiency. For optimization purposes at design point conditions, in-house code programmed into MATLAB platform was used while TRNSYS software was employed for annual plant performance analysis.
Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critic... more Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critical condition (stated as supercritical CO 2 or sCO 2) have attracted the attention of many researchers. Its excellent thermophysical properties at medium-to-moderate temperature range have made it to be considered as the alternative working fluid for next power plant generation. Among those applications, future nuclear reactors, solar concentrated thermal energy or waste energy recovery have been shown as the most promising ones. In this paper, a recompression sCO 2 cycle for a solar central particles receiver application has been optimized, observing net cycle efficiency close to 50%. However, small changes on cycle parameters such as working temperatures, recuperators efficiencies or mass flow distribution between low and high temperature recuperators were found to drastically modify system overall efficiency. In order to mitigate these uncertainties, an optimization analysis based on recuperators effectiveness definition was performed observing that cycle efficiency could lie among 40%e50% for medium-to-moderate temperature range of the studied application (630 Ce680 C). Due to the lack of maturity of current sCO 2 technologies and no power production scale demonstrators, cycle boundary conditions based on the solar application and a detailed literature review were chosen.
The potential of using different thermodynamic cycles coupled to a solar tower central receiver t... more The potential of using different thermodynamic cycles coupled to a solar tower central receiver that uses a novel heat transfer fluid is analyzed. The new fluid, named as DPS, is a dense suspension of solid particles aerated through a tubular receiver used to convert concentrated solar energy into thermal power. This novel fluid allows reaching high temperatures at the solar receiver what opens a wide range of possibilities for power cycle selection. This work has been focused into the assessment of power plant performance using conventional, but optimized cycles but also novel thermodynamic concepts. Cases studied are ranging from subcritical steam Rankine cycle; open regenerative Brayton air configurations at medium and high temperature; combined cycle; closed regenerative Brayton helium scheme and closed recompression supercritical carbon dioxide Brayton cycle. Power cycle diagrams and working conditions for design point are compared amongst the studied cases for a common reference thermal power of 57 MWth reaching the central cavity receiver. It has been found that Brayton air cycle working at high temperature or using supercritical carbon dioxide are the most promising solutions in terms of efficiency conversion for the power block of future generation by means of concentrated solar power plants.
Solar tower aided coal-fired power generation system (STCG) is able to provide high solar utiliza... more Solar tower aided coal-fired power generation system (STCG) is able to provide high solar utilization efficiency with low coal consumption rate. This paper compares performances of a solar tower aided coal-fired power plant, a solar tower power plant and a coal-fired power plant under different operative conditions. The comparison includes various solar multiple and thermal energy storage size. According to solar radiation resource and grid power dispatching demand, STCG, solar tower power generation system (STG) and coal-fired power generation system (CPG) work under off-design conditions all the year around. Results show that STCG has higher solar utilization efficiency than STG and lower coal consumption rate and CO 2 emission rate than CPG. In addition, solar-to-electricity exergy efficiency of STCG is at least 1.83% higher than that of STG. Compared to CPG, the 1000 MWe STCG can reduce coal consumption by 2.0 Â 10 5 t/y, with the saving ratio being 10.4%. The annual average coal consumption rate of STCG is 27.3 g/kWh lower than that of CPG. In addition, the annual average CO 2 emission rate of STCG is reduced by 10.1% compared with that of CPG. Solar tower aided coal-fired power generation can facilitate energy conservation and emission reduction of STG and CPG.
In this paper, a detailed thermodynamic model for a heat exchanger (HX) working with a dense part... more In this paper, a detailed thermodynamic model for a heat exchanger (HX) working with a dense particle
suspension (DPS) as heat transfer fluid (HTF) in the solar loop and water-steam as working fluid is presented. HX modelling is based on fluidized bed (FB) technology and its design has been conceived to couple solar plant using DPS as HTF and storage media with Rankine cycle for power generation. Using DPS as heat transfer fluid allows extending operating temperature range what will help to reduce thermal energy storage costs favoring higher energy densities but will also allow running power cycle at higher temperature what will increase its efficiency. Besides HX modelling description, this model will be used to reproduce solar plant performance under steady state and transient conditions.
The potential of using different thermodynamic cycles coupled to a solar tower central receiver t... more The potential of using different thermodynamic cycles coupled to a solar tower central receiver that uses a
novel heat transfer fluid is analyzed. The new fluid, named as DPS, is a dense suspension of solid particles aerated through a tubular receiver used to convert concentrated solar energy into thermal power. This novel fluid allows reaching high temperatures at the solar receiver what opens a wide range of possibilities for power cycle selection. This work has been focused into the assessment of power plant performance using conventional, but optimized cycles but also novel
thermodynamic concepts. Cases studied are ranging from subcritical steam Rankine cycle; open regenerative Brayton air configurations at medium and high temperature; combined cycle; closed regenerative Brayton helium scheme and closed recompression supercritical carbon dioxide Brayton cycle. Power cycle diagrams and working conditions for design point
are compared amongst the studied cases for a common reference thermal power of 57 MWth reaching the central cavity receiver. It has been found that Brayton air cycle working at high temperature or using supercritical carbon dioxide are the most promising solutions in terms of efficiency conversion for the power block of future generation by means of
concentrated solar power plants.
Polymethylmethacrylate (PMMA) plastic fiber has been used in daylighting system for a long time, ... more Polymethylmethacrylate (PMMA) plastic fiber has been used in daylighting system for a long time, however, the quantitative study of its optical properties is still limited. It has been verified in this paper that shortpass dichroic mirror (SDM) can effectively filter out up to 64% of infrared ray from high flux, resulting in small losses of visible spectrum of natural light. Experiments confirmed as well that SDM can significantly reduce infrared thermal effects effectively protecting PMMA plastic fiber. In addition, the effect of incidence angle on the attenuation of fiber is also measured. It has been proven that attenuation rate increases with the incident angle. Experimental data presented here can be used for daylighting system optimization using PMMA fibers.
Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critic... more Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critical condition (stated as supercritical CO 2 or sCO 2) have attracted the attention of many researchers. Its excellent thermophysical properties at medium-to-moderate temperature range have made it to be considered as the alternative working fluid for next power plant generation. Among those applications, future nuclear reactors, solar concentrated thermal energy or waste energy recovery have been shown as the most promising ones. In this paper, a recompression sCO 2 cycle for a solar central particles receiver application has been optimized, observing net cycle efficiency close to 50%. However, small changes on cycle parameters such as working temperatures, recuperators efficiencies or mass flow distribution between low and high temperature recuperators were found to drastically modify system overall efficiency. In order to mitigate these uncertainties, an optimization analysis based on recuperators effectiveness definition was performed observing that cycle efficiency could lie among 40%e50% for medium-to-moderate temperature range of the studied application (630 Ce680 C). Due to the lack of maturity of current sCO 2 technologies and no power production scale demonstrators, cycle boundary conditions based on the solar application and a detailed literature review were chosen.
Nowadays turbocharging the internal combustion engine has become an essential tool in the automot... more Nowadays turbocharging the internal combustion engine has become an essential tool in the automotive industry to meet downsizing technique requirements. In that context turbocharger unsteadiness is huge since both turbine and compressor work under high pulsating flow conditions, being turbocharger behavior prediction more difficult but still key for matching and predicting ICE performance. The well understanding and modeling of the occurring physical phenomena during turbocharger unsteady and off-design operation seems crucial.
An acoustic one-dimensional compressor model has been developed. This model is based on compresso... more An acoustic one-dimensional compressor model has been developed. This model is based on compressor map information and it is able to predict how the pressure waves are transmitted and reflected by the compressor. This is later on necessary to predict radiated noise at the intake orifice. The fluid-dynamic behavior of the compressor has been reproduced by simplifying the real geometry in zero-dimensional and one-dimensional elements with acoustic purposes. These elements are responsible for attenuating or reflecting the pressure pulses generated by the engine. In order to compensate the effect of these elements in the mean flow variables, the model uses a corrected compressor map. Despite of the fact that the compressor model was developed originally as a part of the OpenWAM™ software, it can be exported to other commercial wave action models. An example is provided of exporting the described model to GT-Power™. The model has been validated using experimental results obtained in a turbocharger test bench under pulsating flow conditions. The characteristics of the pressure waves (amplitude, frequency and mean flow) are similar to those of the pulses that the compressor undergoes when working coupled to a reciprocating internal combustion engine. This facility allows wave decomposition upstream and downstream of the compressor. The experimental pressure waves have been compared versus the results provided by the model analyzing both in frequency domain and in time domain in the two codes used to host the model. Finally, a comparison between the proposed 1D-0D model, which furthermore applies the compressor map, and the standard methodology used by GT-Power™, which directly only interpolates in the compressor map, has been performed. Results show better performance in the case of the proposed model and evidence the interest for the compressor geometrical description.
Solution of governing equations for one-dimensional compressible unsteady flow has been performed... more Solution of governing equations for one-dimensional compressible unsteady flow has been performed traditionally using a homogenously distributed spatial mesh. In the resulting node structure, the internal nodes are solved by applying a shock capturing finite difference numerical method whereas the solution of the end nodes, which define the boundary conditions of the pipe, is undertaken by means of the Method of Characteristics. Besides the independent solution of every method, the coupling between the information obtained by the method of characteristics and the finite difference method is key in order to reach a good accuracy in gas dynamics modeling. The classical spatial mesh could provide numerical problems leading the boundary to generate lack of mass, momentum and energy conservation because of the interpolation methodology usually applied to draw the characteristics and path lines from its departure point at calculation time to the end of the pipe during the next time-step. To deal with this undesirable behavior, in this work a modification of the traditional grid including an extra node close to the boundary is proposed in order to explore its ability to provide numerical results with higher conservation fulfillment.
In the present paper, an unsteady approach to determine the performance of a small radial inflow ... more In the present paper, an unsteady approach to determine the performance of a small radial inflow turbine working under cold pulsating flow is presented. It has been concluded that a reasonably good characterization of turbine behavior working with pulsating flow can be obtained using, in a quasi-steady way, models of the turbine isentropic efficiency and turbo-charger mechanical efficiency. Both models have been fitted using data obtained from a steady flow characterization procedure. Turbocharger-measured parameters from the cold pulsating flow campaign have been compared with the ones obtained from one-dimensional gas dynamics computational modeling. The modeling approach is based on quasi-steady isentropic and mechanical efficiency models. Reasonably good accuracy in compressor and turbine variables prediction has been obtained for most of the operative conditions. Influence of amplitude and frequency of the pulsating flow over the instantaneous and average turbine efficiency has been studied to put some light on the analysis of the involved physical phenomena. The main conclusion is that the biggest effect of unsteady flow on turbine efficiency is through the influence on blade jet to speed ratio. It has been also concluded that, for the same average blade jet to speed ratio, pulses' amplitude does not influence turbine efficiency when it is closed, but does at other variable geometry turbine (VGT) positions. The effect of pulses' frequency is less evident and only influences VGT performance at the highest VGT openings.
Introduction: Work disability is a major consequence of rheumatoid arthritis (RA), associated not... more Introduction: Work disability is a major consequence of rheumatoid arthritis (RA), associated not only with traditional disease activity variables, but also more significantly with demographic, functional, occupational, and societal variables. Recent reports suggest that the use of biologic agents offers potential for reduced work disability rates, but the conclusions are based on surrogate disease activity measures derived from studies primarily from Western countries. Methods: The Quantitative Standard Monitoring of Patients with RA (QUEST-RA) multinational database of 8,039 patients in 86 sites in 32 countries, 16 with high gross domestic product (GDP) (>24K US dollars (USD) per capita) and 16 low-GDP countries (<11K USD), was analyzed for work and disability status at onset and over the course of RA and clinical status of patients who continued working or had stopped working in high-GDP versus low-GDP countries according to all RA Core Data Set measures. Associations of work disability status with RA Core Data Set variables and indices were analyzed using descriptive statistics and regression analyses. Results: At the time of first symptoms, 86% of men (range 57%-100% among countries) and 64% (19%-87%) of women <65 years were working. More than one third (37%) of these patients reported subsequent work disability because of RA. Among 1,756 patients whose symptoms had begun during the 2000s, the probabilities of continuing to work were 80% (95% confidence interval (CI) 78%-82%) at 2 years and 68% (95% CI 65%-71%) at 5 years, with similar patterns in high-GDP and low-GDP countries. Patients who continued working versus stopped working had significantly better clinical status for all clinical status measures and patient self-report scores, with similar patterns in high-GDP and low-GDP countries. However, patients who had stopped working in high-GDP countries had better clinical status than patients who continued working in low-GDP countries. The most significant identifier of work disability in all subgroups was Health Assessment Questionnaire (HAQ) functional disability score. Conclusions: Work disability rates remain high among people with RA during this millennium. In low-GDP countries, people remain working with high levels of disability and disease activity. Cultural and economic differences between societies affect work disability as an outcome measure for RA.
Sustainability
In this paper, a bibliometric analysis was performed in order to analyze the state of the art and... more In this paper, a bibliometric analysis was performed in order to analyze the state of the art and publication trends on the topic of ISCC (Integrated Solar Combined Cycles) for the period covering 1990 to July 2020. The Web of Science (WOS) database was consulted, and 1277 publications from 3157 different authors and 1102 different institutions, distributed among 78 countries, were retrieved as the corpus of the study. The VOSViewer software tool was used for the post-processing of the WOS corpus, and for the network data mapping. Multiple bibliometric indicators, such as the number of citations, keyword occurrences, the authors’ affiliations, and the authors, among others, were analysed in this paper in order to find the main research trends on the ISCC topic. The analysis performed in this paper concluded that the main publication source for ISCC research was Energy Conversion and Management, in terms of the total number of publications (158), but Solar Energy had the highest numb...
SOLARPACES 2019: International Conference on Concentrating Solar Power and Chemical Energy Systems
In this work, it is investigated about the application of an Integrated Solar Combined Cycle (ISC... more In this work, it is investigated about the application of an Integrated Solar Combined Cycle (ISCC) that uses particles as heat transfer fluid at the receiver and as the storage medium to provide flexible electricity dispatch without any supplementary gas burning. The paper investigates two cornerstones' of concentrating solar power technologies (CSP); i.e., the application of highly efficient power cycles and the ability to meet grid demand throughout flexible dispatch strategy. Using particles for the solar loop allows meeting both requirements at the same time. On the one hand, very high temperature can be achieved on the solar receiver which enables the use of highly-efficient power cycles according to thermodynamics second statement. On the other hand, particles ease for handling and storage makes them suitable for thermal storage at CSP applications which results into flexible electricity dispatch of the power block. Results shown in this paper prove the feasibility of flexible electricity dispatch of particles-based ISCC following real curve demand.
SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems
Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerge... more Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerged as the preferred commercial solution for solar thermal electricity in central receiver technology. Despite their ability to store large amounts of thermal energy and efficient receiver designs, further efficiency improvements are constrained by tight temperature restrictions when using molten salts (290 C e565 C). In this work, a novel heat transfer fluid based on a dense particle suspension (DPS) is used due to its excellent thermophysical properties that extend the operating temperature of solar receiver and allow its coupling with higher-efficiency power cycles. In this paper, the design of a DPS solar receiver working at 650 C has been optimized for two commercial sizes (50 MW th and 290 MW th) coupled to an optimized subcritical Rankine cycle. The results showed that a five-extraction reheated Rankine cycle operating at 610 C and 180 bar maximizes power plant efficiency when coupled with a DPS central receiver, giving 41% power block efficiency and 23% sun-to-electricity efficiency. For optimization purposes at design point conditions, in-house code programmed into MATLAB platform was used while TRNSYS software was employed for annual plant performance analysis.
In this paper, combined cycle (CC) power block parameters are optimized for its application coupl... more In this paper, combined cycle (CC) power block parameters are optimized for its application coupled to concentrating solar power (CSP) plant. CSP hybrid plant is based on pressurized air receiver technology using natural gas assisted burner while the CC power block consists on high temperature open air Brayton cycle connected to bottoming steam Rankine cycle. Due to plant layout flexibility introduced by CC arrangements, three preferred configurations will be analyzed and optimized based on the intermediate pressure levels of the bottoming cycle. Benefits and drawbacks of each configuration will be discussed along the paper and the optimum solution will be proposed as the reference power block for electricity production at Integrated Solar Combined Cycle (ISCC) power plants. Results demonstrate that using current solar air receiver technology the system efficiency is far (around 47%) from the one expected from modern commercial CC systems (nearly 60%). The lower power cycle efficiency found was mainly based on pressure restrictions
(below 6 bar) imposed by current air receiver designs what also implied lower temperature for the gas turbine.
In this paper, particles-based thermal energy storage (TES) system for concentrated solar power (... more In this paper, particles-based thermal energy storage (TES) system for concentrated solar power (CSP) is presented and applied to different CSP plant-layout scenarios. The key-component of this system is the fluidized-bed heat exchanger (DPS-HX) that is used for coupling particles-based storage system to the solar loop and to the power block. Mathematical model is used for the design and thermal performance analysis of the heat exchanger coupled to subcritical and supercritical Rankine steam cycles for small and commercial plant sizes. Among the benefits of particles-based thermal energy storage it can be pointed out no temperature restrictions with no freezing nor temperature degradation, ease of handling and no toxicity. It has been found that particles heat exchanger operates at high efficiency (from 91% to 99% for most of cases) and that power consumption for fluidization purposes are negligible compared to thermal power transferred to the work transfer fluid. For large power plant size, it is preferred distributing particles among different heat exchangers connected in parallel instead of passing whole particles and work transfer fluid through just one heat exchanger component.
In this work, mathematical model of molten carbonates electrolyzer (MCEC) has been developed for ... more In this work, mathematical model of molten carbonates electrolyzer (MCEC) has been developed for its integration into concentrating solar power (CSP) plant. MCEC modeling has been based on electrochemical and thermodynamics approach using experimental information from a testing device. Despite the high temperature requirements for MCEC operation (above 500 º C), heat generation during the electrolysis process reduces the requirement of external heat addition. Energy optimization approach using ASPEN HYSYS pointed out that MCEC stable operation could be achieved for a wide temperature range of the feeding steam by using smart heat recovery diagram. Temperature conditions that are covering from exothermal to thermoneutral working conditions have been explored depending on the input thermal and electrical requirements. MCEC model described in this work has been encoded into TRNSYS platform for transient performance evaluation. Optimal integration scheme of MCEC coupled to linear-Fresnel solar plant has been proposed and sized for the hydrogen production of a refueling station.
Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerge... more Concentrated solar power plants using molten salts as heat transfer and storage fluid have emerged as the preferred commercial solution for solar thermal electricity in central receiver technology. Despite their ability to store large amounts of thermal energy and efficient receiver designs, further efficiency improvements are constrained by tight temperature restrictions when using molten salts (290 C e565 C). In this work, a novel heat transfer fluid based on a dense particle suspension (DPS) is used due to its excellent thermophysical properties that extend the operating temperature of solar receiver and allow its coupling with higher-efficiency power cycles. In this paper, the design of a DPS solar receiver working at 650 C has been optimized for two commercial sizes (50 MW th and 290 MW th ) coupled to an optimized subcritical Rankine cycle. The results showed that a five-extraction reheated Rankine cycle operating at 610 C and 180 bar maximizes power plant efficiency when coupled with a DPS central receiver, giving 41% power block efficiency and 23% sun-to-electricity efficiency. For optimization purposes at design point conditions, in-house code programmed into MATLAB platform was used while TRNSYS software was employed for annual plant performance analysis.
Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critic... more Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critical condition (stated as supercritical CO 2 or sCO 2) have attracted the attention of many researchers. Its excellent thermophysical properties at medium-to-moderate temperature range have made it to be considered as the alternative working fluid for next power plant generation. Among those applications, future nuclear reactors, solar concentrated thermal energy or waste energy recovery have been shown as the most promising ones. In this paper, a recompression sCO 2 cycle for a solar central particles receiver application has been optimized, observing net cycle efficiency close to 50%. However, small changes on cycle parameters such as working temperatures, recuperators efficiencies or mass flow distribution between low and high temperature recuperators were found to drastically modify system overall efficiency. In order to mitigate these uncertainties, an optimization analysis based on recuperators effectiveness definition was performed observing that cycle efficiency could lie among 40%e50% for medium-to-moderate temperature range of the studied application (630 Ce680 C). Due to the lack of maturity of current sCO 2 technologies and no power production scale demonstrators, cycle boundary conditions based on the solar application and a detailed literature review were chosen.
The potential of using different thermodynamic cycles coupled to a solar tower central receiver t... more The potential of using different thermodynamic cycles coupled to a solar tower central receiver that uses a novel heat transfer fluid is analyzed. The new fluid, named as DPS, is a dense suspension of solid particles aerated through a tubular receiver used to convert concentrated solar energy into thermal power. This novel fluid allows reaching high temperatures at the solar receiver what opens a wide range of possibilities for power cycle selection. This work has been focused into the assessment of power plant performance using conventional, but optimized cycles but also novel thermodynamic concepts. Cases studied are ranging from subcritical steam Rankine cycle; open regenerative Brayton air configurations at medium and high temperature; combined cycle; closed regenerative Brayton helium scheme and closed recompression supercritical carbon dioxide Brayton cycle. Power cycle diagrams and working conditions for design point are compared amongst the studied cases for a common reference thermal power of 57 MWth reaching the central cavity receiver. It has been found that Brayton air cycle working at high temperature or using supercritical carbon dioxide are the most promising solutions in terms of efficiency conversion for the power block of future generation by means of concentrated solar power plants.
Solar tower aided coal-fired power generation system (STCG) is able to provide high solar utiliza... more Solar tower aided coal-fired power generation system (STCG) is able to provide high solar utilization efficiency with low coal consumption rate. This paper compares performances of a solar tower aided coal-fired power plant, a solar tower power plant and a coal-fired power plant under different operative conditions. The comparison includes various solar multiple and thermal energy storage size. According to solar radiation resource and grid power dispatching demand, STCG, solar tower power generation system (STG) and coal-fired power generation system (CPG) work under off-design conditions all the year around. Results show that STCG has higher solar utilization efficiency than STG and lower coal consumption rate and CO 2 emission rate than CPG. In addition, solar-to-electricity exergy efficiency of STCG is at least 1.83% higher than that of STG. Compared to CPG, the 1000 MWe STCG can reduce coal consumption by 2.0 Â 10 5 t/y, with the saving ratio being 10.4%. The annual average coal consumption rate of STCG is 27.3 g/kWh lower than that of CPG. In addition, the annual average CO 2 emission rate of STCG is reduced by 10.1% compared with that of CPG. Solar tower aided coal-fired power generation can facilitate energy conservation and emission reduction of STG and CPG.
In this paper, a detailed thermodynamic model for a heat exchanger (HX) working with a dense part... more In this paper, a detailed thermodynamic model for a heat exchanger (HX) working with a dense particle
suspension (DPS) as heat transfer fluid (HTF) in the solar loop and water-steam as working fluid is presented. HX modelling is based on fluidized bed (FB) technology and its design has been conceived to couple solar plant using DPS as HTF and storage media with Rankine cycle for power generation. Using DPS as heat transfer fluid allows extending operating temperature range what will help to reduce thermal energy storage costs favoring higher energy densities but will also allow running power cycle at higher temperature what will increase its efficiency. Besides HX modelling description, this model will be used to reproduce solar plant performance under steady state and transient conditions.
The potential of using different thermodynamic cycles coupled to a solar tower central receiver t... more The potential of using different thermodynamic cycles coupled to a solar tower central receiver that uses a
novel heat transfer fluid is analyzed. The new fluid, named as DPS, is a dense suspension of solid particles aerated through a tubular receiver used to convert concentrated solar energy into thermal power. This novel fluid allows reaching high temperatures at the solar receiver what opens a wide range of possibilities for power cycle selection. This work has been focused into the assessment of power plant performance using conventional, but optimized cycles but also novel
thermodynamic concepts. Cases studied are ranging from subcritical steam Rankine cycle; open regenerative Brayton air configurations at medium and high temperature; combined cycle; closed regenerative Brayton helium scheme and closed recompression supercritical carbon dioxide Brayton cycle. Power cycle diagrams and working conditions for design point
are compared amongst the studied cases for a common reference thermal power of 57 MWth reaching the central cavity receiver. It has been found that Brayton air cycle working at high temperature or using supercritical carbon dioxide are the most promising solutions in terms of efficiency conversion for the power block of future generation by means of
concentrated solar power plants.
Polymethylmethacrylate (PMMA) plastic fiber has been used in daylighting system for a long time, ... more Polymethylmethacrylate (PMMA) plastic fiber has been used in daylighting system for a long time, however, the quantitative study of its optical properties is still limited. It has been verified in this paper that shortpass dichroic mirror (SDM) can effectively filter out up to 64% of infrared ray from high flux, resulting in small losses of visible spectrum of natural light. Experiments confirmed as well that SDM can significantly reduce infrared thermal effects effectively protecting PMMA plastic fiber. In addition, the effect of incidence angle on the attenuation of fiber is also measured. It has been proven that attenuation rate increases with the incident angle. Experimental data presented here can be used for daylighting system optimization using PMMA fibers.
Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critic... more Peculiar thermodynamic properties of carbon dioxide (CO 2) when it is held at or above its critical condition (stated as supercritical CO 2 or sCO 2) have attracted the attention of many researchers. Its excellent thermophysical properties at medium-to-moderate temperature range have made it to be considered as the alternative working fluid for next power plant generation. Among those applications, future nuclear reactors, solar concentrated thermal energy or waste energy recovery have been shown as the most promising ones. In this paper, a recompression sCO 2 cycle for a solar central particles receiver application has been optimized, observing net cycle efficiency close to 50%. However, small changes on cycle parameters such as working temperatures, recuperators efficiencies or mass flow distribution between low and high temperature recuperators were found to drastically modify system overall efficiency. In order to mitigate these uncertainties, an optimization analysis based on recuperators effectiveness definition was performed observing that cycle efficiency could lie among 40%e50% for medium-to-moderate temperature range of the studied application (630 Ce680 C). Due to the lack of maturity of current sCO 2 technologies and no power production scale demonstrators, cycle boundary conditions based on the solar application and a detailed literature review were chosen.
Nowadays turbocharging the internal combustion engine has become an essential tool in the automot... more Nowadays turbocharging the internal combustion engine has become an essential tool in the automotive industry to meet downsizing technique requirements. In that context turbocharger unsteadiness is huge since both turbine and compressor work under high pulsating flow conditions, being turbocharger behavior prediction more difficult but still key for matching and predicting ICE performance. The well understanding and modeling of the occurring physical phenomena during turbocharger unsteady and off-design operation seems crucial.
An acoustic one-dimensional compressor model has been developed. This model is based on compresso... more An acoustic one-dimensional compressor model has been developed. This model is based on compressor map information and it is able to predict how the pressure waves are transmitted and reflected by the compressor. This is later on necessary to predict radiated noise at the intake orifice. The fluid-dynamic behavior of the compressor has been reproduced by simplifying the real geometry in zero-dimensional and one-dimensional elements with acoustic purposes. These elements are responsible for attenuating or reflecting the pressure pulses generated by the engine. In order to compensate the effect of these elements in the mean flow variables, the model uses a corrected compressor map. Despite of the fact that the compressor model was developed originally as a part of the OpenWAM™ software, it can be exported to other commercial wave action models. An example is provided of exporting the described model to GT-Power™. The model has been validated using experimental results obtained in a turbocharger test bench under pulsating flow conditions. The characteristics of the pressure waves (amplitude, frequency and mean flow) are similar to those of the pulses that the compressor undergoes when working coupled to a reciprocating internal combustion engine. This facility allows wave decomposition upstream and downstream of the compressor. The experimental pressure waves have been compared versus the results provided by the model analyzing both in frequency domain and in time domain in the two codes used to host the model. Finally, a comparison between the proposed 1D-0D model, which furthermore applies the compressor map, and the standard methodology used by GT-Power™, which directly only interpolates in the compressor map, has been performed. Results show better performance in the case of the proposed model and evidence the interest for the compressor geometrical description.
Solution of governing equations for one-dimensional compressible unsteady flow has been performed... more Solution of governing equations for one-dimensional compressible unsteady flow has been performed traditionally using a homogenously distributed spatial mesh. In the resulting node structure, the internal nodes are solved by applying a shock capturing finite difference numerical method whereas the solution of the end nodes, which define the boundary conditions of the pipe, is undertaken by means of the Method of Characteristics. Besides the independent solution of every method, the coupling between the information obtained by the method of characteristics and the finite difference method is key in order to reach a good accuracy in gas dynamics modeling. The classical spatial mesh could provide numerical problems leading the boundary to generate lack of mass, momentum and energy conservation because of the interpolation methodology usually applied to draw the characteristics and path lines from its departure point at calculation time to the end of the pipe during the next time-step. To deal with this undesirable behavior, in this work a modification of the traditional grid including an extra node close to the boundary is proposed in order to explore its ability to provide numerical results with higher conservation fulfillment.
In the present paper, an unsteady approach to determine the performance of a small radial inflow ... more In the present paper, an unsteady approach to determine the performance of a small radial inflow turbine working under cold pulsating flow is presented. It has been concluded that a reasonably good characterization of turbine behavior working with pulsating flow can be obtained using, in a quasi-steady way, models of the turbine isentropic efficiency and turbo-charger mechanical efficiency. Both models have been fitted using data obtained from a steady flow characterization procedure. Turbocharger-measured parameters from the cold pulsating flow campaign have been compared with the ones obtained from one-dimensional gas dynamics computational modeling. The modeling approach is based on quasi-steady isentropic and mechanical efficiency models. Reasonably good accuracy in compressor and turbine variables prediction has been obtained for most of the operative conditions. Influence of amplitude and frequency of the pulsating flow over the instantaneous and average turbine efficiency has been studied to put some light on the analysis of the involved physical phenomena. The main conclusion is that the biggest effect of unsteady flow on turbine efficiency is through the influence on blade jet to speed ratio. It has been also concluded that, for the same average blade jet to speed ratio, pulses' amplitude does not influence turbine efficiency when it is closed, but does at other variable geometry turbine (VGT) positions. The effect of pulses' frequency is less evident and only influences VGT performance at the highest VGT openings.