Proceedings of the ISES Solar World Congress 2019, 2019
Thermal Energy Storage is a key issue in concentrating solar power plants due to the need to tack... more Thermal Energy Storage is a key issue in concentrating solar power plants due to the need to tackle the conflict between dispatchability requirements of the utilities and the intermittent and unpredictable nature of solar radiation. In this context, molten salt tanks are the more widespread solution because of their effective trade-off between cost and functionality. This work presents a techno-economical assessment regarding the use of different salt mixtures as storage medium in a central receiver solar plant as well as the eventual improvement of its performance due to increasing the specific heat of the salts by the addition of nanoparticles. As case-study, an actual plant in southern Spain has been selected and System Advisor Model was adopted as performance estimation tool. After model validation, a sensitivity analysis involving plant indicators (E gen , CF, V TES , LCOE) and different storage scenarios was carried out. The results show no significant differences between commercial mixtures and an economical advantage of using nanoparticles.
This paper analyzes the impact of photovoltaic (PV) systems on storage and electric vehicles in m... more This paper analyzes the impact of photovoltaic (PV) systems on storage and electric vehicles in micro-grids. As these kinds of systems are becoming increasingly popular in the residential sector, the development of a new generation of equipment, such as more efficient batteries or solar panels, makes further study necessary. These systems are especially interesting in commercial or office buildings, since they have a more repetitive daily pattern of electricity consumption, which usually occurs within the maximum solar radiation hours. Based on this need, a novel control strategy aimed at efficiently managing this kind of micro-grid is proposed. The core of this strategy is a rule-based controller managing the power flows between the grid and the batteries of both the PV system and the electric vehicle. Through experimental data and simulations, this strategy was tested under different scenarios. The selected testbed consisted of the laboratory of a research center, which could be easily scalable to the entire building. Results showed the benefits of using an electric vehicle as an active agent in energy balance, leading to a reduction of the energetic costs of a micro-grid.
In this work, we focus on optimal energy management within the context of the tertiary control of... more In this work, we focus on optimal energy management within the context of the tertiary control of a microgrid operating in grid-connected mode. Specifically, the optimal energy management problem is solved in a unified way by using the optimal power flow (OPF) and day-ahead concepts. The elements considered in the microgrid are a photovoltaic panel, a wind turbine, electric vehicles, a storage system, and a point of common coupling with the main grid. The aim of this paper consists of optimizing the economic energy dispatch within the microgrid considering known predictions of electricity demand, solar radiation, and wind speed for a given period of time. The OPF is solved using three different algorithms provided by the optimization toolbox of MATLAB® (R2015a, MathWorks®, Natick, MA, USA): the interior point method (IP), a hybrid genetic algorithm with interior point (GA-IP), and a hybrid direct search with interior point (patternsearch-IP). The efficiency and effectiveness of the ...
The aim of the current paper is to propose a study of a novel solar adsorptive cooling system, us... more The aim of the current paper is to propose a study of a novel solar adsorptive cooling system, using activated carbon-ammonia pair, coupled with a parabolic trough collector (PTC) and a water-stainless steel heat pipe. A theoretical model, based on the thermodynamics of the adsorption process, heat and mass transfer within the porous medium and energy balance in the hybrid system components, is developed and a simulation code, written in FORTRAN, is carried out. This model, which has been validated by experimentation results, computes the temperature, pressure and adsorbed mass inside the adsorbent bed. The performance is assessed in terms of specific cooling power (SCP) and solar coefficient of performance (COPs). Furthermore, the effect of some important parameters on the system performance is discussed, and an optimization of these parameters is given. The simulation results have shown that there exists, for each aperture width value of the collector (W), an optimum external radius of adsorbent bed (R 2 ). Under the operating and design conditions of evaporation temperature T ev ¼ 0 C, condensing temperature T con ¼ 28 C, adsorption temperature T ads ¼ 24 C, W ¼ 0.70 m, R 2 ¼ 0.145 m and reactor length of 0.5 m, an optimal corresponding COPs is found to be of the order of 0.18.
... Additionally, solar adsorption refrigeration systems are attractive, mostly in remote areas w... more ... Additionally, solar adsorption refrigeration systems are attractive, mostly in remote areas without grid-connected electricity, since solar radiation is freely available, and the demand of refrigeration increases particularly in the sunny regions. ... [2] MA Alghoul, MY Sulaiman, BZ Azmi ...
This article suggests a numerical study of a continuous adsorption refrigeration system consistin... more This article suggests a numerical study of a continuous adsorption refrigeration system consisting of two adsorbent beds and powered by parabolic trough solar collector (PTC). Activated carbon as adsorbent and ammonia as refrigerant are selected. A predictive model accounting for heat balance in the solar collector components and instantaneous heat and mass transfer in adsorbent bed is presented. The validity of the theoretical model has been tested by comparison with experimental data of the temperature evolution within the adsorber during isosteric heating phase. A good agreement is obtained. The system performance is assessed in terms of specific cooling power (SCP), refrigeration cycle COP (COP cycle ) and solar coefficient of performance (COP s ), which were evaluated by a cycle simulation computer program. The temperature, pressure and adsorbed mass profiles in the two adsorbers have been shown. The influences of some important operating and design parameters on the system performance have been analyzed.
In this work the authors present the results of field experiments carried out in Almería (36.83ЊN... more In this work the authors present the results of field experiments carried out in Almería (36.83ЊN, 2.42ЊW), a seashore location in southeastern Spain, in order to evaluate the performance of Eppley precision infrared radiometer (PIR) pyrgeometers. The authors estimate the systematic errors in the measurements of downward longwave radiation caused by solar heating of the pyrgeometer's dome. Pyrgeometer measurements have been obtained in a series of experiments in which the dome of the pyrgeometer has been, alternately, exposed to the solar beam and shaded by a disk. These measurements have been completed with solar direct irradiance and wind velocity measurements. This study confirms previous assessments about the magnitude of this effect and its possible estimation in terms of global horizontal solar irradiance. Additionally, the authors have quantified the influence of natural ventilation on the solar heating effect. The experiments have confirmed the reduction of the solar heating effect with an increase of natural ventilation rates on the pyrgeometer. Nevertheless, this reduction reaches a limit, indicating that the effect cannot be fully eliminated, as has been already pointed out for mechanically driven ventilated pyrgeometers. A formula for the correction of the solar heating effect considering the wind velocity influence is proposed. It estimates the necessary correction as a function of solar irradiance and wind velocity, thus allowing the suppression of systematic errors, which could represent up to ϩ47 W m Ϫ2 for the worst situation (no wind, high irradiation), and providing experimental measurements that are affected by a random error of about Ϯ5 W m Ϫ2 .
Proceedings of the ISES Solar World Congress 2019, 2019
Thermal Energy Storage is a key issue in concentrating solar power plants due to the need to tack... more Thermal Energy Storage is a key issue in concentrating solar power plants due to the need to tackle the conflict between dispatchability requirements of the utilities and the intermittent and unpredictable nature of solar radiation. In this context, molten salt tanks are the more widespread solution because of their effective trade-off between cost and functionality. This work presents a techno-economical assessment regarding the use of different salt mixtures as storage medium in a central receiver solar plant as well as the eventual improvement of its performance due to increasing the specific heat of the salts by the addition of nanoparticles. As case-study, an actual plant in southern Spain has been selected and System Advisor Model was adopted as performance estimation tool. After model validation, a sensitivity analysis involving plant indicators (E gen , CF, V TES , LCOE) and different storage scenarios was carried out. The results show no significant differences between commercial mixtures and an economical advantage of using nanoparticles.
This paper analyzes the impact of photovoltaic (PV) systems on storage and electric vehicles in m... more This paper analyzes the impact of photovoltaic (PV) systems on storage and electric vehicles in micro-grids. As these kinds of systems are becoming increasingly popular in the residential sector, the development of a new generation of equipment, such as more efficient batteries or solar panels, makes further study necessary. These systems are especially interesting in commercial or office buildings, since they have a more repetitive daily pattern of electricity consumption, which usually occurs within the maximum solar radiation hours. Based on this need, a novel control strategy aimed at efficiently managing this kind of micro-grid is proposed. The core of this strategy is a rule-based controller managing the power flows between the grid and the batteries of both the PV system and the electric vehicle. Through experimental data and simulations, this strategy was tested under different scenarios. The selected testbed consisted of the laboratory of a research center, which could be easily scalable to the entire building. Results showed the benefits of using an electric vehicle as an active agent in energy balance, leading to a reduction of the energetic costs of a micro-grid.
In this work, we focus on optimal energy management within the context of the tertiary control of... more In this work, we focus on optimal energy management within the context of the tertiary control of a microgrid operating in grid-connected mode. Specifically, the optimal energy management problem is solved in a unified way by using the optimal power flow (OPF) and day-ahead concepts. The elements considered in the microgrid are a photovoltaic panel, a wind turbine, electric vehicles, a storage system, and a point of common coupling with the main grid. The aim of this paper consists of optimizing the economic energy dispatch within the microgrid considering known predictions of electricity demand, solar radiation, and wind speed for a given period of time. The OPF is solved using three different algorithms provided by the optimization toolbox of MATLAB® (R2015a, MathWorks®, Natick, MA, USA): the interior point method (IP), a hybrid genetic algorithm with interior point (GA-IP), and a hybrid direct search with interior point (patternsearch-IP). The efficiency and effectiveness of the ...
The aim of the current paper is to propose a study of a novel solar adsorptive cooling system, us... more The aim of the current paper is to propose a study of a novel solar adsorptive cooling system, using activated carbon-ammonia pair, coupled with a parabolic trough collector (PTC) and a water-stainless steel heat pipe. A theoretical model, based on the thermodynamics of the adsorption process, heat and mass transfer within the porous medium and energy balance in the hybrid system components, is developed and a simulation code, written in FORTRAN, is carried out. This model, which has been validated by experimentation results, computes the temperature, pressure and adsorbed mass inside the adsorbent bed. The performance is assessed in terms of specific cooling power (SCP) and solar coefficient of performance (COPs). Furthermore, the effect of some important parameters on the system performance is discussed, and an optimization of these parameters is given. The simulation results have shown that there exists, for each aperture width value of the collector (W), an optimum external radius of adsorbent bed (R 2 ). Under the operating and design conditions of evaporation temperature T ev ¼ 0 C, condensing temperature T con ¼ 28 C, adsorption temperature T ads ¼ 24 C, W ¼ 0.70 m, R 2 ¼ 0.145 m and reactor length of 0.5 m, an optimal corresponding COPs is found to be of the order of 0.18.
... Additionally, solar adsorption refrigeration systems are attractive, mostly in remote areas w... more ... Additionally, solar adsorption refrigeration systems are attractive, mostly in remote areas without grid-connected electricity, since solar radiation is freely available, and the demand of refrigeration increases particularly in the sunny regions. ... [2] MA Alghoul, MY Sulaiman, BZ Azmi ...
This article suggests a numerical study of a continuous adsorption refrigeration system consistin... more This article suggests a numerical study of a continuous adsorption refrigeration system consisting of two adsorbent beds and powered by parabolic trough solar collector (PTC). Activated carbon as adsorbent and ammonia as refrigerant are selected. A predictive model accounting for heat balance in the solar collector components and instantaneous heat and mass transfer in adsorbent bed is presented. The validity of the theoretical model has been tested by comparison with experimental data of the temperature evolution within the adsorber during isosteric heating phase. A good agreement is obtained. The system performance is assessed in terms of specific cooling power (SCP), refrigeration cycle COP (COP cycle ) and solar coefficient of performance (COP s ), which were evaluated by a cycle simulation computer program. The temperature, pressure and adsorbed mass profiles in the two adsorbers have been shown. The influences of some important operating and design parameters on the system performance have been analyzed.
In this work the authors present the results of field experiments carried out in Almería (36.83ЊN... more In this work the authors present the results of field experiments carried out in Almería (36.83ЊN, 2.42ЊW), a seashore location in southeastern Spain, in order to evaluate the performance of Eppley precision infrared radiometer (PIR) pyrgeometers. The authors estimate the systematic errors in the measurements of downward longwave radiation caused by solar heating of the pyrgeometer's dome. Pyrgeometer measurements have been obtained in a series of experiments in which the dome of the pyrgeometer has been, alternately, exposed to the solar beam and shaded by a disk. These measurements have been completed with solar direct irradiance and wind velocity measurements. This study confirms previous assessments about the magnitude of this effect and its possible estimation in terms of global horizontal solar irradiance. Additionally, the authors have quantified the influence of natural ventilation on the solar heating effect. The experiments have confirmed the reduction of the solar heating effect with an increase of natural ventilation rates on the pyrgeometer. Nevertheless, this reduction reaches a limit, indicating that the effect cannot be fully eliminated, as has been already pointed out for mechanically driven ventilated pyrgeometers. A formula for the correction of the solar heating effect considering the wind velocity influence is proposed. It estimates the necessary correction as a function of solar irradiance and wind velocity, thus allowing the suppression of systematic errors, which could represent up to ϩ47 W m Ϫ2 for the worst situation (no wind, high irradiation), and providing experimental measurements that are affected by a random error of about Ϯ5 W m Ϫ2 .
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Papers by Manuel Pérez García